Belted magnum brass won't fit in the gun

Ward Thurman

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Feb 18, 2019
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Hamilton, Montana
Hello all. I am Ward Thurman, long time reloader for my sons bountiful hunting (usually). We recently purchased a used M77 in 338 Win Mag. This is our first belted magnum. We also bought some used Remington brass and after I loaded them up, they would not allow the bolt to close. We bought some Federal factory loads too and they went through the gun perfectly. After much dinking around with the Remington brass, I shaved some of the top of the belt off and wal-la, they went into the chamber. So my question is, is the belt groove in the gun machined wrong or is the brass out of spec? We measured the base to top of shoulder an it was 0.215 while the Federal was about 0.210. The book lists that dimension as 0.220. I hate to throw away the brass, but are we doomed to finding the perfect brass to fit this rifle or is there a fix?

Tks so much!
 
Joined
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Messages
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Yakima WA
Hello all. I am Ward Thurman, long time reloader for my sons bountiful hunting (usually). We recently purchased a used M77 in 338 Win Mag. This is our first belted magnum. We also bought some used Remington brass and after I loaded them up, they would not allow the bolt to close. We bought some Federal factory loads too and they went through the gun perfectly. After much dinking around with the Remington brass, I shaved some of the top of the belt off and wal-la, they went into the chamber. So my question is, is the belt groove in the gun machined wrong or is the brass out of spec? We measured the base to top of shoulder an it was 0.215 while the Federal was about 0.210. The book lists that dimension as 0.220. I hate to throw away the brass, but are we doomed to finding the perfect brass to fit this rifle or is there a fix?

Tks so much!
My opinion is that the brass needs to be annealed,and full length sized.How often are you annealing the brass,How many times fired?Also just another opinion i only use Nosler or Norma brass for any of my magnums.
 
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Ward Thurman

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My opinion is that the brass needs to be annealed,and full length sized.How often are you annealing the brass,How many times fired?Also just another opinion i only use Nosler or Norma brass for any of my magnums.
I have no idea how many times the brass has been fired. We bought it used and won't go in the gun after full length sizing. So we have never fired this brass. How many loads are you getting through your magnums before they need annealing?
 
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Hello all. I am Ward Thurman, long time reloader for my sons bountiful hunting (usually). We recently purchased a used M77 in 338 Win Mag. This is our first belted magnum. We also bought some used Remington brass and after I loaded them up, they would not allow the bolt to close. We bought some Federal factory loads too and they went through the gun perfectly. After much dinking around with the Remington brass, I shaved some of the top of the belt off and wal-la, they went into the chamber. So my question is, is the belt groove in the gun machined wrong or is the brass out of spec? We measured the base to top of shoulder an it was 0.215 while the Federal was about 0.210. The book lists that dimension as 0.220. I hate to throw away the brass, but are we doomed to finding the perfect brass to fit this rifle or is there a fix?

Tks so much!
Not to be negative but this is why I got rid of my belted mags..
I've had many issues over the years with Remington and Winchester cases in both 7RM and 300 wm.
Those cases can develop a bulge above the belt that's hard to resize, there's a special die to solve that problem. Might be worth trying http://www.larrywillis.com
 

dok7mm

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It possibly has excessive expansion right above the belt, where FL die doesn't size. Start with new brass, being as you don't know how many times it has been fired. Different chamber sizes cause problems with belted cases. Consider a Willis collet die if you want to continue to use the old brass.
 

odoylerules

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Not to be negative but this is why I got rid of my belted mags..
I've had many issues over the years with Remington and Winchester cases in both 7RM and 300 wm.
Those cases can develop a bulge above the belt that's hard to resize, there's a special die to solve that problem. Might be worth trying http://www.larrywillis.com
This is dead on. I got one of Larry’s dies, works fantastic
 

lancetkenyon

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Arizona
Have you checked the headspace of the Rem vs Federal brass with a gauge? I know in most 7RM brass I have found, regardless of the brand, have a LOT of headspace difference between new and once fired. Usually, something like 2.104" for virgin to 2.123". Then, I bump the shoulder back to 2.121" when I FL size.

