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Posted: 9/10/2004 1:30:55 AM EST
Can I or can't I use regular bolt carriers in a lower with a sear block. I'm not touching trigger/selector/lower. .... I'm talking upper parts...
Link Posted: 9/10/2004 1:51:15 AM EST
My Sporter (Colt w/ sear block) lower has operated with uppers from Colt, DPMS, Rock River, Bushmaster, and J&T, with all having the regular bolt carriers that came with them, so I'd say the answer to your question is YES.

Mike
Link Posted: 9/10/2004 1:57:26 AM EST
You sure Mr. Wilson?

I don't have mine in front of me but I know for sure to get the M16 carrier to work I had to file the damn thing down so it was flush with the sides of the lower. If the full circle types don't have the bottm portion removed far enough back it will hit the sear block. You won't be able to get the upper and lower closed together.
Link Posted: 9/10/2004 3:06:54 AM EST
[Last Edit: 9/10/2004 3:08:46 AM EST by mr_wilson]

Originally Posted By Halfcocked:
You sure Mr. Wilson?

I don't have mine in front of me but I know for sure to get the M16 carrier to work I had to file the damn thing down so it was flush with the sides of the lower. If the full circle types don't have the bottm portion removed far enough back it will hit the sear block. You won't be able to get the upper and lower closed together.



Sorry I don't know squat about M16 carriers, I thought he was asking about standard/regular bolt carriers. All of the uppers spoken above came with "stock" b/bc/ch set-ups.

Never had a problem with fit, but as stated I don't run M16 parts in my semi-auto AR15 rifles.

Lower currently has an LMT M4 upper with standard carrier and LMT bolt, it too has given me no problem with either fit/mating or function.

Mike
Link Posted: 9/10/2004 4:52:23 AM EST
Link Posted: 9/10/2004 4:56:16 AM EST
[Last Edit: 9/10/2004 4:59:15 AM EST by chapperjoe]
obviously, I meant will all uppers and parts work CIVILIAN STUFF?

OH and post 1776... damn! I wasted it on an explanation!!!!!


<-------
Link Posted: 9/10/2004 4:59:16 AM EST

Originally Posted By chapperjoe:
Can I or can't I use regular bolt carriers in a lower with a sear block. I'm not touching trigger/selector/lower. .... I'm talking upper parts...



Depends, the early Colt Sear block would work, but the newer sear block requires a half-moon carrier, and will not work with regular M16 or AR15 SP1 carriers.
Link Posted: 9/10/2004 5:26:38 AM EST
let me re-explain.


I'm talking a sear block lower with an RRA upper of new manufature.
Link Posted: 9/10/2004 6:25:47 AM EST

Originally Posted By chapperjoe:
let me re-explain.


I'm talking a sear block lower with an RRA upper of new manufature.



Same answer. If the sear block is higher than the side rails of the lower, you must use a half-moon carrier.
Link Posted: 9/10/2004 8:17:39 AM EST
Not so. Have a Colt with the pinned protruding sear block, and half moon carrier. My full circle carrier from my Bushmaster fits and works just fine. What you can't use is an M16 carrier, as there is enough material on the underside of the carrier (sear trip) that the block interferes.
Full circle civvie carriers have the sear trip area of the carrier removed...

Mick
Link Posted: 9/10/2004 8:39:44 AM EST

Originally Posted By RenegadeX:

Originally Posted By chapperjoe:
Can I or can't I use regular bolt carriers in a lower with a sear block. I'm not touching trigger/selector/lower. .... I'm talking upper parts...



Depends, the early Colt Sear block would work, but the newer sear block requires a half-moon carrier, and will not work with regular M16 or AR15 SP1 carriers.



The early style block projected from the lower receiver and prevented the use of an M16 carrier. The current style block is just a web of aluminum left between the walls of the lower receiver an even an M16 carrier would work with it.
Link Posted: 9/10/2004 8:43:18 AM EST

Originally Posted By RenegadeX:

Originally Posted By chapperjoe:
let me re-explain.


I'm talking a sear block lower with an RRA upper of new manufature.



Same answer. If the sear block is higher than the side rails of the lower, you must use a half-moon carrier.



Baloney. Here's a pic showing how a typical AR15 carrier interacts with a projecting sear block:



As you can plainly see, there is more than sufficient room.

Link Posted: 9/10/2004 8:46:59 AM EST

Originally Posted By Boomer:

Originally Posted By RenegadeX:

Originally Posted By chapperjoe:
let me re-explain.


I'm talking a sear block lower with an RRA upper of new manufature.



Same answer. If the sear block is higher than the side rails of the lower, you must use a half-moon carrier.



Baloney. Here's a pic showing how a typical AR15 carrier interacts with a projecting sear block:

photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=15199

As you can plainly see, there is more than sufficient room.




Yep. "standard" semi-auto carriers (full circle) will work with the protruding sear block. M16 carriers will not. Oddly enough, I'm pretty sure that 9mm bolts will also NOT work with a protruding sear block. They're full circle, and the "meat" of the bolt goes as far forward as it does on the M16 carrier.
Link Posted: 9/10/2004 9:08:19 AM EST
I stand corrected. Thanks.
Link Posted: 9/10/2004 9:08:25 AM EST
Old stlye colt block (tab/block that stick up).
Everything but a Colt 9mm carrier/bolt, and a full auto carrier will work with the receiver.

This means that even the RRA Improved hooded carrier will work since the bottom trip ledge will still be short of the front of the rear upper lug when the bolt is locked.

New style Colt block,
All carriers will work since nothing protrudes above the top of the receiver, and the block is just a section of the rear shelf that is just not milled out.
Link Posted: 9/10/2004 9:16:43 AM EST
Thanks for the pic Boomer. I'd always wondered if I could run standard cutout carriers in my Colt, and that pic answers my question perfectly.
Now the bonus question: If Colt didn't need the half moon cutout to clear the sear block, why is it there? Why not run a carrier with the same specs as the other guys?
Link Posted: 9/10/2004 9:29:01 AM EST

Originally Posted By Poodleshooter:
Now the bonus question: If Colt didn't need the half moon cutout to clear the sear block, why is it there? Why not run a carrier with the same specs as the other guys?



Probably to defeat the use of a Lightning Link, either in a Colt lower with the block removed or in an earlier unblocked lower or one from a different manufacturer.
Link Posted: 9/10/2004 9:38:33 AM EST
great info guys thanks... exactly as i had suspected. no m16 carriers and no (oddly enough) 9mm carriers. Thankss a bunch.
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