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Old 12-23-2010, 10:22   #1
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Who trims 10mm brass?

I just ordered 1000 shiny new Starline 10mm cases to make reloads for my Glock 20. Naturally, being brand new brass, their overall length will vary a bit - Starline says from 0.984-0.991 in.

I've never in my life trimmed pistol brass. That includes other cartridges I load, .40 S&W and .45 ACP. Trimming just never seemed necessary. Do you trim? If so, what does it do for you?
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Old 12-23-2010, 13:24   #2
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I don't trim, I load and shoot. No problems so far.

If you encounter unusual resistance while seating/crimping the bullet, stop.

Set that round aside, check OAL, pull bullet and check case length, if long discard case. You won't find many that are long.

Long cases will tend to wrinkle or bulge, very obvious when it occurs.
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Old 12-23-2010, 22:12   #3
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i don't trim pistol brass but i do full length resize my 10s because it's the only brand new brass i load.
when i was shooting 45 super i did the same, iirc.
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Old 12-23-2010, 23:58   #4
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Not planning to trim either, but I will run the new brass through my size die as I always do. It is the first die on my progressive press.

I use an Evolution Gun Works U-die. Now I'm wondering whether that will actually screw things up. It sizes a little tighter than your standard carbide size die - but only down to a small distance above the extractor groove. So it's been powerless to fix my Glocked brass, which is one reason I bought the new Starline 10mm brass. I guess I'll have to experiment with a few of the new brass.

Last edited by Objekt; 12-23-2010 at 23:59..
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Old 12-26-2010, 14:36   #5
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You may want to look into the Redding GR-X push through die. It will do the full case resize and get rid of the glock base bulge. I use this in a cheapo c-frame Lee press that was purchased just for this operation and it works great.

Last edited by RacerRon; 12-26-2010 at 14:36..
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Old 12-27-2010, 08:06   #6
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Having a high regard for precision, I trim. Brass for 10mm average .988" Cartridges used for the highest level of precision shots need sorted by length and by mass and trimmed to the same length to ensure concentricity of the rim - This cartridge headspaces on the rim, so case length must be right to ensure the C.O.A.L. positions the ogive of the bullet to meet the "sweet spot" distances from the lands.

I do believe this is one of most important methods to get low standard deviations of velocity, and therefore tighter groups vs. not trimming.
"What's the down side to 10mm again? Oh, that's right, there isn't one."" Carrier21

Last edited by Kegs; 12-27-2010 at 08:14..
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