Authority to the Airgunning World

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Saturday, July 08, 2006

Installing a Apex or Crow Magnum style muzzle brake

This guide is for those of you who are interested in installing a permanent muzzle brake on your airgun barrel that is 16mm in diameter. The apex and crow magnum sleeve do not come with shim inserts that go over the barrel. If you want a brake with on/off flexibility without marring the barrel for iron sight use, look into the Beeman universal or Straightshooters line of brakes.

You basically have two choices for over the counter close-ended muzzle brakes.

Measure the barrel face diameter. Normally they are 16mm, but double check just to make sure. The RX barrels have known to be a little larger.

Take off the front and rear sights from the gun. This should be a relatively easy task, but sometimes you’ll need a gunsmithing screwdriver to take the screws out.

B-Square offers a great set of bits at an affordable price. If possible, try to find the same bits at Sears. The Craftsman tools are guaranteed for life.

However, the B-Square allen heads aren’t the most precision ground bits on the planet. Occasionally I find myself using the Beeman allen head adapters in conjunction with the B-Square bits to not strip the threads.

Measure 4.75” away from the barrel’s crown, and use masking tape to mark off this distance. I wrap the diameter of the barrel twice to make sure the brake stops at its intended destination.

The JM apex brake is 6” (at least the two I purchased were this long). JM recommended to me that inside of the brake should be 1” away from the crown. There is a .25” space between the muzzlebrake crown to the beginning of the inside machining. So mask off the barrel (6” length of brake - 1” proper spacing - .25” space at end of brake = 4.75”) 4.75” away from the crown for proper spacing.

Note regarding Apex brakes: Jim does not screw the two 4mm grub screws into the brake. They are separate in the bag. Do not throw out the bag until you find them! If you do, you can go to your local specialty hardware store and ask for 4mm set screws. If they are too long, you can always grind them down with a pin vise and dremel tool. As of September 17, 2004, each set screw cost $.30 each where I live.

If your barrel is over 16mm consult with JM to make sure the brake will fit your barrel. The last Apex muzzle brake production was a few thou tighter because of Webley non-Walther barreled guns going to .620-.626" on average. BSA barrels sometime run from .610 +. The brake ID is 16mm .6299"+ . Most HW barrels before ‘04 ran about .626 or so. They start at .6299 but polishing prior to bluing should reduce them

If you want to “level” the brake so the screws won’t look like they’re crooked underneath after installation, mark off a 2” piece of paper in .5” increments. Eyeball the marks so they look even while the paper is wrapped around the barrel. When you are satisfied, mark the masking tape on the barrel so you can line up the screw holes when the brake goes on. These lines can also serve as reference points when you apply JB Weld.

There are a variety of methods to grind down the front site. There are:

1. Dremel or similar power tool for small jobs

2. Flat file

Regardless of which method you choose, I recommend using a hand file for filing off the sharp edges from the muzzle when you’re near completion from grinding on the barrel. File one way only in the down position. Be very careful, as it probably won’t take more than 15 strokes for both edges to be grounded off (depending on type of .

The object is to grind the ridges flat to conform to the rest of the barrel. Grind at an angle towards the bottom ridge. I started at the top ridge pointing the file towards the bottom ridge. When the file connected to the bottom ridge I know I’m getting close to completing the job.

You’ll also want to grind smooth the “humps” near the end of the cut grooves (slots closest toward the stock).

If there are any sharp edges at the face of the barrel, round those off too. You will not ruin accuracy if done carefully. In other words, just make the grinding job look and feel like only the bluing was rubbed off.

It took me 15 – 20 minutes of careful grinding (by hand) to achieve the desired result.

Check the smoothness of the barrel every five minutes to check your progress.

Once you have completely filed the ridges and humps off the barrel (with no sharp edges), the part of the job is finished.

Most often a slow installation is from not knowing the exact places to remove on the barrel. If you cut the biggest barrels out there now, its the 16mm R series from Beeman. You’re not doing this as it’s not a good idea unless you choke the barrel.

If you cut an R series barrel the brake slips on with no alteration at all. That tells you that the brake is made to easily slip on a HW barrel and that the filing is critical to fit only because the grooves are there and most 1'st timers are hesistant.

Walther barrels are problems because they are .634-.636+ (Longbow as an example) However a 124-127, Kodiak, Xocet etc are straight push ons. JM’s next run will probably open them back up to .635" or so.

Use just a big lathe file and hit the rails hard and work on one side with several quick swipes, than the other and then hit the center top of the rails. This works fast if your aggresive and takes only a few minutes on R series, 124 etc.

Often people take forever only because the top center extreme front edge is the only hold up but they dont know it.

If you put the brake on a Longbow- your screwed- barrel is a fat Walther. But then again no work is required for a Kodiak, Xocet , Stingray, BSA etc. Now later RWS guns are fat and extra work will be required.

Also if your into speed and dont care about extra mess walk over to the grinder and flatten the rails swiftly and then pretty them up with a few file swipes.

Lathe file or grinder- then I walk over to the buffer and hit it with the 400 grit wheel, then the cut- polish bar and clean up and touch up with Oxpho blue.

Next step is to hand fit the brake onto the barrel. Whatever you do, do not force the brake on! You will need to trial run the brake many times before it provides the proper fit. If you don’t do any internal sanding within the brake, consider yourself lucky.

Most likely the brake will not go on smoothly the first time. There will be a lot of rough spots, but this is normal. From here on you do not touch the barrel after filing the barrel have been finished. Now you will need to sand the inside diameter of the brake to make a proper fit.

