I own an AXMC in 338 LM, and have recently aquired a 6.5x47 Lapua conversion. The conversion is manufactured to CIP specs, and all components are genuine. On fitting the conversion, I was unable to close the bolt on virgin lapua brass. (I don't have a GO Guage) I checked everything I could to ensure mating surfaces were clean and unobstructed with no issue. All was good to go. I found that if I unscrewed the barrel just under 1/8 of a turn, (about 42 degrees) the bolt would close with very little to no resistance. With M20 x 2.0 thread, that works out to be about 0.0092 inch.
I made a number of measurements to see if I could find the issue, and here is what I found;
Barrel tanons were identical at 1.500 in length.
Case head protrusion from both the 338 LM and the 6.5x47 barrels were identical at 0.140 (Base to barrel face)
AI state that the bolt face dimension is taken from the rear set of lugs on the bolt head where it would engage with the corresponding set of lugs in the lock ring; this measured 0.742 on both bolt bodies.
Bolt face depth is where things became different. On the 338, depth of the bolt face was 0.132 and on the 308 bolt face, the depth was 0.120. A difference of 12 thou (0.012). Obviously this effects firing pin protrusion as well which I've also measured.
So my question is this; has anyone else experienced similar, and what types of measurements do others have on bolt face depth? I have contacted AI engineering and await their reply, but I'd like to put it out there.
I have no issue advancing a reamer into the chamber to correct headspace, but if the issue is with the bolt body, am I better off machining some the bolt face to negate the same issues with other caliber conversions in the future?
Any of your info or feedback would be great. Cheers.
I made a number of measurements to see if I could find the issue, and here is what I found;
Barrel tanons were identical at 1.500 in length.
Case head protrusion from both the 338 LM and the 6.5x47 barrels were identical at 0.140 (Base to barrel face)
AI state that the bolt face dimension is taken from the rear set of lugs on the bolt head where it would engage with the corresponding set of lugs in the lock ring; this measured 0.742 on both bolt bodies.
Bolt face depth is where things became different. On the 338, depth of the bolt face was 0.132 and on the 308 bolt face, the depth was 0.120. A difference of 12 thou (0.012). Obviously this effects firing pin protrusion as well which I've also measured.
So my question is this; has anyone else experienced similar, and what types of measurements do others have on bolt face depth? I have contacted AI engineering and await their reply, but I'd like to put it out there.
I have no issue advancing a reamer into the chamber to correct headspace, but if the issue is with the bolt body, am I better off machining some the bolt face to negate the same issues with other caliber conversions in the future?
Any of your info or feedback would be great. Cheers.
