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Californio
03-01-2007, 12:50 PM
I have a buddy that has a registered Colt “Service Rifle” of the 1970’s vintage. I was showing off my Winchester Varmint bolt rifle with the 1x9 twist and 69gr match bullets.

He was impressed. So I told him I would ask.

1. Are Colt A2 HBAR Uppers available in large pivot hole, 20” barrel, 1x9?
2. If not Colt, what is the highest quality Mil-Spec Upper available in the above specs for a 1970’s Colt lower with big pivot hole.
3. Do they make adapters to fit large pivots to small ones?

Thanks

bwiese
03-01-2007, 1:02 PM
I think on occasion some vendors make large-hole "Old Colt compatible" upper receivers. They're not common items.

Sometimes Colt had conversion uppers too but that was some time ago.

The large pivot pins are 0.325" (IIRC) and the newer small-pin (milspec) pivot pins are 0.250". Do note that these holes are not concentric with each other. If your buddy's front pivot pin is .250" he's compatible w/regular uppers.

He can use a small pin upper on his old large-pin lower if he uses a "conversion pin" pivot pin. I believe Bushmaster sells these pins, as well as Brownell's - they cost around $7.95 the last time I saw 'em. I believe these are of the 'double-screw' variety and are not detent pivot pins, so you'd need a screwdriver to separate upper from lower.

With these conversion pins, the guns do open but sometimes there's a slight binding as things get centered (given the offset center of the small pin from the center of the larger hole's opening).

Note: do not confuse "large pin" terminology with the larger hammer/trigger pins in some mid-90s onward Colt Sporters, etc. Many/most of these guns had the smaller .250" pivot pin but had larger ~.170" diam. hammer/trigger pins for the fire control parts. (Milspec hammer/trigger pins are ~0.153".)

tiger222
03-01-2007, 1:30 PM
+1 on what BW said.

I just picked up a NOS Colt R6550 conversion kit with the special screw just like he said :)

The other issue could be the color of the upper. This one is more of a SP1 grey and the other NOS R6550 upper I got is more of a later sporter dark grey.

With a 1/7 twist you could do 77 grain easy :):)

Californio
03-01-2007, 4:01 PM
+1 on what BW said.

I just picked up a NOS Colt R6550 conversion kit with the special screw just like he said :)

The other issue could be the color of the upper. This one is more of a SP1 grey and the other NOS R6550 upper I got is more of a later sporter dark grey.

With a 1/7 twist you could do 77 grain easy :):)

He still wants to be able to shoot the 55gr he has in stock, so I think 1x7 would be too fast.

Californio
03-01-2007, 4:07 PM
I think on occasion some vendors make large-hole "Old Colt compatible" upper receivers. They're not common items.

Sometimes Colt had conversion uppers too but that was some time ago.

The large pivot pins are 0.325" (IIRC) and the newer small-pin (milspec) pivot pins are 0.250". Do note that these holes are not concentric with each other. If your buddy's front pivot pin is .250" he's compatible w/regular uppers.

He can use a small pin upper on his old large-pin lower if he uses a "conversion pin" pivot pin. I believe Bushmaster sells these pins, as well as Brownell's - they cost around $7.95 the last time I saw 'em. I believe these are of the 'double-screw' variety and are not detent pivot pins, so you'd need a screwdriver to separate upper from lower.

With these conversion pins, the guns do open but sometimes there's a slight binding as things get centered (given the offset center of the small pin from the center of the larger hole's opening).

Note: do not confuse "large pin" terminology with the larger hammer/trigger pins in some mid-90s onward Colt Sporters, etc. Many/most of these guns had the smaller .250" pivot pin but had larger ~.170" diam. hammer/trigger pins for the fire control parts. (Milspec hammer/trigger pins are ~0.153".)

If Colt is not available, who makes the best complete uppers in the 20" HBAR A2 style in 1x9?

SemiAutoSam
03-01-2007, 4:08 PM
I would say White Oak Armament.

If Colt is not available, who makes the best complete uppers in the 20" HBAR A2 style in 1x9?

Californio
03-01-2007, 4:27 PM
I would say White Oak Armament.

Thanks, They only show 1x7 but looks like they do custom as well, I will send him over there, maybe they will make the pivot hole for him as well, he is a Physician, he can afford it:D

dw1784
03-01-2007, 4:49 PM
FYI, DelTon's got the offset pin for $3.
Besides the offset pivot pin, there are bushings for large hole lowers. Google for "Colt ar/m16 offset front pivot pins".

bwiese
03-01-2007, 5:15 PM
He still wants to be able to shoot the 55gr he has in stock, so I think 1x7 would be too fast.

1x7" twist will do just fine for 55gr. I shoot Fed XM193 in my 1x7" bbls and it's great.

If Colt is not available, who makes the best complete uppers in the 20" HBAR A2 style in 1x9?

That's a loaded question. There are lotsa good uppers out there esp in the high-priced match-grade arena. Many of these may not be that suitable for casual shooting.

I think for a 1st or 2nd upper you should stick to a chrome-lined barrel, and get an upper from CMMG, Bushmaster, Armalite or Colt.

CMMG has really been getting up there and frankly I think their quality is at Colt's and above Bushmaster's.

Lefkiguy
04-04-2007, 8:33 AM
Does someone make a large hole lower? I just went to check an upper I've had for a few years, and it looks like it's a Colt, marked with a C and the pivot hole is much larger (front end moves about when assembled). the lowers I have all are small pin.:confused:

Bing
04-04-2007, 8:38 AM
The only lowers with the larger pivot holes are Colt (as far as I know). You can get adapters for your upper to fit your lower. You can always sell or trade the upper to someone who has an older SP1 or Colt Sporter 1 or 2.