auto sear clearance?????

[DarkMan]

Hi,

I'm an FFL dealer (Ballistic Corp - FFL - Tampa, Fl) soon to be SOT/C2, once January comes around and I pay my SOT for this year, even though I will miss out on a few months. Again I know ALL the ramifications concerning ATF/NFA legalities. This is a simple inquire.

My question is; what the hell is this AR15/M16 upper with auto sear clearance deal? I keep hearing this a lot. Aren't the FA lower parts kit, hole in the lower receiver to accept the sear & pin, FA bolt carrier the only difference between a semi auto? Thus assuming the required changes have been done to the lower receiver, of course. anybody???? What does the upper have to with the FA operation of the sear? specially when people changes uppers constantly.

Darkman AKA Ballistic Corp FFL:(

[RJ Shooter]

I too thought it was just Carrier and Lower with Sear (whether drop-in or permanent) that were the issue.

Hmmmmmm...

[DarkMan]

RJ Shooter,

THanks for your reply. It seems it's a myth Class 3 owners tend to use to differenciate and avoid non C3's to use the preban uppers configurations. Found out with a C2 that there is no difference, just the lower.

THanks

Darkman AKA Ballistic Corp FFL - Tampa, Fl :D

[HoGKiLLa]

actually there is a difference.. for the GI sear there has to be a slight clearance cut about 1/16-1/8"? deep into the bottom of the upper receiver directly where the auto sear is positioned. The clearance is for the shoulders of the auto sear that slighty stick up above the lower receiver. if you dont have the cut and your using the GI sear that is properly located in the lower the upper simpy wont close all the way on your lower. if your using a ll or dias it wont need the cut.

Jeremy

[Quarterbore]

Here is a photo...

http://www.biggerhammer.net/ar15/uppers/searrelief_ar15_m16.jpg

Yes, there are uppers that will not work with a USGI Autosear!

The photo is from Biggerhammer.net... see http://www.biggerhammer.net/ar15/uppers/

[DarkMan]

Quarterbore

THanks, my upper is like the one on the right , so I shoulkd be OK. THamks!
Darkman:D

[MACVSOG]

Almost any upper receiver you buy will have the sear relief cut into it. However, Colt did make a number of upper receivers for the SP1 that did not have the sear relief cut into it. I have also seen some DPMS upper receivers that did not have the sear relief cut in them. But most upper receivers will have the relief cut into them, so for the most part, even people who do not know about the sear relief cut will tend to buy upper receivers made for full auto shooting just because the odds are in favor of their getting upper receivers with the relief cut. If you know about the relief cut, it makes your odds 100% that you will buy the upper receivers with the relief cut in them.

Charles Tatum
Alamo Professional Arms

[shamayim]

Originally posted by MACVSOG
Almost any upper receiver you buy will have the sear relief cut into it. However, Colt did make a number of upper receivers for the SP1 that did not have the sear relief cut into it. I have also seen some DPMS upper receivers that did not have the sear relief cut in them. But most upper receivers will have the relief cut into them, so for the most part, even people who do not know about the sear relief cut will tend to buy upper receivers made for full auto shooting just because the odds are in favor of their getting upper receivers with the relief cut. If you know about the relief cut, it makes your odds 100% that you will buy the upper receivers with the relief cut in them.

Charles Tatum
Alamo Professional Arms

I know I'm 6 months late with this, but what the hell:D

Actually, the SP1 I had class 3d 25+ years ago had the sear relief cut on the upper. It's when I "updated " it with a later big hole upper that has the forward assist, that I ran into the uncut bottom.

Rather than have that whole area milled out, I simply took a needle file and cut notches into it, on the inner edges, right over where the sear operates. Works just fine;)