AI AXMC tolerances issues

[Canuck1977]

Hi all,

I was told by a really good gunsmith today that in order to get a barrel spun up for my 2018 AXMC, I have to send the gun and bolt. The reason is that there are some tolerances inconsistencies with the AXMC..

first time I heard this about the AXMC.

can you educate me on this?

cheers

 

[Dave62677]

this is my first time heard that too

 

[Kiba]

I know it's only a sample of 1, but the receiver face to bolt face dimension on my AXMC along with 2 AE's, an AT, and 2 AX308s all fall within a 0.0008" band. That's a 0.0008" span from highest to lowest of all the rifles measured, not +/- 0.0008". AI is holding that tolerance over many years of production and multiple generations of rifles. Even playing "musical bolts" between the AEs and AT / 2x AX308s the receiver face to boltface dimension remains within that same 0.0008" span. That's pretty damn good, but it doesn't mean an occasional mistake can't slip out the door (if QC is robust, it shouldn't, but for stupid reasons sometimes "escapes" still seem to happen.)

The tolerance range that I've measured is more than good enough to chamber a prefit barrel and still meet headspace tolerances, but if you want to make absolutely sure your barrel is correct as well as having the smith cut the chamber to minimum headspace for your particular rifle it's always best to measure your rifle, chamber for that measurement, and save that measurement for future barrels. Of course, that implies your 'smith is periodically verifying and calibrating their measurement tools to traceable standards and their equipment can repeat that measurement over time, but that's another issue...

I've dealt with a couple of gunsmiths that want your AI in hand to do the first rebarrel job so they can measure it accurately, then you don't have to send the action back in for barrels after that. Those smiths did cite a bit more dimensional variance in AE's because the seperate recoil lug adds another component for tolerance stacking, but my 2x AE's certainly didn't suffer from it.

 

[solvovir]

See my thread

 

[Canuck1977]

See my thread

Which one?

 

[Jrb572]

Call Dave Tooley or Mile high and have them do your barrel. It’s not a bench rest rifle. All my barrels are very accurate

 

[solvovir]

Which one?

Axmc barrel fit

 

[trophyhunter]

Find a different gunsmith

 

[trophyhunter]

Unless your rifle has in excess of 15-20,000rds your headspace should be identical to any other AXMC. Once it gets into high round count I can see where your breech ring could possibly set back a few thousandths.

 

[solvovir]

Idk, im not a smith. Other smiths i spoke to said it wasn't the original smiths fault. I know tooley and milehigh can build axmc barrels that fit, but in my case the headspace was just a bit to tight. Could have been the round i chose too...

 

[Bravo6niner]

Correct me if I’m wrong but isn’t the measurement from the face of the action to the bolt face differ a few thousandths from a 300wm bolt to a 338LM bolt on an AXMC?? Maybe in @solvovir case the smith didn’t have the correct measurements??

 

[trophyhunter]

What caliber did you choose ?
Are you using new brass or previously fired ?

 

[AIAW]

Back when the AXMC first debuted there was some major confusion on tenon dimensions, which caused a few barrels to be chambered/headspaced incorrectly. Never an issue with the action or bolts - just miscommunication over the barrel specs.

That was many years ago and the spec has never changed. It’s one of the most tightly toleranced actions on the market!

 

[trophyhunter]

Correct me if I’m wrong but isn’t the measurement from the face of the action to the bolt face differ a few thousandths from a 300wm bolt to a 338LM bolt on an AXMC?? Maybe in @solvovir case the smith didn’t have the correct measurements??

As far as I know they are the same.

 

[Kiba]

As far as I know they are the same.

I haven't measured a 338LM bolt in my AXMC to compare with the 300WM bolt that I have, but I would think the receiver face to bolt face dimension is the same too... having different receiver to boltface dimensions for different bolt heads means an additional chambering spec floating around in the shop which introduces more chances for errors... can't imagine why AI would want that. Wish I had a 338LM bolt to drop in the rifle and measure to compare to the 300WM bolt.

 

[Bravo6niner]

I haven't measured a 338LM bolt in my AXMC to compare with the 300WM bolt that I have, but I would think the receiver face to bolt face dimension is the same too... having different receiver to boltface dimensions for different bolt heads means an additional chambering spec floating around in the shop which introduces more chances for errors... can't imagine why AI would want that. Wish I had a 338LM bolt to drop in the rifle and measure to compare to the 300WM bolt.

I have both. If I get time I’ll measure mine again.

 

[trophyhunter]

I haven't measured a 338LM bolt in my AXMC to compare with the 300WM bolt that I have, but I would think the receiver face to bolt face dimension is the same too... having different receiver to boltface dimensions for different bolt heads means an additional chambering spec floating around in the shop which introduces more chances for errors... can't imagine why AI would want that. Wish I had a 338LM bolt to drop in the rifle and measure to compare to the 300WM bolt.

