I have a Colt AR15-A2HBAR with the large double-slotted screw that holds the front of the receiver and upper together. I want to put a 16" flattop upper on it, and will probably get one with the small pushpin hole. I know Bushmaster makes an adapter pin for this. Has anyone ever used one or seen a gun like this? Does it work? Does the upper fit tightly to the lower? I'm just wondering if this makes sense or if I should trade the gun.

David

A friend of mine has done the same thing with his only AR, and the fit and function are just fine. It just looks a little funky.

There is one drawback.  While the converter pin works, it tends to work itself loose as you repeatedly open and close the rifle.  IIRC, there is a design out there that is not as prone to this condition, but I can't remember who made it.  I got tired of the whole mess and had a large hole flat top M4gery upper built so I could just use a large push pin.

i have a few AR-15s that i use large/small pin adaptors on & they function just fine.., in fact i have one lower that i regularly switch uppers on just because i can have several different rifles in one......

Do not buy the converter pin that bushmaster sells. It's a POS that will drive you crazy every time you open up the rifle for cleaning. It shifts position when you open the action but does not shift back when you close it; meaning that you have to drag out two screwdrivers to re set it so the action will close.

The ONLY conversion pin worth having is the piece sold by CDNN ([url]www.cdnninvestments.com[/url]). That unit, once you've set it up, stays in the same relative position when you open and close the action, so once set, you can forget it[:D]

Is this the one shamayim?

[url=http://store3.yimg/|/cdnn_1756_12821363]screw it if the stupid thing doesn't want to work!![/url]

Damn I bought the Bushmaster pin!!!!! I haven't swapped it out yet. But I think I'll order the CDNN one. Thanks for the tip. WarDawg

Well, I can't get flash hider's link to work, but the CDNN unit is the only one they show, so if you find one on their web site, that's it[:D]

The possible bad news is that someone posted last week that they were out of stock; so I'd call before trying to order. It's an 800 number, and their sales people have always been very friendly and helpful.

I just sent one out to a guy in New Zealand a couple of weeks ago. He e mailed me that he loves it[:D], and I hope you guys can find one of that type.  The crappy one has small heads on both sides. The good one has a rather large slotted head on the right side.  The head has a small flat on the edge, which is the indicator for which way the piece should be inserted  (flat to the rear).

Daniel Defense sells the a3 upper for Colt biggie hole lowers so you can still use the two screw pin  The price is $225.00 for the reciever

Heck with that, if you get the large hole upper, you can then use the one piece large push pin.  It's the whole reason I had a large hole upper built.

This is the way to go if you can afford it.  I just sent Bushmaster a Daniel flat top large pin upper and had them build what I wanted so I can use the push pin.  ALL of the small pin upper to large pin lower adapter screws suck and are a pain in the butt to own.

Just curious if this is the conversion pin you guys are talking about from cdnn?  Tryin to decide what to do with mine.  I like options!
[url]http://store.yahoo.com/cdnn/arunfronconp.html [/url]

That's the one[:D]. Now I sgree that having a large hole upper of the type you want is easier and better in the long run, but you can get a Rock River flat top upper for under $100, and the price difference w/the big hole version would sure be a large piece of the cost of top notch sighting equipment.

Since the upper I put on my SP1 originally was an A1 type small hole, I was able ultimately to find an SP2 forward assist type and dispense with the adapter; but that only ended up costing me about $30 net.  If I'd been going the flat top M4gery route, I'd still be using the adapter with an $80-$90 upper.

But then, I'm just a poor state (of Georgia) employee[:D]