colt AR pin size and chip mccormick trigger

[chopinbloc]

i have a colt sp-1 originally purchased in 1986 and i'd like to get one of those chip mc cormick drop in match triggers but i need to know if i have the large pin or small pin style. it sounds like all colt rifles have the large pins but i need to be sure. to further complicate things, i don't have access to the rifle now but my impatient self would like to order the trigger group now (i'd like to have it at home already by the time i get there). can anyone tell me if it's true that all colts have the large pin holes or what size my sp-1 uses?

as a side note if anyone has any experience with the chip mc cormick triggers i'd sure like to hear about it. thanks guys.

 

[willeo6709]

Small pins are 0.156 diameter, or 5/32. To install the CMC triggers, you have to pretty much disassemble your lower. The pistol grip has to come off to remove the safety selector detent, be careful not to loose that. My experience is that Chip makes a sweet trigger, consistant sample to sample, and reliable as well. A terriffic imporvement to an AR.

Leo Williams
Superior Arms
www.superiorarms.com

 

[Henry455]

My 1966 vintage SP1 has the small .156 pins. I know this because I recently installed a Jewell trigger in mine. Colt switched to the large pins sometime later, not sure if it was in the 80's or early 90's. To check, get a 5/32 drill bit and see if it matches your existing pins. If it does you have the small pins.

 

[Onmilo]

Your Colt AR should have standard pin diameter and no shelf in the bottom of the receiver.
In other words, as long as it is an early production rifle and not a mismatch of pre-ban parts cobbled together on an oddball receiver, it should be compatable with the McCormick trigger assembly.

 

[chopinbloc]

still confused. is standard the large pin or small pin? i can't measure the holes 'till i get home and i'd like to have the trigger ready then.

 

[Don't Tread On Me]

No need to be confused. Let me help you.


There are 2 different pins that people talk about when discussing Colt pin sizes.


One is the front take down pin, the other is the trigger/hammer pin.


Old Colt rifles have a large front take down pin. These models have the standard .150 trigger/hammer pins.

Newer Colt rifles have a standard front take down pin, but their trigger/hammer pins are a non-standard .170.

Neither Colt is 100% compatible with any AR. Either you have a large take down pin, or you have large hammer/trigger pins.

All you're concerned with is the hammer/trigger pins.

You said you have an SP1. That is an older design of Colt. This *should* have the large front take down pin. If this is the case, then your hammer/trigger pins are the standard .150 and should work fine with ANY aftermarket trigger system so long as your lower receiver was original to that type of upper...


I believe yours is a "Green Label"...


http://www.biggerhammer.net/ar15/coltcolors.html


Note that the "Blue label" Newer Colts are the only ones with the "large fire control" pins.

 

[chopinbloc]

that helps some, i think. mine has the screw together front take down pin - the one with the slotted head. i think that's the large pin. is that right? according to the chart, it looks like i have a green label like you said. the lower receiver is very flat, no raised ridges like on my other ars and on the m16a2. i think i'll buy the standard pin size trigger group and if for some reason it's the wrong size, i'll just put it in one of my other ars. thanks for the input, guys.

 

[Don't Tread On Me]

Yea, that's the large pin lower you have. It's the older design with the flat sides (slab style)...


Your trigger pins will be the standard .150 type. Go with that and you'll be fine.

 

[Vagabond]

My SP-1 is like yours and I just put RRA 2-stage in

It was the small trigger pin version, fits great, same version as the DPMS lower I have also. THe SP-1 has the offset screw pivot pin and small pin trigger group, as someone else said. Go for it - the stock trigger is a bad dream compared to ANY match trigger!
I cannot believe how sweet the RRA 2 stage is..wow.