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Air Arms TX200 - Mk2 v Mk3: Which is Better?

Discussion in 'Anything Airgun Related' started by cloverleaf, Jul 19, 2013.

  1. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    So, I now have an example of each to hand and can authoritatively wade in on the hotly discussed subject of which is best :D


    Background

    The Air Arms TX200 was launched in 1991, as a genuine competitor to the influx of German rifles that had comprehensively outperformed the archaic, p*ss-poor offerings from our shores. At the forefront of the Teutonic assault was the legendary HW77; a rifle the TX design "borrowed from" substantially, while also incorporating some improvements over the German gun.

    The original HW77 ran a piston bore and stroke of 25mm and 81mm respectively. The Mk1 TX200 followed this closely with a bore and stroke of 25mm and 82mm; so had a little more swept volume. These dimensions were carried over to the TX200 Mk2 when it arrived in 1994, however 1998 saw the introduction of the Mk3 and an increase in stroke to 96mm, with a correspondingly lower-rate spring to keep muzzle energy legal.

    Air Arms justified this increase on the grounds of "reduced" recoil and lower cocking effort. The new longer stroke was shared with the FAC rated version of the Mk1 and Mk2; meaning that AA conveniently now only needed to stock one piston to suit the whole TX range, rather than two.

    Opponents of this increase in stroke argue that, since the piston is traveling around 1.2 times as far with around 2/3rds of the spring force propelling it, the longer stroke increases the shot development time (that between trigger release and the pellet leaving the muzzle); making the rifle more hold sensitive and less forgiving of poor technique and insufficient follow-through.


    Mk2 and Mk3 - A Comparison

    The two examples I have at my disposal are a 1995 .177 Mk2 in Walnut that I've recently acquired, and a 2011 .177 Mk3 in Walnut, that I've owned from new for about 18 months and is representative of the model currently being sold. Both guns are pretty stock; the Mk2 has just had a strip and relube and is now producing around 11.7ftlbs with 8.44gn Exacts. The Mk3 has also been stripped and relubed, but has a shorter, lighter .22 piston weight in place of the original item as it was running a bit warm. It's now also running at around 11.7ftlbs with Exacts. This will probably slow the shot development time slightly compared to a stock setup, but certainly not enough to invalidate any comparisons.

    Mk2 (top) and Mk3:

    [​IMG]

    [​IMG]


    Aesthetics and General Differences

    The Mk2 happens to have a particularly uninspiring piece of Walnut hanging off it while the Mk3 stock is an especially nice example (both models were / are also available in beech too). The Mk2 stock is chunky, angular and slab-sided with conservative panels of diamond chequering, while the Mk3 item is slimmed down at the forend, has a higher cheekpiece and elaborate fish-scale chequering.

    Both rifles have 340mm / 13.3" long, barrels of 16mm major diameter. The Mk2's un-shrouded tube is finished by a muzzle assy that extends past the muzzle by around 65mm and serves as a very small and basic expansion chamber to cut muzzle report a little.
    Conversely the Mk3's barrel is shrouded within a 19mm diameter tube for its whole length; which extends around 60mm past the muzzle and contains a number of baffles at the muzzle again to reduce report upon firing.

    Being un-shrouded the Mk2's barrel is blued throughout, while the Mk3's barrel-proper is left in the white as it's covered by the blued shroud - except at the breech.

    On both models the under-lever is retained by a spung ball detente housed in an assembly bolted to the underside of the muzzle assembly or shroud. Irritatingly and perplexingly the underlever assy on the Mk3 is slightly longer than on the Mk2 (killing interchangeability / potential Mk2 spares availability), however it seems that this difference (just a few mm) is taken up solely by the length of the concave insert in the end of the lever's tube into which the sprung ball detente locates when the barrel is in the closed position.

    The blued finish on the Mk2 is acceptable; having an inferior surface finish / roughness compared to the excellent finish on the Mk3.

    Overall the Mk3 looks like a more evolved, up-market product; although I suspect this would be less exaggerated if the difference in stock wood appearance was less pronounced between the two. The Mk2 looks a touch dated now, but still looks great - especially for a product launched 20 years ago.

