AXMC .338 bolt problem

T

TheRealQuietShootr

Private
Minuteman
Mar 21, 2025
21
7
Indiana
#1
I got a .338LM bolt and barrel for my AXMC but didn't test it until about a year after I got it. Once I did fire it, it was causing what looked like overpressure damage to the case head, which I eventually determined was actually caused by the front of the extractor sitting slightly proud of the bolt face. I tried at the time to get AINA to look at it, but they wanted me to send the entire rifle and would not simply look at the bolt.

The .338 bolt has been shelved for six years at this point. Does anyone know of a smith who really knows AIs who could take a look at the bolt?
 
#5
I am not familiar with AI, but waiting 6 yrs probably doesn't help.

The 338 L with most rifles with m16 style extractors requires the bolt recess be cut to a larger dia to allow the extractor to snap over the extractor groove in the case.

Any interference mess up the brass case rim. It should have never left the factory, but it should have been sent back ASAP.

The counterbore in the barrel or the extractor or a combination could be slightly out of spec...or tolerence stacking. Installing a new extractor could solve the problem, or a slightly larger counterbore.
Easy fix.
 
#6
Well, I've been busy.

And none of that really applies to an AI bolt; it doesn't use an M16 extractor, and the bolt bodies are harder than the hammers of hell; you aren't just going to throw it on a mill and start cutting, this isn't a turd-polished overpriced R700 bolt. Nor would I want to do that with a bolt that cost $600 when I bought it, and is double that to replace now.

I didn't send the entire rifle back because I was using it at the time, and it works beautifully with the .300WM and .308 bolts.

ETA: At the time, and I suspect this is still the case, it was not possible to just order a new extractor...which is a separate irritant.
 
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#7
45-90 said:
I am not familiar with AI, but waiting 6 yrs probably doesn't help.

The 338 L with most rifles with m16 style extractors requires the bolt recess be cut to a larger dia to allow the extractor to snap over the extractor groove in the case.

Any interference mess up the brass case rim. It should have never left the factory, but it should have been sent back ASAP.

The counterbore in the barrel or the extractor or a combination could be slightly out of spec...or tolerence stacking. Installing a new extractor could solve the problem, or a slightly larger counterbore.
Easy fix.
Click to expand...
There is no counterbore feature on AI chambers, unless you are referring to the chamfer, which is specified at only 1.5mm.
 
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#10
IK6243 said:
There is no counterbore feature on AI chambers, unless you are referring to the chamfer, which is specified at only 1.5mm.
Click to expand...
Yeah. I actually did some real leg work at the time trying to figure out the actual problem; I had access to two more AXMCs and bolts that were all fine and worked interchangeably; my bolt causes the same issue in two other rifles with two different barrels each, and those barrels and bolts on my rifle worked fine. The only common denominator was the bolt. There is no issue with my rifle or my .338 barrel.
 
#12
image.jpg

I just got the bolt out - I think i was remembering the problem backwards. the brass was flowing into the cut where the extractor is supposed to be level with the bolt face, but instead it is a few thousandths below where it should be, which creates a nasty mark on the case head that looks very much like terrible pressure signs, except that's not what's happening. Looking for the brass now.

ETA: thought I had the brass with the bolt. If I have to, i can remount the 338 barrel and fire a couple rounds to get more.
 
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#13
Post in thread 'Accuracy International AXMC .338LM - Firing Pin Stuck?'
https://www.snipershide.com/shootin...c-338lm-firing-pin-stuck.6889018/post-7076985

On second thought, I think I now understand the problem you have. I had similar with my brass having marks from the ejector and this was only 6BR on a Swiss target rifle. The ejector could be disabled by pushing it in and turning it, leaving an unsupported hole on the boltface, and the marks occurred in both cases. I never figured out why it was happening as the headspace was within spec and I was using factory Lapua and Norma 6BR ammo, but internet suggested it was just classic signs of overpressure. I just assumed it was the hot weather, I only ever shot this match in peak summer temperatures and didn’t care enough to check in cooler weather.

Are you sure your problem isn’t also from overpressure? Seems to me that the extractor being lower than the boltface is not the main issue here.
 
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#14
IK6243 said:
Post in thread 'Accuracy International AXMC .338LM - Firing Pin Stuck?'
https://www.snipershide.com/shootin...c-338lm-firing-pin-stuck.6889018/post-7076985
Click to expand...
🧐 This bolt did this from the first round I fired with it. it has no more than 15 rounds on it, and I regularly changed the firing pin/safety assembly between the .300WM bolt (which is what I usually shoot) and the .308 bolt, and I cleaned the bolt bodies and pin assembly regularly. There's no debris in there.
 
