When the working of the brass from loading exceeds that of firing, they shrink.
When the working of the brass from loading exceeds that of firing, they shrink.
I can agree with that, noylj, CJB. I guess the minimal amount that I've trimmed was because the mixed cases were of different lengths, and I wanted the crimps all in the same place in each groove. I assumed it was stretch, most likely it was manufacturing because I haven't had to trim for awhile. Thanks.
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As was said, you'll get mouth splits before you get overly long 45acp.
On the 9mm, its different, as the taper makes it such that you're working brass back toward the head at every loading. Soon you'll have swollen case heads that wont chamber unless you use a modified die and shell holder.
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It's because I want all of my straight-wall revolver cases to roll crimp into my cast bullet's crimp groove that I do occasionally check for case length and trim when necessary. I have found that with enough firings that brass cases in .38/.357, .44, and .45 Colt will stretch. YMMV
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There is a lot of good advice in this thread. In my limited experience 45ACP brass never needs trimming. I learned this after buying a Lee trimmer for 45ACP. Waste of money.
Other advice on case prep, etc, was also spot on. I do sort my brass and load full boxes of one head stamp. Like WCC71, etc. OK, I've had that WCC71 since around 1981, and the primer pockets are pretty loose, but the cases still work just fine and do not need trimmed.
Comparing accuracy between my sorted brass and a box of mixed brass - there really is no difference. I've never shot anywhere near a 290 NMC, but I have shot a few in the 280s over the years with my Clark long heavy. I saw an improvement in scores when I switched from Bullseye to W-231. Then I saw an improvement in scores when I switched form W-231 to Bullseye. The point is that when I'm interested in seeing if a load change has made a difference I pay attention more, and scores go up. Complacency is bad when you are shooting for score.
What makes the most difference in accuracy is the bullet. A good square base is the most important thing in my opinion, allowing the bullet to exit the barrel with no tipping or tumbling. Likewise the case mouth has to be square so the bullet exits straight into the rifling. I've read that primer consistency is next most important. I can't confirm this. Powder charge consistency is important too, but I've printed some pretty tight groups with the chronograph showing a wide spread between low to high velocities.
I hope something in there helps.
In an autoloading pistol, setting aside the ability of the shooter, the most important point of accuracy is the fitting of, and the consistent placement of the various parts as the pistol cycles when fired and returns to battery. Next is the consistency of the ammunition not only in velocity, but in the way it interacts with the moving parts during the cycling of the action while firing. A well fit 1911 - and I mean very well fit - will turn in groups from a Ransom rest under 3 moa, and that is about the limit of the platform. It will do that with light loads that basically "just cycle" the action that is fit very very close. And that is bullseye shooting.
For practical shooting... you're not shooting 3moa handheld with loads that will cycle a basically unaltered and rather loose fit pistol (by bullseye standards). There ARE shooters who can shoot close to 3moa at 50 yards with the right 1911 (with a rib on it, and everything fit "just so"). Those guys are very few, very far between.
Accuracy is something to chase, and a fun chase too. Then again, like PeeWee Herman
you gotta know that some things are not really Tour de France material.
What was said about bullet bases, very very true for bench rest rifle, ditto case mouths. And that's just the beginning. They do pullet seating force gauges, look at every little nick and burr on the case, fill cases to measure their inside volume, flash hole gauge and recut with special bevels, primer pocket gauges and seating effort gauges for primers.... you name it, and it does matter. But, so does a good rifle and a good shooter.
I agree with most of what Mr. CJB said. As a bullet caster I know that a bad bullet base will destroy the accuracy of any firearm. Same with an out of square crown on the barrel. Or a bad barrel. Most factory guns are more accurate than the shooter by a large margin, except for the 9mm Luger, in my limited experience.