Brake makes accuracy go to pot?

[milanuk]

Hello,

Have an AR that I'd purchased a nice Miculek brake on when I assembled it, and I just about pulled out what little hair I have left trying to get that blasted thing to shoot. Even my special bullet-fairy pixie dust loads (i.e. known good loads that usually shoot little knots in pretty much any gun I've tried them in) shot maybe 1 MOA at best, most everything else hovered around 1.5-2 MOA. For a heavy AR w/ bipod off a bench, w/ a NXS 3.5-15x scope... that didn't cut it, needless to say. I'd tried all sorts of load development, just couldn't find anything it liked.

Took the brake off and it was like night and day... bullets just clumped together on the paper like they had a homing system or something (as it should be )

So... at this point it looks like the brake was the culprit. Any ideas as to 'why'?

Thanks,

Monte

[dvc40jim]

I worked with some prototype breaks a couple years back that had holes not cut large enough for the bullet to pass thru clean. Very small amounts of copper from the jacket were left behind and accuracy really sucked. The holes might have been the correct diameter but cut slightly off center.... either way I enlarged them just a tiny bit and problems went away.

[mjbine]

if the brake was put on with a wrench instead of hand tight, it could cause your accuracy problem or at least that is what i heard. With brakes and flash suppressor should only be hand tight.

[Dan Sierpina]

I've tightened brakes with a wrench for years, no problem. It sounds like the bullet is hitting the brake. It could be as simple as a burr not removed during production, or the threads aren't concentric with the bore.

[yoshidaex]

reaming the comp while its installed may help if the bullets are hitting the baffles on their way out.

[AlamoShooter]

Why not send Jerry a note and or Clark ?

[blkbrd]

I've tightened brakes with a wrench for years, no problem. It sounds like the bullet is hitting the brake. It could be as simple as a burr not removed during production, or the threads aren't concentric with the bore.

reaming the comp while its installed may help if the bullets are hitting the baffles on their way out.

+1

[P.E. Kelley]

Every response so far is on target.

Another that enters the mix especially since you report groups in the 1.5" range is modal vibration (barrel whip).

The brake is acting as a tuner that is at the wrong point on the barrel.

A very well known AR smith passed on to me on rare occasions a barrel that will not shoot at one lenght

will shoot at another. All else being equal.

Monte what shift are you on and when are your next days off?

I could meet you in Ephrata and hand you a brake or two to compare results.

pk@multigun.com

Patrick

[milanuk]

Thanks for the responses, folks.

The barrel in question is a White Oak Armament 20" Service Rifle tube... Wilson 1-7" twist, full 1" under handguards, .730 forward of the gas block, etc. Probably the third or fourth one of these I've had, and all the rest have just hammered, even with an A2 flash hider installed (on my Service Rifle). Right now this one just has a knurled thread protector whoozit from Adco Firearms on there so I don't have to worry about mucking up the threads.

Okay... I gotta ask... if the bullets were really ticking the brake on the way thru... wouldn't the shooter notice?!? I was always under the impression that sort of thing lead to rapid disassembly of the brake followed by changing of underwear by the shooter...

When I finally pulled that brake off of the muzzle, it was on there tight. Almost thought I was going to have to go search for a bigger hammer

Pat,

Just finished up 'hell' week, coming up on my week of four 8 hr days, then my week off. Running the last 600yd match (for us) of the year tomorrow @ NCW Gun Club.

Thanks,

Monte

[yoshidaex]

if the alignment was WAY off, you'll notice. but if it barely touches the baffles, you won't notice but the accuracy can be way off.

check your comp to see if there is any indication the bullet is touching the comp on its way out

You could always just shoot a ton of bullets out of it, eventually it'll wear the baffle away and you'll get your accuracy back but by that time your barrel might be shot out and your accuracy will have gone out the window a long time ago this is all in jest of course.

proper way to do it is ream it while installed but like P.E. Kelley mentioned the barrel whip is something to look into also. maybe a lighter or heavier comp?

Edited November 2, 2007 by yoshidaex

[AlamoShooter]

If the air that fills in behind the bullet is not equal it will throw the spin off. = that is why you want the Crown of the barrel to be nice and even.

If you go grinding on the thing you never will get them to waranite the probelm

[Merlin Orr]

Loose comp and/or interference with the comp. Look at the exit hole in the comp really close and see if you can see the copper color streaked on some part of the exit hole. And as Alamo says...the barrel crown must be correct. Sometimes they may get a little buggered when/if the barrel was threaded for the comp.....

Edited November 2, 2007 by Merlin Orr

[P.E. Kelley]

FYI guys.

milanuk (monte) is an accomplished LOOOOOONG range rifle shooter.

He did indicate that the rifle shot GREAT without the comp.

"Took the brake off and it was like night and day... bullets just clumped together on the paper like they had a homing system or something (as it should be wink.gif )"

IE the barrel and crown are...OK.

A bullet that kisses the comp MAY shoot ok but probably not 1.5" groups as milanuk indicated.

A bullet that smacks the comp ain't gonna hit the bloody target.

Before we get to far off track.

Patrick

[Bryan 45]

Another item of speculation.... the barrel may not be threaded perfectly.

[Patrick Sweeney]

A White oak Armament barrel not threaded properly? What are the odds?

Try adding a peel washer when you screw on the comp, to push it a turn or two further out. that mgiht change the barrel harmonics. And yes, check the comp for bullet strikes. They don't have to be much to throw off accuracy 9and probably aren't, or you wouldn't have accuracy) but any contact is bad. Look for copper wash, or oxidized copper blue or green.

