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7mmRM TMK Load Development

09 Nov 2020
@ 05:20 pm (GMT)

Luke Holdstock

Hey Team,
Looking for a few quick thoughts on load development as is new to me... I purchased the full set of books last year and subsequently a Christenson Arms Mesa in 7mm RM, topped with a Sightron SIII 6-24. Also picked up a lee handpress (trying to keep the reloading simple and strictly to this hunting rifle, for now anyway).

I was quite happy with initial run, though second set has left me wondering. The second day of shooting was a bit cool (4 deg C) with some wind so that likely contributed. I tightened down my Lee neck sizing die a little more the second round which perhaps had something to do with the increased pressures/velocity. Consistently hit pressure at 68.5 on the second round, which was sticky bolt extraction and light ejector marks (row of brass just below loaded cartridges) . Rifle COAL is 3.422 and Sierra TMK 160g's were loaded to 3.405. I think my next set may be 67.5g H4831SC and varying the freebore from 0.01 - 0.04...? My scale is electronic and I wondered a bit about it, though I am getting some solid ES with some loads so may just be paranoid.

If you have thoughts let's hear them - if not I'll keep working though various loads. Primary intent top accurate load for deer hunting. Pics have the details.[img][img] [/img][img] [/img][img]


09 Nov 2020
@ 05:21 pm (GMT)

Luke Holdstock

Re: 7mmRM TMK Load Development
09 Nov 2020
@ 05:24 pm (GMT)

Luke Holdstock

Re: 7mmRM TMK Load Development
Buggered up the pics the first round.

14 Nov 2020
@ 02:00 am (GMT)

Paul Leverman

Re: 7mmRM TMK Load Development
You will have to check, but I believe that tightening down the neck die (assuming it is the collet style) will not alter bullet grip. It seems to me that I read somewhere that the collets/mandrels were designed to provide a .001" press fit. If you are looking for more bullet grip, you need to look at the Factory Crimp die. There is also a section in the Book about why there was a difference "with the increased pressures/velocity." in your second round. Also, have a look again at the section on barrel fouling and the presence of copper vs. accuracy.

Just my thoughts, and opinions


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