9mm SBR Barrel crown - Damage?

[rouchna]

I have always shot my 9mm SBR suppressed as the 4.5" barrel sits within the 10" rail. I've never had a single issue with it. The suppressor threads on without a hitch. I finally decided to clean it today and noticed this (picture below). I haven't taken the rail off yet but plan to do so this weekend.

Any idea why this is happening? This is an ADCO barrel by the way.

Thanks.

As I shoot it:





Without the suppressor:

 

[DutchV]

Is that some sort of damage? Or just crap building up from blowback? Looks sort of like lead.

 

[rouchna]

Is that some sort of damage? Or just crap building up from blowback? Looks sort of like lead.

It does look like lead. This is the first time I've noticed it. As I said, I won't have time to closely inspect it until this weekend. I just wanted to get everyone's thoughts. Thanks.

 

[JBinDC]

+1 on lead idea... That thing looks wicked btw! Can I ask what the build is!? --JB

 

[rouchna]

+1 on lead idea... That thing looks wicked btw! Can I ask what the build is!? --JB

9mm SBR AR. Here is the parts list.

Upper:

Vltor MUR1s stripped upper
CMMG ramped 9mm bolt
Adco 4.5" barrel
Seekins 10" Rail
BCM Charging Handle
DD Fixed front sight
Troy Rear sight
Aimpoint H1 w/American Defense mount

Lower:

Quarter Circle 10 Colt Pattern 9mm lower
Spikes LPK
POF Trigger
KNS pins
BCM Mod3 grip
Vltor Imod stock
Spikes Buffer tube & spring
Heavy Buffers 9mm buffer

 

[clandestine]

If its not lead or carbon buildup its likely just erosion.

If its erosion buy some valve grinding compound from the auto parts store and get a crowning ball here. You can do it with a hand drill if you remove the rail.

http://www.brownells.com/gunsmith-t...custom-brass-muzzle-crowning-lap-prod855.aspx

 

[rouchna]

If its not lead or carbon buildup its likely just erosion.

If its erosion buy some valve grinding compound from the auto parts store and get a crowning ball here. You can do it with a hand drill if you remove the rail.

http://www.brownells.com/gunsmith-t...custom-brass-muzzle-crowning-lap-prod855.aspx

Thanks Chad. I will have a closer look this weekend. If it isn't lead or carbon, I will follow your advice.

 

[BradMacc82]

Flame/gas etching was my line of thought as well.

 

[outrider58]

Thinking lead from the color.

 

[BradMacc82]

4140 steel, I'll still stick with erosion/etching.

 

[outrider58]

4140 steel, I'll still stick with erosion/etching.

Yes, I have one. You're the expert.

 

[BradMacc82]

Yes, I have one. You're the expert.

Well we never inquired about ammo type, so...

 

[rouchna]

Well we never inquired about ammo type, so...

Ammo type is a mix of Freedom Munitions 147gr fmj and Tomkat 158gr.


Sent from my iPhone using Tapatalk

 

[DutchV]

How many rounds have you put through it?

 

[rouchna]

How many rounds have you put through it?

Just over 1K.

 

[PowPow]

If it's lead, is it normal for a suppressed firearm to collect lead on the crown like that? If it's not lead, what woulds cause erosion like that? If and when I get a suppressor or two (or three), I want to know what to look for. Thanks

 

[JBinDC]

9mm SBR AR. Here is the parts list.

Upper:

Vltor MUR1s stripped upper
CMMG ramped 9mm bolt
Adco 4.5" barrel
Seekins 10" Rail
BCM Charging Handle
DD Fixed front sight
Troy Rear sight
Aimpoint H1 w/American Defense mount

Lower:

Quarter Circle 10 Colt Pattern 9mm lower
Spikes LPK
POF Trigger
KNS pins
BCM Mod3 grip
Vltor Imod stock
Spikes Buffer tube & spring
Heavy Buffers 9mm buffer

Sweet build dude! Respect. --JB

 

[j_h_smith]

That's lead. It does happen. Looks like you have a small gap between the threads of the barrel and the threads of the suppressor. Does the suppressor bottom out against the barrel? What are you shooting out of it? Do you have a pick that you can stick through the rail and see if you can scratch or possibly even remove it.

Have you taken the suppressor apart to see what build up you have on the baffles?

 

[EKing]

Could it be that the suppressor was not screwed down all the way initially? If there's a small chamber between the crown and the beginning of the suppressor, it would seem to give those hot gases a little more time to cause damage.

Very interested to learn how it happened.

 

[rouchna]

Sweet build dude! Respect. --JB

Thank you

That's lead. It does happen. Looks like you have a small gap between the threads of the barrel and the threads of the suppressor. Does the suppressor bottom out against the barrel? What are you shooting out of it? Do you have a pick that you can stick through the rail and see if you can scratch or possibly even remove it.


Have you taken the suppressor apart to see what build up you have on the baffles?

The suppressor screws on all the way. I also had it checked for concentricity prior to shooting it. It is tight and I always check to make sure it is screwed on all the way. It is definitely lead build up. I was able to easily scrape some of it off. Having said that, I haven't had time to take the rail off to try to completely clean it off.
As for the build up on the baffles, it is completely normal. I have 3 suppressors and the build up is as expected.

Could it be that the suppressor was not screwed down all the way initially? If there's a small chamber between the crown and the beginning of the suppressor, it would seem to give those hot gases a little more time to cause damage.

Very interested to learn how it happened.

See above. It is screwed on tight and it is concentric. I'm also curious to see if this is normal.