Velocity question for Experienced Reloaders...


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ILikeLead
December 19, 2009, 11:10 PM
If I were to use same bullets and same powder and same rifle and only change cases, I know pressures may be different. Would it be fair to assume that a rifle's "sweet spot" with a certain bullet is velocity dependent?

In other words, If I know the sweet spot/ velocity with one load and only change the case, would I try to first find the powder charge that produces that same velocity and work it up around that charge? Or could the sweet spot with a different case be totally different velocity even with same identical bullet?

I hope the question makes sense!

Thanks from a newbie...

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Rancho Relaxo
December 19, 2009, 11:18 PM
I have experimented with mixing cases when shooting groups with my CZ527 Varmint 223. I shot a 5-shot group with it's favorite load using all winchester brass that was all trimmed and another five shot group with mixed headstamp brass (LC, Win, Rem, Federal) and the difference was minimal, not hardly worth mentioning. Both shot group sizes within the normal range for that load (.3-.65"). That's been my experience.

WNTFW
December 19, 2009, 11:59 PM
The whole point of finding a "sweet spot" is to load to the center of the sweet spot. A true sweet spot will be wide enough to allow for the variance. Everything makes a difference. Some stuff is just not worth chasing. Your sweet spot may have a ranges of .3 grains. So if you are in the middle you can be off .15 either way in charge weight or case capacity and should be OK. My goal is to control the charge weight which I can control closely. I don't worry about the case weights.

I get pretty decent results with my handload and don't weigh cases. I only sort by headstamp. I inspect for safety and try to keep the lot of brass loaded the same number of firings. Matter of fact on my "match brass" I just use 22 round lots and some is RP, NNY, Win or whatever. I use 22 like headstamp in one stage. I put more effort into how the case fits the chamber and case prep. I also don't weigh or trickle every charge any more. I am finding my thrown charges to be working just fine.

Military brass is a different issue than commercial brass.

I know my cheek weld is more important than case weight. Finding the sweet spot is the thing.

You might pick up some stuff here:
http://optimalchargeweight.embarqspace.com/

45ACPUSER
December 20, 2009, 12:00 AM
If you change the parameters you work the load up again. The velocity will vary. Swapping cases is not a good idea.

mongoose33
December 20, 2009, 12:17 AM
My understanding is that sweet spot is velocity dependent. Rifles have a sort of resonance that causes them to flex, and finding the velocity that has the bullet exit the muzzle at the same point of flex is part of accuracy.

Ol` Joe
December 20, 2009, 11:18 AM
My understanding is that sweet spot is velocity dependent. Rifles have a sort of resonance that causes them to flex, and finding the velocity that has the bullet exit the muzzle at the same point of flex is part of accuracy.

Velocity is only part of it. The burn rate of the powder affects how hard the barrel is initially hit, the bearing surface of the bullet can change the vibration, how the primer ignites the powder goes back to the powders burn rate, etc.
Think of a hammer and a pipe. how big the hammer is, how hard you hit the pipe and where on its length, are you useing a leather or rubber mallet, how about a metal headed tack hammer, is any dampening present, all change the frequency.

ants
December 20, 2009, 01:00 PM
If you shoot at 600 or 1000 yards and you're good at it, everything prepped perfectly, yes it certainly makes a real difference on the target to use a different case.

If you shoot 100 to 200 yards (or maybe even 300) for most sport shooting, you may find no measurable difference, or you may find a small difference that you can ignore.

Your experience may vary, but I use carefully matched cases when I'm working up a sweet spot. Then I don't worry much about my brass after that. Unless I get challenged to a match at 600 yards.

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