What were original M16 bolts made of? C158 didn’t exist in the late 50’s, did it?
Were they phosphate, or chrome? When did chrome bolts come into play? As I understand it, chrome bolts are still “deployable”, is this correct, just not chrome carriers?
When were chrome-bolts no-longer used, and why?
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Just get a BCM and cowitness it.
Good info…
I was told that the original bolts were made from 9310. This has been mentioned many times before in the hundreds of other threads regarding bolts. If you do a search on the net, there are original pics of the first USAF M16’s which had chrome bolt carrier bodies and bolts as well. It was my understanding that the chroming process back then was less than desirable and there were issues with flaking of the bolts.
Thanks! Very interesting that they started as 9310!
Also curious…was the chrome plating issue the reason that the first M16’s in Vietnam were not chrome-lined bores and chambers? Did they then solve their issues with chrome plating and issue them as such? What about the bolts, were they then chrome-plated again, as well? If not, did it ever start back up (the chrome-plating of the bolts), or was it a one-time deal? It would seem it started back up, as I read somewhere that chrome-plated bolts were fit for use outside of base perimeter, while carriers plated as such were not.
I heard that the chrome was done away-with due to some corrosion under the chrome plating, which was apparently the result of poor manufacturing/plating processes and not of the actual chrome plating itself.
It is my understanding that the initial removal of the chrome, the magazine issue and the change in propellant were all part of the cost cutting measures. The chrome issue as I understand it was more of a bolt issue than that of the carried, etc… Which makes sense since the carrier is a low stress part where as the bolt isn’t since the lugs pass through the barrel extension.
I believe if you read the 23&P that is mentioned for Air Force guns only or some such nonsense. Probably because they think that the enemy will see your BCG and you will be compromised…whatever.
No chromed bores and chambers existed in service rifles in WWII. The lack of chromed barrels in the early M16s was due to a lack of understanding by Def. Sec. Macnamera who thought army ordinance was trying to delay the adoption of the M16 by specifying chromed barrels who, to be fair, were actually trying to sabotage and delay adoption of the M16. In short it had nothing to do with the technology at the time, it was all political.
Was Mr. Stoner’s original “final iteration” (the weapon first “finally” submitted after revisions/testing) equipped with a chrome bolt, per Mr. Stoner’s recommendation?
It was, as is typical of such things, a stinking stew of reasons, good and bad, and of personalities, likewise.
McNamara correctly viewed Ordnance as wanting to kill it, and willing to do anything to stall until they could come up with something better.
Stoner had demo’d the rifle around the world, and it had not malf’d. So, the whiz kids McNamara installed, simply told Ordnance, every time something “had to be changed/improved” that’s not the rifle Stoner showed us. that rifle never failed, it is perfect, you’re just trying to be dicks about this.
It took actual problems, in the jungle, to get some of them to admit they were wrong. That didn’t make Ordnance right, however.
This is a pretty thorough technical history of early M16 modifications, although some pages are hard to make out:
I thought the original bolt head material was 8620?
chromed bores and chambers existed in service rifles in WWII.
In WW2 The Japanese Arisaka’s (before they got crunched for resources) had both a Chrome Bore and a chrome Bolt head. I have one and it still looks new inside, no flaking or rust under the chrome or any mess like that. So at least the Jap’s knew how to do it right back then. I don’t think any other country in WW2 had chromed bores.
The original bolts were chrome and not the same design… Search gun of the week here and look at my postings of early xm16 and 607s
No hits.
Is it truth, or myth that a chrome bcg will cause wear at a faster rate in the upper vs. a phosphate bcg?
How so? The 607 bolt I saw was Nearly identical to the current aside from chrome
My sample of 3 bolts and 3 cam-pins arrived direct from Young. Machining is beautiful, finish is very smooth. All bolt-tails mic’ed 0.250" diameter, and all bodies at the contact point mic’ed 0.5280". The cam-pins each mic’ed 0.310" diameter. I noted no variance between my 3 sample’s on these 3 critical points, although 1 bolt had a bit of flash in the firing-pin channel, which I displaced by inserting the firing pin and the cam-pin by hand without any un-due force. It is now just fine. Likely someone less detail oriented never would have cared to notice, nor would it have mattered.
All of my bolts are marked “MPI”.
So far, the facts:
-Dimensionally correct.
-MPI (individually, not batch).
-No HPT (A good thing, IMO).
-Grade 8 bolts are used on the gas-key/carrier (for all of you who feel that the charging-handle and gas-key have any relation…they don’t, the charging handle interfaces with the BCG unit only at the front, about 1/4" back from the face of it, using that “step” machined in said carrier. Go look at your CH and that step…the wear-point on the CH will be plain to see).
-Carrier is ground AFTER heat-treat.
-Bolt is C158 steel, per mil-spec.
-All plated parts are IMMEDIATELY baked to prevent hydrogen embrittlement.
All of this information has come to me through powers of science and observation (regarding measurements), and from Mr. Young, regarding technical data discussed via telephone with him.
It appears that this is the best I can find for a chrome BCG, short of an original, and this is arguably better, IMO.
How COULD a slicker surface increase wear? 