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Posted: 2/16/2013 6:29:19 PM EDT
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i'm curious as to what factors barrel length brings into play with reloading.
Does a longer barrel typically require less powder because it has longer to build pressure? I went to run my test loads again today 3 types of 55gr. I noticed using N130 and my 16inch 1in7 twist it appears that the FMJ and the lead tipped dogtown bullets both start getting much tighter groupings up near max load. While the zmax appeared to give good results at both a high load and a mid load, the high being better by a hair, The max is 23.5 g the start is 21.8 Best groups dogtown - 23.2 FMJ - 23.4 Zmax - 22.6 AND 23.2 Strange...didnt expect that. The groups in-between were not as good. and all shots fired on benchrest. Looks like 23.2 might just be the load em up and go for all three. |
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longer barrel = higher velocity given the same load.
Longer barrel means more time for powder to push against bullet so: a slower burning powder will mach a faster burning powder from a shorter barrel Longer barrel has more surface area so: a low velocity bullet will drag harder on a longer barrel increasing the chance of a squib round. You can max load for a short barrel and be way over out of a longer barrel. making it unsafe (think 44mag from a revolver vs a Henry Lever action) So: Barrel length is a HUGE consideration when loading. (I have posted about 6 posts tonight I think half of them had something with barrel length.) Edit: Sorry got a little off topic. You will find that each rifle will "like" or "dislike" loads that almost defy logic. They quite literally will have a personality. All you can do is load a bunch of different types and test. If your rifle likes a max load of HPBT 55gr loaded so the bullet is touching the rifling....than that is what you feed it. :) |
| Loads are generally the same, there are some exceptions for SBR type barrel lengths, but for typical rifle length of 14.5+ use standard data. You can get the same or higher velocity usually with less powder and a longer barrel, but most don't do that, length doesn't really effect peak pressure (unless its an extreme diff, like 8"vs16") and downloading kinda defeats the purpose of longer barrels, though optimal accuracy is not always at a given velocity. |
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If you have a really short barrel and are concerned about excessive muzzle flash (perhaps for night shooting), a reloader can select a different poweder to reduce muzzle flash. Changing powders may affect ballistic performance but that may be acceptable if reducing the muzzle flash is important.
Other than that, I don't think there's a lot of leverage because peak pressure is achieved before the bullet exits the bore (even a short bore). |
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