AXMC 338 Lapua to 300 PRC Conversion Issue

[dfloomis]

I recently picked up an AXMC in 338 Lapua. My local range does not allow anything over 300 caliber, so I also purchased the 300 bolt body (part 20013) and a 300 PRC barrel (part 2527073BL). After the conversion to 300 PRC, the pin is either not or barely making contact with the primer. Does this setup need the small firing pin or is this most likely a headspacing issue with the barrel?

 

[IK6243]

Shouldn't be a LFP vs SFP issue.

Check the firing pin protrusion with the magnum bolt body vs the Lapua magnum bolt body, and also the headspace if you have gauges. Issue could be one or both.

 

[Kiba]

Firing pin protrusion should not have to be adjusted between bolt bodies.

However, if you had a 1.6mm small firing pin 338 bolt and firing pin already, it will not work with the large firing pin #20013 300wm bolt you purchased.

If you want to confirm, pull your current firing pin assembly out and measure, or look at the picture below. 1.6mm small firing pin on left, 2.0mm large on right. An AXMC should have came with the 2.0mm firing pin by default, but someone may have swapped it out and I've heard rumors that some late production AXMCs came with 1.6mm firing pins from AI.

If it's not a firing pin mismatch issue, it's probably a chamber issue with the 300 barrel.

 

[dfloomis]

Firing pin protrusion should not have to be adjusted between bolt bodies.

However, if you had a 1.6mm small firing pin 338 bolt and firing pin already, it will not work with the large firing pin #20013 300wm bolt you purchased.

If you want to confirm, pull your current firing pin assembly out and measure, or look at the picture below. 1.6mm small firing pin on left, 2.0mm large on right. An AXMC should have came with the 2.0mm firing pin by default, but someone may have swapped it out and I've heard rumors that some late production AXMCs came with 1.6mm firing pins from AI.

View attachment 8781673

If it's not a firing pin mismatch issue, it's probably a chamber issue with the 300 barrel.

Thank you - That is the issue. This is a new AXMC LE version and it did come with the SFP and not the large. Is there a chart anywhere detailing which pin is needed for which caliber?

 

[Kiba]

Thank you - That is the issue. This is a new AXMC LE version and it did come with the SFP and not the large. Is there a chart anywhere detailing which pin is needed for which caliber?

If you have a small 1.6mm firing pin you need all 1.6mm small firing pin bolt bodies.

You can also buy a complete 2.0mm firing pin assembly to use with that new large firing pin 300wm bolt body you have, but that's $500+. I would send the large firing pin 300wm bolt back and exchange it for a 1.6mm small firing pin 300wm bolt, #27777.

 

[Jrb572]

If you have a small 1.6mm firing pin you need all 1.6mm small firing pin bolt bodies.

You can also buy a complete 2.0mm firing pin assembly to use with that new large firing pin 300wm bolt body you have, but that's $500+. I would send the large firing pin 300wm bolt back and exchange it for a 1.6mm small firing pin 300wm bolt, #27777.

If you can not send it back have LRI bush it.

 

[dfloomis]

If you have a small 1.6mm firing pin you need all 1.6mm small firing pin bolt bodies.

You can also buy a complete 2.0mm firing pin assembly to use with that new large firing pin 300wm bolt body you have, but that's $500+. I would send the large firing pin 300wm bolt back and exchange it for a 1.6mm small firing pin 300wm bolt, #27777.

Just confirming this part will work -

AI AX Replacement Firing Pin/Safety Assembly 6679​

And is there anyway to know as I try new calibers, which firing pin is best for each caliber?

 

[Kiba]

If you can not send it back have LRI bush it.

LRIs bushed bolts and modified firing pins are not compatible with the factory AI 1.6mm bolt bodies, and a factory AI 1.6mm firing pin won't work in an LRI bushed bolt. I've had both. While the LRI turned down firing pin will fit in a factory AI 1.6mm bolt body a good portion of the LRI modified firing pin tip will be unsupported in a factory AI 1.6mm bolt and the firing pin tip will break after a bit of use.

