So I built an upper and was just waiting for the Troy Alpha rail to show up.  

It will not slide over the standard barrel nut.  WTH.

Has anyone else had this problem?
Can someone recommend a barrel nut that might actually work?

Do you have the bolts that you tighten down loose enough? And you need to line it up with the standard barrel nut then rotate it about 45 degrees until  vertical. When I installed mine it was actually hitting the FSB that I shaved down so it wasn't letting me rotate the rail.

Any pics? I've installed a couple and they fit like a glove.

No pics. The rail will not slide onto the barrel nut at all.  I have watched a few videos on youtube where guys have just slid them over the barrel nut easily and they lock on. I realize your have to angle it slightly.  My rail will not even begin to slide over the barrel nut.   I think either the teeth on the barrel nut are too wide or the nut is just out of spec.

The barrel nut is probably out of spec.  I mean you are talking about a eight dollar part.

The screws need to be barely on the back piece of my alpha rail for me to get it on. Try calling Troy if you keep having problems.

Are you sure it's an alpha and not a TRX Extreme. Are the three mounting screws around the circumference or two screws at 6:00?

Yeah, It is an alpha rail with the three screws.  Not the TRX version.   I finally decided to grease it up real good and then I put a hair dryer on the rail for about 15 minutes.  I was finally able to work it over the barrel nut.   It's snug now.  I don't think I will have to worry about it coming off.   I really need to take it back off and remove the grease and see if I can slide it on again.

Thanks for all of your help.

I just put a bravo BR13 on my last build and I had this same problem. the problem was however, that it is a 14.5" pinned to 16 build so I was SOL if I didn't get it to fit. I had a spare TRX nut that slid in with no problem. I sent Primary Arms and email about it immediately because I was so sure it wasn't my fault and it had to be troy. After throwing the upper across the yard, I decided to check it again. It lined up, but WAS TIGHT. I believe the same as previous poster in that the barrel nut was out of spec. I placed the rail onto the nut after tightening, and placed a towel around the top. I gently tapped on each corner of the rail to make sure if was seated properly. I slid it on, and indexed properly with the 5 degree turn necessary to wards the end at the clamp location. No harm no foul. tightened up, feels good and solid. If you know this is the handguard that will always be on the gun, you might be able to take emery cloth to each tooth and it may slide down a tad easier. I understand that tapping on it with a tack hammer might sound a bit too barbaric, but its not a wall hanger. Its going to be abused and used so I wasn't too upset about it.

Just my .02

My alpha rail had to be tapped on the first time and then tapped off.  I installed and removed it a couple of times for various reasons and it got easier each time.  I think that the rail coating was just a little thick in the spine area causing the issue.

I really think the trick to getting the Alpha Rail to fit over the barrel nut was to heat the rail with a hair dryer.  I know Aluminum will expand much more than steel when heated.  Even though I applied an generous amount of grease on the inside of the rails and barrel nut, I still heard that metal on metal scraping sound as I used a back and forth rocking motion to wiggle it on.  I wiggled the rail back and forth gently while applying downward pressure with my hand.  I wanted to be able to feel it going on without doing any damage to the rail.  But it was clear by the metal scraping sound that is was a tight fit.  The rail does look pretty nice.  It is a 15" Alpha rail matched up to a PSA upper receiver on a 18" douglas barrel.  The color of the Rail and Upper match really well.   I will try to take some pics when i get it all finished.

What wrench did you use to install the barrel nut? Any chance you could of fubbed up one of the teeth on the nut? It is a very tight fit and one fubbed up tooth could throw it off a bit.

Some nuts on the market have more material on them to lock up tighter to handguards.  The Core-15 nut is one example.

 

Which typically means O.O.S.

Mine took a lot of finnagling at first. Now it slides on perfectly. All of a sudden it just worked, but I remember it being a pain in the ass to get on the first time, it took like 10 minutes and eventually a friend just pushed on it and it popped in.


Also, as mentioned, you're barrel nut may be out of spec

I had to place the retaining tab in about the two o'clock position to get mine on, then rotate counter clockwise back to noon.
you probably already did this but hope it helps.

it must be one of those new dale monroe editions

I'm not sure the Core 15 nut would be able to work with an Alpha. I bought one because Core 15 bragged on how good it was and held to spec while machining, then found out the recess at the front, needed by the Alpha for tab lockup, isn't there.

In my experience Troy Alpha rails work best with Colt, or CMT barrel nuts.

I was told by a gunsmith that Core 15 barrel nuts are not mil-spec.
he also told me that my troy rail would not work with a core 15 barrel nut.
I used a core 15 stripped lower / stripped upper but made sure that I used a mil-spec barrel nut.
mine fits well.

Don't know what brand barrel nut I have but my Alpha rail would not fit either. No matter how I turned it, it would not slip on. I took my dremel and a small cone sander and hit in between each of the teeth on the nut until the rail would slip over. Probably took about 3 times around hitting each spot for a couple of seconds.