I like an idiot bid on a Bushmaster 22 lr upper and forgot about the pin size difference. Will an offset pin allow the 22 upper I am bidding on to work on my Colt 6290 with .176 pins when the upper takes .155 pins. Thanks for  the help
Pat

I don't have a Bushmaster .22 upper, but I do switch small pin uppers between my Colt Green Labels (large pin) all the time.  The BM upper should be the same dimensionally as any small pin upper.  I can't see why the offset pin would not work! Good Luck, ALLONS11

Hey Pat,

Well, I don't wish to offend, but the diamentions you quoted in your post are closer to the fire control pin diamentions (.154" being Mil. Spec. diameter and .169" being Colt's current production diameter).  I'm guessing your concern isn't fire control but front pivot pin (.250" being Mil. Spec. diameter and .320" being Colt slabe side diameter).  Since Bushmaster uses Mil. Spec. front pivot push pins, you could have the .22lr upper switched to a slab side upper.  Or since there is very little recoil with the .22lr, I would think, if you were careful and did it very slowly, you could open up the front pivot hole on the BM upper.  I personally would get an old SP1 upper receiver and have the uppers switched.  The SP1 receivers have been going cheap.  I would think you could sell the BM for the cost of switching them.  And with a switch you'll have a gray instead of black upper to match your gray lower.

I have went the Ceiner .22lr route with my .22lr project.  Since I have a M16, 10rds isn't enough.  I bought a Colt A1 barrel with the 1/12 twist.  I had it cut down to seven inches and treaded.  I installed the barrel with the original flash suppressor in a Colt A3 upper.  Billbo is a great sourse for Colt uppers.  You might want to check with him if you are switching uppers.  I placed an old Bushnell HALO sight on top.  The .22lr kit has a very fast cyclic rate so 25rds goes really fast.  It is a pile of fun and a great way to introduce new shooters, especially those of small stature, to an AR.  Good luck with your .22lr project.

Scott

Your right  I am an idiot. The specs I quated are from the fire control unit.  The front pivot pin was what I was concerned with and I got the two figures mixed up in my memory from the armorers course. I found out my pivot pin is the industry standard .250 pins.  I am still waiting for the upper to come in. Anyone know if there are high cap mags in the works for it.
Pat