mating AR upper and lower

buzzmagoo

buzzmagoo

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So I am working on this old sp1 lower and was in the process of installing a new upper ( short barrel) to it. The front take down pin lower is bigger as compared to the upper smaller diameter and it's allso off set. The rear pin I am able to insert . There isn't much slop ( movement) between the halfs. My question is is there a adjustable pin of some sort .( for an easy fix) or do I drill out the holes to align them. Don't really want to have to start carving in to the new upper.( it would kill resale value). I did read the forum but didn't find much reference to this problem. I am able to machine a pin but would like to use the proper parts if they exist and are available. Any help would be much appreciated in any information and where to find it thanks! New to these AR guns just figured it was going to be easier for parts compatible.
 
buzzmagoo said:
So I am working on this old sp1 lower and was in the process of installing a new upper ( short barrel) to it. The front take down pin lower is bigger as compared to the upper smaller diameter and it's allso off set. The rear pin I am able to insert . There isn't much slop ( movement) between the halfs. My question is is there a adjustable pin of some sort .( for an easy fix) or do I drill out the holes to align them. Don't really want to have to start carving in to the new upper.( it would kill resale value). I did read the forum but didn't find much reference to this problem. I am able to machine a pin but would like to use the proper parts if they exist and are available. Any help would be much appreciated in any information and where to find it thanks! New to these AR guns just figured it was going to be easier for parts compatible.
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There are over sized, a combination of over with under on the same pin, adjustable, pinch pins, shims and standard pins.
 
Measure the takedown pin diameter.
Some early Colt lower receivers had 0.315" diameter takedown pins.
Modern A.R. 15's have 0.250" diameter takedown pins.
Daniel Defense makes large pin upper receivers.

Otherwise search for an AR-15 Lower Receiver blueprint and start taking measurements.
If something is out of spec on the new upper you should return it or sell it with full disclosure.
Best of luck and let us know the outcome.
 
U probably have a big hole lower since it being an older colt. Try to find the adapter on brownells or in the US.
 
buzzmagoo said:
Did some digging at Brownells, and they do carry the pin that would do the job, but as luck would have it they are out and are on back order. Are there some other places that might have something ?
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Is it a large pin lower?
Did you measure the pins?
There is no adapter that will do what you want.
If you had a small pin lower with a large pin upper DPMS makes bushings for the upper.

banger said:
http://www.brownells.com/rifle-part...d7591.aspx?avs|Manufacturer_1=J+P+ENTERPRISES

I have one, brand new. Lmk if interested.
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That will not work for him.
That is just a tensioning pin for .250" rifles.
 
sky52 said:
U probably have a big hole lower since it being an older colt. Try to find the adapter on brownells or in the US.
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Yup... AFAIK the original SP1s (like mine) were intentionally made with a different sized pin to make them incompatible with the M16 of the day. I strongly suggest you don't carve up your lower; wait until you can find the correct conversion pin. You may be better off buying a new lower.

Modern ARs are far more modular and compatible, especially if you stick to North American manufacturers.
 
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Phat Eagle said:
Yup... AFAIK the original SP1s (like mine) were intentionally made with a different sized pin to make them incompatible with the M16 of the day. I strongly suggest you don't carve up your lower; wait until you can find the correct conversion pin. You may be better off buying a new lower.

Modern ARs are far more modular and compatible, especially if you stick to North American manufacturers.
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That or find a big hole upper and sell your small hole to recoup some funding
 
I am going to still attempt to find an adapter pin. Just missed one by a couple of days. So they are out there just need to track one down thank you all for the leads. """" so I finally found what I was looking for Gun partscorp.com. ordered it last night. Evidently it will take up to a week to process my order ( the weighing game begin's) I ordered two and a couple of small pieces 38.00 $ and then there's 42.00 $ for shipping and handling. Hope I don't get nailed at Customs to badly ( last time 50.00$ on a 120.00$ ) don't know what's worse the weight or the cost . Well I had to bite the bullet,, time will tell! Thanks to all that gave me directions in my quest.:cheers:
 
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buzzmagoo said:
I am going to still attempt to find an adapter pin. Just missed one by a couple of days. So they are out there just need to track one down thank you all for the leads. """" so I finally found what I was looking for Gun partscorp.com. ordered it last night. Evidently it will take up to a week to process my order ( the weighing game begin's) I ordered two and a couple of small pieces 38.00 $ and then there's 42.00 $ for shipping and handling. Hope I don't get nailed at Customs to badly ( last time 50.00$ on a 120.00$ ) don't know what's worse the weight or the cost . Well I had to bite the bullet,, time will tell! Thanks to all that gave me directions in my quest.:cheers:
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Was that shipping with ups? I have had that happen before and always try to ship usps instead.
 
Latest up date got a package from them just one piece ?? Is this how they ship orders? One at a time! USPS shipped 9.82$ for a 12.32$ part ( sling adapter AR). Times rolling along. Got the feeling that I am getting gouged on this shipping . Three more parts on the way .:bangHead:
 
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