    While not illustrated here both the late Mk2 and Mk3 were / are also available in "Hunter Carbine" / "HC" guise that has a shorter (240mm / 9.5"?) barrel with a slightly fatter 20mm diameter shroud on both models that ends about 40mm past the muzzle and contains a 1/2" UNF female thread to allow fitment of a mod. The underlever of the HC is fitted with a textured steel cocking aid. From the breech backwards the HC remains the same as the standard length rifles of the same era; additional preload washers to account for the lesser efficiency of its shorter barrel notwithstanding!


    Mechanical Components

    Both guns share a large amount of components and are mechanically very similar. Broadly speaking the differences are the plain barrel of the Mk2 compared to the shrouded item of the Mk3, and longer stroke piston (shorter latch rod) and lower rate spring of the Mk3. Spring guides and piston weights are also different. The Mk2 has 11 evenly-spaced ratchet cutouts for the "Safe-Lock" anti-beartrap mech, while the Mk3 only has three at uneven spacings - no doubt due to complaints about noise from users who choose not to hold down the anti-beartrap latch during cocking.

    Many parts are shared between the Mk2 and Mk3 including the main action cylinder, trigger assy, cylinder end plug, safety catch and trigger guard. Build quality is broadly comparable between the two, however the finish is better on the Mk3.


    Handling

    Both rifles are approximately the same overall length and broadly weigh a similar amount, although the Mk3 will be a touch heavier on account of the full length shroud. The later gun certainly feels significantly more muzzle-heavy; which helps with stability on standing shots but is getting towards the limit of my personal taste despite the fact that I like some mass up front.

    Both stocks are comfortable and functional, although that of the Mk3 feels more ergonomically accommodating; fitting the hands better and giving more complete and comfortable eye alignment with the 'scope on account of the higher cheekpiece.

    Cocking the Mk2 is reasonably stiff but certainly manageable. The Mk3's stroke is longer (the lever comes back further) and a lot lighter than the Mk2. I prefer the shorter lever displacement of the Mk2, and while the lighter Mk3's stroke takes less effort, it feels almost disconcertingly light.


    Firing Behaviour
    The trigger on both rifles is an identical unit with slightly different setups on my two rifles. Both are set to give a decent 1st stage with a crisps 2nd stage release at probably 1.5-2lbs. In this case the Mk2 has a little more first stage travel.

    I've never really "gelled" with the shooting characteristics of the Mk3. The firing cycle feels somewhat lethargic, with a lot of crosshair displacement under recoil. By comparison the Mk2 feels more immediate and "snappy", with the crosshairs tending to deflect less under recoil and in a generally consistent direction. At the end of the shot cycle you find yourself reasonably near the target and consistently in roughly the same place with the Mk2, while the Mk3 feels like it could leave you pointing anywhere.

    The Mk3 feels slow and sloppy while the Mk2 feels immediate, composed and consistent. Subjectively I much prefer the firing cycle of the Mk2.


    Ultimate Accuracy Potential

    I've fired the Mk3 from an appropriate rested position and the accuracy is excellent for a springer. Maybe 8-10mm c-c groups at 35yds, an inch - give or take - at 55yds being the norm in still conditions.

    I tried a comparison between the two earlier this evening; however there was a fair headwind and both guns were printing at around an inch c-c at 35yds. I think it's safe to say that when all user error is removed, these guns are capable of very similar levels of accuracy.


    Accessible Accuracy Potential

    This is where it gets interesting.. a tack-driver on the bench is useless if it won't allow the user to access that potential in the field. Many factors can affect accessible accuracy potential (ergonomics, trigger quality) but of course we're interested in the effect of the longer stroke and subsequent firing cycle.

    I decided to investigate this earlier by testing the guns back to back from a standing position. The range was consistent at about 35yds and both rifles were firing 8.44gn Exacts. The Mk2 is fitted with a Weaver K6 6x40 'scope, while the Mk3 has a Hawke Panorama 4-12x40; set at 6 mag. Both guns were zeroed at 35yds from the bench. 20 shots were fired from the Mk3, followed by 20 from the Mk2. Wind was present but of approximately consistent orientation and magnitude throughout the tests.

    I was quite shocked by the very visible difference between the two targets, below:

    [​IMG]

    Counting all shots the Mk3 group is a little over 70mm c-c; discounting two fliers it shrinks to around 42mm c-c. By contrast the Mk2 managed 20 shots within 46mm c-c; with 19 shots going into 32mm. The core group of the Mk2 was around 1.3 times smaller than / 75% the size of that of the Mk3.

