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Problems with locking bolt on reloaded ammo, Mossberg 4x4 .338 Win Mag

3K views 19 replies 7 participants last post by  slayer 
#1 ·
Hi, guys
First off, had this rifle for few years, shot multiple rounds of reloaded ammo through it,not a single problem.
I purchased a batch of Winchester Brass, trimmed to specs, reloaded with Varget 64 gr (max is 65)on Hornady 185 gr GMX, OAL 3.2900 in. On range, couldn't lock the bolt...just wouldn't close without considerable force. Finally closed it, shot a round (accurate, no problems),couldn't open it (had to use 2 hands and assistance). Bolt was NOT dry, no issues locking when I got home. I tried my other reloads ( I have bunch of Federal and even other Winchester brass), all heavier bullets though (225-250gr)- no issues at all. Suspecting it is the brass, I used caliper to measure other dimensions on it- but all came back within a margin. I could not even lock an unloaded brass.
I saw some other threads suggesting it may be an issue with the bolt or the brass. Any comments/recommendations are appreciated. Rifle is Mossberg 4x4 LTA in .338 win mag.
Thank you all in advance.
 
#2 ·
Interesting predicament. The only thing I can think of to check is the length from the bottom of the case to the end of the belt and compare it to cases that chamber. I would also measure the neck thickness of a loaded round and again, compare it to a round that chambers.
 
#3 ·
I don't own or shoot a .338 win mag so I am not sure if it head spaces on the shoulder or if it has a "ring" near the base. The very first thing I thought of was the shoulder being bulged out when seating the bullet, but when you said that it does the same thing with a piece of unloaded brass, that idea went out the window. I am at a loss.
 
#5 ·
Thank you, slayer!
I already did that, but I will go back and recheck again. I even had compared the old Winchester loaded brass I had that locks normally to the new ones that doesn't and measurements match. The only other thing I'm thinking is a groove depth(couldn't measure that) but otherwise, at loss just like gdmoody
 
#8 ·
Slayer, I tried Sharpie and it worked well!the problem was clearly the 'belt', sharpie was gone over it. The distance you asked was the same (0.22) but diameter was different (see pics 0.5285 vs 0.5305). Wow, must have been tired last night, didn't see it...wonder what did it and how can I fix it? Any good ideas? Spent 20 bucks, shame to waste it.
 
#11 ·
#12 ·
A problem that belted mags have is that after a couple of firings, they swell right in front of the belt. Most sizing dies don't reduce this sufficiently, there is a collet die that sizes this portion of the brass back to original factory specs, (no I don't recall the name of it right now). A friend of mine has had a few .338 mags and he said he never got more that 5-6 re-loadings from any of his brass.
 
#15 ·
The infamous belted mag bulge........absolute nonsense IMO. Here's why, that tiny bit of space that the die doesn't contact is part of the case web. It is quite thick. The sizing die contacts the only part of the case that should swell upon firing. If a case is swelling there, you have a major problem with pressure and chamber dimensions.

 
#14 ·
As far as I know, it was only once-fired brass. I went back and measured in front of the belt- it's less than .511 but close...I don't think collet die will get the belt itself. I agree with slayer, from what it appears on Sharpie, it was getting stuck on the belt.I wonder if I can somehow preform it with torch?
 
#17 ·
After seeing your responses to others suggestions, I would suggest checking the overall lengths of the ammo you're having a problem with and comparing it to the OAL of ammo that functions well. If there is no problem with OAL between the good and bad, fill a cartridge from the new brass and another from brass that works well (unfired or full length resized) brimful with salt. Weigh the two portions of salt and you might find a difference in case capacity. Some folks use water but tamped down salt is close to being as accurate and neater to work with.

If that doesn't find the problem, I would back off about 5 or 6 grains on your powder charge and see if the problem subsides. If so, you can work up 1 grain at a time until you have a working load. This sounds pretty basic but experienced hand loaders sometimes take the basics much too for granted.

Have you measured the thickness of the cartridge rim?
 
#18 ·
I had a problem recently, actually two simultaneously that we're keeping me from closing a bolt, and found that I was setting up my sizing die incorrectly on a .243 Win. (New gun and first experience with the cartridge). I reload for several different rifle calibers, never having a single issue. What I found to be my solution was to adjust the die down to the point that the shell holder was actually pressing against, and lifting up the sizing die. Problem one solved. My second issue was that while I was using load data for a given bullet, same type and weight, the manufacturer was different and I found so was the ogive. Once I figured out the correct seating depth problem number two vanished. Now she works like a champ. Not sure if any of this will help but good luck on solving your problem.
 
#19 ·
Ok, here is the case resolution:
Just like firpo post suggested, I took the reloads apart, lube 'em and size them down to as far as I can, then tested (empty) brass and it finally locked! Reloaded again to previous specs and no problem! How interesting, been doing this for 10 years and never had experienced that. Big thanks to twicepop, slayer and of course, firpo!
 
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