#15
TheRealQuietShootr said:
🧐 This bolt did this from the first round I fired with it. it has no more than 15 rounds on it, and I regularly changed the firing pin/safety assembly between the .300WM bolt (which is what I usually shoot) and the .308 bolt, and I cleaned the bolt bodies and pin assembly regularly. There's no debris in there.
Click to expand...
The link to that post was to show another photo of a 338 AXMC boltface which also sort of seems to have a lower extractor.
 
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#16
TheRealQuietShootr said:
Well, I've been busy.

And none of that really applies to an AI bolt; it doesn't use an M16 extractor, and the bolt bodies are harder than the hammers of hell; you aren't just going to throw it on a mill and start cutting, this isn't a turd-polished overpriced R700 bolt. Nor would I want to do that with a bolt that cost $600 when I bought it, and is double that to replace now.

I didn't send the entire rifle back because I was using it at the time, and it works beautifully with the .300WM and .308 bolts.

ETA: At the time, and I suspect this is still the case, it was not possible to just order a new extractor...which is a separate irritant.
Click to expand...
Yes with the M16 "Type" extractor doesn't mean a real M16 extractor...but an extractor that functions like an M16 does.

They always chamber the 308 and the 300WM without a problem but the 338 LM is quite often the problem as I have stated, the larger case head diameter runs into interference as the extractor snaps over the rim...simple.
And my cheap ass 338 bolt functions great with no problems...and one can cut hardened steel, and you won't be cutting the bolt.
It appears "you" are the one with an "overpriced turd."
People and their expensive crap, with a giant ego, run rampant around here...expensive doesn't mean better, it means you just paid more, with the possibility of being better.
In your case it failed...it's still an easy fix.
And ya wait 6 years and the price doubles, lesson don't wait 6 yrs, send it back immediately, and you could be enjoying your 338 LM for 6 yrs instead of bring angry at me for pointing that out...People.
 
#17
45-90 said:
Yes with the M16 "Type" extractor doesn't mean a real M16 extractor...but an extractor that functions like an M16 does.

They always chamber the 308 and the 300WM without a problem but the 338 LM is quite often the problem as I have stated, the larger case head diameter runs into interference as the extractor snaps over the rim...simple.
And my cheap ass 338 bolt functions great with no problems...and one can cut hardened steel, and you won't be cutting the bolt.
It appears "you" are the one with an "overpriced turd."
People and their expensive crap, with a giant ego, run rampant around here...expensive doesn't mean better, it means you just paid more, with the possibility of being better.
In your case it failed...it's still an easy fix.
And ya wait 6 years and the price doubles, lesson don't wait 6 yrs, send it back immediately, and you could be enjoying your 338 LM for 6 yrs instead of bring angry at me for pointing that out...People.
Click to expand...
Sir, it may look like I'm new here, and to precision shooting, but I'm not. I could have been "enjoying" my .338 barrel, but i was out doing shit you only read about on the internet. Since you don't know AIs and your primary purpose in this thread was to offer advice about something you admitted you don't know anything about, why don't you show yourself out.
 
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#18
IK6243 said:
The link to that post was to show another photo of a 338 AXMC boltface which also sort of seems to have a lower extractor.
Click to expand...
ahh. Well, it could be a problem with the depth of the bolt face, which obviously isn't something that could readily be corrected. as i recall we did carefully measure the depth of the bolt face with reference to the face of the lugs, and compared to two known good bolts it didn't show significant difference.
 
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#19
IK6243 said:
Post in thread 'Accuracy International AXMC .338LM - Firing Pin Stuck?'
https://www.snipershide.com/shootin...c-338lm-firing-pin-stuck.6889018/post-7076985

On second thought, I think I now understand the problem you have. I had similar with my brass having marks from the ejector and this was only 6BR on a Swiss target rifle. The ejector could be disabled by pushing it in and turning it, leaving an unsupported hole on the boltface, and the marks occurred in both cases. I never figured out why it was happening as the headspace was within spec and I was using factory Lapua and Norma 6BR ammo, but internet suggested it was just classic signs of overpressure. I just assumed it was the hot weather, I only ever shot this match in peak summer temperatures and didn’t care enough to check in cooler weather.

Are you sure your problem isn’t also from overpressure? Seems to me that the extractor being lower than the boltface is not the main issue here.
Click to expand...
no, the load was a starting load and showed no pressure signs with the other two rifles, or with their barrels and bolts in my rifle. New Lapua brass, 300gr Berger MT Hybrid, and the powder was Retumbo; I have to pull my notebook out for the charge, but it was very much a starting load. I also tried 5 rounds of factory to verify.

ETA: It's coming back to me now. the reason I concluded it was NOT the depth of the bolt face was that that would have amounted to excessive headspace, which would have been measurable in the fired brass. IIRC we measured the shoulder on brass fired with this bolt in my barrel, which showed the defect, next to brass fired in my barrel with another bolt, which did not have the defect, and they measured the same/similar.
 
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