    It can also be seen that the Mk2 group has shifted upwards by maybe 10mm from the bench zero, while that of the Mk3 has tracked perhaps 15mm up and 20mm to the left.

    From the difference in group sizes and displacement of outlying shots, it can be suggested that the Mk3 is far less forgiving of poor technique than the Mk2; probably on account of a significantly longer shot development time. After using the Mk3 the Mk2 seemed to "magically" drop shots in the right place; with called fliers being much closer to the centre of the group with the Mk2. With the Mk3 shots I fully expected to go wide, went wide. With the Mk2 called fliers were still inside the main group.

    The displacement from the "bench zero" when shot freehand implies a much larger degree of hold sensitivity with the Mk3 compared to the Mk2.


    Shot Development Time

    Driven by my findings at the range, I attempted to test the shot development time when I got home using this method.

    It seems harder to define the sear release point with springers; likewise the built in mods complicates the location of the pellet exit point somewhat. Long story marginally less long, over a number of fairly repeatable tests I recorded a shot development time of around 12.3ms with the Mk2, and a whopping 17.2ms for the Mk3 (although this was a lot harder to measure; will be open to some degree of inaccuracy and may well be a bit shorter than stated). By comparison an S400 series PCP is around 8.5ms.

    Even allowing for the 3" of moderator the pellet (and air behind it that the mic picks up) travels through only shaves around 0.3ms off the abysmal time of the Mk3; meaning that at best the shot development time of the Mk2 was around 1.35 times faster than / 75% that of the Mk3.


    Conclusion

    Congratulations to those who've made it this far :p

    From these findings and in my opinion, the Mk3 is a nicer looking, better finished and mostly better-handling rifle (not to say that the Mk2 is at all bad).

    However, I'm now firmly part of the camp that thinks Air Arms perpetrated a cock-up of epic magnitude by increasing the stroke length of the Mk3. They've taken a consistant, composed, predictable and forgiving rifle and made it slow, sloppy and hold sensitive; ultimately making it far more difficult to use accurately.

    The Mk3 is far less forgiving of imperfect trigger control and follow-through; making it significantly harder to use well than the Mk2.

    I think it's interesting to note the apparent correlation between the Mk3's approximately 35% longer shot development time 30% larger groups sizes, compared to those of the Mk2.


    The logical solution to the apparently w*nk performance of the later rifle is to replicate the Mk2 internals in the Mk3 for the best of both worlds. Parts are interchangeable without modification, however Mk2 pistons and compression chambers are no longer available and we don't want to go butchering any lovely Mk2s for bits :)

    Quite a few people have shortened the Mk3 stroke while retaining to original spring and guide by fitting a piston nose extension with appropriate seal, or by fitting custom Mk2 length latch rods to Mk3 pistons and using a Mk2 spring setup.

    I think either of these solutions are well worth considering - I may well look into the cost of a batch of longer length / shorter stroke latch rods myself a I can't see the Mk3 getting much use now I have the Mk2 :rolleyes: :p

    *Edited to correct some technical inaccuracies - bore, stroke etc and later barrel length*
     
    Last edited: Oct 2, 2019
  2. Alex.mc

    Alex.mc Busy Member

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    Great write-up!

    I'm glad I've got a Mk2!
     
  3. Jfrwhite

    Jfrwhite Posting Addict

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    Excellent review/comparison. Good reading even though I don't own either and am currently not considering buying either. Must have taken you ages!
     
  4. 177

    177 Donator

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    Excellent, objective, and very informative !

    I had a mark 1 back in the day which suffered horribly from a mechanical fault, resulting in the gun going back and me getting a refund :(

    On the plus side, during the brief fling I had with it, it shot beautifully from the get-go and was much admired by all who tried it. I distinctly remember the quality of fit and finish was outstanding and I've often regretted throwing my toys out the pram instead of accepting a replacement. The immaturity of youth, which has at least partially made it well into adulthood :rolleyes:

    I've not owned an Air Arms since but if I find a "mint as a packet of Trebor's" pre mk 3 example I'll snag it.