All the bolt bodies are cut the same and interchangeable, lugs on the bolt head are the same as well. The only thing that changes is size of face diameter.

 

[mercracing]

Order a barrel from Mike at Mile High and run it.

 

[RRW]

Axmc barrel fit

In your case it appears to be an issue with whoever chambered your barrel. Not an issue with AI tolerances or specs.

 

[redneckbmxer24]

That's a whole bunch of bullshit. Call a different gunsmith or just order an AI or Proof prefit.

 

[solvovir]

What caliber did you choose ?
Are you using new brass or previously fired ?

300prc. Throated for factory 225s. I only shoot factory and do not reload. Also the chassis was new. The smith i used got the print for my barrel from adam and milehigh.

 

[DAVETOOLEY]

All the bolt bodies are cut the same and interchangeable, lugs on the bolt head are the same as well. The only thing that changes is size of face diameter.

Not so. The HS changes with bolt face diameter.

 

[Long Range 338]

With multiple components and manufacturers possibly involved in one rifle, how would you decide the problem lies with the tolerances of the AI action, bolt, or headspace? AI maintains their actions within a spec'd tolerance. Barrel makers maintain their pre chambered barrels within a tolerance as well. If you just happen to hit on opposing ends of the spec from each manufacturer it is possible to have issues. AI recommends/sells headspace gauges for swapping barrels, it is for good reason.

It sounds like your smith is being cautious and wanting to provide quality that he can stand behind, good on him. There are plenty of barrels sitting on the shelf you can buy without sending your action in to document but there is a certain amount of inherent (albeit small) risk in a chambering issue. Educate yourself and be aware, you will be fine. I'm certain any of the prefit barrel makers here on the Hide are willing to discuss this with you if you are purchasing a barrel from them. By the way, Mile High is a stellar outfit. I'm certain the others are as well.

 

[Lowlight]

I would send it in,

I have been saying this forever, if you do it right the first time and not use off the shelf products, there is no primer piercing. I got yelled at for saying this.

Most spec the tolerances to 308 in short action calibers, a 6.5 is actually slightly different, but every off the shelf barrel is just off enough and then people wonder why they pierce primers.

My 1998 AI has been a 260 since 2007, it was sent in and spun up by GAP, and it NEVER ONCE pierced a primer. Fast forward, everyone buys an off the shelf pre-fit barrel from who ever the fuck is the first one with the right price they stumble on and suddenly there is a problem.

And then you all wonder why.

 

[gconnoyer]

It sounds like your smith is being cautious and wanting to provide quality that he can stand behind, good on him.

Yup^

While prefits for AIs are super common and doable, he probably just doesnt feel comfortable or want to put his name on it without checking the work.

 

[trophyhunter]

Not so. The HS changes with bolt face diameter.

Then how do you make prefit barrels for rifles that you’ve never seen ?

i recall you were the one doing a lot of barrels for AI’s. Did you just average the “changes” or how did you ensure they would headspace correctly.

 

[DAVETOOLEY]

Very simple. I have a set of drawings and make them to meet the specs.
Were there surprises along the way? Sure there were but very few and I learned from it and then worked in a narrower tolerance range once I figured out what the UK was doing. Nothing was ever off enough to matter in the real world.

 

[trophyhunter]

So with somewhat certainty you could make a barrel that would fit on most rifles, unless it had an excessive amount of rounds on the rifle or that rare oddity, without having the rifle in your shop.

that’s what I was getting at, once you have a good set of tenon prints you don’t need the rifle.

 

[DAVETOOLEY]

So with somewhat certainty you could make a barrel that would fit on most rifles, unless it had an excessive amount of rounds on the rifle or that rare oddity, without having the rifle in your shop.

that’s what I was getting at, once you have a good set of tenon prints you don’t need the rifle.

I did thousands of barrels for AI and the only time I had rifles in the shop was for military submissions that I was testing.

 

[Kiba]

Not so. The HS changes with bolt face diameter.

So the nominal receiver face to bolt face dimension on the AI specs differs between the 300WM and 338 bolts? Interesting.

As usual, thanks for the info Dave!

 

[Lowlight]

In the main calibers for the AXMC,

308, 300, and 338 you never really saw issues, very forgiving.

it's the 6.5s people see the problems with it, I was at the SHC last year and a guy bought an AXMC and used a pre-fit 6.5CM barrel that blew primers every time, his gun jammed up and he walked over to me with it, I removed the firing pin from the bolt and it was full of primer discs that prevented the pin from going forward and wondered why it didn't shoot any more.

