View Full Version : Brake indexing: crush / peel washer
Working on a build and test-fitting my brake; it needs to be indexed a certain way for intended function. Just hand-fitting with a crush washer, it's about 90 degrees off of where it needs to be. That seems like a long way to go. I tried "pre-crushing" the crush washer in a vise and I didn't see much difference. In spite of the name I'm a little skeptical of the crush washer's ability to give without causing thread damage.
I've never used a peel washer.
Open to comments / suggestions. Thanks.
Brake is the AAC non-mount single chamber, if that matters.
fivefivesix
01-13-11, 07:17
sounds like you need shims. 90 degrees off means to add shims instead of going 3/4 more turn.
someone with more know how will be along im sure. did you use the search between calender and the faq up at top there orange tabs.
Either try another new crush washer or go the peel washer route.
I like peel washers even though they are more time consuming to set up correctly. Sould be able to find them at one of the vendors off the forum here or thru Brownells.
Here is a good thread about peel washers!
https://www.m4carbine.net/showthread.php?t=34303
another huge vote for a shim set, it makes life much easier. You can get them a couple of places, here is a set from Spikes.
http://www.spikestactical.com/new/z/alignment-set-for-fake-cans-muzzle-devices-p-358.html
the one I use from PWS:
http://primaryweapons.com/store/pc/viewPrd.asp?idproduct=109&idcategory=19
Instructions from site:
This shim set is comprised of 3 different sized shims: 1 large, 8 medium, and 1 small.
The large shim can be used to give the installer one half of a rotation or as a spacer for barrels that do not have relief cuts behind the threads.
Shim 2 is used in varying quantities to achieve the proper alignment of your muzzle device. This shim gives the installer approximately 45 degrees of rotation.
If needed, Shim 3 can be used where smaller degrees of rotation are needed for proper alignment.
sounds like you need shims. 90 degrees off means to add shims instead of going 3/4 more turn.
someone with more know how will be along im sure. did you use the search between calender and the faq up at top there orange tabs.
Shims are only necessary when the muzzle device doubles as a suppressor mount. The crush washer allows for one full revolution after your muzzle break has been hand tightened. I suspect you may not have the tools to properly fixture your upper receiver to install the muzzle break.
90 degrees is only a quarter turn. You'd get probably another sixteenth to one eighth turn before it starts to really crush the washer
90 degrees is the least amount you'd turn a crush washer. Anything less an your torque value is likely insufficient. I've used both methods...hard to imagine anything simpler than a crush washer for this kind of install.
On your install, you can go the 90 degrees and you'd likely be fine, or you can very likely go around 360 + 90 to get there too.
Use the correct tools and tighten it properly. You can still turn the flash hider the 90 degrees necessary to make it happen.
I also recommend a small amount of anti seize on the threads.
Shims are only necessary when the muzzle device doubles as a suppressor mount. The crush washer allows for one full revolution after your muzzle break has been hand tightened. I suspect you may not have the tools to properly fixture your upper receiver to install the muzzle break.
I do have the proper tools, I just didn't realize the crush washer would allow that much turn. I have only tried hand-tightening as stated earlier.
Thanks for the info!
If the crush washer is brand new and never used (i.e. crushed), you should have no problem. Just hand tighten, mount the upper correctly in the vice, and align it correctly.
If you have never done this before, crush washers can be a bit deceiving as to how much they will crush.
Use the crush washer, you'll be fine.
I do have the proper tools, I just didn't realize the crush washer would allow that much turn. I have only tried hand-tightening as stated earlier.
Thanks for the info!
I think the most important tool is likely some kind of secure barrel clamp. I'd recommend against using a receiver block. A completely serviceable set of barrel blocks can be made with a couple of pieces of 2x4 with some V-grooves cut or routed into them across the grain - clamp in vise. Slip a bicycle innertube over the barrel where you clamp it. Wrench the comp down with an open end wrench or armorer's wrench.
Sometimes you do need to crank on those crush washers quite a bit - they will crush, but it takes a bit more effort than you might think. Right tools definately make all the difference.
If you have a fixed front sight base, but no barrel clamp that will fit, you MIGHT try grabbing the FSB, gently, in a padded vise. It'll resist the torque needed to crush the crush washer.
