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Posted: 7/29/2017 8:31:58 AM EST
Folks,

I just disassembled an old Bushmaster in preparation for installing a new LaRue barrel. When I removed the A2 "birdcage" flash suppressor, I was surprised to see a LARGE rim of carbon residue on the crown of the barrel. That prompted me to pull out the caliper...

If you cut the A2 "birdcage" in half, its internal structure would look like an "H". The bottom half is threaded, the top half has the slots for gas escape, and the crossbar has the hole for the bullet. Measuring up from the bottom, the threaded portion measures .690". The crushwasher, as installed, measured .110". That gives a total height of .800" from the bottom of the crushwasher to the beginning of the "H" crossbar.

The carbon fouling seems to have accumulated underneath that crossbar region, in that gap.

My new LaRue barrel has a threaded end of the barrel which measures .625", from the crown down to the shoulder where the threads end. That means, if I were to re-use the A2 flash hider, there would be about .175" of gap between the crown and the A2 crossbar.

That would, again, allow a large accumulation of carbon. I doubt it would accumulate in an even manner. It would have to have an effect on accuracy.

Is there any muzzle device which allows for fully seating against the barrel without damaging the crown or leaving such a large gap?

I've got a basic thread protector on order, but I'd rather not shoot an AR without some sort of flash hider or compensator.

Any knowledge on this would be appreciated...

Thanks,
Ken
Link Posted: 7/29/2017 9:31:38 AM EST
[Last Edit: 7/29/2017 9:33:23 AM EST by giantpune]
I don't know how you'd make one flash hider that you could correctly time on every barrel with 1/2-28 threads and not have a gap there. If I took your same flash hider and put on my gun, there may be a smaller or large gap because my threads are not started at the same place as yours.
If you wanted to get rid of that gap, you would either have to get very lucky or take care when threading the barrel and flash hider to start them at the right place. Like for your barrel, you might need to start the threads on the flash hider at 2 o'clock to have it timed in the right orientation and have no gap between the two.

If you have more than 1 rotation worth of gap there when its timed in the proper direction, you can take material off the back of your flash hider (or get a thinner crush washer).
Link Posted: 7/29/2017 9:36:19 AM EST
[Last Edit: 7/29/2017 9:52:18 AM EST by Hollywood_Shooter]
Yes, that build up can effect accuracy if you let it go too long.

Typically the pressure from .223/5.56 blows out a lot of the crud where some other cartridges don't.  However, that's no reason you can't remove your muzzle device on occasion (when cleaning the barrel is a good time), and clean it.  Bore Tech C4 Carbon Remover is an excellent choice for this task, as is Slip 2000 Carbon Killer.  Get a small container, like a small old tupperware or a plastic cup, and fill it with enough C4 to cover the muzzle device, let it soak a few hours or overnight, and then wipe clean.  Q-tips work well here too.  Problem solved.   

You might want to have some soft jaws in a vice to clamp the barrel to make it easy to torque the muzzle device off and on.

Cleaning the barrel's crown is also a good idea.  You want to do that semi-delicately though so as not to damage the crown.  I just use q-tips again, soaked in C4.

Good luck with the new barrel.
Link Posted: 7/29/2017 10:53:23 AM EST
Thanks.

Removing the flash hider every time I clean the barrel is a pita, but that may be the only way to prevent carbon fouling/clean the muzzle crown.

I can't believe that folks remove them every time they run a bore snake! ;)

There's got to be a better way.
Link Posted: 7/29/2017 11:33:46 AM EST
I would venture to guess that almost no one removes their muzzle device every time they clean, not necessary.
Link Posted: 7/29/2017 1:29:06 PM EST
Using an appropriately sized brass or plastic bore brush with a decent solvent should very easily clean the crown (the part that matters) when you're cleaning the barrel.

I've never removed a muzzle device from one of my guns after install.
Link Posted: 7/29/2017 3:27:53 PM EST
Link Posted: 7/30/2017 12:34:17 AM EST
First -- I didn't mean to suggest, nor did I actually suggest, that you should clean your muzzle device EVERY time you clean your barrel.  That would certainly be excessive. 

