Please refresh my memory as to why handgun bulletts of same constuction and profile may be sized differently.An example are the Xtreme bulletts on sale.The lighter weight 9mm are all .355,the heavier ones can be .356 and .357. I know lead is usually(not always) sized .001 over jacketed to seal gas blowby.I have not slug measured any of my barrel diameters. There has to be some pressure/accuracy issues here. I don't believe rifle bullet diameters vary of same construction.Thanks
sizing of bullett variations
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Blue68f100
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All depends on the mfg control of the process. Some vary more than others. My 229-9mm actually has a 357" dia bore. It shoots the jacketed ok at .355. I normally shoot the Berry's since they run slightly larger. There are a lot of calibers in the .356" range which explains for a lot of different weights and profiles.
First of all, jacketed bullets should be the same diameter as the actual, and not the assumed, groove diameter of the barrel. Lead bullets need to be AT LEAST 0.001" over groove diameter.
Next, 0.001-0.002" is not that big a deal and often can improve accuracy a lot--particularly, in my experience, for 9x19. You start with the starting load and work up.
Finally, I found that the size the bullet is listed at is not always the size that the bullets actually are. Plated bullets often are 0.0005-0.001" smaller. Jacketed bullets are often -0.0005/+0.0005". For almost all purposes, it doesn't matter until you get a machine rest and careful load workup.
Per SAAMI, a 9x19 bullet should be 0.3555 +0.000/-0.003" and the barrel's groove diameter should be 0.355 +0.004/-0.000". As reloaders, we can use bullets that match the groove diameter and improve accuracy.
Even rifle shooters should KNOW the actual groove diameter of their barrel.
Next, 0.001-0.002" is not that big a deal and often can improve accuracy a lot--particularly, in my experience, for 9x19. You start with the starting load and work up.
Finally, I found that the size the bullet is listed at is not always the size that the bullets actually are. Plated bullets often are 0.0005-0.001" smaller. Jacketed bullets are often -0.0005/+0.0005". For almost all purposes, it doesn't matter until you get a machine rest and careful load workup.
Per SAAMI, a 9x19 bullet should be 0.3555 +0.000/-0.003" and the barrel's groove diameter should be 0.355 +0.004/-0.000". As reloaders, we can use bullets that match the groove diameter and improve accuracy.
Even rifle shooters should KNOW the actual groove diameter of their barrel.
Buy the X-Treme bullets with confidence, if that is the question.
A plated or jacketed bullet can get away with being slightly undersized, while a lead bullet most of the time cannot. That is simply a leading issue. Whether it affects accuracy is something different.
That is interesting as the the sizing difference in the X-Treme 9MM bullets. I would like to know the reasoning behind it. I guess we could call them and ask. The .40s are all .400. The 45s are either .451 or .452. The 200 Gr SWC is .451 while the 200 Gr RN and HP are .452. 225 and 230 are .452, but 255, which I assume is for the .45 Colt, is .451. That's what I shoot it in anyway. Hmm.
A plated or jacketed bullet can get away with being slightly undersized, while a lead bullet most of the time cannot. That is simply a leading issue. Whether it affects accuracy is something different.
That is interesting as the the sizing difference in the X-Treme 9MM bullets. I would like to know the reasoning behind it. I guess we could call them and ask. The .40s are all .400. The 45s are either .451 or .452. The 200 Gr SWC is .451 while the 200 Gr RN and HP are .452. 225 and 230 are .452, but 255, which I assume is for the .45 Colt, is .451. That's what I shoot it in anyway. Hmm.
FROGO207
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The lighter weight ones are also (really) for use in the 380 so are sized to accommodate that caliber also IIRC.
LiveLife
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I think unlike FMJ with exposed soft lead base that expands readily to seal high pressure gas, plated bullets with harder lead alloy core experience more gas leakage which effects maintaining consistency of chamber pressures which in turn effect accuracy.
IIRC, Jay Phillips from Berry's MFG mentioned a few years back that for the lead alloy core they were using at the time, in-house accuracy testing improved with slightly larger sizing of their bullets. On their website, they are still advertising 9mm bullets to be sized at .356" but the latest batches of bullets I have received from them recently have been sized more around .355".
The reason why X-Treme offers different sized 9mm bullets for some of their heavier bullets may be due to the same reason. For the hardness of lead alloy core they are using, the heavier bullets benefit from larger sizing to better seal the high pressure gas to improve accuracy.
Berry's MFG addressed this issue by offering hollow based plated bullets that allow expansion of bullet base to seal with the barrel to produce more consistent chamber pressures and accuracy.
IIRC, Jay Phillips from Berry's MFG mentioned a few years back that for the lead alloy core they were using at the time, in-house accuracy testing improved with slightly larger sizing of their bullets. On their website, they are still advertising 9mm bullets to be sized at .356" but the latest batches of bullets I have received from them recently have been sized more around .355".
The reason why X-Treme offers different sized 9mm bullets for some of their heavier bullets may be due to the same reason. For the hardness of lead alloy core they are using, the heavier bullets benefit from larger sizing to better seal the high pressure gas to improve accuracy.
Berry's MFG addressed this issue by offering hollow based plated bullets that allow expansion of bullet base to seal with the barrel to produce more consistent chamber pressures and accuracy.
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