Colt A2 upper capatibility

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tdool

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OK, My friend has passed on some old AR parts for me to do a build. I have an older Colt A2 upper. I think it had the larger takedown pin, not 100% sure yet. I know its was a bolt style not an easy push take down like my Armlite M4 was like.

I want to put this upper on a stripped Aero Lower. has anyone had issues matching a Colt a2 upper with a new milspec lower? I guess I need a new takedown pin and a bushing for the reciever if it is the older larger takedown?

Also I have some of the original lower A2 parts aswell. Mostly the Trigger assembley and pins. Will these fit in the Aero Lower? are they different sizes too?

If I can use it all then it will make this builder cheaper, if not I guess I will need to get a new lower kit.


So basically I want to know to use the upper is it safe for me to order the Aero lower. don't want to be stuck with a lower if it will not work
 
Yes, you can use the large hole upper but you'll need to buy reverse off-set pins to make it fit on the small hold (mil-spec) lower receiver.

As far as the trigger pins go, no the Colt pins are larger and you'll need the smaller mil-spec ones. If you're going to all the trouble to buy a brand new stripped lower, why not just do it right and install a new LPK while you're at it? That way, you know everything is new and you're not worrying about parts compatibility issues and you've got peace of mind in doing so.
 
The large pin upper will not mate with a small pin lower without using bushings. So, the answer to your question is more of a no, but it can be worked around. Also, Colt trigger parts are inconsistent even between Colt rifles. Odds are that unless you're putting parts from the one type of colt rifle into a similar style and aged Colt lower, they probably won't work.
 
I wouldn't write off your lower parts just yet. Do you know what kind of lower the parts are from? Some of the 90s Colt AR15 rifles have far nicer triggers than the newer stuff.
 
If the parts came from a large hole rifle then the trigger mech will be mil spec dimensions. They should work no problem. I certainly wouldn't replace them with a new LPK from DPMS or anything like that.
 
Ya did my research and found the parts are from a Colt A2 Military Model. and the parts are all milspect except for the front takedown. Thanks everyone for the help. Im getting a areo lower from Saskatoonworks and will be getting a adapter bushing or just JBweld teh front takedown pin hole and redrilling it. Finding a New Front takedown pin and a new detent and spring to put into the new reciever seems tuff to find in stock. those are teh only parts I need to finish the build.
 
just ordered my aero lower reciever from saskatoongunworks.com.

Found some detents adn springs for the Front take down that I will need. but can not find any Front swival/take down pin anywhere in stock. anyone have any ideas?
 
or just put a shim in it, thats what i did, large hole colt upper, TI15 lower normal take down pins, with a brass fitting popped in to the large hole, works great
to get the measurement grab a caliper.
mine was 6.21 inside diameter
7.52 outside diameter
12.71 wide, all in millimeters

brafasco or one of the specialty fitting shops should have some
 
ya I was going to make a shim, or fill with weldond and re drill. just need to find a new swivel / takedown front pin to install into the lower and I'm all set. have detent and spring on its way to hold it on, but no pin :-(
 
reid134 said:
or just put a shim in it, thats what i did, large hole colt upper, TI15 lower normal take down pins, with a brass fitting popped in to the large hole, works great
to get the measurement grab a caliper.
mine was 6.21 inside diameter
7.52 outside diameter
12.71 wide, all in millimeters

brafasco or one of the specialty fitting shops should have some
Click to expand...

Do you have any issues opening the rifle? Reason I ask is that the holes are offset, so the bushing needs the hole to be offset in order for it to work properly.
 
Got my Arrow Lower from Saskatoon Gun Works Yesterday.

All the LPK from an old Colt fit 100% Just had to get Front Take Down Pin, Spring and Detent. JBweld the Old Colt Upper (Large Pin) and redrilled it while matching it to lower reciever. Worked Perfectly. Repainted the old Mold/chemical stained Plastic Furniture I was also given. so now it looks all new. All I have to do now is get the upper reciever refinished as its the Old Colt Grey and the reciever is Flat Back.

Thanks to everyone that has helped me find a reciever, parts and advice. Heres some pics

mg1679.jpg

mg1669edit.jpg

mg1671.jpg

mg1672.jpg
 
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