    I have to say, the stock on yours looks lovely, and I imagine it will really pop with some CCL coupled with a bit of "it's mine and I'll polish it as much as I like" :D

    My uncle's neighbour in Canada has a recent vintage TX200 running at some outrageous FPE and my uncle said it shot beautifully, so perhaps at least some of the anomalous behaviours you observed would 'level off' once we start operating outside the UK's legal limit. That's obviously of no consequence or direct interest to most over here but it does make sense that the gun would be a far more pleasant shooting experience when it is running as intended instead of being built to offer more but throttled down and restricted for our market.

    I wonder if they are available to the German market and, if so, what one would shoot like at their 6 FPE legal limit ?

    Hmmm...
     
  5. Kai87

    Kai87 Donator

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    Great. Write up! Thanks for that, iv always like the tx but now I know a lot more about them, cheers!
     
  6. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Thanks chaps - I'm glad some of you found it interesting / informative :)

    Yes, I think that despite the Mk3's frilly bits and eye candy, the Mk2 is the better gun if you actually want to hit things with it :p


    Yeah - thought I'd have the write up done in an hour; took more like 2 1/2.. I've genuinely written shorter uni assignments in the past :rolleyes:


    That is a shame about the Mk1.. it's very rare to find a decent one nowadays. Just out of interest what was wrong with it? AA certainly aren't perfect, but in my experience are significantly better than everyone else with regard to the QC on their springers.

    The Mk3's stock is definitely in line for a good seeing-to with some Trade Secrets oil (much the same as CCL), and I agree that it should look very nice when finished. Unfortunately I already have two stocks in progress, the work is thoroughly boring and laborious and I'm absolutely sick to the back teeth of oiling, flatting, rubbing..

    That said I can't see me using the Mk3 again until it's been short-stroked; so perhaps it's a good opportunity to refinish the stock in the meantime. On the basis of last night's performance I think the Mk2 has earned the reblue I was considering; so I ought to get that sent up North I suppose.

    I agree that your uncle's neighbour's gun should be better than a neutered 12ftlb Mk3; probably somewhere between that and a 12ftlb Mk2 in terms of hold sensitivity and useable accuracy.

    I never thought about the German market, however I suspect demand would be extremely limited given the availability of HW97s and the like at favourable domestic rates. Regardless a later gun running the original stroke and a lower rate spring to bring it down to 6ftlbs would probably be a proper bag of horrors to use :p


    Glad you enjoyed it. The TX range are fantastically well-built and engineered guns, however knowing what I do now I'd only buy a new one with the intention of short-stroking it - out of the box I bet the HW97k is a far easier rifle to shoot accurately..
     
  7. 177

    177 Donator

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    I am going to give a very woolly '"there was something wrong with the cocking arrangement/anti bear trap mechanism" answer. It was a long time ago now and the immaturity of youth (far different to the immaturity my middle age brings to the table ;) ) was more interested in getting a working gun in the field :rolleyes:

    There was some serious galling going on and every time the gun was cocked loads of metal filings were building up above the underlever pivot and some ended up in the loading port area. All within about a hundred shots, which began very well and ended up going south big time :(

    I remember setting the gun up on the banks of the river Till, just outside of Milfield, and within a couple of dozen shots it was pellet on pellet before it went awry.

    I bought it just after they were first released, on the strength of all the glowing reports in the airgun comics, from Bagnall and Kirkwood in Newcastle. I also remember the guy behind the counter exclaiming "Jesus !" when I took it back to show him what was going on with it.

    Its stock was gorgeous, and I'm making myself sick just thinking about the lost opportunity of having it fixed/replaced and subsequently keeping it forever instead of "I'll take that Fenman instead" :rolleyes:

    Mad that I can remember all that but I have no blimmin idea what actually went wrong with it...
     
    Last edited: Jul 19, 2013
  8. Darren Petts

    Darren Petts Temporarily Alive

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    I agree wholeheartedly that for 12 ft/lb use the short strokers are superior. A 14mm longer latch rod in the piston soon corrects AAs error, though I believe the early top hat is required too.
     
  9. 177

    177 Donator

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    I've seen a lot of varied opinion on shortstroked air rifles in general.

    I have a nicely tuned HW80 and a nicely tuned shortstroked HW80 and while I like both, several shooting friend who have tried them haven't liked the shortstroked one's shooting characteristics.

    I appreciate it's a totally different end product to a shortstroked TX200 but, on its own, shortstroking the gun can result in a very subjective outcome.
     
