Belted mag brass after 2-3 firings sizing issues?

zr600

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How many people have had issues with sizing or chambering, pressure after 2-4 firing on belted mag brass? I’m running a 7mag adg brass, retumbo, 180 bergers at 2950ish. I’m not going to post the actual load. I have seen many people running these speeds or more with same setup. I know I’m running on the top end but don’t believe I’m over pressure, I developed the load in the summer never had an issue then during hunting season when it like 30-40 degrees cooler was showing more pressure. I have been measuring just above the web and not getting it sized. So do you guys use, or think the larrywillis collet does will be a problem solver? Any advice would be great.
 

Laelkhunter

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Larry Willis collet die is what worked wonders for me. I had my .340 Wby rebarreled, and even after full length resizing of the fired brass, they would not chamber in the new Lilja barrel. I bought the Larry Willis collet die, and it worked like magic. ALL of my fired brass fits the new barrel after resizing. I had a ton of fired brass from the old barrel that was useless, but now I can use them. The Larry Willis die might cost a little up front, but the savings you experience when you can reuse all of your brass will quickly offset the price you pay for the die.
 

19 Badger

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I have the Larry Willis collet die and tried it out when I first got it cause I was curious. It does work and does exactly as claimed. I have loaded my 270 wby mag for 25 years now and have never needed to use it once. If you want to try it out I can send it you to see if you actually need it before you make the purchase. Sounds like the load may be a little warm. PM me if interested in borrowing it.
 

DJ Fergus

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What powder are you running. There are a few powders that people have found to build more pressure when it got cold.
 

zr600

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I have measured brass and it seems to be more a sizing problem. Brand new brass shoots the load fine with no issues, 1 fired brass, twice fired I haven’t check again but I think it did work, but anymore then that it starts changing.
 

DJ Fergus

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I use retumbo also in a 7mm mag. I haven't noticed increased pressure in cold weather. I believe it was 8831that showed an increase in pressure when colder. I run nosler brass because I got alot of it for a deal but the primer pocket wont hold for more than 3 firings so I cant give you any useful info about sizing. I have always heard the Larry Willis die works but I haven't had to cross that bridge yet.
 

cape cove

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Own and used the Willis die. It works but you may be able to do the same job if you have a longer mag die on hand, like the 300 win or 7mm STW, 300 Weath etc. If yes then run your case into the die until the shell holder bottoms out on the die. This has worked for me in the past also. It should size the portion of your case just north of the belt yet not touch your case shoulder so, as to maintain your .002-.003 shoulder bump giving good case life. If it works it will cost much less than a Willis die JME
 

Olevern

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Jan 28, 2013
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plus one on the Innovative Technologies collet die; costs about a hundred bucks but well worth it in saving brass that has a lot of life left in it but the standard full length sizing die couldn't resize the brass just forward of the belt.
 

dok7mm

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Own and used the Willis die. It works but you may be able to do the same job if you have a longer mag die on hand, like the 300 win or 7mm STW, 300 Weath etc. If yes then run your case into the die until the shell holder bottoms out on the die. This has worked for me in the past also. It should size the portion of your case just north of the belt yet not touch your case shoulder so, as to maintain your .002-.003 shoulder bump giving good case life. If it works it will cost much less than a Willis die JME
Tried that many years ago with zero luck. The dies have a bevel on the base that keeps it from being able to adequately size the area above the belt. If the die is machined on the base to reduce that tiny area, it increases shoulder bump, so that won't work.

The Willis die is the only way to solve the problem. I've had one on my bench for ten years and it's saved more money than it cost.
 

AZHTR

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I sent zr600 a PM explaining I also have the same 7 Mag brass issue. I also stated the Larry Wilson Collet Die did not fix my belt issue ( measures .521 just above the belt). The LW die could not compress the brass at the belt. I ordered a used set of 7 Mag dies and was going to machine the belt end to compensate for the “bulge”

BUT I just went and tried Cape Cove suggestion using a 300 Win Mag die I have and it worked flawlessly.

Thanks Cape Cove!!
 

cape cove

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Glad it worked for you. Learned this after I purchased my Willis die. If you would need more sizing you could sand off appx .010 off a shell holder and use it just for this purpose. This doesn't always work. It depends on the die and your chamber specs.. The nice thing is when you run a 7mm Mag case up an STW or 300 Win/Weatherby die you never have to worry about the shoulder being pushed back. JME
 

AZHTR

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I still might modify the used due I have coming to “bump the shoulder”. Just adds another step on the process! Thanks for the info👍🏻
 

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