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Posted: 3/2/2006 1:47:16 PM EDT
I have a Colt HBAR sporter, with .315 dia front take down pin, with a A2 upper. The replacement upper A4 that I purchased, (as well most available) seem to have .250 diam holes.
It appears that milling the .250 hole out will not leave suffiecient material in the A4 upper, does any one know of an addition process to remidy this problem?
Link Posted: 3/2/2006 1:59:07 PM EDT
try this:
DPLR-OS2 $ 5.95
Offset adapter front pivot pin
to mount standard .250 pin upper assemblies on large pivot pin Colt lowers
here: www.jprifles-store.com/menu_prod.php?indx=11
down towards bottom
Link Posted: 3/2/2006 2:30:36 PM EDT
Yeah, you'll definitely need an adapter. Not only are the PIVOT pin holes different sizes, but the centers of the holes aren't in the same place.
Link Posted: 3/2/2006 2:32:38 PM EDT
Thank you for the quick replys, this is alot better of an alternateive than I thought it would be.
Link Posted: 3/12/2006 9:20:08 AM EDT
I am going through the same thing also. I also have a Colt Sporter with the large front hole. I also just purchased a RRA flat top upper complete assembley with the milspec smaller front hole. I was told about the front pivot pin offset adaptor and have one on order, but my question is, Am i taking any chances of breaking the lowers flanges off by using this set up? My greatest fear is breaking this lower as it is a Registered pre ban in Calif. If i ruin this lower i'm screwed here.
Link Posted: 3/12/2006 1:23:22 PM EDT

Originally Posted By Gunfighter01:
I am going through the same thing also. I also have a Colt Sporter with the large front hole. I also just purchased a RRA flat top upper complete assembley with the milspec smaller front hole. I was told about the front pivot pin offset adaptor and have one on order, but my question is, Am i taking any chances of breaking the lowers flanges off by using this set up? My greatest fear is breaking this lower as it is a Registered pre ban in Calif. If i ruin this lower i'm screwed here.



Just be gentle with it, as I'm thinking that some types of adapters bind upon hinging the upper and lowers open or closed. If you ever did break the flanges, Mike Klos could always weld it back like new. In fact, Mike could weld up your original large pivot hole, and redrill it with a genuine Colt drilling jig to small pivot specs. If guys are sending $10K full-auto SP1 lowers to Mike for the conversion, you should have no fear sending your Cali-registered lower.

American Manufacturing
Link Posted: 3/12/2006 1:35:02 PM EDT
A word of caution about those adapter pins.Don't over tighten them or you'll stress the metal and they will break later while your out shooting. It happened to me.No big deal.The replacement one I got I put blue loctite on the threads and tightened it up real snug but didn't torque it hard like the first one. Been working great for a couple of years.I do keep a spare in my parts box just in case. HTH,Nick
Link Posted: 3/12/2006 2:30:59 PM EDT
Yeah, i dont want to change the hole size in the lower, because i have the original Colt upper, which is a 20" match HBAR. What i thought about checking into though was,,, maybe having the RRA upper machined out to match the large hole in the lower, you think this could be done? If i screw up an upper that can be replaced in Calif. I'm even thinkin maybe i should hop on this Calif band wagon of getting an off list lower just as a back up.
Link Posted: 3/12/2006 2:35:34 PM EDT

Originally Posted By Gunfighter01:
What i thought about checking into though was,,, maybe having the RRA upper machined out to match the large hole in the lower, you think this could be done?



No, as the centers of the large and small pivot holes are not in the same location -- they are offset.
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