[milanuk]

Pat Kelley,

Not sure about 'accomplished' . More like 'lucky' Thanks, though!

Patrick Sweeney,

Kind of what I thought about the threading... I think Holliger has Frank White down @ Compass Lake do the machining on those barrels in a CNC setup. Not impossible to get a lemon, but I'd be dang surprised.

I was using the supplied jam nut to secure the brake in place once I had it 'timed' where I wanted it. If overtightening can cause problems, that might have been it. Either that thing self-tightened with firing, or I must have gotten carried away snugging it down, as it was awful tight when I took it off. I ordered some crush washers when I put the A2 flash hider on my Service Rifle... I don't know what it takes to actually 'crush' those things, but it was more than I was willing to put my considerable weight behind with my upper held in an action block for fear of tweaking something I shouldn't.

I'll try the tuner thing this next week as I get some time to make some trips to the range (about five minutes from my house).

Thanks,

Monte

Edited November 2, 2007 by milanuk

[AlamoShooter]

The thing with the air was... if the comp is not letting the air "fill" in behind the bullet evenly when it passes the comp = that would be just like having a crown that is off. One of the old school things was the thought that a comp would hurt acuracy if it was fit close. The smaller the hole the bullet has to pass the better the comp works. = it catches more gas.

I don't know much, and Im not too good , but if you gave me a comp for my barrel that I shoot long range with I would not take it. if I had to use it all the time.

[Dan Sierpina]

Monte,

When checking the exit hole, you may actually see the lands and grooves from the bullet. The barrel on my AR was originally 20 inches. It's a take off from a prize gun I supplied years ago. The winner said it didn't shoot, I replaced the Wilson Arms with a Douglas. I then shortened the Wilson to 18 1/2", threaded it and put a comp on it. It's still a tack driver with good ammo. So, the comp can alter the harmonics on that particular barrel as Pat Kelley suggested.

[fastshooter03]

Miculek comps usually have an exit hole bigger than 1/4" which gives you at least .012" per side on bullet clearance if the threads are done right. They have very short length of thread so you can't use just a peel washer. I think they are mass produced on a multi-axis lathe so it is doubtfull that it is that far out of whack but YOU NEVER KNOW UNTIL YOU INSPECT IT. Whenever somebody I know wants/has a miculek comp I will take it and cut the threads all the way to the first port so you can install with a peel washer and save about 5/16" worth of OAL on your barrel. It also allows for cleaning of the crown. I will also add a couple of top holes too just to make it interesting. If you know a machinist, see if he/she can help you out. A machinist should be able to tell you if the thru hole and threads are indeed concentric/straight as well.

I charge $20 per brake to do both the thread lengthening and extra holes at whatever position(righty or lefty) you want.

I make my own brakes but the miculek version is very cost effective for it's performance. Normally.

Nick

Edited November 3, 2007 by fastshooter03

[scirocco38s]

I have also seen this accuracy issue rise up when installing a miculek comp. There was no evidence of the comp baffles being hit by the bullets or any other clearance issues. But we had the same problem, when we removed the comp the gun went back to sub-moa and point of impact returned to original spot. The only answer I could come up with is that the barrel did not like the change in harmonics that the comp introduced. Just to be certain we also tried a cooley comp on the same barrel and the group opened up again and shifted to a different point of impact.(different than the A2 flash hider or Miculek comp.) So after about 2 hours of expierementing we returned it to original with a vortex flash hider and the accuracy came back and we called it a learning expierience.

[Bronco]

There can be carbon build up inside the first chamber in front of the threads. This chamber doesn't have a port so gets all the unburnt powder and builds up carbon very quickly (as few as 400 rnds.) I had one "ticking" the bullet and about drove me nuts before I found the problem.

[BPiatt]

Let's K.I.S.S it

Just like practice... eliminate one item of interest at a time. Put another brake on and shoot it. If you get similar results, you can focus on the rifle and not the brake.

[mscott]

This is a very interesting topic. I found a great load when using a JP tank brake. I shot without the brake and my point of impact moved a little over an inch to the right. I got my new F2 comp and that good load that shot 5/8" went to about 1 1/2". I tried a few more loads and found some that were real good with the F2, but didn't work so well with the JP. Looks like you need to start over when you start changing barrel parts.

[wsimpso1]

My practical rifle shot fatastic with that brake. A few thoughts:

I don't like to mess with the bore by cinching down on the barrel at the crown. I hand tighten muzzle devices with loctite to make sure that they are not going anywhere and that the barrel is not shrunk down at the crown. On this brake, I put only a few drops on the brake, and one dinky drop on the lock ring. It came off when I needed it to with just a bit of heat gun waving;

I would check that the marks on the baffles are all the same, not just "no copper". If the bullet flies too close to the baffles, it will deflect it too;

Reaming the brake to align with your bore is good practice for accuracy. So is cutting the threaded portion through like Fastshooter3 described.

Billski

[kurtm]

I don't know about all the bullet kissin, non over tightenin, wizzmo-gizzmomounting techniques, but I have never had good luck with using the "jam" nut on the Miculek comp (nor the old Smith comp)! Never could get one to shoot that way! BUT when I installed the darn thing with a peel washer with just about a 1/16 of a turn at the end to center with a wrench or wood dowel through the comp port almost all of em would do okay! I think threads can be a bit off, but usually the shoulder on the barrel is pretty darn square to the bore as is the back of the comp, and that seems to center them a fair bit. It also might cut out a weird vibration right where the barrel steps down to the threads as that is it's thinest part. KURTM