I bought a Guatemalan contract pre sample AR-10.  It has one issue the rear sight spins.  I figured it was missing probably a roll pin (there are two holes in the rear of the upper forging, one for a rear sight windage screw and the other presumably for a roll pin keeping the sight oriented but thats a guess). I have the Armalite AR-10 history book and it has one not legible parts schematic.  

If anyone knows what size the pin was or what kept the rear sight from spinning let me know via pm please.  

Otherwise I can probably figure it out when it is transferred but it would be cool if anyone has knowledge of that or reference material like an early manual or just knows the answer or something.

I can’t remember and my cell pic didn’t get the serial.  It was right around 3200. The seller is going to paper form it in the mail so it will be a while to see it.

That schematic is bad ass.  Thanks for the help.  

I didn’t pay much attention to the number. I figured it would show up in the picture but it didn’t. I think the first two numbers were 32

How exactly do you know history on individual numbers?  

I sort of feel like the ar-10 is more of a great gun to collect than to really shoot much.

It seemed from the book that the guns didn’t get the more robust bolt lugs until sometime into the portugese ar10’s probably in the 4000’s or something.

That seems to imply the bolts had an integrity issue and weren’t ideally safe.  

The same book does talk about the sales guys shooting a lot of rounds on the sales demo guns though.  

The seller mentioned he had only shot it once or twice and that it was really tough to control on full auto.  That makes sense since the rifle doesn’t have the big recoil compensator and is fairly lightweight.

I agree a collectable gun shouldn’t be a high rd count shooter, but 3000 rds is pretty low.  Serial 1002 was a hand built prototype on the same design and went 5564 rds before a barrel failure, and then 7500 rds in an austrian test once refitted with a new barrel.  

Maybe it had a new bolt for test 2, but it may not have, as stupid as Armalite was at poorly outfitting guns for military trials.  The book mentions a barrel and handguard replacement but not a bolt, so it may have been the same bolt.  

The first 5664 rounds were fired of a experimental higher pressure armor piercing round.

The book mentions two rifles completing 7500rd tests successfully, also talks about breakage of lugs in tests over 10,000 rds.  Also mentions accuracy loss of .2moa over 6000 rd endurance tests. Implying shorter tests that didn’t produce bolt failures as they weren’t mentioned.  

So its obvious the bolt wasn’t as strong as they wanted it to be, but not necessarily horribly inadequate either.

They did mention a few freak short rd count failures traceable to poor heat treatment at a different vendor in CA.  I would assume the Dutch tightly controlled heat treatment at the state run plant like they did everything else so probably not going to have freak failures on Dutch parts.

Probably a good idea to load low pressure as if for an m1Garand for example where in 3006, people commonly load 100-150 fps reduced velocity loads for M1’s.

When its not the only machine gun you have, it’s probably ok to baby it a little so you don’t wear out an original gun you can’t get spare parts for.  

I think its cool to keep the guns surviving too.

There are a lot of other machine guns that have way better parts support.