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Question for you brainiacs...

Permanently deleted user
I was working up loads for my short barreled 45-70 yesterday and I have a question about my velocities. The published load data was shot in a 22" barrel. I have a 16" barrel. My question is this: With my starting load, I was only 50 fps under the published velocities. The intersting part is that with my max load, I was 125 fps under the published velocity. Do you think this is b/c I'm not getting a complete powder burn with the hotter loads.?.?...or is there another reason??? The only thing I can think of is that I have a shorter barrel and the bullet is not in the barrel long enough to give me a complete burn.?.? Interestingly enough, my most accurate loading was the hottest load though.
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6 comments

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  • Rocky Raab
    It's damn hard to say with so few specifics. But in general, velocity loss or gain is a proportional thing: the harder you push the more (or less) velocity change you get.

    An undersized bullet, an oversized bullet, a rough bore, an under- or oversized bore, wrong powder, wrong primer, or poor bullet choice could all be reasons or contributing causes. Of course, your chronograph could be screwy, or you didn't shoot enough samples to get a reliable average velocity, also.
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  • lksmith03
    quote:Originally posted by ECC
    I was working up loads for my short barreled 45-70 yesterday and I have a question about my velocities. The published load data was shot in a 22" barrel. I have a 16" barrel. My question is this: With my starting load, I was only 50 fps under the published velocities. The intersting part is that with my max load, I was 125 fps under the published velocity. Do you think this is b/c I'm not getting a complete powder burn with the hotter loads.?.?...or is there another reason??? The only thing I can think of is that I have a shorter barrel and the bullet is not in the barrel long enough to give me a complete burn.?.? Interestingly enough, my most accurate loading was the hottest load though.

    That would make sense since more powder needs longer to completely burn and if you run out of barrel before you run out of unburnt powder you will not be able to achieve that velocity. since the lite load was (Likely)almost burnt out by the time your bullet exited you wouldn't lose much speed
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  • bpost
    The powder is burned, most likely in the first couple of inches of bullet travel. However, the pressure is not fully used in a shorter barrel for projectile acceleration. The acceleration stops when drag equals force.

    You also note another known phenomenon, most cartridges, and the guns shooting them, reach peak accuracy at or near max pressure.
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  • RCrosby
    What powder??
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  • Permanently deleted user
    quote:Originally posted by RCrosby
    What powder??



    RL-7
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  • JustC
    often when you surpass maximum load for that particular chamber/brass/bore dia (etc) your velocity will drop as you have reached an inefficient point in your equation.
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