FN 20" upper question

MattTheGunslinger · Mar 9, 2018

I just bought an FN upper with 20" hammer forged barrel to upgrade a pre-2013 rifle. I was going for a plain M16A2/A3 look. When I received the upper, I was a bit confused. It's a 20" government profile barrel...mostly. Forward of the FSB there is the M4 style grenade launcher cut out in the barrel. Why? The receiver has FN markings as does the barrel. So it's all FN stuff. Has this ever been a thing for military 20" barrels? It's a great looking upper. Fit and finish is excellent. I'm just kinda bummed they put an M4 cut on a 20" barrel. What gives?

danb · Mar 9, 2018

I would not be bummed about the cut for a grenade launcher. I'd be bummed I did not have a grenade launcher to put on the thing.

Only real solution I see here is to get a grenade launcher.

MattTheGunslinger · Mar 9, 2018

That is actually a really good way to look at it. lol I've just never seen a 20" barrel with that cut.

Now to get that grenade launcher!

Dan44 · Mar 9, 2018

The which distributor did you get it from ?

MattTheGunslinger · Mar 9, 2018

Nobody stone me, but I got it from Optics planet.

outrider58 · Mar 10, 2018

Funny thing is(and I am not a military guy), on 20" M-16 A2, the 'cut-out' isn't used. The forend of an M-16 A2 carries the whole launcher. The cut-out is for the shorter M-4 carbines. Weird.

MattTheGunslinger · Mar 10, 2018

That's what confuses me. I've actually never seen an M4 style cut out like this on a 20" barrel. I contacted FN to see if this is a mess up. Just waiting for their responses. Either way, I think I'll just keep it and make it into a Magpul MOE rifle. I need another upper to make my A3 build now.

NatBoh · Mar 12, 2018

As a fire team/squad leader, I carried an A2 with an M203 attached. It was a standard A2 with a heavy barrel, no cut-out.

MattTheGunslinger · Apr 15, 2018

So I ended up sending back that first upper that had the incorrect barrel. It took about a month to receive my replacement.… and it has the same incorrect barrel as the first one. I think it's time for BCM.

MattTheGunslinger · May 13, 2018

If anyone is curious how all this turned out, Robert from FN stepped in and got me the correct upper from their own FN pro shop since Optics Planet couldn't, twice. FNs uppers do look amazing. Can't wait to get it out to the range. Thanks again to Robert from FNUSA!

BossmanPJ · May 13, 2018

That’s a nice looking rifle.

aklax11 · May 13, 2018

Looks much better without the cut out haha

dreadpirate · May 16, 2018

outrider58 said:
Funny thing is(and I am not a military guy), on 20" M-16 A2, the 'cut-out' isn't used. The forend of an M-16 A2 carries the whole launcher. The cut-out is for the shorter M-4 carbines. Weird.

Yep - M16A1 did not have a cut out.

dreadpirate · May 16, 2018

Yeah - if it's an FN it ought to be top shelf. That being said, I have a BCM 20" upper on a pre-ban lower and it really shoots well!!

GuitarmanNick · May 17, 2018

Got my 20" HBAR upper from DS Arms and after placing it on the lower, I will have to get an A2 stock to really finish this build right. The barrel looks like an M-16 barrel, only thicker and without the cutout. Surely, this will lead to the acquisition of the proper bayonet at some point in the future.

I got it to the range last weekend for testing and sighting in and must say that it is now my favorite AR.

FN 20" upper question

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