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7mm-300 Win Mag

I would skip the Norma brass and run either ADG or Peterson if you can find it. Have 5-6 loadings on ADG 300wm brass running 215 Bergers at RUM velocities with no issues yet.

You need to clarify because there are guys running over 3100 with a RUM and 215s. I can run my 30 Nosler up to 3100 with no pressure with 215s and H1000. You are NOT running a 300 WM that fast. I have had three 300WM tubes and even with long barrels and slow powder can't get there.
 
You need to clarify because there are guys running over 3100 with a RUM and 215s. I can run my 30 Nosler up to 3100 with no pressure with 215s and H1000. You are NOT running a 300 WM that fast. I have had three 300WM tubes and even with long barrels and slow powder can't get there.

I lol’d. Not sure there’s a need let alone much to clarify. A long throat 300wm, hard brass, and 28” gain twist 5r barrel 3100 is obtainable. Es actually got better as we got closer to 3100 but accuracy went down.
 
But for what little extra speed I’d see the added case prep isn’t worth it to me. I thought the mashburns parent case was the 300 H&H? Shortened, necked down and blown out. Plus I can neck down the 300 win mag brass in my 7 rem mag die backed out. Resize with a type s 300 win mag and proper bushing. Swap out the 300 win mag seating stem from the die and replace with my 7mm seating stem. Load and go shoot. No fire forming shoulders or anything
If you read the schematic I posted you will see it falls in the Parameters of 300WM brass, same shoulder width and all, nothing exotic. If you're stating you have to fire-form from 20 degree to a 30 degree shoulder yet don't have to fire-form going from 30 caliber down to .284? I'd say you don't have to fire-form either. Brass will stretch less with 30*, it's not about speed, it holds less powder actually. Nothing at all wrong with the 7-300WM as is. Can't wait to hear how it does.
 
Hello all,just incase anyone was wondering. FURMAN 's reamer print works great for the 190 grain berger with vihtavuori n565 also. I'm using a 28 inch brux 1-9 twist barrel getting 3050 fps under 1/4 minute accuracy
 
The 7 Mashburn is what the 7 Rem Mag should have been, long neck, 30* shoulder angle. 160's at 3200, 180's a tad over 3000, no pressure on Win brass. 3350 is max on the 168's, accuracy node not included. R#26 not in the picture.

30* stops brass flow into the neck, or at least retards it.

Just bump back the shoulder on the 300 WM case and fire form, or hunt while you are fire forming if you do not like the cream of wheat and Bullseye method.

7 Practical, 300 WM necked down, Manson has the dies and reamer.

All this stuff of necking down leads to neck turning if you are OCD Picky as heck! Doughnuts form when necking down, and you may elect to have your gunsmith use a unithroater to keep the bullet out of the shoulder neck junction, OR monitor for doughnuts and cut them out as they form with a K&M Mandrel cutter.

Magazine length is an issue, so consider going Wyatts extended magazine box, or even better, "One Shot, One Kill" mentality. Many long range hunters do themselves a favor and never even think of Mag box length opting for a single shot maxing out the barrel's accuracy potential getting close to the lands.
 
I have, but for me it came down to already having everything for the 7-300 win mag anyway. I just use some 7 remington magnum rcbs full length dies to size cases and seat bullets. I use my 300 win mag sizing die with decapping and expanding mandrel removed to size the body. I'm getting great consistency in accuracy and velocity out at 1200 yards on an IPSC target. I've been coyote hunting alot lately so I haven't been able to take it farther.
 
I have had Three 7 STW's, no down side other than brass. The older Winchester brass is tough as nails. I heard that Peterson or other was making 7 STW brass.
 
I did the 7mm Practical. Used RWS brass at first. Big mistake. Necks to thick and case capacity lower. Switched to Winchester brass. Happy with it now
 
But for what little extra speed I’d see the added case prep isn’t worth it to me. I thought the mashburns parent case was the 300 H&H? Shortened, necked down and blown out. Plus I can neck down the 300 win mag brass in my 7 rem mag die backed out. Resize with a type s 300 win mag and proper bushing. Swap out the 300 win mag seating stem from the die and replace with my 7mm seating stem. Load and go shoot. No fire forming shoulders or anything
Today I tried necking down 300 win mag to 7mm the shoulder crimped, I'm going to annealing first then try again!
 

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