Hence the change to a small firing pin, attempting to fix the problem. The same thing with my AX, I never popped a primer until I switched to a pre-fit barrel from an AI one to an aftermarket version, then started to pop primers. I went back to an AI barrel and it stopped, but I had the larger firing pin.

Do a search on here for old AWs popping primers in 260s, and 6.5s going back before the Quickloc system, guys had other gunsmiths build pre-fit barrels for actions that were sight unseen, vs the guys that sent them into gunsmiths for their barrels. Why would a 260 pop a primer and 308 not, same parent case, so the firing pin should not be an issue, but it was, according to folks. I always contend it was small deviations in the spec that made the difference. I backed that up when using the Quickloc, we had several on the line where guys with a brand new rifle would suddenly start to pop primers only to find out the barrels were loose under the Quickloc system. Re-tighten the barrel properly and add a few inch pounds to the Quick-Lock and it stopped.

It's not huge, but it was enough to get attention.

 

[trophyhunter]

So prefits are not ideal ?
And you should send your rifle into a quality gunsmith ?

 

[Lowlight]

I would say that they are not all created equal, and to be safe, send it in.

In my mind, better safe than sorry with the AXMC especially if you are asking for something not, 308, 300, 338, if you are just getting one of those calibers, no big deal, anything else, send it in.

 

[6brshooter]

Several guys with 6.5 factory barrels on ae's pierced primers. Mine was good to go from mr tooley, but I know a few guys that had 260 ae's and they were limited to around 2700fps and 140.

 

[NoLegs24]

LOL....

I remember having to send back my AX308 (SFP) back cause the original barrel (WinTac) was off, as well as a Tooley barrel that came off a LFP AX308, and a Gradous 6.5x47L.
I became a believer in just sending my AI’s to my preferred smith to make sure nothing was was going to be “off”
Same goes with my PSR not being identical with my buddies AXMC.... not far off to matter; but still not exactly the same.
Best believe I’m sending in the ASR to my buddy at Sawtooth Rifle’s to get barrels for that system. Plus, how else will he be able time the engraving ???

 

[Robert Gradous]

I usually don't do this so I'll apologize up front,,,,,, what was off,,,,,

 

[NoLegs24]

I usually don't do this so I'll apologize up front,,,,,, what was off,,,,,

We cleared this "issue" 3yrs ago, sir.

Headspace was off when the barrels where put on that particular rifle. Wasn't the case when it was on the previous rifle. Same rifle, only one was Large Firing pin vs small.

I just brought it up, since they can be off if you buy prefit/ drop in barrels.

I know I know, but I remember Adam at Mile High saying he was the only one, besides AI/ AINA that had the blueprint to the barrel specs..

I strickly run AI's, but that doesn't mean I buy prefit/ drop in barrels anymore. Unless the person I am buying it from has the specs to that specific action.

 

[Robert Gradous]

Thank you as If one bolt headspace is correct and the other is not where does the problem exist on my end. PS who do you think taught mile high.

 

[NoLegs24]

Thank you as If one bolt headspace is correct and the other is not where does the problem exist on my end. PS who do you think taught mile high.

Exactly. I just had to throw in the all the barrels. Not saying that your work was at fault.
And yup, I remember you telling me that when we talked. That’s why I added the “I know I know” lol

 

[richthe1]

I’m a beginner, so I apologize in advance if the answers to my questions seem obvious - trying to learn.

If I purchase an AXMC, a SFP 308 bolt, and Proof (or Tooley, or Gradous - someone reputable) pre-fit barrels in SA and LA calibers from Mile High would I be good to go? Would an AI barrel be better? Or still safest to send it in?

What about a SFP AIAX with Proof pre-fit barrels - any difference?

Will the AXSR make any difference because I think I heard it’s a SFP for SA and LA calibers everything?

A big appeal to me about the AI is quickly ordering pre-fits in a variety of calibers, but I DO NOT want to deal with any issues. If it’s worth sending it in to avoid any problems I can do that. I’m just chasing down this rabbit hole of long range shooting and learning new things everyday (who knew prefit barrels didn’t always fit?! - not me!). Thanks!

 

[AIAW]

I’m a beginner, so I apologize in advance if the answers to my questions seem obvious - trying to learn.

If I purchase an AXMC, a SFP 308 bolt, and Proof (or Tooley, or Gradous - someone reputable) pre-fit barrels in SA and LA calibers from Mile High would I be good to go? Would an AI barrel be better? Or still safest to send it in?

I’ve personally never had a single issue with a prefit. It’s a set standard on barrel dimensions, headspace, etc. I personally don’t think anything is safer, as if it’s not right a reputable company will make it right. That being said, if it’s AI related it comes from Mile High for me. I have utmost confidence in AI prefits. If you are willing to buy a blank and ship it to a smith then that also works equally as well. I would avoid having to send an AXMC in unless having a custom barrel made. Even then, not required.

