04-18-2020, 07:08 PM
Yes, the bolt issue for 6mmARC is a conundrum. My personal opinion is that the industry should voluntarily standardize on one or the other, on Mk125 or Mk136. I'm leaning toward Mk125 for the slightly greater lug support and because I can engineer it to get the same extractor claw dimensions as a 5.56 extractor. To me, that's the best of both worlds.
Availability of either bolt is NOT the issue. Both Mk125 (think the community of AR15 7.62x39 users) and Mk136 (6.5 Grendel users) bolts are out there in quantity. You can get one as easily as the other and the price is the same.
What IS the issue?
Extractor claw strength. (The issue is NOT the 0.125 boltface counterbore depth in and of itself, cuz even AR10s use 0.125).
If we had the extractor claw strength, we'd be using 0.125 and wouldn't think twice.
What if we get the extractor claw strength back to the same dimensions as a 5.56 extractor claw?
In that case, what is the argument for a 0.136 bolt?
Unless I'm missing something, the best argument is for those who want to use the exact same bolt unit in multiple weapons. It's a valid argument, cuz I've got more uppers than I know what do with and I'll just transfer BCG "X" to upper A, B, or C, depending on what upper I want to play with. Same bolt, multiple weapons.
But that's neither ideal nor recommended. I do it to save money and cuz I know my MONSTER bolts have always been dead nuts on in terms of headspace and are interchangeable.
Another example: I have zero interest in 5.56 AR15s. But many, if not most, of you own AR15s in both 5.56 and 6.5 Grendel.
You have Mk125 bolts for 5.56
You have Mk136 bolts for 65G.
If any of you have a commie AR15, then you've got a Mk125 bolt for 7.62x39.
And that's cool.
Taking it even further, most, of course, have Bolt A for Rifle A, and Bolt B for Rifle B, and Bolt C for Rifle C. In that case, the argument for using one bolt in multiple weapons evaporates.
So, I'm willing to have Mk136 bolts for 65G and Mk125 bolts for 6mmARC provided the technical issues of lug and extractor strength are resolved.
Having said ALL that, nothing is set in stone. I want to hear what you guys think about the subject and your arguments for or against.
Availability of either bolt is NOT the issue. Both Mk125 (think the community of AR15 7.62x39 users) and Mk136 (6.5 Grendel users) bolts are out there in quantity. You can get one as easily as the other and the price is the same.
What IS the issue?
Extractor claw strength. (The issue is NOT the 0.125 boltface counterbore depth in and of itself, cuz even AR10s use 0.125).
If we had the extractor claw strength, we'd be using 0.125 and wouldn't think twice.
What if we get the extractor claw strength back to the same dimensions as a 5.56 extractor claw?
In that case, what is the argument for a 0.136 bolt?
Unless I'm missing something, the best argument is for those who want to use the exact same bolt unit in multiple weapons. It's a valid argument, cuz I've got more uppers than I know what do with and I'll just transfer BCG "X" to upper A, B, or C, depending on what upper I want to play with. Same bolt, multiple weapons.
But that's neither ideal nor recommended. I do it to save money and cuz I know my MONSTER bolts have always been dead nuts on in terms of headspace and are interchangeable.
Another example: I have zero interest in 5.56 AR15s. But many, if not most, of you own AR15s in both 5.56 and 6.5 Grendel.
You have Mk125 bolts for 5.56
You have Mk136 bolts for 65G.
If any of you have a commie AR15, then you've got a Mk125 bolt for 7.62x39.
And that's cool.
Taking it even further, most, of course, have Bolt A for Rifle A, and Bolt B for Rifle B, and Bolt C for Rifle C. In that case, the argument for using one bolt in multiple weapons evaporates.
So, I'm willing to have Mk136 bolts for 65G and Mk125 bolts for 6mmARC provided the technical issues of lug and extractor strength are resolved.
Having said ALL that, nothing is set in stone. I want to hear what you guys think about the subject and your arguments for or against.
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