Gas leakage at front sight tower

AR/M4 AR Technical Discussion
1

I have a BCM 14.5 LW with a pinned A2x, I’ve been running a G2 light mounted to the forward most point on my MOE handguards and I’ve recently noticed the side of the light that is directly adjacent to the sight tower is getting blackened from what I believe is carbon/gas from firing.

The head of the light is well back from the muzzle in this config, so I was wondering, is it normal to have some gas leakage at the sight tower?

The rifle functions flawlessly even with lower power .223 e.g. steel case, but I was curious.

Thanks in advance, Jeff

2

Some pics would be wonderful.

3

I’ll post a pic tonight when I get home from work.

4

Is this a new rifle?

You can put some clear finger nail polish around the base until the carbon has a chance to seal it up.

5

I have a couple rifles that did this, it usually was in the beginning and eventually carbon cakes up and makes a seal.

Unless you are short stroking or suffering reliability issues, I would keep shooting it, but keep an eye that it does not get worse

6

Rifle has several hundred rounds thru, probably close to 850 or so.

7

Given that you have no issues with function, it does not sound like a misalignment. You might go with the old fingernail polish trick to help the seal form a bit quicker or just give her some more time. This is to the best of my knowledge from similar experience.

8

I was kinda thinking that it was something along those lines, rifle runs great, no issues.

9

i have two uppers that do this. one is at about 6500 rds. the other is over 14,000 rds. never had any issues other than carbon on my lights.

10

Some gas escapes from where the gas tube goes into the front sight base. I wouldn’t worry about it, it will probably seal itself up with carbon after a few thousand rounds.

11

Here is a photo, I think this probably normal.

I recently remounted the flashlight and when I did I rotated it in the mount so the gas/carbon fouling ended up on the outside of the handguard.

The does however show the relationship of the flashlight to the front sight.

Most likely it’s coming from the gas tube roll pin.

12

When I put an Omega X FSP rail on my 6920 and was able to move my hand out further I started noticing carbon blacking on my right hand around the area where your seeing it on your light.

13

Same experience here, give it time and just watch it.

14

Is part of your flashlight burned towards the base of the bell portion? It looks like some rubber has been burned, just curious. I have a BCM Midlength 16 with a surefire in an IWC mount that is in close position to your setup. I have had no gas leaking problems and the rifle has 400 rounds through it. It may just be the picture.

15

I have a BCM 16 inch LW middy with a low pro gas block and there is a bit of carbon on the side of my omega rail. Even a bit of build up as in a little mound of it. Rifle functions fine. I figured it was just part of owning an Ar.

16

I’m pretty sure it’s just the pic. I’ll look it over shortly…

17

I looked over the flashlight, it is indeed just the pic, no damage to the light at all.