What about a SFP AIAX with Proof pre-fit barrels - any difference?

AIAX has no quick-change capability. Given the price point of AXMC’s, just go for the AXMC. You will not have mixed LA and SA use with an AX either. You get one or the other with an AX.

Will the AXSR make any difference because I think I heard it’s a SFP for SA and LA calibers everything?

Not really. It’s a different rifle pretty much, but at the same time it’s the same rifle. If SFP is really important to you, then you could go this route. Be aware that the cost of an AXMC and the SFP would still be well below the cost of an AXSR. Depends if you are a “latest thing out there” kinda guy. You will pay a premium though for this. The barrels will not be portable between the two from what I understand.

A big appeal to me about the AI is quickly ordering pre-fits in a variety of calibers, but I DO NOT want to deal with any issues. If it’s worth sending it in to avoid any problems I can do that. I’m just chasing down this rabbit hole of long range shooting and learning new things everyday (who knew prefit barrels didn’t always fit?! - not me!). Thanks!

Remember, you can’t judge the entire engineering behind AI’s “prefitability” based on a few smiths with either wrong specs, or human error. To say you’ll never have issues - no one will ever guarantee that. You’ll hear about a few badly cut barrels on the Internet, but you’ll rarely ever hear about the thousands upon thousands of perfect barrels.

 

[918v]

Can someone describe the mechanics of the primer piercing as induced by a prefit AI barrel? Or how does the prefit barrel cause this problem. I understand headspace and clearances for the bolt, but don’t understand how these dimensions cause primer piercing.

 

[AIAW]

Can someone describe the mechanics of the primer piercing as induced by a prefit AI barrel? Or how does the prefit barrel cause this problem. I understand headspace and clearances for the bolt, but don’t understand how these dimensions cause primer piercing.

It’s the firing pin diameter/protrusion. It will pierce small rifle primers occasionally.

AI released a replacement “SFP” bolt to remedy this, but people were also having the originals bushed by smiths. I haven’t heard of any prefit induced primer issues (outside of issues when headspace was a problem).

 

[918v]

So new AIs with the SFP bolts won’t have piercing issues? Just headspace issues maybe?

 

[trophyhunter]

So new AIs with the SFP bolts won’t have piercing issues? Just headspace issues maybe?

The bigger reason for piercing primers is caused by excessive headspace. When the firing pin strikes the primer, the case expands to every knuck & cranny filling any voids. Once the firing pin has ignited the primer the firing pin will draw back into the housing every so slightly allowing for primer flow. If their was a slight gap between the firing pin and firing pin hole it’ll flow in their also. If headspace is off it’ll slam towards the rear & shoulders. You’ll notice with excessive headspace ejector Marks in brass.

it’s allowing to much brass to flow.

 

[AIAW]

So new AIs with the SFP bolts won’t have piercing issues? Just headspace issues maybe?

Yes, the AXSR bolts will be SFP. A modified or retail SFP in the AXMC is it’s equal.

Headspace will depend on the smith. If he has good prints then all should be well. I’ve never heard of issues with a WinTac (factory) barrel though.

 

[White Mamba]

There is a reason that well known smiths and forum members are telling you to send your rifle in. Once you do they will have a print for your rifle and can spin one up anytime.

 

[Sniperwannabee]

well crap the main reason i bought a AX was to buy barrels on line and put them on myself.

 

[Steel head]

well crap the main reason i bought a AX was to buy barrels on line and put them on myself.

Send it to your favorite Smith once, after that perfect pre fits.
Not a big deal.

 

[Kiba]

well crap the main reason i bought a AX was to buy barrels on line and put them on myself.

Chances are if you buy an off the shelf AI barrel from a quality shop it will headspace correctly and you won't have a problem. If the AI prefit headspace problem was rampant there would be tons of questions and complaints, and instead we only hear of a few cases here and there. And if the barrel is from a good shop they will take care of it.

In an ideal world, everything would headspace the same for prefits... but since you can have some variation in the receiver to bolt face dimension on the rifle and variation in the tenon length and chambering depth on the barrel, there's always the chance you can have tolerance stacking work against you-- a receiver to boltface dimension on your rifle that's in tolerance but on the long side of tolerance, and a barrel with a chamber and tenon cut in tolerance but on the deep side of tolerance on the barrel, and then add in a little bit of variation in the measurement equipment being used you could end up with a bit too much headspace. You could also run into the opposite in regards to tolerance stacking and measurement error and have a barrel that is a little too tight on headspace.

I would have no hesitation buying an off the shelf barrel from a well known shop and rolling with it, but if you want the barrel chambered to minimum headspace for your particular rifle then the smith needs to measure your particular rifle.