So I finally got around to assembling my 300 BO.  I ran into a little trouble trying to install a STNGR RPTR 8.25" Free Float handguard onto an AP MilSpec forged upper receiver.

The assembly is running into my ejection port cover rod.  This is milspec, and is the exact same length as another one I compared it to.  The C-Clip is installed in the correct spot.

Looking at the pictures, it appears to me that the included barrel nut, when installed so the bottom hex screws align with the bottom tab, the barrel nut is recessed too far into the tube.

The problem is, the bottom tab will not align to allow the screws to go in.  The handguard will not go on far enough.  See pictures below.

So.. I could grind my ejection port cover rod - any downside to this.  I don't have anything to grind it down with, so will take a couple of hours getting friend to help.
I could call STNGR on Monday, but what a hassle.

Any other suggestions.

Picture below shows how the tab blocks the screws from being able to insert all the way through.  Also, see the ejection port rod hitting the rail, preventing the rail from sliding.



In this picture below, you can see the tab the keeps the rail from sliding off.  This is the correct orientation.  Turning it doesn't work.  Also, notice the rod scraping metal off the barrel nut.  Something aint right.

Because you need the barrel installed. The flange from your barrel will create the gap you need.



If the barrel is installed on the first pic, are you sure the insert is the right direction?

Your pin should not extend past the front of the upper. I can't tell from you photo, also what previous poster said, have you tried with barrel installed? If so, how far off is it? Could always add a shim or two to the barrel.

This was just a dry fit...  without the barrel.  Excellent information.  let me go try with the barrel installed.

DOH!!

My 15” Styner handgaurd fit perfectly, but I did use a traditional dust cover I guess.

It happens

Now hang on a minute.  So I corrected my bonehead mistake, and installed the barrel.  Torqued the barrel nut to 40 ft pounds, and it still won't line up for the screws.

I feel like the barrel nut, when properly indexed to accept the anti slide plate, is recessed too far into the barrel.  Here is a picture of the barrel nut installed with the screws and anti slide plate.

What happens when you flip the alignment plate around?

I'll look at mine when I get home, I've got that rail.

Update....

I removed the ejection port door.  As I suspected - the rail is bottoming out on the door rod.  The rail will install without the ejection port door rod.  Although, not exactly perfect because I feel the anti slide plate should be absolutely flush - but it is not.  You can see it protrudes slightly.

I'd appreciate it if you could look at your anti slide plate and see if it fits a bit more flush than mine.

The alignment plate really only goes one way.   There would be no daylight visible in my screw holes if I turned it around.

So, what would you all do?  I did email STNGR.  Probably won't hear from them until first of the week.  Should I try and shorten my ejection port door rod?  That would finish this build today.

If that rod is preventing a good fit, I'd trim it. But that's me

Personally. That’s what I’d do. Those are small problems to me. Grind 1/16 off the rod and flush up the plate by eye then darken it.

I’d probably still send pics to stngr though.

I’m a get it done tonight kind of guy.

I got 'er done.  Used a bench grinder to trim a touch off the end of the rod.  The rail still bottoms out on the receiver making one of the screws ever so tight, like it's threading onto the alignment tab.  But it does snug up just fine.  I'll post up some more pictures when the rod finishes drying from the rattle can job.

Thanks again for you'alls help!

I had the exact same thing happen with an ALG rail.  I just ground the end of the ejection port rod and called it a day.  I have since changed most of my AR's over to Strike Industries Ultimate Dust Covers which don't use the rod.

I have a couple of the Strike Industries Ultimate Dust Covers that do not use the rod.  I would have gone this route, but I wanted to have my marked 300 AAC dust cover.  This is the first problem like this I've come across.  I'm using a 9" barrel with a 8.25" rail.  Are there any other suggestions for a 8.25" rail?  I like the minimal gap between the threads and handguard.

My favorite build is my 8.5" 300blk with a 8.75" Diamondhead VRS-T 556 rail and a partially nested KAK slimline flash can.  Love the ergos of the Diamondhead rail.

I'm kicking myself for not using a longer rail.  I would have liked the look of a partially nested slimline flash can.  My RECCE  7 can is still in jail, but I may look for a rail that will fit over the suppressor when I finally get it.

Here are a couple of pictures of the finished product.  I'll be mounting up a PA Raptor 1-6x tomorrow.

I had the same problem with the same hand guard. I ended up using a strike industries rodless dust cover.

Update:  I did receive an interesting email back from STNGR USA...



I'll try the new anti slide plate when it arrives.  This may help to move the rail ever so slightly forward, as I get some pretty good rubbing when I pull the take down pin and let it pivot on the pivot pin.

I have 2 STNGR RPTR rails. One, a 15", on a rifle build with a billet upper. it required a couple passes with a jewelers file on the anti rotation tabs to fit. Everything else bolted right up. The second, an 8-1/4", on a pistol build with a forged mil-spec upper, required nothing. A straight forward installation with nothing going wrong. Both builds the anti slide plate fit perfectly.

Just by looking he could tell it was the wrong one?

He thanked me for the pictures.  I'm assuming this picture was what he was going on.  I received shipping info today that they sent out the part.  We'll see.