bolt key bolts help [Archive] - M4Carbine.net Forums

cz7

10-29-09, 20:22

the use of grade 8 or 12.9 - best one ?and torque specs.... my young man. bolt carrier popped the head of one of gas key bolt !

Eric

10-30-09, 06:27

As far as I know, grade 8. The spec is 35-40 inch pounds. Armalite has a Tech Note recommending 50 inch pounds FWIW. Source. (http://www.armalite.com/images/Tech%20Notes%5CTech%20Note%2047,%20Increased%20Carrier%20Key%20Torque,%20011125.pdf) Screws are single use items, to be replaced once torqued. Depending on the condition of the gas key, you might want to replace that as well, then properly stake it.

cz7

10-30-09, 17:14

As far as I know, grade 8. The spec is 35-40 inch pounds. Armalite has a Tech Note recommending 50 inch pounds FWIW. Source. (http://www.armalite.com/images/Tech%20Notes%5CTech%20Note%2047,%20Increased%20Carrier%20Key%20Torque,%20011125.pdf) Screws are single use items, to be replaced once torqued. Depending on the condition of the gas key, you might want to replace that as well, then properly stake it.
thank you for the help its testing time !
i found some grade 12 but no grade 8 --aircraft grade --young man. uses red loctite red a pain to remove them or what's left them !!r and r both them and staked !

Heavy Metal

10-30-09, 19:11

Would not grade 12 bolts be superior?

TheGhostRider

10-30-09, 20:34

Would not grade 12 bolts be superior?

It's possible that grade 12 would be too hard.
The grade of a bolt not only determines it's hardness but also it's elasticity (ability to stretch).
When one torques a grade 8 bolt of a given size it has a specific range determined by grade and size of bolt.

If one were to jump to a grade 12 bolt, attempting to reach the proper torque based on that particular fasteners grade and size may exceed the the bolt carriers ability to maintain its thread integrity... (strip the holes).

I feel that if a grade 12 bolt were superior to the grade 8 then the TDP would call for a grade 12 and it would be commonly used.

I would stick to grade 8 bolts, proper torque and proper staking.

Just my 2 pennies...

fdxpilot

10-30-09, 21:52

I feel that if a grade 12 bolt were superior to the grade 8 then the TDP would call for a grade 12 and it would be commonly used.

I would stick to grade 8 bolts, proper torque and proper staking.

Just my 2 pennies...

Just remember, the TDP (i.e. Mil-Spec) just spells out the minimum specs that will get the job done to military requirements, not the absolute best materials and parts available. While most discussions of mil-spec concern manufacturers who don't even meet the minimum specs, not being mil-spec could also mean using parts or materials that exceed the spec, such as a grade 12 bolt.

As an example, a 24" stainless steel 1 in 12 twist fluted barrel is definitely not mil-spec, but could be exactly what you want for shooting 40-45gr soft points at prairie dogs or coyotes.