Shot peening

[Slater]

Back in 1968 there was a proposal (by Colt, apparently) to shot peen both upper and lower receivers to "provide a more durable finish and to aid in the prevention of
exfoliation and inter-granular corrosion". It seems this was never approved by the Army, but looking at it in 2017 would this make sense or is it just something that was impractical/theoretical?

http://www.dtic.mil/get-tr-doc/pdf?AD=ADA953121

[MegademiC]

It might be "better" but you can't justify the cost. What real benefit would it provide?

[GH41]

It might be "better" but you can't justify the cost. What real benefit would it provide?

The cost would be minimal. Shot peening is similar to sandblasting but beads of steel or ceramic are used. The beads don't abrade the surface they peen, work harden and stress relieve the metal's surface. Having said that I can't see it even being worth a dollar for a somewhat disposable receiver set. Maybe Colt would benefit from doing it to their civilian receivers... It would probably improve the shitty aesthetics Colt is famous for.

[WS6]

Back in 1968 there was a proposal (by Colt, apparently) to shot peen both upper and lower receivers to "provide a more durable finish and to aid in the prevention of
exfoliation and inter-granular corrosion". It seems this was never approved by the Army, but looking at it in 2017 would this make sense or is it just something that was impractical/theoretical?

http://www.dtic.mil/get-tr-doc/pdf?AD=ADA953121

3/4 of that document looks more like *please waver our qc faux pas*

[tom12.7]

That's an old document that was a proposal to reduce displacement that could have been done in other ways, compared to some better options that we've seen already. Old news.

[Slater]

That's an old document that was a proposal to reduce displacement that could have been done in other ways, compared to some better options that we've seen already. Old news.

True, but I'd never heard that they wanted to shot peen anything other than the bolt.

[tom12.7]

No, they offered that option. It was less of a cure and more of delay. Today, we have better options.

[Slater]

Well, something must be working. I've never heard of "exfoliation and inter-granular corrosion" being much of an issue with the M16/M4 family.

[MistWolf]

It was a problem when early AR receivers were made from 6061 forgings

[shotpeen]

[QUOTE=Slater;2505874]Back in 1968 there was a proposal (by Colt, apparently) to shot peen both upper and lower receivers to "provide a more durable finish and to aid in the prevention of
exfoliation and inter-granular corrosion". It seems this was never approved by the Army, but looking at it in 2017 would this make sense or is it just something that was impractical/theoretical?

http://www.dtic.mil/get-tr-doc/pdf?AD=ADA953121[/QUOTE

The dimples caused by Shot Peening also create more surface area for coatings to bond to the part.

In addition to the bolt, the extractor is also peened. In a addition to increased fatigue life peeing also helps lubricants stay of the parts surface further preventing wear. Http://Peeningtechnologiesga.com

[MegademiC]

...

That is funny.

Staying on topic, yes, shot peening does great things, but I don't think one can quantify its value on mil-spec ar-15 receivers.

[lysander]

3/4 of that document looks more like *please waver our qc faux pas*
Normally, most of those proposals would have been addressed during testing, development, and low-rate pre-production. Unfortunately, the AR-15 was sold to the USG as a "fully developed system", and it wasn't until they started to make them in quantity, that both the Government and Colt found out it wasn't.