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PCP muzzle energy variation with pellet mass - results of a small test

Discussion in 'Anything Airgun Related' started by cloverleaf, Jan 20, 2014.

  1. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

    Likes Received:
    We're all aware of the general trend of pre-charged rifles to produce more muzzle energy with heavier pellets.

    In prep for some testing later in the week (hopefully) I ran a few strings over the chrono with the NJR and five of JSB's .177 offerings. A few things of note; the pellet weight is the average taken from a batch of 10 weighed at once. The rifle's reg is set to 80-90bar (from memory), the barrel length is around 480mm.

    [TABLE="width: 704"]
    [TD="align: center"]Pellet
    [TD="align: center"]Mass, gn[/TD]
    [TD="align: center"]Velocity, ft/s
    [TD="align: center"]Energy Avg, ftlb[/TD]
    [TD="align: center"]Energy, % of Max.[/TD]
    [TD="align: center"]Falcon Accuracy Plus[/TD]
    [TD="align: center"]7.33[/TD]
    [TD="align: center"]805.0[/TD]
    [TD="align: center"]10.55[/TD]
    [TD="align: center"]90.1[/TD]
    [TD="align: center"]Air Arms Express[/TD]
    [TD="align: center"]7.87[/TD]
    [TD="align: center"]795.6[/TD]
    [TD="align: center"]11.06[/TD]
    [TD="align: center"]94.5[/TD]
    [TD="align: center"]Air Arms Field[/TD]
    [TD="align: center"]8.49[/TD]
    [TD="align: center"]779.0[/TD]
    [TD="align: center"]11.44[/TD]
    [TD="align: center"]97.7[/TD]
    [TD="align: center"]Daystate FT Heavy[/TD]
    [TD="align: center"]10.34[/TD]
    [TD="align: center"]714.2[/TD]
    [TD="align: center"]11.71[/TD]
    [TD="align: center"]100.0[/TD]
    [TD="align: center"]JSB Monster[/TD]
    [TD="align: center"]13.47[/TD]
    [TD="align: center"]619.4[/TD]
    [TD="align: center"]11.48[/TD]
    [TD="align: center"]98.0[/TD]

    (For those interested copying and pasting from Excel works quite well for tables on the forum :))


    As can be seen from the table and graph, muzzle energy rises approximately linearly as pellet mass increases from 7.33gn to 8.44gn, then at a decreasing rate until 10.34gn, before falling off as it heads towards the heaviest pellet at 13.47gn. The least efficient pellet (7.33gn Falcon Accuracy Plus) gave around 10% less muzzle energy than the most efficient pellet (10.34gn Daystate FT Heavy).

    I've seen similar behavior (with the heaviest three pellets) from my S410k; which operates at a higher pressure and has a shorter barrel (both of which may well affect the rifle's behavior with pellets of different mass). That said this is just one test with one rifle and manufacturer of pellets.. there may be other factors to consider between the pellets besides their mass alone; although hopefully at least the lead properties should be reasonably constant across all pellets.

    Anyway, I think the graph shows quite an interesting trend; suggesting that efficiency peaks (in this case) at a pellet mass of around 10-11gn :)
    Last edited: Sep 26, 2019
  2. mark112

    mark112 Engaging Member

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    Thanks Cloverleaf. This was just the info I was looking for. Interesting how quickly the graph rises and then fairly rapidly levels off. Shows the preference for Daystate Heavies to good effect also (or is it just the ideal weight for that barrel/rifle combination? Would a different pellet of the same weight show the same result?). Definitely will need to check my power output again against some heavies (and I don't mean shooting a night club doorman :)). Keep buying different pellets for setup but always come back to AADF for use!

    Is any of this type of data not published. I know there are airgun books but when I have glanced through copies it all seems a bit 'old fashioned' and heavy going! What we need is someone who can present this information in a more up-to-date and readable form using words and pictures that I can understand (maybe even in popup form ;)). This someone needs to be closely situated to one of our countries fine literary cities ... say Oxford. Well volunteered that man! Seriously though there seems to me to be little written during the PCP age.

    Could include a bit on modern valve setup which might even help me with a small problem I have but more on that at a later date.

    Many thanks. Your time spent is much appreciated on this type of work.

  3. Stevie Darling

    Stevie Darling Sexual tyrannosaurus

    Likes Received:
    St. Andrews, Jockland.
    Any chance of some of the same in .22:)

    very interesting posts though, I did a few very basic tests, no graphs or formulas. I tested about 15 brands of .22 pellet from 10g up to 16g, a 30y range and a bag of beef rib bones(scientific I know) anyway, the pellet that hit the hardest creating the most damage was H&N ftt!

    i don't know if was pellet weight, mass, composition, velocity, but the hardest hitter I found so far.

    A good laugh as well
  4. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

    Likes Received:
    Thanks :)

    As stated I can't say if this trend would transfer to other types of pellets; I suspect for similar weights but different types the shape of the graph would stay roughly the same, but might shift up or down the weight and energy ranges. Likewise I imagine that variations in barrel length, rifle operating pressure and (of course) calibre will have a significant effect on the gun's sensitivity to pellet mass.

    Thanks for the book suggestion - In view of all the stuff I spew fourth into the void of the internetz, I have considered writing a book on the subject. The problem is mainly that of being able to carry out the necessary, exhaustive testing to cover all bases; plus the time, commitment and resources required.

    Looking at the dated, arguably flawed but still useful Airgun from Trigger to Target by G. Cardew illustrates just how much time and effort has gone into producing such a book, and I suspect that much of the information we're all interested in is already summarised in that text (although obviously it does not cover more modern rifles and ammunition)...

    I'm open to suggestions though, if there are any tests forum members would particularly like to see :)

    Ta - probably not much chance of a similar test in .22 I'm afraid, for the simple reason that I don't have a sufficient range of pellets to use in the test (and am not prepared to spend £30+ to get them, sorry :p). Neither do I have a regged rifle in the knuckle-dragger's calibre (thinking about it I might have something suitable, once it's been repaired).

    That's interesting about the FTTs, and raises another question regarding impact on bone rather than softer matter..
  5. Soximus

    Soximus Busy Member

    Likes Received:
    Behind you! Mwhahahahah Just kidding. Christchurch
    Simply love reading your posts on this stuff.....brilliant work....

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