Some folks run a bore snake after every range session, which I also find excessive.  But then, I don't even consider bore snakes a proper cleaning.

And - I'm well aware that there are a majority of AR owners who never clean their muzzle device.

That being said, beyond my own personal first hand experience, there were some rather convincing (to me at least) tests of the loss of accuracy when you let it go so long that it build up to the point of solidifying - creating an uneven surface - which does impart influence on the bullet as it departs...but unfortunately I can't locate the links.  It was some good reading.  If I find it, I'll come back to this thread.

Bottom line, if you want to get rid of the build up, clean it.  If you don't care, don't.
Link Posted: 7/30/2017 1:09:16 AM EST
You're massively over thinking this.
Link Posted: 7/30/2017 5:18:19 AM EST
Lol... probably. But, then, I'd NEVER even THOUGHT about it until I pulled my old barrel and saw the horrific ring of hardened carbon which had stacked up between the crown and the buffer on the flash suppressor. I'd not been happy with accuracy (that's why I bought the LaRue barrel for it): this could explain a lot of the problem. The carbon was uneven and very hard. (About 5,000 rounds?)

As for tests, well, I'd love to run enough ammo through one to build up the crud. As it is, I've purchased 3 muzzle devices for the new barrel; a thread protector (so nothing is between the crown and the target), a Wilson Combat 3-prong flash suppressor, and a new A2 birdcage. I'll see how all 3 compare as to POI and groups. I'll do it in the next 2 weeks or so. (If I get really motivated, I may crush up a charcoal briquette and stuff some of the powder around the crown. I'd think that would be close to the crud I found, even if it's not as hardened.)
Link Posted: 7/30/2017 8:43:21 AM EST
Originally Posted By c3k:
I've got a basic thread protector on order, but I'd rather not shoot an AR without some sort of flash hider or compensator.
View Quote


Why not? There's no harm in shooting with a bare muzzle or thread protector, unless you are afraid of being seen without a cool whiz bang attachment in the end...

The way you've phrased it makes it sound like you think flash hiders and compensators do something similar. They don't.

flash hiders greatly eliminate flash, slightly reduce sound (a few db), and have basically no effect on recoil. On the other hand compensators greatly reduce recoil, greatly increase volume, and greatly increase muzzle flash.

So, given that they do opposite things, it seems odd that you are so set on having either one of those 2 opposite things...

By the way, a bare muzzle has it's advantages also -- it's light weight, making it faster to point your gun and easier to hold on target, quiter than a compensator (good for hunting esp if you don't use ear pro), and legal everywhere!
Link Posted: 7/30/2017 10:11:01 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By pebble:


Why not? There's no harm in shooting with a bare muzzle or thread protector, unless you are afraid of being seen without a cool whiz bang attachment in the end...

The way you've phrased it makes it sound like you think flash hiders and compensators do something similar. They don't.

flash hiders greatly eliminate flash, slightly reduce sound (a few db), and have basically no effect on recoil. On the other hand compensators greatly reduce recoil, greatly increase volume, and greatly increase muzzle flash.

So, given that they do opposite things, it seems odd that you are so set on having either one of those 2 opposite things...

By the way, a bare muzzle has it's advantages also -- it's light weight, making it faster to point your gun and easier to hold on target, quiter than a compensator (good for hunting esp if you don't use ear pro), and legal everywhere!
View Quote
Well not always the case but there is a big difference bwtn a comp and a brake which the above in red are more characteristic of a brake. On a quest to find a muzzle device that reduced muzzle movement with reduced flash and somewhat minimized concussion that is typical of a brake, the griffin flash comp seemed to be the ticket for my needs and seems to work just as advertised.
Link Posted: 7/30/2017 6:52:25 PM EST
Not the link I was originally looking for but none the less, some light reading for ya'll:

