Gas key screws

[springfield30-06]

I've done some research here and on other sites about staking AR-15 gas keys but still have some questions...

I have a Bushmaster and I plan to torque the screws to 55-60 in/lbs as this document states Technical Note 47: Increased Carrier Key Torque and then correctly stake the key.

I have read somewhere that someone measured the Bushmaster screw heads to be a little small, should I get new screws? Should I use adhesive like Locktite on the threads? Do I need to get a new carrier key all together or can I re-use the factory one since the staking job was done so shallow?

Thanks!!!

 

[MCMXI]

I have a Bushmaster and I plan to torque the screws to 55-60 in/lbs as this document states Technical Note 47: Increased Carrier Key Torque and then correctly stake the key.

What size screws were/are Armalite using? I use WIHA torque screwdrivers (7.5~20 in-lb and 20~70 in-lb) and when I installed a new carrier key from POF on my DPMS bolt carrier, one of the screws sheared off at less than 45 in-lb. I found that spec (45~50 in-lb) on this forum. Luckily I was able to remove the broken screw. I ended up using one of the original screws as a replacement, torquing them to 35 in-lb and staking them. Maybe the POF screw was defective, but 55~60 in-lb seems like a lot for such a small screw ... a #10 I think. There's plenty of information out there for torque specs for screws/bolts with different diameters, thread pitch and material. I have a hard time believing that 55~60 in-lb is suitable for common carrier key screws.

DPMS seems to recommend 35~40 in-lb for their screws.

http://www.midwayusa.com/viewProduct/default.aspx?productNumber=542658

 

[Bartholomew Roberts]

The gas key screws are supposed to be hardened and meet certain specifications. You don't want to use just any screw that fits or you can have problems with shearing them off. The NSN for the screw is 5305-00-992-7284. CAGEC is 19204. Part Number 844508.

The TM-9 calls for 35-40 inch pounds as the proper torque for gas key screws. Page 3-37 of the Armorer's Manual details the military approved way to stake a gas key.

However, Mark Westrom who runs Armalite was formerly Col. Mark Westrom, U. S. Army Ordnance and he knows a thing or two about making the M16 family of weapons run well. If he says 55 inch pounds is the way to go, I'd listen.

 

[MCMXI]

The TM-9 calls for 35-40 inch pounds as the proper torque for gas key screws. Page 3-37 of the Armorer's Manual details the military approved way to stake a gas key.

If I'd followed this advice, I probably wouldn't have sheared a screw.

 

[dfariswheel]

I've found that it's always smart to follow several rules in cases like this.

1. Don't use non-gun parts even if they look just like gun parts.
Whenever possible use parts supplied by the gun maker.
Screws may look like the screws used on guns but are usually not made to the same standard.
Usually, the difference in price is for a reason, and it's not because the gun company is selling hardware parts at big mark ups.

2. Do things the way the maker of the gun recommends.
I don't care what an ordnance manual says, if the maker says to do something differently, it's usually for a good reason.
It may be a standard looking AR, but the maker may have done things differently than a USGI contract supplier does it.
If the maker of the firearm says to stand on one leg while tightening a screw, a smart person stands on one leg.

Fail to follow these simple rules and don't be shocked when things go bad.
NO ONE knows more about a specific firearm than the company that manufactured it.