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Brazos_Jack
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Posted: 3/19/2007 8:34:06 AM
I need a 7.62x39 AR-15 bolt. I would prefer a Leitner-Wise ACB (1st choice) or Colt (2nd choice). If anyone here either has one to sell or knows a source where I can get one, please contact me.

L-W has evidently improved their design and is having to wait on their supply of unobtainium before they can begin manufacture.

Has anyone had any problems at all with the 7.62x39 L-W ACB's or were all the reported problems with the 5.56 version?
nugentgl
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Posted: 3/19/2007 11:39:09 AM

Originally Posted By Brazos_Jack:
I need a 7.62x39 AR-15 bolt. I would prefer a Leitner-Wise ACB (1st choice) or Colt (2nd choice). If anyone here either has one to sell or knows a source where I can get one, please contact me.

L-W has evidently improved their design and is having to wait on their supply of unobtainium before they can begin manufacture.

Has anyone had any problems at all with the 7.62x39 L-W ACB's or were all the reported problems with the 5.56 version?


I have been hunting for a COLT 7.62x39 bolt forever! I bought one of LW's ACB's for the 7.62x39 and it works very well. However, I use my COLT bolt primarily. And you are correct, that all the problems with ACB were the 5.56 variety. However, that doesn't mean that the same problems don't exist in the 7.62x39 version. The problems just haven't surfaced since there are not that many 7.62x39 rifles out there that are seeing the same use as the 5.56 rifles.
If you act like a bitch, you get slapped like a bitch!
Wirebrush
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Posted: 3/19/2007 1:24:31 PM
Have you considered using an Alexander Arms bolt. The Beowulf and the Grendel use the same size rim as the 7.62x39 and AA has never been accused of putting out junk.
" Better to keep ones mouth shut and be thought a fool that to open it and remove all doubt"
Brazos_Jack
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Posted: 3/19/2007 1:55:42 PM

Originally Posted By Wirebrush:
Have you considered using an Alexander Arms bolt. The Beowulf and the Grendel use the same size rim as the 7.62x39 and AA has never been accused of putting out junk.


AA bolts are excellent but cannot be used with 7.62x39.

Though the rim dia. is the same, the bolt face depth is different (I don't remember which is the deeper).

So 7.62x39 bolts will give improper headspace with the AA family of cartridges and an AA bolt will give improper headspace with 7.62x39.
user426
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Posted: 3/19/2007 8:02:32 PM
Have you tried Numrich.....

www.e-gunparts.com/dept.asp
M9Powell
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Posted: 3/19/2007 8:52:15 PM

Originally Posted By Brazos_Jack:

Though the rim dia. is the same, the bolt face depth is different (I don't remember which is the deeper).



The AA bolt is 11 thousandths deeper if I recall correctly. You could use it for 7.62X39 if you were cutting the chamber with a reamer. Just cut the chamber 11 thousandths shallow. I don't know why you would want too though. Cutting the bolt deeper will make it weaker, not stronger. A very good educated guess is that its a CMT 7.62X39 bolt cut 11 thousandths deeper. I'd rather have the normal cut CMT bolt. AA says its too improve extraction. It seems more like a dodge too ensure you use their parts. Or make it difficult for anyone else trying to cut chambers. Actually it'd be pretty simple to work around this dodge. M9
steezo757
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Posted: 3/19/2007 8:58:59 PM
[Last Edit: 3/19/2007 8:59:24 PM by steezo757]
Brazos - I've been watching your posts as I'm also building a 7.62x39mm upper. I understand your search for quality, but I think I might break down a buy a Del-Ton or M1S bolt.

Have you found any feedback on the Del-Ton or M1S 7.62x39mm bolt?
Brazos_Jack
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Posted: 3/20/2007 12:38:01 AM

Originally Posted By M9Powell:

Originally Posted By Brazos_Jack:

Though the rim dia. is the same, the bolt face depth is different (I don't remember which is the deeper).