Accuracy degradation from muzzle brake erosion.
By Jim See
Occasionally our precision bolt action rifle may start to have sudden
unexplained accuracy issues. Often overlooked are the erosion forces on
the muzzle brake which can cause the bullet clearance holes to
“tighten”. We have all seen carbon build up in our muzzle device and
this absolutely will cause accuracy loss. But if that accuracy loss
remains after a good carbon removal cleaning we need to look deeper.
I first encountered this in 2008, when a new customer sent in a
specialty pistol in 6.5x284. After 200 rounds his groups had opened up
well over an inch and he was requesting me to fix the issue. After a
quick inspection of action screws, rings and bases, and a bore scope
barrel inspection, I turned my attention to the muzzle brake.
Clearance holes through muzzle devices should be at least .020” over the
bullets diameter, so with a few pin gauges I attempted to measure the
holes. This particular brake had less than .005” bullet clearance. Upon
closer inspection I could see that the brake was opened up .025” over
bullet. But the effects of gas and powder blast on the baffle surfaces
had created a steel bur on the leading edge of each clearance hole. That
bur subsequently rolled into the leading edge of the thru hole causing a
reduction in clearance.
The end result was a bullet that was being adversely affected as soon as it left the muzzle. My inspection also
revealed that the original gunsmith used a brake that was of stainless
steel of a non-heat treated variety that was softer than barrel steel,
this promoted the deformation and movement of the steel into the
clearance hole.
My later testing revealed that harder brakes tend to take longer for the erosion/metal displacement to occur to a
point that accuracy is affected. I have also learned thru the
inspection and construction of thousands of rifles and muzzle brakes
that greater erosion/displacement occurs based on these other factors;
short barrels, slow burning powders, and large capacity cases (which use
slow burning powder) all tend to increase the erosion factor.
The solution;
Well really that starts during the brakes manufacturing and
installation. Since that very first revelation of thru hole tightening, I
have sought to combat the occurrences and what I learned in building
muzzle brakes and testing processes has paid off.
Now I bore all my muzzle brakes to .030” over bullet diameter during installation. This
helps slightly but the real key is to chamfer the leading edge of each
baffles clearance hole with a 45 degree chamfer for about .015 of an
inch.
To properly explain the location of this chamfer picture each baffle that the bullet passes thru as a small funnel, I am removing
the material that creates the bur. When the baffle is a perfectly flat
surface the material around the clearance hole gets pounded by pressure
and carbon residue, thus it deforms at the 90 degree edge and flows into
the area of bullet clearance. By cutting this very small “funnel” the
material does not get a 90 degree impact, thus it is much more resilient
to deformation.
The process of chamfering the baffle holes is accomplished right after brake install when the clearance hole is being
bored to its final dimension. I simply walk my HSS boring bar to the
leading edge of each hole and cut the correct chamfer with the angle
that is ground on the cutting surface of the tool. Done this way most
brakes that are of 28 rockwell hardness will last the life of the rifle
barrel with no issues related to clearance hole erosion/burr creation.
Repair of an already damaged muzzle brake;
This is relatively simple, slide a pop-sickle stick in the first port
of the brake closest to the muzzle or remove the brake from the rifle.
The intent is to simply protect the rifle bore and crown from the
process of de-burring the clearance holes.
I take a ¼” brass rod with a slit in it to hold a small wrap of some 320 grit emery cloth. I
then chuck the brass rod in the drill and hone out the clearance holes,
which in the process will fracture off all the burs and get you back to
your original clearance dimensions. This process may have to be repeated
during the life of the rifle depending on barrel length and powder burn
rate ect. That I outlined above.
So remember these tips if you’re having an unexplained accuracy loss that you cannot contribute to other accuracy gremlins.
View Quote

https://www.facebook.com/EliteAccuracyLLC/posts/1753033075014430:0

and:

