I have a preban colt sporter lower with the pinned "colt stamped" sear block and wish to convert to a 9mm upper.
I was looking at the colt factory parts website and noticed the rear portion of the 9MM bolt carrier is ROUND (my currently 5.56 carrier is 1/2 circle)
1. Do I need to get the block removed or ground down before I can use the 9mm carrier?
2. If so, is it possible to grind the upper portion of the sear block away, so the full circle carrier will clear the sear block, or will it need to be removed totally?
3. Or is there a 9mm carrier with the 1/2 circle rear?
Colt made some 9mm Sporters, as I recall. So it can be done. If you screw with the weight of the carrier, you will probably have reliability issues. I advise you pay the small fee and have the block removed. I dont know more. I'm not a Colt guru and I sold my Colt Sporter because of the block and pin bullshit.
Just for grins, here's what JAFO found for me over on [url]http://www.biggerhammer.net[/url] dealing with the patent of the stupid-assed sear block:
(that's in one of the patent PDFs over there) So. There you have it. That block needs to be (at least) ground down to the level of the top of the lower receiver. But get that damn thing outta there all the way, if you're gonna grind it down. (I'm PRETTY sure that's legal to do, right?) Oh, and BTW. [b][red]FUCK Colt's sear block.[/b][/red] [:D]
"The top section 222 of the block 206 projects above the top of the lower receiver 28 into the bolt asselbmly cavity of the upper receiver 29. Bolt carriers in prior art generally have a slot in their bottom such that their hammers can strike their firing pins. Howerver, these slots do not extend along the entire length of the bolt carrier. In fact, rear bottom sections of the bolt carriers for automatic firing rifles, such as shown in FIG 3, are needed in order to hit and operate their automatic sear. Thus, if a bolt carrier such as that showin in FIG 3 was attempted to be installed in the rifle 10, the top section 222 of the block 206 would hit the bottom of the bolt carrier and prevent the upper receiver 29 from completely closing onto the lower receiver, hence preventing operational installationof an automatic firing bolt assembly."