I know some of you don't trim pistol brass, but I have some 9mm I sorted last night. One of my manuals calls for a trim to length of .750 and on .754. NONE of my Winchester Wally World brass is that long. If I trim to .740 I can use it all (200 cases). I've got an RCBS trimmer I would like to fool around with. This is no big deal for me- I have it set up and do a little work on it as I watch the evening news or old movie, so it's no chore. I would like to see if a uniform batch improves my groups any. Thanks for your input.
Trim length for 9mm
- Thread starter callgood
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Although I trim new revover cases the first time and some .357 brass more often I've never trimmed 9MM or .45ACP brass. Although others may disagree I've always found auto cases to run a hair short especially .45s. I think your overall length is more important. Since you're using a taper crimp it's not like crimping a revolver rd in a cannelure but I would still check the brass length just to be sure occasionally. Also it's hard to get the exact same overall length when using mixed 9MM brass so it's good to sort them. The Speer manual no. 13 calls for a trim to 0.744.
Yep, and either the Lee or Sierra (maybe both, I was checking all 3 of mine)calls for .750. Since all of the cases worked fine the first time around out of the box, I'm guessing the .01" or .014" difference between .740 and either .750 or .754 will not make a huge difference. It should give a uniform crimp if all are trimmed to the same length. This may or may not result in measurable improvement in performance. (I am using a Forster CoAx, which may tell you where I'm coming from).
I'm a new reloader and I tend to agonize over .001 or .0001. I have some new Starline cases in .45ACP and every dimension you can measure is slightly smaller than what the manual calls for. Since I've used 200 out of 500 with good results, I'm beginning to realize that you don't have to toss them if they don't perfectly match the manual. Of course I seat the bullets to the correct depth, etc.
I've yet to find a case that is longer than what the manual calls for. Trimming 200 cases with a manual trimmer may break me of this concern, but I would like to tinker with it even if I do retire it!
I'm a new reloader and I tend to agonize over .001 or .0001. I have some new Starline cases in .45ACP and every dimension you can measure is slightly smaller than what the manual calls for. Since I've used 200 out of 500 with good results, I'm beginning to realize that you don't have to toss them if they don't perfectly match the manual. Of course I seat the bullets to the correct depth, etc.
I've yet to find a case that is longer than what the manual calls for. Trimming 200 cases with a manual trimmer may break me of this concern, but I would like to tinker with it even if I do retire it!
All you are looking to do with the crimp is take the bell out of the case that you put in the case to seat the bullet. Trimming won't make this more consistent, since a short case will get less bell than a longer case. The short case with less bell will get ironed flat again just like the longer case in the crimp die. If you are crimping more than just taking the bell out you can lose the case tension and have bullet setback on the feedramp, this can lead to dangerous pressures.
fecmech
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What HS said. Also from an accuracy standpoint most 9's shoot 2-4" groups at 25 yds, so unless you have an accurized pistol the last place I'd be looking for accuracy would be case length.
This may all be academic. I set it up last night, and the Forester Classic case Trimmer is TOO LONG TO TRIM 9MM! You can vary the length of the 2 end pieces a bit by removing two screws and moving them out to a second screw hole. However, the carbide cutter still won't reach the 9mm case. On their web site they list a shorter base to use for 9mm. I didn't see this in the literature prior to buying it and it came with the collet for 9mm, don't remember if the pilot was included. A second hole on the frame at the collet end would have solved this problem for the Forster customer. Anyway, looks like I'll just go with the flow. My record is still perfect. I have yet to find pistol brass that needs to be trimmed back to the suggested length in my manuals.
Thanks for the input.
hsmith, re- "If you are crimping more than just taking the bell out you can lose the case tension and have bullet setback on the feedramp, this can lead to dangerous pressures." One step I use after crimping a few rounds is to measure them, make a note of the lengths, and load & eject them several times. I then re-measure them. This lets me know if I am crimping enough to keep them snug in the case. I don't get the benefit of actual recoil, but it gives me some idea.
Thanks for the input.
hsmith, re- "If you are crimping more than just taking the bell out you can lose the case tension and have bullet setback on the feedramp, this can lead to dangerous pressures." One step I use after crimping a few rounds is to measure them, make a note of the lengths, and load & eject them several times. I then re-measure them. This lets me know if I am crimping enough to keep them snug in the case. I don't get the benefit of actual recoil, but it gives me some idea.
Callgood, cycling the rounds several times each is a good idea. I take the firing pin out first and make darn sure I don't have any high primers first ......... I prefer to use a bathroom scale and press the bullet against it, if I can get 60 pounds or so of pressure on it without bullet movement I consider them good to go.
I'm not sure I was clear in my first post, so I'll restate that crimp has NO effect in making sure setback does not occur in a taper crimped round. Setback prevention is 110% done in the sizing die, and taper crimping can only LOWER case tension. Granted, it will only lower case tension if overdone, but it is possible. When taper crimping and you have setback in testing the first thing to do is back off the crimp and see what happens.
Taper 'crimping' is a misnomer, all you are doing is closing the case mouth on the bullet so it will not hang up on chambering.
I'm not sure I was clear in my first post, so I'll restate that crimp has NO effect in making sure setback does not occur in a taper crimped round. Setback prevention is 110% done in the sizing die, and taper crimping can only LOWER case tension. Granted, it will only lower case tension if overdone, but it is possible. When taper crimping and you have setback in testing the first thing to do is back off the crimp and see what happens.
Taper 'crimping' is a misnomer, all you are doing is closing the case mouth on the bullet so it will not hang up on chambering.
The Bushmaster
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Now I have to add a Bathroom scale to my loading room.... 
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