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Sgt_Skrb_25 07-09-2013 11:32 PM

No good 7.62x39 Bolts left!!
Anyone have a line on good 7.62x39 AR bolts. All I can find is the MGI kit, but have heard of lugs and extractor breaks under 500 rounds. AR performance super bolts are not being made anymore, and same goes for LMT. All that's left is garbage.

purehavoc 07-10-2013 01:44 AM

I put another 120 rds thru mine on friday no issues with lugs , bolt still looks good. I will go pull it and snap a pic here shortly, thats roughly 340 rds now.
Maybe its because im getting older but my shoulder was bruised sat morning when I woke up. The days total was over 400 rds all rifle ammo

purehavoc 07-10-2013 02:03 AM

6 Attachment(s)
Heres a few pics.

purehavoc 07-10-2013 02:11 AM

And yes this one is on the conquest also to see how long it will continue to run without any love. AK style ;) I will say its beating the piss out of the deflector

Sgt_Skrb_25 07-10-2013 04:00 AM


Originally Posted by purehavoc
And yes this one is on the conquest also to see how long it will continue to run without any love. AK style ;) I will say its beating the piss out of the deflector

Nice work Pure, that's the Sota bolt right? I might end up with that one. Do you know if it is made of 158 carpenter steel? All the other bolts are not. I thing the superbolt was the only one. I need to get something soon. My parts are parts are almost finished getting cerekoted. I have everything but the damn bolt.

Sgt_Skrb_25 07-10-2013 04:02 AM

I think I'll start a build thread on my 7.62 a soon as I get the parts next week. I hope to have a bolt by then. I might just have I get the Sota

purehavoc 07-10-2013 12:47 PM

Yeah mines the Sota , I have no idea but Im guessing its not 158C , honestly its not that big of a deal , I got it bought cheap enough so if I have to buy another down the road no biggy
I think I will give them a call at 9:00 and find out for sure what its made of ;)

purehavoc 07-10-2013 03:05 PM

Hmm , this is pretty interesting and I did not know they made bolts from this material . 4142 CFHT Its used for ejectors and bolts according to the specs and looks like a pretty decent material

Heres the specs :

4142 CFHT is a chromium-molybdenun alloy steel that has been hardened to 27 to 32 Rockwell C and is ready to use while still machinable and of exceedingly high strength. The chromium content provides good hardness penetration, and the molybdenum imparts uniformity of hardness and high strength. 4142 resists creep in temperatures up to 1000 F and maintains its properties even after long exposure at these relatively high working temperatures. Other desirable properties include good wear resistance, excellent toughness and good ductility in the quenched and tempered condition. 4142 CFHT is produced in rounds with its ready to use hardness with no further thermal treatments necessary.
Carbon (C) Manganese (Mn) Silicon (Si) Chromium (Cr) Molybdenum (Mo) Phosphorus (P)

Sulfur (S)

0.4-0.45 0.75-1 0.25-0.35 0.8-1.1 0.15-0.25 0.04 0.04

cold roll bars conforms to ASTM A-193 Grade B7
Tensile Strength (PSI) Yield Strength (PSI) Reduction of Area Elongation in 2" Brinell Hardness
140,000 90,000 45 20 300

The above values are average and may be considered as representative of 4140 CFHT

4142 CFHT can be used for as wide variety of applications where greater toughness and wear resistance is needed over lower carbon grades. Typical applications include ejectors, back up and support tooling, cams, drill collars, bolts, stubs, couplings, reamer bodies, axles, shafting, piston rods, rams, hydraulic machinery shafts, gears, sprockets, valves, chain links, spindles, tool bodies, tool holders, tie rods, boring bars, machinery parts and components, etc. This material roll threads, knurls, and may be plated.

4142 has a machinability rating at 63% of B1112. Average cutting speed 95 ft/min.
4142 Prehard is not recommended for welding. It is best suited for welding in the annealed state, with preheating prior to welding and stress relieving after the welding operation.

4142 CFHT is pre-hardened to 27-32 Rockwell C (261/321 Brinell) and is used where no further heat treating after machining is needed due to the likelihood of warpage. 4142 CFHT can be flame hardened at wear parts to approximately 85% of a 1.00 carbon steel.

purehavoc 07-10-2013 03:42 PM

It looks as though the 4142 Tensile strength and yield strength is alot higher than 8620
4142 is 140,000 PSI tensile and Yield 90,000 PSI and a Brinell Hardness of 300 compared to 8620 steel . 100,000 PSI Tensile and 85,000 Yield PSI and a Brinell hardness of 185

I cant seem to find much on the specs of 158C :confused:

purehavoc 07-10-2013 04:43 PM

Found it better known and ANSI P6 tool steel
the 4142 is right in between the 158 and the 8620 but doing some research on the machining forums it seems as though there may be better choices than the C158

ANSI P6 / C158 alloy specs:

Tensile / PSI 165,000 , Yield / PSI 135,000 with a Brinell hardness of 352, 0.10% Carbon , 0.30% Silicon, 3.50% Nickel , 0.50% Manganese , 1.50% Chromium and a balance of Iron

Heres a link to some info on a machining forum

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