Gunsmithing Keyholing due to Cerakote or Break-in Procedures ?

[RemmyMaxhit]

I posed this as a reply to another thread, but it might be worthwhile to make it it's own topic for future reference.

I was having a keyholing problem on a recently cerakoted .308 with a surefire compensator. The problem went away after maybe 20 rounds. We ran patched down the bore every few rounds and that didnt fix it. The problem simply went away later in the afternnon, with zero keyholes thereafter.

It wasnt until cleaning everything up later at home that we figured out what happened. The cerakote coated the inside diameter of the last ring of the compensator. You could see that all of the cerakote inside the diameter had been forcefullly scraped off by the rounds just barely contacting the cerakote inside the outer diameter of the hole. Cerakote adds a few thou to the finish, so this, we believe in our case was what caused the issue. So, moral of the story, dont get any cerakote inside the bore or compensator.

hope this helps anyone with this issue in the future

 

[Beef_Supreme]

Re: Keyholing due to Cerakote

It should have had the bore plugged prior to ever having been painted with anything.

 

[RemmyMaxhit]

Re: Keyholing due to Cerakote

yes, agreed....in this case, you want to coat the compensator, but it has so may openings, that you will need to go maybe one step further and get a wooden dowel in the proper diameter to make sure no cerakote swirls around inside the compensator. Surprising how tight the tolerances are on it!

 

[LoneWolfUSMC]

Re: Keyholing due to Cerakote

Baffle strikes aren't just for suppressors.

 

[shoepop]

Re: Keyholing due to Cerakote

Glad you found the cause. I'm amazed anyone would produce a compensator that would be affected by a mere few thousandths.

 

[300sniper]

Re: Keyholing due to Cerakote

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mark S</div><div class="ubbcode-body">Glad you found the cause. I'm amazed anyone would produce a compensator that would be affected by a mere few thousandths. </div></div>

my guess is that it was more than a few thousandths of buildup. there are so many nooks and crannies on some brakes that it hard to not get some spots thicker than others while making sure to coat the entire surface.

 

[Kells81]

Re: Keyholing due to Cerakote

Aren't you supposed to have a decent amount of clerence on the brake exit. Cerakote is supposed to be pretty thin so maybe you just hinted at a much larger issue...

 

[Straight Shooter]

Re: Keyholing due to Cerakote

You have more going on than Cerakote here. I believe you have a serious concentricity issue with your compensator. A quick and dirty test is put a range rod in through the compensator and observe the clearance around it. What do you see?

Cerakote put on super thick after baking should not exceed say .002" if you ran a pool of it. You compensator should have at least .010" per side clearance. This leaves plenty of room for coating and still have .008" to spare. Every compensator I have measured had more like .040"+ clearance through them over bullet size. Brakes are fit at .020" over bullet size.

 

[RemmyMaxhit]

Re: Keyholing due to Cerakote

Whatever the problem was, it's no longer there. This was a new GAP M40A5, so all of us at the range pretty quickly ruled out a concentricity problem.

The only non-professional factors were the cerakote and break-in.

Maybe initial break-in could have been a contributing factor, but all is good now as far as we can tell. I like the range rod idea, and will do that next week after the holidays and report back if there is anything weird there, but I doubt it.

 

[9H_Cracka]

Re: Keyholing due to Cerakote

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mark S</div><div class="ubbcode-body">Glad you found the cause. I'm amazed anyone would produce a compensator that would be affected by a mere few thousandths. </div></div>

Per Badger's FTE installation instructions:

"To determine the correct diameter for the comp’s I.D.
Take the bullets O.D. and add .020” (example: .308 bullet dia. +.020”=.328”)"

Sounds to me like the "Surebreak" (whatever that is - google came up with nothing) was installed improperly and is off center with the bore if a little paint gave you a problem.

 

[300sniper]

Re: Keyholing due to Cerakote

i'm still leaning toward a sloppy cerakote application, i.e. a drip/run/thick spot in the bore of the muzzle brake.

 

[RemmyMaxhit]

Re: Keyholing due to Cerakote

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">i'm still leaning toward a sloppy cerakote application, i.e. a drip/run/thick spot in the bore of the muzzle brake. </div></div>

Hard to say...no Cerakote runs anywhere on the exterior of the weapon, but inside all the nooks and crannies of the interior of compensator, could have been a different story.

It is the Surefire M40A5 spec compensator....installed by GAP

In following their recommended break-in procedure, it's possible that a bit of a cleaning patch could have gotten stuck in there as well.

 

[300sniper]

Re: Keyholing due to Cerakote

if it was a surefire muzzle brake, i have seen some of those pretty far out. i had to open one up quite a bit to ensure there wouldn't be a strike. the last one i installed checked out ok, not perfect, but not anywhere near where i suspected there might be a strike.

 

[RemmyMaxhit]

Re: Keyholing due to Cerakote

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">if it was a surefire muzzle brake, i have seen some of those pretty far out. i had to open one up quite a bit to ensure there wouldn't be a strike. the last one i installed checked out ok, not perfect, but not anywhere near where i suspected there might be a strike. </div></div>

OK, this sounds like the most plausible explanation then!

Ive been going a bit nuts trying to figure out what happened. Will check the tolerances on the compensator in-place on the barrel with a rod.

 

[buffybuster]

Re: Keyholing due to Cerakote

Wonder when they threaded the muzzle they centered up on the exterior of the barrel instead of indicating to the CL of the bore. Not uncommon for the bore and the exterior of the barrel to not be on the same center.

 

[Shortdraw]

Re: Keyholing due to Cerakote

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: buffybuster</div><div class="ubbcode-body">Wonder when they threaded the muzzle they centered up on the exterior of the barrel instead of indicating to the CL of the bore. Not uncommon for the bore and the exterior of the barrel to not be on the same center. </div></div>
I'm fairly confident that GA Precision indicates on the bore for barrel threading.

 

[HPLLC]

Re: Keyholing due to Cerakote or Break-in Procedures ?

+1

That would suggest either the Surefire brake bore is VERY tight, or the surefire brake is not very well aligned.


Eccentric apertures will cause a reduction in accuracy, so maybe your rifle would be shooting better if the brake was better aligned.

 

[RemmyMaxhit]

Re: Keyholing due to Cerakote or Break-in Procedures ?

the rifle is shooting great now. No keyholing, and about 1/2 MOA, with me holding it back I think from being better than that. My impression is that halfway during the day, the keyholing resolved itself either by excess cerakote and/or cleaning patch bits being blowed out. Ill report back after next week if it looks like we had a misalignment, but I have to doubt that was the problem at this point

 

[HPLLC]

Re: Keyholing due to Cerakote or Break-in Procedures ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RemmyMaxhit</div><div class="ubbcode-body">the rifle is shooting great now. No keyholing, and about 1/2 MOA, with me holding it back I think from being better than that. My impression is that halfway during the day, the keyholing resolved itself either by excess cerakote and/or cleaning patch bits being blowed out. Ill report back after next week if it looks like we had a misalignment, but I have to doubt that was the problem at this point </div></div>

I'd clear the gun, pull the bolt and visually inspect it. If there is more than .0005" eccentricity, some accuracy degradation is likely to occur. How bad it will have to be to be serious I'm not sure, but I've seen an Ops brake with a bad crush washer cause a 5/8 MOA gas gun to shoot 2-4MOA. That was probably .01" out of concentric.

Maybe the rifle is a Sub 1/4MOA gun, and 1/2 MOA isn't nearly its potential? Certainly 1/2 MOA is good performance, but the paint might have brought an issue into the spotlight.