Question on misaligned gas block set screw dimple

AR/M4 AR Technical Discussion
1

Here are pictures:

These two pictures are taken of a Vltor set screw gas block installed into the factory drilled dimple. The rail is a NSR and the upper receiver is a Vltor MUR. The NSR is aligned with the MUR via an acog screw mount to ensure straightness. Notice how, when looking down the barrel, the gas block is canted to the left?

I’m still at home recovering from surgery so I can’t actually test fire right now, but is this acceptable? Does this happen a lot? I usually run complete factory uppers or fixed FSBs so I’ve never actually run into this problem before.

Putting slight pressure on the barrel is enough for the gas block to touch the inside of the rail on the left side (as looking down the barrel).

2

what barrel is that?

3

Centurion

4

I had the same experience with the last three Centurion Arms Hammer Forged 16" Mid Length, Light Weight Barrels I bought. I used a Rainier Arms Gas Block Barrel Dimpler to verify the factory dimple was not at bottom dead center but was off center and to re-drill the dimple at bottom dead center. This solved the problem.

5

Its a non-issue. Undo the gas block and look at the size of the hole. Then look at the port.Its several times larger. More than likely what causes the issue is the holes for the screws are not perfectly centered and when you tighten the screws it pulls the block left or right.

6

my Colt 6720 with low profile gas block is also misaligned like that. Shoots fine.

7

It will work…but for the money I wouldn’t tolerate it. If it was a free barrel than rock on. :wink:

Either re-drill the dimples or send it back.

8

At a minimum I would contact Centurion. They are a good company and would want to know about errors like this.

Sent from my iPhone on tapatalk

9

^this. Theyre probably going to ask you to send it back, in which case, i’d go ahead and pay extra to get a factory pinned block on the replacement.

10

As mentioned, the hole in the gas block is larger than the port in the barrel, so it should run fine.

That said, I wouldn’t spend a dime of my hard earned money on crooked parts. This is basic stuff.

11

I would like to seek some clarification here.

  1. Do you know for sure that the dimple is not centered correctly on the barrel?

  2. Who built this upper and is it possible that that person misaligned the block when it was installed?

  3. These blocks are only dimpled and set screwed correct, and not pinned?

12

Let’s allow the OP to contact Centurion and address this and then we’ll open it back up.