SRC bolt, S7 tool steel

[Zeneffect]

https://www.srcarms.com/bolts/6.5-grendel-type-2-bolt

Discuss.

Lifetime warranty makes me want to get spicy... lug design makes me want to stay away because I don't want to have to deal with the warranty every week.... but it's s7 so that's a new one to me.

[grayfox]

So... are we saying that use this bolt, and you can go to higher load... 60,000 psi?
Or do the barrel extension lugs now become the part to fail under that scenario, thus no real extra benefit?

I'm not schooled in properties of S7 steel vs carpenter 158 or 8310 or whatever, nor whether doing the DLC coating - while it increases hardness, does it also increase brittleness under bcg operating environment, or what else does it do, ie, no such thing as a free lunch.

How many times has this been tested to say, 10,000 cycles, under 52Ksi or better, to 60Ksi chamber pressures.

when they say s7 is best thing since sliced bread "when heat treated 'properly' ".
What is this proprietary heat treatment and what else does it do to the material that we don't know about.

All questions, no answers... so idk if it's something to jump on or not.

[grayfox]

And that "lifetime" warranty, is only against mfr defects. So first time you send it in, they will say "you used it wrong" or something like that. So "warranty" is kind of iffy if you ask me.
As opposed to Vortex's lifetime warranty, no questions asked, you break, we fix.

[grayfox]

This adjustable gas key thingy in their bcg might be more intersting...
the adjustment screw is in the back of the gas key.

SAGRS AR-15 Xtreme Performance Bolt (XPB) Carrier Group in Nib-X (srcarms.com)

[Zeneffect]

I do like their carriers enough to own 4 though I know a s7 carrier is a silly thing... they are stupid easy to clean, everything just wipes off with no effort. If you want any closeups of a sagrs I have one bnib.

Maybe I'll build an arc, give the bolt a spin, abuse the living hell out of it, break it, then report back. Should be able to test quite a few things within that cycle.

[grayfox]

If you do, I'd be interested in the results.
I'm not opposed to them, just cautious. More questions than answers, is all

[Zeneffect]

Same here... no info or testing. I'll be willing to break a bolt for the cause, I doubt they would deny warranty given their previous heat treat issues.

[LRRPF52]

They had a lot of broken 5.56 bolts with the S7 Reliabolt, not sure how they addressed it moving forward.

S7 is better on simpler parts that don’t have articulate and detailed features (like AR-15 bolt lugs under load). Works fine on the giant Barrett triangular M82 bolt, not so much on AR-15 bolts.

S7’s elasticity modulus varies dramatically (it gets brittle) as the temperature goes down as well.

Bill A. and I discussed it a number of years ago, and he shared some interesting insights into its capabilities and limitations in bolt applications.

He also talked about the importance of matching the bolt material and strength to the barrel extension, so that a particularly strong bolt or bolts with certain surface treatments don’t cause undue wear on the extension (like with NiB).

[SDguy]

Did Bill A offer a better alternative to S7? I have worked with S7 a little bit years ago for making shear blades for corrugated steel. Was nice to work with in terms of machining. If Cost was not a factor & or machining ease, A2 might me most preferred hardened to roughly 58 rockwell for a great mix of toughness & hardness. Would be interested in reading more on temperature effect on brittleness of various materials at various hardnesses.

Would also be interested on pro's & cons of meloniting the bolt.

[LRRPF52]

There’s a new Low Plasticity Burnishing process developed to double the life of M4 bolts for the military, with interesting papers on it published by RDECOM:



Using existing alloys like C-158 or 9310 with the LPB process would be the most economical approach, based on the testing they have done with those bolts already.

They increased the failure point to 26,000 rounds with the M4, vs 13,000rds for standard bolts during the test with control group.