Power trimming on a progressive press

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admin's picture
Joined: 07/07/2010

Dominant paradigm on some forums is there is absolutely no reason to trim pistol brass, but I've never been one to buy into that opinion.
Unfortunately, most trimmers for pistol brass gauge on the top of the rim, and crimp dies gauge on the bottom of the rim, causing inconsistent OAL and crimp roll.  Also slow, one at a time operation. I typically run several hundred rounds of whatever I am currently loading, so one at a time is not my way. 
Another roadblock for fast, accurate trimming is Dillon does not support pistol caliber trimming on their press. 

Need a few parts. One challenge is the Dillon RT1200 has internal thread of 13/16X20, not the typical 7/8X16 die thread. 
First attempt was to turn the threads on the end of a sizing die, but the resulting wall thickness at the waist of the die was inadequate. 
Also, there would have been no extraction route for the trimmed material. 


First setup, only to find out the cutter orbit was barely over 44 brass dia, so the radius on the corner of the cutter insert made a mess out of the case mouth.

Made an oversized cutter insert out of a HSS parting tool. 

Setting up height to finalize locking ring thickness. 
One of the challenges is there is not enough room for the trimmer locking ring and the die locking ring, so locking ring locks both and thickness sets trim depth. 

Final iteration. Ran 450 cases this morning, very acceptable results, +/- .001 or so. 

admin's picture
Joined: 07/07/2010

800 cases trimmed, random sampling 1.2705 to 1.2730 so +/- a fat thou. Reason I'm a little under the books trim to length is a large quantity of the brass I have accumulated is in the low 1.270's after sizing, some even shorter. If I don't hear a "Zing" when the ram hits home I pull that one and toss aside, when I get around to it I'll probably spin up a thinner lock ring and trim the culls to 44 special length. 

Joined: 08/07/2010
Are you talking one brand of

Are you talking one brand of brass needing trimming or mixed brass?


admin's picture
Joined: 07/07/2010
More then 1

many years/ 2000 rounds or so of collected 44 mag brass, every headstamp known to man, unknown times reloaded, 1.2600" to 1.2900" in length before trimming.
I use to sort by length, then by brand, keep groups together and adjust crimp accordingly. Trimming eliminates the sorting by length and resetting the crimp die, and I believe results in more consistent crimp and neck tension. At the range the chrono doesn't show as much of a difference between mixed brands or sorted, or variations in length, as it does with a uniform crimp. (IMAO)
Current set up:
Dillon 650 press
Dillon sizing Die
RCBS seating Die
Lee factory Crimp Die
Latest loadings:
Hornady 265 jacketed FP's over H110
Nosler Partition 240 jacketed HP's over H110
Keith Style 240 lead over H110 (or Tightgroup) 
Old Chrony Master Beta
New LabRadar
Bad eyes 
Shaky hands

admin's picture
Joined: 07/07/2010
range report

Got good consistency,but something, maybe not unexpected, velocities were up 50 fps on my reduced recoil loads. Previously subsonic 1040 +/- fps clocked 1090 or so. The full blow loads not so much difference but was up 20+ fps on the 240 HP's and on the 265 FP's. And it was cold out. The slightly shorter length may have had a little to do with it, but I typically use the shorter case batches for the subsonics, so I wasn't expecting that big a jump. I think the real difference was removing the material that had been worked several times from crimping and firing allowing a more robust crimp, reducing jump and increasing pressure. The reduced recoil loads I shortened up to 44 special length really jumped in velocity, as to be expected, reduced powder 1 gr to get back down to subsonic.