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Posted: 1/7/2005 3:56:45 AM EDT
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Hello Gents, I'm pretty sure I'll be buying a Colt Sporter lower in the coming days. The lower has the infamous sear block in place, which doesn't bother me in and of itself. The concern I have is that the block will impede functioning with the older Colt "full circe" carriers I have. Do these "blocked" lowers require the use of the later carriers that are milled away at the bottom? Thanks for your help, Brewer |
Ohhhh. Those blocks are very different from the ones I was thinking of. I can see how a few thousandths of an inch one way or another would impact whether or not you'd need a half-circle carrier. What a stupid idea! BAD Colt! BAD! 
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yes..!! i have two new Colt half circle bolt carrier asemblies, i'll trade you one for one, as i need a FULL circle B&C assy., reply by IM if interested.., Thanks |
| I have never ran a half circular carrier, I hate those things. Never had a problem running a regular full circle Colt AR-15 carrier with a sear block. The only ones that don't fit are the full auto ones, check the pic above, plenty of room for a semi carrier of any type. |
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In The 2 Colts I have with sear blocks the Block seems to be higher than the ones pictured above, There is a ridge that rides about 1/4 inch higher on one side of the block that prevents fill circle carriers from working. Colt, Go Figure!! How much of a PITA is it to remove the block? Has anyone done it? |
Even if your sear block were a little a higher, it would not impede the function of a typical semi-auto AR15 type bolt carrier. Perhaps you have an M16 type carrier? |
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I have a 6530 with a sear block and it doesn't work with M16 carriers. It works fine with full circle AR15 carriers (RRA, LMT, DPMS, etc.). The length of the full circle component of the M16 carrier contacts the top of the sear block and prevents the upper from closing on the lower. Don't know if Colt used the same sear block in all its lowers - maybe there's a high block and a low block. ETA: See this thread. The block in my rifle is identical to this one: 
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Maybe half hour. The first part goes pretty fast. It's when you get the last couple of 10 thousandths over the top edge of your lower that you have to slow down. (I just filed mine flat +/- about 1/16" above the top edge of my lower.) |
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Correct me if I am wrong but the newer Colt lowers no longer have the sear block correct? My understanding is that the newer lowers just have less material milled out of them? If I am right, exactly when did Colt stop using the sear blocks and go to the way they currently mill their lowers? I ask because I just ordered a Colt lower and planed on using it with a Colt M16 carrier. Thanks |
Late '90s. |
You are correct Sir! Here is one of my current Colt lowers: 
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Cool, thanks...I was getting nervous there for a second! 
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