The AA bolt is 11 thousandths deeper if I recall correctly. You could use it for 7.62X39 if you were cutting the chamber with a reamer. Just cut the chamber 11 thousandths shallow. I don't know why you would want too though. Cutting the bolt deeper will make it weaker, not stronger. A very good educated guess is that its a CMT 7.62X39 bolt cut 11 thousandths deeper. I'd rather have the normal cut CMT bolt. AA says its too improve extraction. It seems more like a dodge too ensure you use their parts. Or make it difficult for anyone else trying to cut chambers. Actually it'd be pretty simple to work around this dodge. M9


I'm using an existing Colt barrel, so the option of cutting the chamber shallow isn't there. Besides, non-standard headspacing in a quickchange platform like the MGI Hydra sounds like an accident waiting to happen.
Brazos_Jack
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Posted: 3/20/2007 12:52:38 AM

Originally Posted By steezo757:
Brazos - I've been watching your posts as I'm also building a 7.62x39mm upper. I understand your search for quality, but I think I might break down a buy a Del-Ton or M1S bolt.

Have you found any feedback on the Del-Ton or M1S 7.62x39mm bolt?


I haven't seen any feed back on the Del-Ton or Model 1 Sales bolts. All the threads I've seen related to best 7.62 bolt have been between L-W and Colt.

It is my understanding that Colts are CMT's that have been shot peened and magnafluxed (MPI). Regular CMT's may or may not be MPI'd, but will not be shot peened. MPI is only an inspection technique to cull flawed bolts - those that developed microcracks during heat treat or manufacturing. Shot peening greatly increases fatigue resistance by placing the surface in residual compressive stress. This makes it harder for the surface to reach a high enough tensile stress during operation for fatigue cracks to initiate. Since AR bolts, particularly in 7.62, tend to fail in fatigue, I consider this a big deal.

I don't know if L-W ACB's are shot peened or not. But since they have an even better reputation for longevity than Colt, I have to assume that they either do shotpeen, or their modified design reduced the tensile stresses below the fatigue crack initiation threshold.
Gamma762
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Posted: 3/20/2007 1:15:35 AM

Originally Posted By nugentgl:
.... And you are correct, that all the problems with ACB were the 5.56 variety. However, that doesn't mean that the same problems don't exist in the 7.62x39 version. The problems just haven't surfaced since there are not that many 7.62x39 rifles out there that are seeing the same use as the 5.56 rifles.

What were the problems with the ACB?
That would explain the fireball...Yeah--I'm about a mile away I figure....just ordered a pizza. - Gravity_Tester
Brazos_Jack
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Posted: 3/20/2007 3:00:00 AM

What were the problems with the ACB?


It is my understanding that they were making a tool clearance undercut at the bottom of the bolt face and 5.56 rims sometimes got caught on it, causing a jam.

Someone correct me if this is incorrect.

They have since redesigned it to eliminate the problem, but are having to wait on the material they make the ACB from.
M9Powell
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Posted: 3/20/2007 8:31:19 PM
[Last Edit: 3/20/2007 8:44:54 PM by M9Powell]

Originally Posted By Brazos_Jack: MPI is only an inspection technique to cull flawed bolts - those that developed microcracks during heat treat or manufacturing.


There is a little more too it than that. Colt shotpeened the bolts, then proof tested with "Blue Pills" & then magnufluxed. This magnafluxing after proof firing makes a difference. If you buy the same bolt without the proofing & MPI you might be buying the bolt that would have failed if it had been subjected to the testing. Anyone who builds racing engines that are restricted to "stock" parts does the same things. They usually prefer used pre-stressed seasoned components. Then they magnuflux it. You stress it first, then you magnuflux it. An engine builder restricted to "stock" rods may go through 30 or 40 to pick 8 that are suitable. Newbies want new rods. The really good rods are the ones that didn't fail in the engine the other guy blew at 9,000 rpm. You get them & check them. They've been pre-stressed & didn't fail. M9
Brazos_Jack
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Posted: 3/21/2007 7:49:46 AM

Originally Posted By M9Powell:

Originally Posted By Brazos_Jack: MPI is only an inspection technique to cull flawed bolts - those that developed microcracks during heat treat or manufacturing.


