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Oh no, not another lube thread! Read this first: Lubrication 101.
I have always tested bolts by placing it in the locked position, holding the lugs with the bolt and carrier vertical and seeing if the suspended weight of the bolt carrier will cause the bolt to unlock. The other way is with the bolt in the unlocked position place the bolt face down on a table, again so the bolt and carrier are vertical, and see if the weight of the bolt carrier will cause the bolt to move to the locked position.
I use air pressure and oil to check the seal when I install a carrier key. I place oil around the base of the carrier key, hold the bolt in the locked position with my thumb and use an air gun that has the rubber end to pressurize the carrier key with 30-45 psi and look for leaks around the carrier key base. If I do not find a leak then I stake the carrier key.
ETA: As others have pointed out the gas rings failing the test is merely an indicator that the gas rings may be worn, or about to wear out, not a definitive answer. I do change them if they fail the test though. If you do not have gas rings on hand then taking the gun out of service until they come in is a personal choice/decision. You must decide on how worn the rings seem to be and whether or not you have a replacement gun to put in service.
Last edited by az doug; 01-28-12 at 21:06.
Not all gas rings are created equal either.Ive had some USGI type rings a couple years ago with odd shaped ends that were best described as slash cut like // rather than the usual tear drop shape.These rings failed very early,losing tension and collapsed in at the ends at approx. 500 rounds on two different assemblies.Replacements from the same OEM had the same results.These rings were very soft material.
All I use is the McFarlands now.Sourced mine from G&R Tactical,Armalite,DPMS(Midwayusa).
Here are a few previous discussions on the subject:
https://www.m4carbine.net/showthread...ight=McFarland
https://www.m4carbine.net/showthread...ight=McFarland
https://www.m4carbine.net/showthread...ight=McFarland
https://www.m4carbine.net/showthread...ight=McFarland
https://www.m4carbine.net/showthread...ight=McFarland
See last question of the Armalite FAQ regarding the McFarland ring:
http://www.ar15.com/forums/t_2_27/16...ome_FAQ_s.html
and
http://www.armalite.com/ItemForm.asp...e-c76eaa613b0a
http://www.armalite.com/ItemForm.asp...e-c76eaa613b0a
Last edited by Blankwaffe; 01-28-12 at 22:25. Reason: ETA
Glock Certified Armorer
Armed Protective Services II
Just 00.1cent,
1500 more or less with one piece gas rings in f/a. No problem. Still passes test(did this last night on that bolt). Just my one sample from one year ago. FWIW. YMMV
And that is my concern. My buddy's shorty has over 3k rounds and still passes the field test. I'm starting to think the inside of the carrier is out of spec. Is there a way to check that?
I have a McFarland ring on it now. It lasted 700rds before failing the field test.
It is interesting to see Armalite spreading the idea that if the gaps in the 3 rings of traditional gas rings are lined up you get leakage. Hasn't that been debunked?
You see, that is a problem. If the manufacturer of AR style rifles is putting that out, it's a problem because it will be believed.
If you have a proper bolt carrier and you insert the bolt into the carrier you can feel slight resistance as it enters and is close to closing. This is the gap in the rings actually compressing (much like rings on a piston in an engine).
Where I could see it being an issue would be a carrier with an out of spec internal diameter.
Owner/Instructor at Semper Paratus Arms
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Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com
Ive seen it mentioned by alot of manufacturers,if not most,both in print and verbal discussions.Most OEM's Owners Manuals has the same,mentioned at least once in PM and/or troubleshooting sections,including the U.S.G.I. -10 and -23&P which states "stagger ring gaps to stop gas lose" and "check for proper staggering of bolt rings" etc. very clearly.
Which is most likely,and my very best guess, the source for commercial manufacturers statements regarding the gas ring stagger topic.
Take it for what its worth.....right or wrong.
But yes it has been debunked.
Last edited by Blankwaffe; 01-29-12 at 17:59. Reason: ETA
Glock Certified Armorer
Armed Protective Services II
Staggering isn't a bad idea, not from a gas loss perspective, but to prevent the chances of the rings from binding up when inserting the bolt.
Here is a little gas lesson l learned today. I have an AR that I was using for 3 gun competition and has run 100%. After using it last I cleaned it and put it in the safe. Took it out yesterday and it's short stroking. Took it home and checked the gas rings, found them very worn, in fact the rear ring was so worn that the ends were gone and there was a huge gap. So I replaced them with some Colt gas rings. Took it to the range today, Short stroking again. Pull the BCG and checked the gas key, seems tight. Check the gas tube roll pin to make sure it didn't rattle out. Roll pin installed and minimal carbon at block and gas tube. Put a wrench on the rear key screw, tight. Wrench on front key screw seems tight, turn a little harder, moves and doesn't tighten. Hmmm, broken screw! Pull it apart and have to punch out the screw heads because of the staking.
Lesson learned: with a broken screw the key can still feel tight when attempting to move by hand. Screws will still feel tight due to proper staking.
Now to get to the drill press and try to get that hard ass broken off screw out!
Until that day,
Darkop
Right or wrong, black or white. Cross that line, your gonna pay, but in the dawn before the light, we live or die by shades of gray.
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