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same reload different rifles 4.5% delta in speed

rp85rp85 Member Posts: 360 ✭✭✭

same reloads but two different rifle makers, same cal. per chronograph there was a 4.5% (85fps)difference in speed. anyone ever see this difference?? thanks for any input



  • FrancFFrancF Member Posts: 35,278 ✭✭✭
    edited November -1
    I personally would not even blink an eye at a 85fps Deviation between two rifles. Now if it was 850Fps between 2 rifles that would get my attention.
  • bpostbpost Member Posts: 32,643 ✭✭✭✭
    edited November -1
    Very common, every rifle is a world of its own. Every little variance either adds or subtracts from accuracy and MV.
  • MobuckMobuck Member Posts: 13,542 ✭✭✭✭
    edited November -1
    I just ran some 7.62x39 handloads over the Chrony this week. A conservative load ran right at listed max velocity(2450) from my Remington 799 but only about 2150 from a 16" AR. I was expecting 100 fps diff but not 300. In this case, I'm pretty sure I know the problem.
    85 fps is not such a big deal. You didn't say whether barrel lengths are equal or what velocity range you're talking about(assuming 4.5%=85 fps I'm guessing around 2000?)
  • AmbroseAmbrose Member Posts: 3,128 ✭✭✭
    edited November -1
    You don't hear this as much anymore but do you remember old-timers referring to ole Betsey with phrases like, "shoots hard!" or "carries up!"? Maybe they weren't just bragging. In chronographing, it is surprising how much difference there is in velocity among similar rifles chambered for the same cartridge. The most predictable effect is barrel length but other mysterious factors come into play. An example: A friend had a Remington 40X in .30/06 with a 27" barrel. Since it was a target rifle built with, one would presume, tighter tolerances, I expected velocities approaching .300 Magnum. Not so; it was slower than most 24" barreled rifles. So you don't know until you check. That's one of the things that make shooting experiments fun!
  • JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    velocity doesn't mean as much as consistency. Every barrel is different,..some will be faster, some will be slower. It is very common.
  • Tailgunner1954Tailgunner1954 Member Posts: 7,734 ✭✭
    edited November -1
    The worst I've personally seen was with the same barrel & ammo, but a different chamber reamer. Reloads, all out of the same batch/lot.
    Chamber 1, 26" barrel, 2675 average over 10 rounds
    Chamber 2, 25" barrel, 2995 average over 10 rounds
    Yep, a 10% difference, with the shorter barrel being the faster.
    The only area, of the chamber, that varied was between the case mouth and the start of the rifling (reamer 1 cut the throat .005 larger in diameter than reamer 2 did)
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