AXMC hard bolt opening?

[racerbart]

Hello all. First I want to say this is a great forum with amazing wealth of knowledge from the members. I've been lurking around, learning and enjoying this forum for a while but this is my first post.

I have a new AI AXMC in 338 LM that I have had (painfully) in my possession for over a month but finally had a chance to get to the range today and try out.

I basically did a barrel brake in and overall it performed well. Groups were good but not consistently sub- MOA, maybe me, varied ammo or the frequent barrel cleanings? Fired about 30 rounds total. Followed the break in instructions in the manual and I fed it 5 different types of factory ammo only. I plan to eventually reload for 338 so I spent some extra time and chrono'd all of them.

All the ammo ran well except for difficulty opening the bolt when using Sellier & Bellot 250 gr HPBT Match. The bolt lift was normal. The problem was at the top of the bolt opening. I could not open it with moderate pressure. If I jiggled and partially closed and then reopened the bolt it would then function normally and easily extract the casing. All the other ammo worked fine before and even after I used the S&B. (Other ammo included Berger, Hornady and PPU).

I don't see anything unusual on the casing. or the bolt head so I don't know how to explain this. Soft or poorly sized brass? Primers a little flat but no other signs of pressure. I am able to rechamber the spent cases with no problems.

I am looking for opinions or if anyone else has experience this before. I suspect it's something with the ammo but want to be sure I don't need to check anything on the rifle.

Thanks in advance for any assistance.

 

[Supersubes]

If it just did it with one ammo type, and a lower quality one at that, you’re right to blame the ammo.

 

[Huskydriver]

Sb is on the hot end when I chronograghed some for a buddy

 

[racerbart]

If it just did it with one ammo type, and a lower quality one at that, you’re right to blame the ammo.

Thanks Supersubes for your feedback. Fortunately, I only bought 20 rounds of this stuff. It's still not quite 9mm but I can live with trashing the other 15 rounds.

 

[racerbart]

Sb is on the hot end when I chronograghed some for a buddy

Sb is on the hot end when I chronograghed some for a buddy

Thanks for your input. That's what I was thinking as well but beside some flattening of the primers I see nothing much else. I had a chrono running and with 27" barrel saw an average MV of 2872. Factory spec with shorter (60 cm) barrel is 2848.

Made some measurements with a Hornady headspace comparator on unfired cartridges . FWIW, I did find the SB has the shortest headspace of all 4 manufacturers by about .002 at 2.319. (The fired brass is 2.328). Not sure that is enough to make a difference. but interesting.

 

[sharpshot50]

I would hold on to the others for now since you plan to handload the cartridge.

When I first shot my AXMC, I used factory Lapua ammunition and it operated perfectly. I then tried other various brands while I was building a collection of brass but I discovered S&B would chamber easily but it had the exact same issue you're mentioning. Bolt lift wasn't bad, but I had to use a dowel rod to tap the bolt back.

After lots and lots of trial and error and re-sizing with multiple sets of dies, I discovered that some brass wasn't quite sized right. Once I figured out the problem, I pulled all the questionable ammo apart and sized the brass, then re-assembled the ammo as it was. I haven't had a problem since, but I do steer clear of S&B now.

I hope this helps.

 

[silentheart]

I had similar issue with s&b 338lm 2 yrs ago with my data srs a1. I bought 4 boxes/40 rd. First round was fine. 2nd round the case stuck. And had to bring out my Steyr ssg04 and shoot for the rest I of the day. Got back home and use a rubber hammer to get the casing out. The casing looks fine. Put the s&b away for 6 month. Tried again and all shot fine. Go figure. I feel s&b loads are a little on the hot side vs other manufacturers even with other cal ammo.

 

[racerbart]

Thanks for the great info everybody. This helps me a lot. I did search this forum and others and couldn't find any reference to this issue but now I have already found at least two others that have seen a quirk with S&B. I think at least now I'm sure there's probably nothing wrong with my new baby.

Great idea sharpshot50 about trying to recycle the S&B. Once I get up and running with the 338 reloads I'll give that a look.
My measurements seem to indicate the S&B shoulder may pushed back a few thousandths too far. If that's true resizing won't fix it so I will have to fire form them first but at least I can reuse the brass.