Chad Roberts added 2 new photos.October 11, 2016 ·
Copper and Muzzle Brake issue on train up Friday before the match: Hopefully this helps others out in the future.
So as most have heard I had a rough morning Friday before the match
with my gun shooting a half MOA group at 100 yards and just not
performing as it usually does. Typically this is a one hole puncher and
I've shot a 3 inch group at 1000 yards, so typical for this rifle is
perfection. Certainly not throwing shots all over the zero range like it
was.
Brian Allen spotted my muzzle break being all kinds of fouled up and honestly I just didn't
realize it had gotten as bad as it had. So as first steps go we took it
off and fired a group, it was still throwing shots. When I say throwing
shots it would be two touching, two or three spread out. I then put my
suppressor on and same thing, throwing shots. To make sure it was not
just me Brian Allen shot a group and results were conclusive that the
gun was just not grouping. Pissed off, I went back to RV to collect my
thoughts, etc.
As luck would have it this big beautiful looking guy named Brian Bowling who was a stranger to me at the time decides to park beside our RV. He
gets out of his truck and proceeds to yell across lot to his buddy that
he has a bore scope with him if his buddy needs it. I immediately asked
if he wouldn't mind checking mine out because I couldn't figure out why
my gun was throwing shots. So him being a great dude that he is, he
takes a look for me. Turns out my barrel is coated with copper and some
pretty bad spots built up at the muzzle and at chamber, one deep spot
about halfway down barrel also. At this point there is 817 rounds on the
barrel.
I grab my Eliminator copper remover that's been collecting dust for years and run four soaked patches down barrel
followed with 20 passes of a nylon brush. I repeat this about 8 times
until I'm getting no blue on my patches.
Up until that moment I hadn't used a copper cleaner, just clean my barrel about every 300
rounds with a bore cleaner (not going to name which one because I'm no
pro at cleaning and that wouldn't be proper etiquette)
The pictures of the chrono are from before cleaning the rifle and after
cleaning the rifle. Same ammo loaded all at the same time before the
match. The 5.4 SD was before cleaning the copper out.
The seven shot chrono with zero sd was rounds 3-10 after cleaning. I tossed out first three shots bc barrel was re-fouling.
After cleaning the copper out and putting a clean muzzle break on the
rifle it was back to shooting solid one whole 5 shot groups at 100 and
zero SD's.
I hope this helps some of you out there who were like me and honestly didn't understand the effects of copper issues. I will
certainly be buying a barrel scope now after seeing how great of a tool
they can be. A big thanks to both Brian Allen and Brian Bowling for your
help.
View Quote

https://www.facebook.com/search/str/chad%2Broberts%2Bmuzzle%2Bbrake/stories-keyword/stories-public?esd=eyJlc2lkIjoiUzpfSTI2NTAzNjQzOjEwMTAyNDYzODQ3M­jI3NDY2IiwicHNpZCI6eyIyNjUwMzY0MzoxMDEwMjQ2Mz­g0NzIyNzQ2NiI6IlV6cGZTVEkyTlRBek5qUXpPakV3TVR­BeU5EWXpPRFEzTWpJM05EWTIiLCIxMDAwMDEwNzc2NjMx­NzQ6MTEwNzIzMTAzOTMyMjgwOCI6IlV6cGZTVEV3TURBd­01UQTNOelkyTXpFM05Eb3hNVEEzTWpNeE1ETTVNekl5T0­RBNCJ9LCJjcmN0IjoibWVkaWEiLCJjc2lkIjoiMWM1OTR­hODk5YmY0ZDc4MTQ1YjdhYTY2NDliZDc0YzAifQ%3D%3D­
Link Posted: 7/31/2017 11:00:28 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By c3k:
Thanks.

Removing the flash hider every time I clean the barrel is a pita, but that may be the only way to prevent carbon fouling/clean the muzzle crown.

I can't believe that folks remove them every time they run a bore snake! ;)

There's got to be a better way.
View Quote
If it isn't building up right on the crown you probably won't see negative effects for a long time.

On my precision rifles I let the carbon cleaner work the crown and clean off. Gives me a shiny area about .050-.100 around the bore, seems to be no issue. 
Link Posted: 7/31/2017 3:05:30 PM EST
[Last Edit: 8/1/2017 9:21:31 AM EST by c3k]
Thanks, all.

Yeah, the build up was ON the crown, filling the gap between the crown and the first "baffle" of the birdcage. If it didn't fill the gap evenly, then I'd think it would be a problem. Plus, the crown of most rifles receive a bit of attention to make sure they're even/symmetrical. I doubt that the surfaces of most muzzle devices receive similar machining.

The gap. If I were to cut a similar groove inside my barrel, less than a caliber in from the muzzle, I'd think it would affect accuracy. If I were to ROUGH cut that same groove, it would be worse. That's the effect that the carbon in the gap seems to have...in my mind.

