heavy pellet issues

[safrole]

I have a hatsan 125 sniper and I did a good string the other day with 14.3 crossman pellets
and I was getting an average of 965fps at the muzzle which puts me at about 29.6 FPE at the muzzle.

Then I did a string with some 21.14 beeman heavy pellets and I was getting about 763fps which puts me at 27.3 FPE

Now obviously the heavier pellets are going to be slower and of course they are going to deliver more energy down range. But it seems that even with the slower velocity the energy at the muzzle should be the same no matter what the weight of the pellet is.  Anyway I was just curious what other peoples experience was and if this sounds normal.

[LAalex]

     There is a point of diminishing returns with powerplants and projectiles.  I remember reading about a guy who had a gunsmith slightly ream the chamber of his 30-06 so that he could shoot 220gr. (or was it 225?) accurately.  He hunted moose, and the heavier slug gave better penetration, if less energy.  The big bullet just ate up too much case capacity for the cartridge to push it fast enough for the energy figures to keep up with the 180 gr.  I think the same holds true for our springers--we have to find that happy place where accuracy, trajectory and energy are in their best balance.  JMO.

Scotty

[HYspd]

heavier pellet = higher pressure spike

higher pressure spike = harder piston kick back

harder piston kick back = longer time to resume forward motion

longer time of non forward motion = lower total pressure when averaged over time of shot cycle

lower pressure = less power


I think that covers it....now I need some intellectual mydol for my brain cramps

[MicErs]

I have a hatsan 125 sniper and I did a good string the other day with 14.3 crossman pellets
and I was getting an average of 965fps at the muzzle which puts me at about 29.6 FPE at the muzzle.

Then I did a string with some 21.14 beeman heavy pellets and I was getting about 763fps which puts me at 27.3 FPE

Now obviously the heavier pellets are going to be slower and of course they are going to deliver more energy down range. But it seems that even with the slower velocity the energy at the muzzle should be the same no matter what the weight of the pellet is.  Anyway I was just curious what other peoples experience was and if this sounds normal.

Apparently (I was surprised also because the same dynamics are not at play with archery equipment) heavier pellets are usually less efficient in spring air systems.  That is probably for the reasons listed above this post but I did not take my intellectual mydol so...  The Airgun Academy is a great place to read by the way.

[safrole]

ya the 14.3 grain pellets seem to do pretty darn good in my gun. at 965fps in a springer that is pretty freaking awesome and pretty flat trajectory too. thanks for the info guys I can sleep better now.

[Roadworthy]

Overall your conclusions are not surprising, but you are probably measuring your speed somewhere near the muzzle.  A study of physics will tell you that force is half the mass of the projectile multiplied by the square of its velocity.  The mass will not change on its trip downrange but the velocity will decrease.  Projectiles moving at a greater velocity tend to shed their velocity faster.  In short, even though the heavier projectile (with its lower velocity) has less fpe as it leaves the barrel it will retain it better than the light one.

[f4milytime]

heavier pellet = higher pressure spike

higher pressure spike = harder piston kick back

harder piston kick back = longer time to resume forward motion

longer time of non forward motion = lower total pressure when averaged over time of shot cycle

lower pressure = less power


I think that covers it....now I need some intellectual mydol for my brain cramps

 

[safrole]

Overall your conclusions are not surprising, but you are probably measuring your speed somewhere near the muzzle.  A study of physics will tell you that force is half the mass of the projectile multiplied by the square of its velocity.  The mass will not change on its trip downrange but the velocity will decrease.  Projectiles moving at a greater velocity tend to shed their velocity faster.  In short, even though the heavier projectile (with its lower velocity) has less fpe as it leaves the barrel it will retain it better than the light

basically the piston is transferring its energy into the pellet and maybe some sound energy and excess gas and what not. Lets pretend that the piston is transferring its energy perfectly into the pellet. if this is the case then both pellets should have the exact same energy at the muzzle or say it this way the minimum distance away from the point at which the pellet receive its energy from the piston.
basically there is some serious friction issues going on with the heavier pellets considering I am losing over 2fpe of energy at the muzzle by using heavier pellets. maybe this 21.14grain pellet will still retain more energy down range but I haven't really done the math to see how much more and frankly I like having a flat trajectory. 14.3 grains is still a fairly decent weight and I dropped a crow like a sac of potatos with 1 shot just the other day from about 20 yards or so. it was beautiful.

[HYspd]

yeah there is some frictional loss too, but not all of the loss is frictional by far, but the only way to tell is to shoot pellets of the same basic design and same weight by different manufacturers....Crosman's that fit well will usually shoot the quickest as they are a higher antimony alloy and barely take any rifling imprint compared to say JSBs stuff...too bad Crosman pellets in the tins are radically size inconsistent...I've one pellet fall out of the barrel and the next i couldn't load deep enough by hand to get the barrel closed...quite irked my hide as that was my second tin and the first tin was reasonably consistent for pellets that retail for 1/3 the cost of their own brown boxed "good" pellets...


the quickest and heaviest soft pellet i can shoot in my gun the HN FTT 14.66 only lose 10fps with them and they deform significantly more on impact than the Crosman's do... that only costs about .07 fpe...

gonna get some krytech next time i think...

[avator]

I think Thomas (Roadworthy) hit the nail right on the head. You are measuring at the muzzle. The heavier pellet is going to retain more of it's energy down range. Would you rather get hit by Ray "boom boom" Mancini's barrage of lightning fast strikes or one of Mike Tyson's knock out cannon balls? JMO

[grauhanen]

The Beeman heavy pellet in question is made by H&N.  In the same rifle H&N pellets are often slower than many other brands of pellets of similar weight.  And, as noted by others above, it is important to keep in mind that as it goes downrange a heavier pellet will invariably retain its energy longer than a lighter pellet.  Generally the BC (Ballistic Coefficient) of a heavier pellet is greater than that of a lighter one.

[cnjl3]

If you know the velocity of the pellets you are using then you just need to download Hawke Chairgun Pro and plug in your pellet data. Then you will see the FPE at various distances and you will see how the heavier Kodiak pellet retains its downrange energy at a much better rate than your CPL. Looks like the Crossman starts off faster at the muzzle and maybe at 10yds - but beyond that the heavier Kodiak pellet will have a higher FPE. But the most important piece of info is which of the two pellets that you are testing yields the best groups at whatever distance you are hunting,plinking  -- The accurate one is the one you should be using and stocking up on. Hey, if you don't want to mess around with Chairgun Pro then hop on over to StraightShooters web site and pull up an airgun which is close in velocity to your airgun and click on the "Our Take" tab and you can see some velocity/FPE figures at muzzle/10 yds, 25yds and 50yds for most pellets. Check it out: http://www.straightshooters.com/webley-patriot-.25-beech.html