There is a little more too it than that. Colt shotpeened the bolts, then proof tested with "Blue Pills" & then magnufluxed. This magnafluxing after proof firing makes a difference. If you buy the same bolt without the proofing & MPI you might be buying the bolt that would have failed if it had been subjected to the testing. Anyone who builds racing engines that are restricted to "stock" parts does the same things. They usually prefer used pre-stressed seasoned components. Then they magnuflux it. You stress it first, then you magnuflux it. An engine builder restricted to "stock" rods may go through 30 or 40 to pick 8 that are suitable. Newbies want new rods. The really good rods are the ones that didn't fail in the engine the other guy blew at 9,000 rpm. You get them & check them. They've been pre-stressed & didn't fail. M9


And now we have proceeded to where we started. Yes, for a number of very good reasons, Colt and L-W ACB's are the best 7.62x39 bolts on the planet.

Now the big question remains - anyone got an extra lying around that they'll sell me or know where I can get one?
shotgun1
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Posted: 3/22/2007 8:24:57 PM
Recently had a long conversation with Tom Lyons of MGI regarding the use of AA bolt in 7.62x39. He in turn had a long conversation with Bill Alexander. I am in the middle of similar conversations with Bill. I think you might be incorrect in assuming the AA 6.5 Grendel bolt won't work as a replacement for 7.62x39. I won't reprint Bill's answers to my questions in a public forum as I know he monitors these threads and apparently has chosen not to air his view. I'll summerize in confidence to anyone who'd like to contact me off board. In the mean time I'd invite Bill to chime in at any time.

-Glen
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Gamma762
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Posted: 3/22/2007 9:03:27 PM

Originally Posted By Brazos_Jack:

What were the problems with the ACB?


It is my understanding that they were making a tool clearance undercut at the bottom of the bolt face and 5.56 rims sometimes got caught on it, causing a jam.

Someone correct me if this is incorrect.

They have since redesigned it to eliminate the problem, but are having to wait on the material they make the ACB from.

Thanks, I wasn't aware of that issue.
That would explain the fireball...Yeah--I'm about a mile away I figure....just ordered a pizza. - Gravity_Tester
Brazos_Jack
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Posted: 3/23/2007 7:55:03 AM

Originally Posted By shotgun1:
Recently had a long conversation with Tom Lyons of MGI regarding the use of AA bolt in 7.62x39. He in turn had a long conversation with Bill Alexander. I am in the middle of similar conversations with Bill. I think you might be incorrect in assuming the AA 6.5 Grendel bolt won't work as a replacement for 7.62x39. I won't reprint Bill's answers to my questions in a public forum as I know he monitors these threads and apparently has chosen not to air his view. I'll summerize in confidence to anyone who'd like to contact me off board. In the mean time I'd invite Bill to chime in at any time.

-Glen


Glen,

E-mail sent
shotgun1
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Posted: 3/23/2007 9:32:27 AM

Originally Posted By Brazos_Jack:

Originally Posted By shotgun1:
Recently had a long conversation with Tom Lyons of MGI regarding the use of AA bolt in 7.62x39. He in turn had a long conversation with Bill Alexander. I am in the middle of similar conversations with Bill. I think you might be incorrect in assuming the AA 6.5 Grendel bolt won't work as a replacement for 7.62x39. I won't reprint Bill's answers to my questions in a public forum as I know he monitors these threads and apparently has chosen not to air his view. I'll summerize in confidence to anyone who'd like to contact me off board. In the mean time I'd invite Bill to chime in at any time.