So, yeah, I know that I don't -need- anything on the end of the barrel. As fun as it is to make fireballs at twilight with each trigger pull, I'll forgo that pleasure and put SOMETHING there to tame it.

Lots of good thoughts here.
Link Posted: 8/6/2017 9:06:07 AM EST
Want to see your testing results with the various muzzle devices OP. I've done tests of my own and found accuracy differences.
Link Posted: 8/11/2017 10:21:07 AM EST
[Last Edit: 8/11/2017 10:21:42 AM EST by CK1]
Honestly, I think constant removal, cleaning, and reinstalling the flash hider is more like to mess up accuracy than carbon build up. All that cleaning is begging to booger up the crown.

The build up doesn't change appreciably between shots so accuracy and precision will be very stable and consistent shot to shot for any practical application. Even precision rifle.

The only type of shooting where this matters, might be benchshooting. Those guys are chasing groups in the 0.0Xs and they don't use muzzle devices.
Link Posted: 8/11/2017 2:14:09 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By CK1:
Honestly, I think constant removal, cleaning, and reinstalling the flash hider is more like to mess up accuracy than carbon build up. All that cleaning is begging to booger up the crown.

The build up doesn't change appreciably between shots so accuracy and precision will be very stable and consistent shot to shot for any practical application. Even precision rifle.

The only type of shooting where this matters, might be benchshooting. Those guys are chasing groups in the 0.0Xs and they don't use muzzle devices.
View Quote
They use tuners.
Link Posted: 8/22/2017 7:31:11 PM EST
I recently encountered this same issue in a new barrel I tried. My groups were not what I expected and I suspect fouling of the crown is the culprit.
I pulled the flash hiders off 4 well used AR's that I have had for up to 17 years. These barrels have hundreds of rounds thru them and one is a surplus military barrel that I have no idea how many rounds have been thru it. I have never cleaned their crowns and can't recall the last time the flash hider was removed.

Here are their pictures .... why do I not have the carbon buildup others indicate they have while shooting the same ammo produces it in another barel?



20" A2 1990's surplus -



16" Mossberg CHF about 2-3 years old



This is a 11.5" DPMS Pistol barrel with about 500 rounds and a speck of carbon...



This DPMS barrel is 17 years old, has been on many varmint trips and lots of rounds- one small speck visible.

All of the flash hiders except the A2 bridcage have a gap (chamber) between the end of the muzzle and the baffle where the device starts.


Link Posted: 8/22/2017 7:39:47 PM EST
@SyberSniper...those crowns look great.

Carbon fouling between the crown and FH is not usually a concern especially if your guns aren't run hard. I clean that area with some oil and q tips and just clean the crown. Groups seem to tighten up, but I may only do that every once between 500-1k rounds.
Link Posted: 8/23/2017 10:30:41 AM EST
[Last Edit: 8/23/2017 10:59:38 AM EST by SyberSniper]
OP- I'm not trying to hijack your thread- just add info to it to help get more info on our common issue... sorry if it seems that way.

I measured several Flash Hiders I have and the depth/length of threads like you did. Then I measured the washers too.
The only one that came close to having no gap between the crown and FH baffle (.016") was the A2 birdcage on the A2 barrel (but then that washer was torqued down), every other one had a gap (.10-.20") forming a "chamber" before the baffle. None of my devices have any trace of carbon in that area. They include a JP-3 prong, Strike 4-prong, YHM Phantom and the birdcage. Each FH has a different thickness washer - so they are not interchangeable and still time the device correctly but shims could be used I suppose.

Are you able to take pics of your situation?

Since this thread is also talking about muzzle carbon deposits, here is the one I was talking about above.
I usually shoot my own reloads but also test groups with various milsurp ammo (mostly LC) and common oem brands like Win, S&B, Rem, PMC. I almost never shoot steel cases like Wolf or Tula etc except for rare 5 or 10 round testing of a new barrel.

This one only has 300 rounds of the same ammo loads thru it and I am puzzled why it carbon'd up so much ... it also appears to have jacket material, but I know the bullets weren't flying apart because of the target holes and there is no deposit inside the FH... it certainly doesn't look like all of my other crowns.

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