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Originally Posted by MichiganScott
Normally I don't disagree with WR Moore because of his experience, but I have to disagree with his insistence on crimping bullets. I come from a high power competition background. You will be hard pressed to find a competitor that crimps. They get around that by using full cases of powder, like 55gr of H4895 behind a 55gr bullet, and by reducing the expanding ball a thousand or two from stock. Admittedly, the rifle length gas system is much more gentle than the carbine, but many of the competitors also have carbines for other purposes. They don't usually crimp that ammo either.
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Some years back the bench rest crowd discovered that crimping bullets resulted in a more uniform neck tension (even with all the stuff they do to cases) and powder burn leading to increased accuracy. You'll note that bench rest bullets notoriously lack crimping cannelures. If those nit-picking folks find no issues with crimping, I see no reason why the rest of us should shy away from it.
Back in 1999 I bought a .222 bolt gun and after fitting a .223 match barrel decided to pull the bullets of the remaining famous factory .222 ammo to use in the .223. I was shocked to discover that the non-cannelured bullets were crimped so deeply, you could see a wasp waist in the bullets with your bare eye. They still shot one ragged hole regardless of what rifle I shot them out of.
So far as I can tell, the LC M118LR ammo I have is crimped. I see no reason to avoid the practice despite what certain competitors may do.
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As far as the charge of powder that the OP is using being max, we need to remember that the printed data is mostly for .223. A similar charge fired in the NATO or .223 Wylde chambers will have lower pressure. I firmly believe in following book data and not exceeding it and don't recommend anyone else doing so either.
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True to a point, and also with reference to a later post about currently listed charge weights......the published data is what produced maximum pressures in the test firearms/test barrels & universal receivers and were valid IN THE TESTED EQUIPMENT. If you check several load data sources you may find differing maximums. I had a lengthy discussion about this several years back with a Sierra tech and someone from Alliant*. To simplify the response: "If you don't see the velocity, you're not seeing the pressure". One can relatively accurately gauge pressure using new cases and an accurate micrometer to measure case webbing before and after firing. The range of charges I noted are not over maximum (or even real close with IMR 4198) in my equipment-or in 4 different published data sources I have. You'll also note my use of the term "around", meaning approximately or on the order of the weights noted.
All that said, riding the maximum pressure limits isn't wise, it leaves little room for variables and/or
error. If you exceed published data, you own all responsibility for the results.
*What prompted the call was a significant change in maximum load data between issues of the Sierra data manual. A safe charge I'd been using for several years without pressure indicators was suddenly beyond maximum. Sierra noted they changed test rifles and Alliant noted no changes in powder.
FWIW I've found that Alliant data will duplicate factory loads in caliber, but you will almost never get the velocities Alliant does.