Finally found a good way to make 7mm rem mag out of 300 win mag brass...

MPFD

MPFD

Well-known member
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Start by sizing 300 win mag brass in a 300 full length die.
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Then trim to 30-06 length and debur the case mouth. I used a Lee trimmer.
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When finished it should be trimmed almost down to the shoulder.
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Then full length size in a 7mm Rem Mag Die. I used RCBS, go in slowly till you feel it reach the top of the die and slowly but firmly make one stroke till it bottems out.
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Last I like to turn the case 180 degrees andsize it again to make sure it is shaped evenly. Finally you have a nice piece of 7mm rem mag brass.
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I have 1000 pieces of 300 win mag brass and I sold the gun to a guy that didn't want any reloading stuff. I have been messing with this process for 3 months on and off and I think I finally got it figured out.
 
Good Job. You may want to check the neck thickness of your brass to make sure its not too tight though.
 
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They are .2810" ID, measures the same as the full length sized piece of 7mm Rem Mag brass. They come right out about five thousandths shorter then the trim to length of of the 7mm rem mag. I think I hit it right on the head this time. The shoulders even look good, no stress marks or even any waves in almost all of the resized pieces. The outside diameter is .3120 with a bullet seated, the OD of a unsized fired case from my rifle is .3140, there is a small amount of taper from the base of the neck to the top but it is very minor and I think it will form out after the first firing and resize. The brand new brass from Winchester that I full length sized and seated a bullet in is between .3080" and .3100" OD. Any input is apprecatied as this is my first attempt at case modification.
 
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I hunt with a bunch of guys who shoot 7mm Rem Mags and they leave their spent brass at the clubhouse for me. I would like to turn their brass into .338 Win Mag cases as I don't shoot the 7mm Rem mag. Anyone done this? I would suppose you would want to size it up in steps like .284 then .308 then .338 but I'm just guessing.
 
...should I FL size it or just neck size it before I put it in the mail? By the way...nice piece of equipment, my Massey only pulls with the back wheels.
 
IF your looking to get rid of it shoot me a pm of what you want for it and I will size it. If you can find a way to make my 300 win mag brass I will trade you pieces even up. Might be easier IDK.

It's only my tractor for this 6 month's then I will get the AGCO DTb for the second half of the year. I do dealer tech training for Massey Ferguson, Agco "Allis", and Challenger tractors. On my old mans farm we've got a 666 international gasser, 600 series Case, and an old Hesston baler. I've found a great deal on an 3510 Massey with low hours but I can't get him off the fence about it. Nothing to spectacular....
 
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Later in the season I will get my hands on some 7mm brass and I'll shoot you a PM. I shoot 7mm, but in 7mm-08. Traded my .300 Win Mag but kept my .338 Win Mag, a real thumper.

As far as tractors go, mine is an older 135 that I use around the deer camp for bush hogging and food plots, and although low on the HP end, it's a fine machine.
 
Well I'm gonna try these first few pieces I've made and if there are any problems I will probably do as you said and sell the rest, and get new. I was just trying to make something out of what I already had.
 


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