  10. darklord

    darklord Can’t beat a tx200 at 30m

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    2012-02-13 15.14.51.jpg new tx mk3 177 30 yards 20 shots bench rested. with 177 aa diablos 4.52.
     
    dougs likes this.
  11. hairyarms

    hairyarms .

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    Mine is the same if it aint broke ...Really interesting write up mate. I struggle doing a few sentences!
     
  12. Bluefrog

    Bluefrog Busy Member

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    So what your saying is that a MK2 rifle with a MK3 stock would be the perfect mix ?

    Thought so :D
     
  13. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    That is odd - I've not heard of a similar issue before. Mine did have a small burr on the cocking link where it pivoted within the underlever (it had galled the inside faces of the pivot on the lever a bit but not terribly).

    A Fenman! I had one for about 6 months before I thankfully got shot of it :p


    Yes. If using the Mk2 (spec) piston you need the stiffer Mk2 spring, which requires the Mk2 guide (since the wire is thicker the guide has a smaller OD) and piston weight / top hat (since they fit differently to the spring) :)


    I agree - I took the Mk3 down to 70mm with a modified piston and higher rate spring some time ago; it was underpowered and utterly horrible to shoot (harsh, lots of vibration). I think this was because the short piston travel time gave an insufficiently small time window for the air to act on the pellet before bounce set in.

    Some time ago Prof. Mike Wright suggested in AGW that you need a certain amount of time for the energy transfer from the compressed air to the pellet; so I think we have to accept that we'll never comfortably get below development times of maybe 10-12ms for .177 calibre 12ftlb rifles. I'd be interested in measure a gas ram rifle; since they seem to fit the model perfectly (fast development time, poor efficiency, violent recoil).

    Broadly speaking it seems that longer-stroked guns are more efficient but slower and less forgiving to shoot. Shorter stroked guns sacrifice some efficiency for an improved shot development time (and hold sensitivity); however the time comes when the inefficiency (and additional recoil / NVH that come with it) outweigh the speed benefits. Much like everything else in life it's a compromise..

    How do you find your HW80s? I must admit I'm not a huge fan of the 80 at 12ftlbs.. in standard trim I suspect it takes a long time to get the pellet of of the barrel, and while short-stroking it should help, I think the bore's too big for 12ftlbs. I'd like to measure the development time on some, but don't currently have access to anything suitable.

    I have a '35e (30mm bore and 65(ish)mm stroke) which feels very "bouncy" to shoot. I suspect that for a given swept volume guns with a large bore:stroke ratio are less efficient; causing more disturbance during the shot. I like the idea of running a TX with a smaller diameter piston (say 22 or 20mm); reducing the swept volume without ending up with a short stroke and harsh firing cycle; the problem is finding suitable springs to fit the packaging constraints..


    Good work - how's it do freestanding? :D


    Thanks - I could talk the legs off a Donkey, which isn't always a good thing :p


    Possibly.. though I prefer the idea of Mk2 (spec) guts in a Mk3 myself :cool:
     
    Last edited: Jul 20, 2013
  14. 177

    177 Donator

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    I honestly can't remember the specific details, but the noise was terrible and a serious quantity of metal shavings resulted, which is never good :(

    Quite possibly my favourite overall self-contained rifle of all time, in spite of its trigger :rolleyes:

    :)

    If I'm honest, I much prefer my tuned HW80 with standard piston than the shortstroked one. That said, I consider myself an enthusiastic amateur tuner rather than an expert. I am sure that someone with a proper blueprint for the HW80 could do a much better job and influencing factors like the currently unaltered transfer port would form part of the larger picture. Basically what I'm saying is that the shortstroked gun is not everything it could be but it's about as far along as I am willing to take it.

    My shortstroked 80 is horribly fast when you pull the trigger by comparison to the tuned-but-standard 80. I've not done any recoil tests yet mind and, even if I do, it will only be to rest the butt of the gun on a set of digital scaled with a target/backstop above and measure the recorded maximum weight over 5 shots for each gun and establish an average. Needless to say, I'm not talking about bathroom scales here...

    My mate has a sleeved down HW80 which is the nicest 80 I have ever shot by a long margin. I have handled a lot of HW80's over the years, some of them very highly modified, but the sleeved down 80's have been the nicest to shoot by a country mile.

