ok...maybe im dense and beating a very dead horse but here goes anyhow.

i have an old sp1 colt and it has the offending large hole in front. now before going further,,,i love my origanal sp1 in almost all respects.

i have always wanted to turn it into a flattop without the handle and front sight, but have always been stuck in the large pin area.

so here is my question at last...can i ream the small hole in the popular flattops that currently tease me with their cheap prices,,to the larger [ i believe .312 dia.] without ruining the complete upper reciever?

it seems like there is no noticeable stress or harsh preassure in this area to me and i wonder if there is enough meat in the forward lug area to ream to the larger diameter.

what makes me wonder about this is the pins that are for sale are offset with the middle area at the standard .250 diameter with the outside area of these pins at the .312 diameter. seems like the offset in the pin would make the reciever not line up properly. am i full of ^&(% or is the distance between the center of these holes the same on large pin recievers and small pin recievers? also is the distance from the rail to center of pin the same on both?...i know....questions questions questions...i have been perplexed about this long enough and will risk the fun poking to finally break down and ask.

ted

Or one could just get a bushing for his lower. I used a off set bushing on a older large hole upper to mate it up with a small hole lower worked well.

Another reason not to buy Colt products all their poltical correctness. So many other good AR makers out there.

I put a bushing on a friends and it's been A-ok. I was very skeptical but it has lasted at least 3k rounds with no issue.

BTW: Step up to LMT and/or NOVESKE and dont be bothered anymore

quote:

Can I ream the small hole in the popular flattops that currently tease me with their cheap prices to the larger [I believe .312 dia.] without ruining the complete upper receiver?

Yes. I have done it with a simple 5/16 drill. Just hold the two halves nice and tight together (bungee cords come to mind) and proceed slowly. There is also a neato pushpin that replaces the cumbersome double screw. I think I got it from DPMS or from Brownells. Just fifteen bucks. You wanna see some pictures of it?

The offset screws work fairly well, but they will bind the halves together if they rotate too far inside the large-hole upper. If you plan to keep the gun forever (I would in this political climate), I'd just drill the small hole out to the bigger hole and go 'head on...

http://www.brownells.com/.aspx...BUTTON_RECEIVER_PINS

They used to have adapting pins for the small hole upper to adapt to a large hole lower or vice versa. You might want to check with Colt, due to their sporter model with large holes.

Just checked Brownells site, they have the adapter screw for the Colt Sporters Part # 231-015-016.

I know several people that have used the adapter pins with no problems.

at last,,,finally ordered the adapter pin from brownells. hoping for the best. more when it gets here.