A couple of months ago I got everything I needed to put together what I would consider a pretty solid ar. Went with the aero precision m4e1 receiver (the version with the threaded barrel nut, not their proprietary thing) and a YHM quad rail. When I got everything I did a test build before putting it together to make sure everything should fit well and the jam nut for the barrel lug for the YHM quad rail does not marry up to the aero precision m4e1. There winds up being a gap of about 1/8" where the only contact is between the barrel lug and the picatinny rail. Either I am being a spaz about it and the jam nut is supposed to tighten up away from the receiver rather than against it like I had assumed or I need to find a hand guard that will fit the m4e1.
Can anyone recommend a rifle length quadrail that will fit the m4e1?
Hmmm. I thought the M4E1 was pretty proprietary - it ain’t mil-spec at any rate. I got this info from TOS so take it with a grain of salt. But I hope it helps.
Supposedly a couple of more vendors that have BAR type handguards are Primary Arms and Radical Firearms. I bought a Primary Arms BAR rail once. It was literally (and you can ask docsherm) the FREAKIN’ FUGLIEST handguard in the known universe. No, I take that back It was “To Infinity and Beyond” fugly. When it was created in the bowels of hades, it must have fallen out of the FUGLY tree and hit every fugly branch on the way down. The designer must have been a methhead off the streets of Taipei and born an inbred with the majority of his frontal lobe missing. That said, it will fit your M4E1 and if you want it, I’ll sell it to you for - air quotes - “A Great Deal” just so I can stop hating myself and kicking the neighbor’s cat around like a soccer ball for even buying such a SUPER FUGLY handguard. But yeah. I’ll sell that fugly mutha for some shekels.
If that doesn’t tantalize your taste buds and seem like the deal of a lifetime of a sea urchin, and frankly, I do not know why on earth it wouldn’t - you can check the rails in the links below. Granted they are not as fugly, I mean unique as my rail, but then again, my rail is very unique and you can’t find them in the whole world. Ever.
If you look at the pics, you’ll see that the barrel nut, is that what you called a “jam nut” Like literally jam? Anyway, what I call a barrel nut (ahem and the rest of the world) looks like the same BARREL nut that the M4 Echo 1 uses. If I had to choose one of the below, I’d lean towards the Seekins. They have a pretty solid reputation.
Just out of curiosity. If you didn’t plan on using the Aero Quantum rail, why did you buy the M4E1, since the BAR type rails are not very abundant? Just curious.
The m4e1 that I got is not bar, it is threaded for a standard milspec barrel nut. https://www.aeroprecisionusa.com/m4e1-threaded-assembled-upper-receiver-black This is it. I got it because the specs looked good and the price looked right. But it turns out that the barrel nut that came with the YHM handguard does not screw on perfectly, there remains a pretty significant gap. The ‘jam nut’ is what yhm calls the additional nut that comes with it because the barrel nut they sent is threaded inside and out on both ends and honestly I have no idea what the jam nut is supposed to do.
I read a lot of reviews, after buying it of course, that its common for yhm handguards to be way out of spec so I was assuming that was the problem and not the receiver.
The barrel nut/jam nit design is well known and massively outdated. We had the same set up on our Bushmasters overseas. The nut is to be tightened and aligned with the receiver. The rail slips over the nut and is tightened down/rotated until is almost to the rear. You then rotate the jam nut towards the rail and torque it down. Once that is done you then tighten the anti-rotation screws.
I had a YHM handguard. It was near gapless with the receiver rail.
Since the YHM handguard threads onto the barrel nut you’re at the mercy of timing luck and threads per inch. IIRC, TPI is 18 so the gap should be between near zero and something less than 1/18th of an inch. You’re saying the gap is 1/8th of an inch. Sounds like you’re either overestimating the gap or the jam nut wasn’t backed off enough to allow the handguard to turn another rotation. When spinning the handguard onto the barrel nut make sure the jam nut is far enough forward that it isn’t interfering with getting the handguard as close as possible to the receiver. Then tighten the jam nut against the handguard.