-Glen


Glen,

E-mail sent


Eyes on for reply
Know what you Know and Know what you do not Know.
Never fight a battle when Nothing can be gained by Winning.
No One is thinking if Everyone is thinking Alike.
Always keep something in Reserve.
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M9Powell
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Posted: 3/23/2007 1:25:24 PM
[Last Edit: 3/23/2007 1:31:23 PM by M9Powell]

Originally Posted By shotgun1: I think you might be incorrect in assuming the AA 6.5 Grendel bolt won't work as a replacement for 7.62x39.
-Glen



If as reported here in an earlier thread, its a CMT 7.62X39 bolt with the recess cut 11 thousandths deeper, yes you could make it work. If you were cutting the chamber, you could just cut it .011" shallow. If you are using a barrel with the chamber already cut, you might juggle barrel extensions to get headspace closer too spec. If you were using handloads only, you could easily adjust your dies to make it work. I just don't understand why anyone would want to do this. The reason seems to be that they consider this bolt superior to a regular CMT 7.62X39 bolt. I've seen no evidence that this is so. Cutting it deeper would make it marginally weaker, or so logic would seem.
I'd go with the regular CMT bolt & have it shotpeened, then test it with some heavy loads, remotley from cover & then magparticle test it. That should be very near to identical to a Colt bolt, if it passes the magnufluxing. M9

PS If you really want a Colt bolt badly enough, you could buy an entire Colt 7.62X39 AR & rob the bolt out of it. I see them quite frequently at gun shows for sale, both used & new in the box. They ain't exactly cheap though. I imagine you could replace the bolt with a CMT bolt & resale it & recoup most of your expended cash though.
Grendelizor
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Posted: 3/23/2007 1:44:59 PM

Originally Posted By M9Powell: If as reported here in an earlier thread, its a CMT 7.62X39 bolt with the recess cut 11 thousandths deeper, yes you could make it work.


What do you mean, "as reported earlier"? You mean: As rumored earlier . . . by you!

For the record: CMT does not make AA's .50 Beowulf and 6.5 Grendel bolts. Period.

And I'm still not entirely convinced that CMT even makes 7.62x39 bolts, as far as that goes. What makes you think they do?

John

==========
6.5 Grendel: World's Best Combat Cartridge
M9Powell
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Posted: 3/23/2007 2:01:23 PM

Originally Posted By Grendelizor:
What do you mean, "as reported earlier"? You mean: As rumored earlier . . . by you!
John

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6.5 Grendel: World's Best Combat Cartridge


No there was a previous poster that stated he called CMT & even gave the name of his contact at CMT. The contact gave detailed specs for the bolt provided. I do rember they specified the use of the same steel that CMT had used in producing Colt 7.62X39 bolts. I suspect they have been made by various subcontractors as in lowest bidder. M9
twl
MGI Military:The Future of Small Arms Development
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Posted: 3/23/2007 2:02:46 PM
Okay.
I was advised by phone from the manufacturer, that AA bolts will work in a 7.62x39.

I am not the manufacturer of those bolts.
I don't have one here to measure, nor have I ever actually used one myself.

I'm going on what I've been told.
Please subject the bolt to your scrutiny and measurement before using it, for fit issues with your barrel, as you would with any new bolt.

Since the AA bolts are designed to be used at slightly higher pressures than the normal 7.62x39, it seems that they would have the necessary strength to handle the 7.62x39 loads encountered in commercial ammo.

From what I've been told, there is a backorder situation on the AA bolts, and that it may be a while before you could get one.

That's all I know about it, folks.

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M9Powell
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Posted: 3/23/2007 2:07:04 PM

Originally Posted By Grendelizor:

And I'm still not entirely convinced that CMT even makes 7.62x39 bolts, as far as that goes. What makes you think they do?

