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Posted: 4/15/2011 3:20:08 PM EDT
| I've heard that the three B's is where accuracy comes from. Barrel and bullet are easy to understand but what effect does brass have when trying to shoot a tight group? If brass also pertains to powder and primer then it easily makes sense but if that's not it's meaning then please help me understand. |
| Variances in brass concentricity, and make up (harder/softer in weird places) cause inconsistent chamber pressures and off center release of the bullet. Its not a huge thing, but using lapua brass instead of remington will give you slightly tighter groups, and more loads per case before case failures. |
| Well, large variences in internal capacity would make slight changes in pressure, inconsistant primer holes will effect ignition, just off the top of my head. When I loaded for maximum accuracy I would try to stick with same make and lot of brass, I never went to the trouble of trying to weigh the brass or anything. |
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Accuracy shooters Match condition their brass to eliminate variances that affect accuracy.
I have a buddy who shoots Matches and he preps his brass as follows.....As far as I can remember: He buys all brass from a single manufacturing lot. He weights the brass to eliminate too heavy or too light cases. (I think he actually weights something like 1000 cases and does a standard deviation math program to find the most consistent brass. The brass that's off is used for practice or discarded if it's too far off). He uses tools to uniform the primer pocket and insure there's no small brass disk left inside from when the primer hole was punched during manufacture. He uses case neck turning tools to uniform the inside and outside case neck. He trims the cases to a uniform length. He uses a precision resizing die to size the case. Since he's shooting auto rifles, I think he full-length resizes. In short, the idea is to make each case as alike as each other case to eliminate any variations. The more uniform ammo is, the more consistent the accuracy. |
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Quoted:
Well from what everyone has said it's about consistency. I guess as with all of the other aspects of precision shooting, duplicating the previous shot in every way will get you the best result. Accuracy=Consistency. As others have said, internal case volume, primer hole size, primer pocket tension, overall case length, case neck thickness, and neck tension all play an important role in consistency, ergo accuracy. |
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Quoted:
Accuracy shooters Match condition their brass to eliminate variances that affect accuracy. I have a buddy who shoots Matches and he preps his brass as follows.....As far as I can remember: He buys all brass from a single manufacturing lot. He weights the brass to eliminate too heavy or too light cases. (I think he actually weights something like 1000 cases and does a standard deviation math program to find the most consistent brass. The brass that's off is used for practice or discarded if it's too far off). He uses tools to uniform the primer pocket and insure there's no small brass disk left inside from when the primer hole was punched during manufacture. He uses case neck turning tools to uniform the inside and outside case neck. He trims the cases to a uniform length. He uses a precision resizing die to size the case. Since he's shooting auto rifles, I think he full-length resizes. In short, the idea is to make each case as alike as each other case to eliminate any variations. The more uniform ammo is, the more consistent the accuracy. You hit on all the most important aspects of uniforming cases. For a more detailed answer read, The Ultimate In Rifle Accuracy by Glenn Newick. Its not an expensive book, I paid about $10.00 6 or 7 years ago. |
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Quoted: Quoted: Well from what everyone has said it's about consistency. I guess as with all of the other aspects of precision shooting, duplicating the previous shot in every way will get you the best result. Precision Accuracy=Consistency. As others have said, internal case volume, primer hole size, primer pocket tension, overall case length, case neck thickness, and neck tension all play an important role in consistency, ergo accuracy. |
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Quoted:
Quoted:
Quoted:
Well from what everyone has said it's about consistency. I guess as with all of the other aspects of precision shooting, duplicating the previous shot in every way will get you the best result. Precision Accuracy=Consistency. As others have said, internal case volume, primer hole size, primer pocket tension, overall case length, case neck thickness, and neck tension all play an important role in consistency, ergo accuracy. Absolutely true, but group sizes are almost invariably measured against a standard (MOA, for example). Therefore, both accuracy and consistency are close enough as to be indistinguishable from a shooter's perspective. |
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All of the above case prep will help consistency, but one extra step that can be taken is to index the round through the entire loading process. For example the loader may mark the rim of each case in the same spot on the head stamp for each case. That ensures any alignment issues in the loading process are consistent.
On a bolt gun you can then also index the mark straight up in the magwell or in the chamber. In that case however neck sizing makes more sense than FL resizing. in a semi auto you can also index, and some shooters prefer small base dies that take the case back to new dimensions. That helps it lie consistently in the bottom of the chamber. The case weighing and flash hole prep steps aid consistency in pressure and velocity while the rest tend to aide concentricity or at least consistent alignment of the bullet enters the barrel. In black powder cartridge rifle shooting you can get the ultimate in case consistency by using the same case and reloading it for each shot with a hand press. I've gotten standard deviations of only 5 fps doing that. |
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Quoted:
All of the above case prep will help consistency, but one extra step that can be taken is to index the round through the entire loading process. For example the loader may mark the rim of each case in the same spot on the head stamp for each case. That ensures any alignment issues in the loading process are consistent. On a bolt gun you can then also index the mark straight up in the magwell or in the chamber. In that case however neck sizing makes more sense than FL resizing. in a semi auto you can also index, and some shooters prefer small base dies that take the case back to new dimensions. That helps it lie consistently in the bottom of the chamber. The case weighing and flash hole prep steps aid consistency in pressure and velocity while the rest tend to aide concentricity or at least consistent alignment of the bullet enters the barrel. In black powder cartridge rifle shooting you can get the ultimate in case consistency by using the same case and reloading it for each shot with a hand press. I've gotten standard deviations of only 5 fps doing that. I agree with most of what you're saying with the exeption of indexing the cartridge, unless its to be used in a target gun with a trued chamber and bore and all the necks of every cartridge turned uniform in thickness. That's a game for people with a lot more money and time on their hands than 99% of us I think, and most impracticle in all but one application. |
Then again, I know guys in LR BPCR that in addition to the case, also index the bullet & primer !!
Having watched the World Champion reload in South Africa- HE does not.. Quoted:
All of the above case prep will help consistency, but one extra step that can be taken is to index the round through the entire loading process. For example the loader may mark the rim of each case in the same spot on the head stamp for each case. That ensures any alignment issues in the loading process are consistent. On a bolt gun you can then also index the mark straight up in the magwell or in the chamber. In that case however neck sizing makes more sense than FL resizing. in a semi auto you can also index, and some shooters prefer small base dies that take the case back to new dimensions. That helps it lie consistently in the bottom of the chamber. The case weighing and flash hole prep steps aid consistency in pressure and velocity while the rest tend to aide concentricity or at least consistent alignment of the bullet enters the barrel. In black powder cartridge rifle shooting you can get the ultimate in case consistency by using the same case and reloading it for each shot with a hand press. I've gotten standard deviations of only 5 fps doing that. |
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