    Personally I think a sleeved Mk 3 TX200 would kick the tar out of any shortstroked TX, but I appreciate that shortstroking is a solution, of sorts, given the associated challenges of suitable parts to sleeve one down.
     
  15. ithica -john

    ithica -john Posting Addict

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    tx200 hc mk 1 serial number 031880
    in good condition few dints to varnish on underside of stock [not by me]
    good accurate little shooter now surplus to requirements so up for sale £150 posted


    just missed this on A****....................:eek:
     
  16. man-tee

    man-tee Engaging Member

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    As others have said 'nice post' thanks for the time and effort in doing and writing about it.
    I've found it a fascinating read, Cheers.:)
     
  17. sharpsman

    sharpsman Keyboard Hero

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    Well done and a great read ive always prefered the shooting charecteristics of the mk2 over the mark3 and for me the mark2 is more accurate of the two,airarms forgot about the British market when they introduced the mk3 to satisfy the needs of our shooting cousins across the pond.Second hand mk2's always seem to sell a lot faster than mk3's maybe airarms should take note of this and supply UK shooters with a rifle with the same stroke as the mk2.
     
  18. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    *I'd like to point out that the bore of the TX200 is actually 25mm, not 26 as wrongly stated in my original post* Thursday night was a long one :p

    I'd also like to point out that the aforementioned shorter, lighter .22 piston weight fitted to my Mk3 will probably result in a bit more piston bounce than would be present in a standard Mk3. Certainly not enough to invalidate the observations in my first post, but sufficient to make it a bit worse behaved than a standard rifle.

    That's interesting about the Fenman - I agree about the trigger, but found the rest of the example I owned to be pretty crappy too :p

    Interesting to hear your thoughts on the '80s too... by how much has the stroke been reduced on the modified one, and how's it been done? As with my 70mm TX I suspect that the piston's completing it's stroke too fast; transferring less energy to the pellet and creating a lot of recoil and inefficiency. I suspect adding some mass to the piston would help :)

    An interesting observation about your mate's sleeved down '80 (is that one of Bigtoe's efforts?) I suspect it very closely approximates that firing behaviour of a '77 now as it's bore and stroke will now be very similar. It's very subjective, but interesting to compare the firing characteristics of of guns of similar output and swept volume but differing bore and stroke (as with the HW80s you mention).

    I'd very much like to sleeve down a TX, however I'm not sure of the practicialities and there has to be a lower limit to the swept volume whereby 12ftlbs can no longer be achieved. The HW99s has a swept vol of around 37cc (I think) and is as efficient as any other gun, but often struggles to break 11ftlbs in .177.

    That said, perhaps this is more on account of the shorter stroke; and that fitting a stiffer spring would drive it too fast and kill efficiency.. I can't help but think that the firing manners of most rifles could be improved by reducing their swept vol; thereby reducing the volume of "surplus" air present to drive piston bounce when the piston reverses direction near the end of it's stroke.

    Short-stroking is of course another way of achieving reduced swept vol, however this brings with it the need for lots of piston mass to slow the firing cycle, and silly-high cocking efforts..

    That would be a Mk2 ;)

    But yeah, sounded worth a look; although there are sadly a lot of neglected Mk2s about now :(


    Thanks :)


    Cheers - and yes, I think AA should definitely go back to the old format. Sadly I think the golden days of really listening to their customers are gone; conversely, it might just be that superficial reasons (lighter cocking effort, "softer" recoil) appeal more to buyers than proper reasons like actually being able to hit the target :p
     
    Last edited: Jul 21, 2013
  19. 177

    177 Donator

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    I don't consider short stroking to be the panacea some seem to think it is (I'm not suggesting you're one of them) but I can see the appeal, up to a point.

    My HW80 shortstroked piston is one of UKNeil's which adds 24mm onto the piston length:

    [​IMG]

    [​IMG]

    I've actually been advised to reduce piston mass on the shortstroked gun but, as I say, I'm an enthusiastic amateur and it's easy for folks who have a full blueprint for any given gun to offer throwaway suggestions which help, up to a point, but they are irreversable and require access to tooling that I just don't have.

    I have spare HW80 pistons and other stuff but I'm not risking faffing with teh transfer port on the basis that opening it out and chamfering the end(s) is a lot easier than having to sleeve it down if it goes that strange shape of pear...

    Likewise, lightening the piston is all well and good but if it doesn't have a positive effect it's basically only fit for the bin.

