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View Full Version : Upper/Lower receiver play - replacement method for the front O-ring trick!


missiontrails
10-02-2009, 7:09 PM
By no means am I supporting the FUD that looseness between upper and lower receivers decreases accuracy. However, I decided that if I could find a "natural" way to snug my fit, utilizing ONLY necessary parts, I would do it. I WILL NEVER put a red marshmallow in my lower, nor will I put tiny irrigation o-rings around my front upper lug to create a temporary solution. I calipered my existing pivot/takedown pins, and the measured .2475 in diameter, and when you push one of these pins through one side hole of the lower, they have some play, which IS milspec by design. I thought that if I could find some pins that are a pinch wider in diameter, there would be no play. Armalite sells National Match "oversize" pivot/takedown pins on their website for use with standard lowers, and they are advertised as being +.001 larger than standard. I bought a pair. They both measure EXACTALY .250. I started with the pivot pin install. I rubbed the pin with lube, and then needed to lightly tap it into place with the upper installed. This pin alone completely solved the slight bit of rocking, and the upper and lower now fit like a glove. I will continue to use the KNS push button take-down pin in the rear that measures .2475, that will keep the stress relieved at the rear lug when firing the weapon. Not that it was a problem, but my fit is better than milspec now. Many people have reported a similar effect when using YHM EZ-Pull pin sets, but those pins are not machined larger, they just have an extra thick and gritty parkerized finish, that will probably eventually wear thin...

tomd1584
10-02-2009, 7:36 PM
Lol if it makes you happy....seems like you're disecting EVERY party of your rifle.

I'm glad you're happy though.

-tom

missiontrails
10-02-2009, 7:40 PM
Lol if it makes you happy....seems like you're disecting EVERY party of your rifle.

I'm glad you're happy though.

-tom

Yes, I know... I'm just bored:). You just know a bunch of OCD people are gonna jump on this method though.