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Old colt lower/new AA 6.5 Grendel upper - Printable Version

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Old colt lower/new AA 6.5 Grendel upper - Typan - 04-18-2012

Does anyone know if Alexander Arms offer their current 6.5 Grendel upper being able to mount on the old large pin/small pin Colt lower

Old colt lower/new AA 6.5 Grendel upper - jkingrph - 04-19-2012

I have two Colt receivers, one has the sear block or whatever they call it and will not work with mil spec bolt carriers like came with my AA upper. After I figured out the problem and used proper carrier everything was good.

Dependin upon which type receiver you have you may have to use an adapter for the hinge pin. One model of the Colt uses a very large hinge pin and adapters must be used.

I finally got tired of playing games with fitting different types so got specific lowers, using Rock River in my case because of local availability, for the mil spec type uppers, and am keeping the Colt as a pure Colt.

Old colt lower/new AA 6.5 Grendel upper - Variable - 04-19-2012

Typan Wrote:Does anyone know if Alexander Arms offer their current 6.5 Grendel upper being able to mount on the old large pin/small pin Colt lower
More info needed.... Do you mean you have a large front takedown pinned Colt lower (SP1 and similar)?

If so:

http://blackrifleworks.com/colt-ar-15-universal-front-conversion-pin-p-164.html

Or

http://shop.ar15sport.ihoststores.com/productinfo.aspx?productid=ARPART-CLT-ADAP

Or

http://www.brownells.com/.aspx/pid=24948/Product/AR-15-M16-RECEIVER-ADAPTER

There are likely also others. What is the diameter of your front takedown pin? Is it .315 inch?

Old colt lower/new AA 6.5 Grendel upper - Typan - 04-19-2012

Yes, the front hinge pin is the large pin, the back pin is the standard size found on most other upper receivers. I did check out the blackrifle web site and think the offset bushing will do the trick. Thank you all for all your help. Typan

Old colt lower/new AA 6.5 Grendel upper - davidj - 04-19-2012

I finally got tired of playing games with fitting different types so got specific lowers, using Rock River in my case because of local availability, for the mil spec type uppers, and am keeping the Colt as a pure Colt.[/QUOTE]

I did the same exact thing

Old colt lower/new AA 6.5 Grendel upper - Typan - 04-19-2012

Thanks Davidj for your help and advise.