K31: Did I do something wrong?

[7.62x51NATO]

Hey guys, I just took out my K31 for the first time yesterday with reloads and was running two loads: Both of which used the 175 SMK over 45.0 gr of H4350 and one with 46.5 of H4350. Bother were loaded to 2.900". The load with 45.0 of H4350 produced excellent groupings of about .75" for 5 shots. I was VERY impressed with the accuracy I got out of this load surpassing even GP11 in accuracy. However, the problem was that every single round was very difficult to fully chamber. The bolt would go forward and partly chamber a round, but it would not go fully into battery. It would require a few hard taps from my palm to fully close the bolt. I'm not sure if this has anything to do with improper cartridge sizing or whether I just didn't oil and lube the bolt well enough. If anyone can possibly give any insight despite my vague details it would be greatly appreciated. Thanks.

 

[desidog]

To clarify, Your first time shooting the rifle, or the first time shooting reloads in the rifle? (it sounds like you shot GP11 in it already)?

Where did the casings come from? Did you fire GP11 and reuse? Did you resize? Or were they new/unfired?

It could just be a little bit of junk in your chamber. Have you tried a chamber brush?

 

[mookiie]

I would say you may have to give your sizing dye a half turn or full turn down, than see about clambering the shells. I would guess that you did not push the shoulders back far enough. I could be missing something though.

 

[Mauser lover]

Sounds like a dirty chamber, or unsized brass... Are you only neck sizing?

 

[rcmodel]

It almost has to be one of three things.
1. Sizing die is not adjusted far enough down to resize the shoulder back where it came from.
(Try chambering a sized case before you load it.)

2. Bullet is seated too long and hitting the rifling leade.

3. You are crimping when seating the bullet, either on purpose or accidentally, and buckling the shoulder.
(Seating die is also a crimping die and will crimp too much if adjusted too far down.)

Use a Magic Marker to "color" one of your reloads, then try to chamber it kicking & screaming.
Then eject it carefully.

Wherever the black marker rubs off the round is your problem.

rc

 

[7.62x51NATO]

I used once-fired brass from Prvi that I had shot previously from the rifle. As far as if it was my first time shooting the gun, I have shot about 20 rounds of GP11 and 40 of Prvi through the gun. Yesterday I only shot about 9 reloads through it before stopping from the bolt problem. However I did only neck size. If I have extra of the Prvi ammo laying around that I didn't reload yet and still have it unfired I'll measure the brass to my reloads and compare them from there with my calipers and see if there is a difference. Chamber is clean as well. Will edit in a second when I figure out brass lengths. Thanks for the info so far guys! Very helpful.

Upon checking brass lengths my once fired brass and reloads were slightly longer than the unfired brass. Seems like that would have to be the problem.

 

[Sam1911]

However I did only neck size.

Bingo!

The K-31 doesn't give you the benefit of a nice long lever (bolt handle) to cam that round into the chamber. Gonna need to size a little more.

 

[tulsamal]

I would recommend adjusting the die with the rifle handy. You will have to keep sizing the brass a little bit more and more until the brass will easily chamber. I've got two K-31's myself and it's true that they don't have a lot of extra force to push the brass in that last few thousandths of an inch.

Once you have the sizing of the brass figured out.. one more issue will have to be addressed. And it drove me wild. The OAL length can be tricky and it can vary a lot depending on the shape of the bullet. I've been reloading since 1982 and I've never seen any other cartridge/rifle combination that took so much effort to figure out the sweet spot. If you change bullets, you have to work it out again. My beech stock 1930's model really likes the bullet seated way out there. It's worth the effort, these rifles will really shoot if you get the bullets just right and make sure their stock screws are tightened right. Really wonderful rifles.

Gregg

 

[tulsamal]

Upon checking brass lengths my once fired brass and reloads were slightly longer than the unfired brass. Seems like that would have to be the problem.

That _could_ be an issue if the brass length is over spec. Compare the length right now to what the manual says is the length when you are supposed to trim them. If it is longer than that... sure, you could be jamming them into the front of the chamber.

Really, the fix is the same though. Figure these things out at the loading bench with the rifle and empty brass. Size up some empty brass and play around until you figure out what it takes to get it to chamber easily. If it needs to be trimmed, then get to trimming. Or size it some more. Once you have it chambering easily as empties, then you are ready to load up some more for the range.

Gregg

 

[forshoes]

The K31's have a short throat so OAL is important.

Save your GP-11 cases, they are not easily reloaded as they are Berdan primes. Resize without the deprime pin and create a dummy round with the bullet you want to use. Adjust your seating die until the bolt will easily close on the round and you will be good to go at that length.

I had to learn this the hard way.