John

==========
6.5 Grendel: World's Best Combat Cartridge



When the falling out between CSS & AA first occured Arne clearly stated that his uppers used CMT 7.62X39 bolts. It was also shown & listed as a seperate item for purchase on his website. I haven't checked to see if its still there. But you could if you have doubts. I also know that you & him are well aquainted, why don't you ask him. M9
M9Powell
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Posted: 3/23/2007 2:13:39 PM
[Last Edit: 3/23/2007 2:15:10 PM by M9Powell]

Originally Posted By twl:

That's all I know about it, folks.



I belive in a previous conversation with you that you told me MGI was devolping a high-strength 7.62X39 bolt & in the interim that MGI was using the CMT 7.62X39 bolt. Any confirmation of that? And how is the work on the high-strength bolt coming? Thanks M9
twl
MGI Military:The Future of Small Arms Development
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Posted: 3/23/2007 2:24:06 PM
[Last Edit: 3/23/2007 2:36:35 PM by twl]

Originally Posted By M9Powell:

Originally Posted By twl:

That's all I know about it, folks.



I belive in a previous conversation with you that you told me MGI was devolping a high-strength 7.62X39 bolt & in the interim that MGI was using the CMT 7.62X39 bolt. Any confirmation of that? And how is the work on the high-strength bolt coming? Thanks M9


Yes, that's right.
The high-strength bolt project is an outgrowth of the .308 kit for our gun, which still is not completed.
Our bolt will not be in the price-competitive range with these other bolts, and will cost significantly more money. We may see something like this by mid-summer.

Regarding what we use now for our 7.62x39 bolts, we stock whatever we can get supplied with from other manufacturers. We do not make the normal bolts for any rifle caliber options at this time. We outsource all the bolts, currently.
CMT and DPMS have both supplied us in the past, for 7.62x39 bolts.

Regarding the materials used by CMT for their bolts, Carpenter 158 is the steel which is called-out in the mil-spec, and that is what CMT uses. I don't know specifically what DPMS uses for bolting steel, but the Carpenter 158 is available and inexpensive, and I wouldn't see any reason for them to deviate from spec on the steel.

As far as AA is concerned, I've had many conversations with Bill Alexander, and he knows what he's doing. I would feel perfectly confident in any bolt that I sourced from Bill, or any other parts, for that matter. Bill has had a wealth of experience in military weapons testing and knows about engineering parts. His name is staked to his company's products. He is not going to market an inferior or dangerous product, and I'm sure about that. Whether you personally like him or not, his experience or capability is not in question.

If you have questions about fit for your chamber, then by all means check it out before using it. If you are reaming a chamber for a custom gun, you can/should ream the chamber using the bolt you will use with the barrel.
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or email twlyons@juno.com
CALL ME TO ORDER YOUR MGI PRODUCTS !!!!!!!!!!!!!!!!!!!!!
M9Powell
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Posted: 3/23/2007 2:35:45 PM

Originally Posted By twl:Our bolt will not be in the price-competitive range with these other bolts, and will cost significantly more money. We may see something like this by mid-summer.


If your bolt is significantly stronger than a normal 7.62X39 bolt then its worth more. I want one ASAP. I feel I must tell you though that I don't really see your project of getting 7.62 NATO into the AR-15 as feasable. I hope I'm wrong though. I do have some thoughts on how your work in this area would be useful if I'm proved right however. M9

PS I love your lowers. Now if you could work on the price a little.
M9Powell
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Posted: 3/23/2007 2:40:28 PM
[Last Edit: 3/23/2007 2:42:49 PM by M9Powell]

Originally Posted By twl:
Regarding what we use now for our 7.62x39 bolts, we stock whatever we can get supplied with from other manufacturers. We do not make the normal bolts for any rifle caliber options at this time. We outsource all the bolts, currently.
CMT and DPMS have both supplied us in the past, for 7.62x39 bolts.



I suspect that AA's bolt procurement process is VERY SIMULAR too your own, with the exception of cutting the case head recess deeper. M9
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