Check your brass to see if that is the case. I am wondering if the chamber the brass was originally shot in was just a touch longer than yours, and if you are bumping your shoulder back far enough. Also, if you have fired any of the new brass, what the difference is to your Rem brass.
 
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I have no idea how many times the brass has been fired. We bought it used and won't go in the gun after full length sizing. So we have never fired this brass. How many loads are you getting through your magnums before they need annealing?
I anneal mine every 3 firings.My opinion is if the brass is still good an annealing will make the brass like new.Brass will get springy after a couple firings and after sizing it will just come out of die and go back to where it was pre sizing or close to it.New brass after firing a couple times will most likely bring you right back to this point again.So its either learn the annealing process or be prepared to buy new brass after say 5 or 6 firings.
 

Azrael

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Saskatchewan
The problem is the used brass you bought. Thats not to say there's something wrong exactly with them; they probably go back into his chamber perfectly. ;) Treat every instance of used brass from different as a salvage operation. You can go decades without a problem, but sooner or later you'll get what you got.

Chambers vary in size, and dies vary in size. Not every case fired in every chamber can be resized with every die to fit in every other gun. If they made the dies small enough and short enough to guarantee it we'd all be screaming blue murder about short case life.

First thing to check is that your FL die is set to cam over hard. I don't care if your die setting has worked just fine every other time, because this isnt every other time. Perhaps you've already done this, it is the logical first step.

If that doesnt work, a low buck trick is to slip a few thou feeler guage between the case head and the shell-holder. Remember to take the decapping pin out first. Size a case like that and see if it chambers. If that works, its probably the only time you'll need to do it. Cases fired in a rifle tend to go back into the same rifle.

If that doesnt work, a small base die usually will. We used to call the .300 version a BAR die. Not so much because the Brownin gas gun needed more squeeze; it was more that those owners usually shot factory ammo and were a source of free or cheap brass. Their chambers tended to be huge, and SB die would get the cases into our guns. Usually once was enough; then you're back to the theme of cases fired in a rifle tend to go back into the same rifle. The .300 Win SB die is a handy thing to have around because with the guts taken out of it it can put a little extra squeeze on every Mag that is shorter and a smaller caliber. That's most of them. Thing is, new dies cost money and you have to have enough salvage brass to make it worth while.

The Willis tool is a handy tool, if the interference is right tight in front of the belt its about the only thing that will work. (A black Sharpie is handy for telling where the problem is) Its not that common until you do what doing. I got mine when I had a few hundred once fired Weatherby brass fired in a rifle I sold and wanted to use in one I'd kept. Paid for itself on the one job; but it cost money and you shoukd have enough brass to justify it. If you do end up with one; it works on all the H&H based cases.
 

CO_Guy

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Nov 16, 2018
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CO, USA
There's plenty of good, new 338 brass to get vs something unknown.
Nothing wrong at all with belted magnums. I cooked up a dandy 210gn Barnes TTSX load that my Tikka T3 in 338 just loves. 69.1gn IMR4350. cheers
 

J E Custom

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Jul 29, 2004
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Texas
The place to start is with a SAMMI belted head space gauge. It sounds like your chamber is not cut correctly because it should be around .220 from the case head to the front of the belt. Lately there has been a rash of factory ammo that is maximum length or more than the .220 and will not chamber.

It is hard to measure this dimension on the case it's self so by verifying it with a SAMMI head space gauge it will tell you if the chamber is cut to short or the ammo is to long. i recently had an issue with some Hornady custom ammo that was exactly .220 (Maximum SAMMI length) and the chamber was .218 so it wouldn't chamber. All other ammo brands fit/chambered fine. Most of the time, belted ammo has a dimension less than .220 so it will chamber in any SAMMI cut chamber.

This short dimension works well for those that re load because after the fire forming, it becomes a shouldered case if you only size enough to chamber.

J E CUSTOM
 

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