    If I had access to tooling I'd sleeve both my HW80's down in a heartbeat.

    My 25mm HW77's shoot beautifully and, having experienced a sleeved down 80 (yes, one of Bigtoe's), I was astonished at how gentle such a 'robust' gun as the 80 could become.

    I guess the alternative is to take a 95 and bulk it up a little to help tame it down.

    Funny old game - guns are like the weather; it's always too something. Too hot, too wet, too loud, too light, too heavy, too much swept volume, etc,.

    ;)

    The HW99 is a potentially epic gun let down by a god awful cocking mechanism that actually contrives to make cocking harder !

    HW95 or 98 is a breeze by comparison - go figure.

    Were it not for that I think the HW99 could easily become a legendary gun since it offers so much in such a lightwight and inexpensive package. Ho hum...

    My Fenman was stunning to shoot with a superbly engineered finish throughout, and I miss it terribly :(

    On the plus side I recently got the action back from America for a very early Sirocco (700 range serial number) which has been over with Martin Rutterford at Rapid Air Weapons having a new gas ram built for it. Please don't burst my bubble because I am soooooooooo looking forward to getting it back in the field for a bit of old school (for me) reminiscing :rolleyes:

    It's one of airgunning's many oxymorons that we try and make heavier guns behave like their smaller, lighter stable mates (HW80/HW95)

    My shortstroked 80 is scarily fast when shooting it. Everyone who shoots it comments on that aspect of it, and I must do some recoil tests to establish some sort of comparison to a stock and tuned standard volume 80. Also of note is that the barrel drops about 30 degrees when you break it before any resistance is felt - many who have tried it thought they had broken the gun when cocking it for the first time :)

    Regarding the TX I am genuinely surprised that there is no drop-in kit available for them to sleeve them down which, I still think, would give a far better overall result than shortstroking.
     
  20. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    I agree about the short stroking; it's all about optimisation - no point shortening an already perfect stroke. Some guns got it right from the off (HW77), some didn't.

    It looks like your '80 is pretty extreme. The extension leaves a stroke of around 59mm; which is shorter than a '35 I think. If you do anything to it I'd try weighting the piston - lightening it will only speed things up further; making it even more snappy and inefficient. You could get a custom top hat made from brass - shouldn't be too expensive and is reversible (I totally agree about the transfer port etc) .

    There was a Bowkett article in AGW many moons ago where he tuned a '77 by fitting an extension similar to that on your '80 - but in steel, shortening the stroke to something like 70mm. I'd certainly be interested to try one of those :)

    I totally agree about the '99s too - it's an absolutely fantastic gun in every way, excepting the nasty cocking linkage problem.
    I found it to be an incredibly forgiving rifle to shoot (for a springer), which was reinforced when I tested the shot development time at around 11ms - everything else I've tested has been 12ms+ ('97, '98, TX200).

    I'd have one in heartbeat were it not for the galling issue (word on the street is that it's being looked into, though :))

    You say about making the '80 more like the '95 (the mass of the former with the piston geometry of the latter) - I think the '77 does a pretty good job of this :cool:

    The problem with the TX is that to reduce the bore any more pushes you for space. The 25mm piston is around 2/3rds the area of a 30mm piston, so a reduction of a similar amount would seem worthwhile; giving a desirable diameter of about 21mm.

    Allowing a piston wall thickness of 1mm and a 0.5mm clearance on the OD gives a piston ID of 18mm. Assuming the spring guide could survive with a 1mm wall (12mm OD) this gives you an absolute max spring wire diameter of 3mm; in reality more like 2.5mm. A spring of this wire dia only gives a rate of around 5N/mm, while the normal Mk2 spring is around 9N/mm.

    To counter this you'd need a lot more preload (probably more spring than you could fit in), and the smaller OD spring would want to buckle more so would probably need more support too. Going to a 22mm piston would give you a bit more room for thicker wire and about 80% of the original swept volume.

    You could alternatively run a really short piston that doesn't extend rearward of the front of the spring (apart from the latch rod) although I suspect this would be very unstable compared to the existing setup and you'd probably have issues getting enough mass too..

    Finally after all this you might just find that there's insufficient swept volume to get the required muzzle energy - I'd love to try, though!

    Good luck with your Theoben - I'll look forward to reading about it once it's back ;)
     

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