Once the crush washer starts crushing, the axial load pretty much goes constant. That means that the torque also plateaus once you reach plastic deformation of the crush washer. Schmear a little anti-sieze or grease on the threads and you'll be able to tighten it down pretty easily.
Now to dumb it down another step: the crush washer goes on with the raised part of the inner diameter contacting the barrel, and the raised rim of the outer diameter contacting the brake, correct?
uhhh... ya, wide side out towards the FH.:D
For good info on using a crush washer, regardless of muzzle device, go to Battle Comp site, and look for installation instructions. They recommend tighty loosy... till indexing is complete.
Mark
For good info on using a crush washer, regardless of muzzle device, go to Battle Comp site, and look for installation instructions. They recommend tighty loosy... till indexing is complete.
Mark
They must have removed it; all I could find there is:
How do I install my BattleComp 1.0?
Any competent gunsmith can install a BattleComp, and we always recommend a gunsmith do the installation.
Please be sure the BCE Logo is at 6 o’clock (the bottom of the compensator)
The "tighty/loosie" method is generally considered to be.... screw it down finger tight - tighten it 90 degrees (crushing the washer a little) - back off a hair - another 90 degrees (crushing the washer a little more) - back off a hair - another 90 degrees....etc until you get somewhere between 90-100 degrees short of clocked, then tighten down that last 90-100 degrees to clocked.
You are right, JCKnife, I could not find it either, even in FAQ. Instructions were included in package, but you have a different brake.
I've read a post by PRGGodfather, who is the manufacturer of Battlecomp, recommend what Hmac says.
Some people also recommend lubing the threads first.
As others have said, a barrel vise of some sort is invaluable.
Mark
I neglected to mention that this barrel is heavily dimpled. That being the case, wrapped in a heavy-duty cloth and clamped in the vise was enough to index the brake with the crush washer. Without the dimpling this would not have worked.
Thanks, all.
I guess, while this thread is active though, I'll go on and ask this:
If using a barrel clamp is the only recommended way to do this, that seems to mean that if you have a free-float rail installed, the whole assembly has to come off in order to change the brake the right way? Is that correct? Because leaving the rail on, the only way I could see doing it would be with the upper in an upper receiver vise block.
I guess it's true that if you don't have any exposed barrel at all, you'd have no choice but to remove that rail. I didn't have to do that on my 11.5 SBR with 9 inch rail when I installed the FSC556, however. Took me about 10 minutes to install the brake, and that's because it took me 5 minutes to find a 5/8 open end wrench. Likewise, no trouble installing Battlecomps on either of my other two rifles, both of which have 16 inch barrels.
http://mccollister.info/clamphere.jpg
You may have to cut down the barrel clamp pieces, as I did, to clear the rail, but its do-able.
mark
I have used upper receiver vise jaws and never had a problem. You just need to use some finesse.
I guess, while this thread is active though, I'll go on and ask this:
If using a barrel clamp is the only recommended way to do this, that seems to mean that if you have a free-float rail installed, the whole assembly has to come off in order to change the brake the right way? Is that correct? Because leaving the rail on, the only way I could see doing it would be with the upper in an upper receiver vise block.
MichaelZWilliamson
01-19-11, 14:05
I have used upper receiver vise jaws and never had a problem. You just need to use some finesse.
Yeah, I've had some brakes where the barrel just spun in the barrel block, but an action block made it work at once.
For what it's worth, when I install comps I always use an armorers wrench which allows the torque to be applied without side loading, or inducing off axis force, while applying rotational force. I've never had any issues using an action block.
MichaelZWilliamson
01-19-11, 22:02
For what it's worth, when I install comps I always use an armorers wrench which allows the torque to be applied without side loading, or inducing off axis force, while applying rotational force. I've never had any issues using an action block.
Good point. Noted and thanks.
Just an FYI. Rotation of 90 degrees (1/4 turn) will impose a crush distance of .0089" or about 3 strands of hair for the layman.
Just an FYI. Rotation of 90 degrees (1/4 turn) will impose a crush distance of .0089" or about 3 strands of hair for the layman.
More importantly...what are the torque characteristics of a crush washer on a 1/2 x 28 thread? Once it begins to crush, does the torque stay constant? Or does the torque increase as it crushes?
I had always understood that 90-100 degrees gave the appropriate torque value - about 25 ft-lbs. Do you know if that's correct? I mean, it's how I've always done it except for the time I used shims on an FSC556, which came loose.
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