Just confirming this part will work -

AI AX Replacement Firing Pin/Safety Assembly 6679​

And is there anyway to know as I try new calibers, which firing pin is best for each caliber?

That's for an AX short action. AXMC 2.0mm firing pin by itself is #20346 and you could install that on your current firing pin shroud to use with your 2.0mm 300wm bolt, and I'm trying to find the part number for a complete 2.0mm firing pin shroud assembly... Looks like Euro Optic and Mile high both took the 2.0mm firing pin assembly off their websites and only list the 1.6mm assembly now.

Just get all 1.6mm firing pin bolts, that's the best option as you only need 1 firing pin assembly to share between all 3 bolts... Unfortunately they're not always in stock. 308 1.6mm RH bolt is # 27773, 300wm is 27777.

 

[dfloomis]

LRIs bushed bolts and modified firing pins are not compatible with the factory AI 1.6mm bolt bodies, and a factory AI 1.6mm firing pin won't work in an LRI bushed bolt. I've had both. While the LRI turned down firing pin will fit in a factory AI 1.6mm bolt body a good portion of the LRI modified firing pin tip will be unsupported in a factory AI 1.6mm bolt and the firing pin tip will break after a bit of use.



That's for an AX short action. AXMC 2.0mm firing pin by itself is #20346 and you could install that on your current firing pin shroud to use with your 2.0mm 300wm bolt, and I'm trying to find the part number for a complete 2.0mm firing pin shroud assembly... Looks like Euro Optic and Mile high both took the 2.0mm firing pin assembly off their websites and only list the 1.6mm assembly now.

Just get all 1.6mm firing pin bolts, that's the best option as you only need 1 firing pin assembly to share between all 3 bolts... Unfortunately they're not always in stock. 308 1.6mm RH bolt is # 27773, 300wm is 27777.

 

[dfloomis]

Thanks for all the help. I will be on a lookout for the 1.6 300 body.

 

[Jrb572]

Well guess I have been lucky so far after about 400 rounds with mine. Guess I’ll have to wait for it to break and will have to have two firing pins or my other bolt bodies drilled back to fit large pins and buy another cocking/saftey piece

 

[Kiba]

Thanks for all the help. I will be on a lookout for the 1.6 300 body.

You may want to call Mile High or Euro Optic and see if they have any 1.6mm 300WM bolts that aren't spoken for in their next AI order and get on the backorder list now so you don't miss out and have to wait for the next batch. Euro Optic has a bunch of AI parts (including AXMC bolts) that are supposed to be arriving in about 45 days, as I have a backordered 1.6mm 338 AXMC bolt in that shipment.

Well guess I have been lucky so far after about 400 rounds with mine. Guess I’ll have to wait for it to break and will have to have two firing pins or my other bolt bodies drilled back to fit large pins and buy another cocking/saftey piece

If you're running a turned down LRI firing pin for one of their bushed bolt heads in a factory AI 1.6mm bolt body, it will break eventually.

LRI's bushing job leaves a longer bushing in the bolt head that fully supports their turned down firing pin with a longer turned down tip length. If you run LRI's turned down firing pin for their bushed bolts in a factory AI 1.6mm bolt body, while it will work and protrude properly and go bang the factory AI 1.6mm bolt body and head leaves a portion of the longer LRI turned down firing pin tip unsupported and the LRI turned down firing pin will eventually buckle and break at that unsupported portion. Either go all LRI bushed bolts with the LRI turned down firing pin, or go all factory AI 1.6mm firing pin with factory AI 1.6mm bolt bodies.

Also, if you try and run a factory AI 1.6mm firing pin in an LRI bushed bolt body the factory AI 1.6mm firing pin won't even protrude from the bolt face, the factory AI 1.6mm firing pin has a very short tip and the taper right behind it hits the longer bushing inside the LRI modified bolt head.

LRI's bushing jobs are great, but you have to use the correct parts combinations if you want them to be reliable.