M16 BCG wont fit in Colt Sporter lower?

[Soxfan9]

I have a Noveske upper with a Noveske M16 BCG. I have had this on an SP1 lower and it has worked fine. I tried to switch it over to a Colt Sporter lower so I would not have to deal with the screw in take down pin in front. With the M16 BCG installed, the upper will not fully close on the lower. If I swap in a half circle BCG it closes fine. Is this due to the sear block in the Sporter lower?

[Jay Cunningham]

Is this due to the sear block in the Sporter lower?

That would be it.

[Amicus]

Most likely. You can have the sear block shaved down, or, go with most semi-auto BCGs or a "C" style BCG.

I understand complete removal of the sear block is a real PIA.

[BillBond]

Have someone like ADCO remove that dang sear block.

:cool:

[BillBond]

go with most semi-auto BCGs


A standard semi auto carrier will not work with a sear block, only the shaved carriers will work.

:cool:

[Amicus]

A standard semi auto carrier will not work with a sear block, only the shaved carriers will work.

:cool:

I respectfully disagree. My LMT SA BCG works just fine with a Colt sear block receiver. Is a LMT not standard? (Not sarcasm, I may learn something here.)

[ForTehNguyen]

why is it built like that anyways with a sear block?

[sundance435]

why is it built like that anyways with a sear block?

For many years it was Colt's attempt to save us from ourselves, since we just can't stop ourselves from converting our guns to full-auto.

[RogerinTPA]

why is it built like that anyways with a sear block?

My view, it was a political decision with Colt to put in the sear block so no one could say it was a "machinegun" or capable of being converted into one, during the AWB Era.

I also have a Colt Sporter lower with the sear block, with a Sabre Defense Middy upper on it. It will function with the AR15 BCG that came with the upper.

[Jay Cunningham]

Please check out the following thread:


https://www.m4carbine.net/showthread.php?t=14534

[Amicus]

The problem lies with the length of the "completed circle" at the rear of the BCG. In the photos shown at the thread listed above, the "enhanced" has a "circle" midway in length between the M16 and the SP1. The "C" or "half circle" type has no such problem.

As Billbond points out, some SA BCGs may not work. I do not believe (but do not know) there are standardized specs for a SA-type BCG. All I know is my LMT SA works fine.

The biggest problem with the BCGs, I believe, is that the BCGs that have a small "completed circle" often have unshrouded firing pins. This means that the hammer will slap into the firing pin during cycling instead of into the shroud, which may put additional wear and tear on the pin.

The long term solution is to get rid of the block.

[Jay Cunningham]

The long term solution is to sell that particular lower receiver and get a different one. If you are at the point where you actually understand and realize the difference between BCGs and you understand what a sear block is and what it does, it is time to buy what you want and not modify something that you can probably sell to a Colt collector.

[Amicus]

The long term solution is to sell that particular lower receiver and get a different one. If you are at the point where you actually understand and realize the difference between BCGs and you understand what a sear block is and what it does, it is time to buy what you want and not modify something that you can probably sell to a Colt collector.

Katar:

Your point is well-taken, but poor Soxfan9 lives in Massachusetts, where the federal "assault weapons" ban is still in effect. If he wants to have a flash suppressor, threaded barrel, bayo lug, or other "evil" features, he has to have a preban lower to start with. The most common and best quality prebans are Colt, and at least half of the time, they have the sear block.

If you live in Mass and you want to have a "real" rifle/carbine, you have very few choices and you have to start with a 15+ year old setup and modify it. Folks in Mass actually have to pay a premium to find small-hole lowers and/or no sear block lowers.

[scottryan]

The long term solution is to sell that particular lower receiver and get a different one. If you are at the point where you actually understand and realize the difference between BCGs and you understand what a sear block is and what it does, it is time to buy what you want and not modify something that you can probably sell to a Colt collector.



The OP lives in MA which has an AWB. He can't just sell it, because it is the only quality lower he can own that can take a front pushpin.

The long term solution is to shave down the sear block.

[Jay Cunningham]

Ah.

Then just use the half-moon carrier and don't worry about it. It will work fine unless you have OCD and cannot sleep because of it.

[Soxfan9]

Ah.

Then just use the half-moon carrier and don't worry about it. It will work fine unless you have OCD and cannot sleep because of it.

That is what I am going to do. Thanks for the help guys.

[CaptainDooley]

If you want/need an additional half-moon carrier, I've got a Colt one I'll swap you for a semi or F/A version...

[andy t]

ADCO firearms has a service where they will professionally remove the sear block.