On your first run, continue to push the brake until it bottoms out by hand. Make sure the pressure is light because the brake can easily seize.

Initially I tried soap and water as a lubricant. When the brake did bottom out, I had a hell of a time getting it off. When the brake eventually came loose, rust was already forming on the grinded area.

I used soap and water because I have a weight training station that uses foam handles. The grips on the weight equipment eventually went bad, and I ordered new ones. I was having problems installing the new grips, and the manufacture told me to use soap and water to work the foam grips on. It worked. Apparently the soap and water method didn’t work for this application.

This will give you an idea how much to sand the inside of the brake. There are two methods:

1. Purchase a wooden dowel at Home depot that is a smaller diameter than the internal diameter of the brake. Bring the brake only to Home Depot for testing. Purchase coarse sandpaper for metal finishing. The scratches from the coarse sandpaper will also create better gripping power between the muzzlebrake and barrel too.

2. Use 5/8” drill rod attached a hand drill. At the end of the drill rod, cut a 1” slot so it can accept sandpaper. Roll the sandpaper around the rod until it fits the inside of the brake snugly.

Make sure you are careful inserting the sandpaper into the brake. You do not want to ruin the finish at the entrance of the brake when you are finished.

I used method #1 because I didn’t have the drill rod setup. Wrap the sandpaper around the dowel, and gently insert the dowel with the sandpaper into the brake. Pay careful attention that you don’t hit the sides of the muzzlebrake entrance. They are finished too.

Make sure to hold onto the sandpaper while inserting and sanding, otherwise, the sandpaper will ride up the dowel. Now sand the brake in five-minute intervals. Blow the sandpaper out the muzzle brake and insert onto the barrel until it fits nicely.

Once you have determined the brake goes on without bottoming out along the entire course of the barrel until it stops at the masking tape, I use Beeman MP-5 oil to clean the inside of the muzzle brake and the outside of the barrel.

The final task is to permanently attach the muzzle brake to the barrel. I use JB “cold weld” epoxy adhesive that is available at Wal-Mart or Home Depot.

Do not apply JB Weld to the inside of the brake. This could possibly collect on the crown of the barrel during installation.

Don’t waste your time thinking the brake won’t move ever again with loctiting the grub screws. I tried this on an R-1. After three attempts (even drilling tiny holes in the barrel with a dremel tool for the grub screws to grab), this procedure is useless on magnum springers.

To prep the surface, I use JB weld clean and prep adhesive surface preparation. Then, mix two equal size epoxy components into a nickel-sized spot, then dab in a dot fashion with JB at north/south/east west points on the barrel. Immediately put the brake one, aligning up screws to the pencil marks on the underside of the masking tape. Once everything is aligned up, remove the masking tape. Clean up excess glue with a q-tip. Use a flat-headed toothpick as the glue expands out of the crevice.

You can use either blue/red loctite, or JB weld when you put the grub screws back in. this ensures the grub screws don’t fall out. Doesn’t really matter what threadlocker you use, as the brake isn’t coming off again.

Wait 24 hours for the adhesive to cure, and then start shooting.

Additional Notes from various posters:

If any traces of the front dovetail is left above the surface, they will merely "lock-up" in the aluminum brake and twisting it will cause the high spots in the barrel to gouge and tear up the aluminum, further worsening the situation. This is why you have to achieve a full length slip fit with these or Crow Magnum style brakes. They should never be forced on. If you can't do a direct 'tap off' of the brake, you'll probably have to slit it full length, spread it slightly to remove it, then toss it in the trash and start over again.

Take a block of hardwood about 2 inches wide and six inches long. Drill a hole in it about the diameter of the barrel., then cut a slot to meet the sides of the hole such that the slot width is the same as the diameter of the barrel and the hole you drilled. Carefully clamp the barrel in a strong vise and drop the block over the barrel. Slide it up to the Apex brake, and carefully, holding the open side of the block., tap the other end with a hammer against the end of the brake.

I've used it successfully myself several times. Pay the extra for oak or similar hardwood.

The main thing I'll add is, you could drizzle some oil where the barrel and brake meet--be generous with the oil, and adding a little moly or graphite to the oil wouldn't hurt if you have some to add. Let gravity do the work, and let it sit that way for at least an hour or two--even overnight.

After the oil has had some time to penetrate, commence to secure the barrel, and hammer away at the wood in the direction that will remove the brake. Tapping note: It's not for the timid. Quite sharp raps will often break something loose where weak little rap-a-taps will not. Whack it. And I'd definitely forget the twisting thing---99 times out of a 100 it will just make things worse, as noted.
tape the barrel just behind the MB along with a plumber's hard seal cut so you can put it against the rear of MB. Use a little
tape to secure that hard seal in place. Now with a boxed/open end wrench ( size to fit close to barrel dia. ) or two, with
work glove on hold the wrench open end firmly in place behind the MB and wack some solid blows with a hammer
near the open end mouth of the wrench(es). Heat, lube if ya think it'll help. Wack some more.

. If your barrel is over 16mm consult with JM to make sure the brake will fit your barrel. The last Apex muzzle brake production was a few thou tighter because of Webley non-Walther barreled guns going to .620-.626" on average. BSA barrels sometime run from .610 +. The brake ID is 16mm .6299"+ . Most HW barrels before ‘04 ran about .626 or so. They start at .6299 but polishing prior to bluing should reduce them.


Anonymous Anonymous said...

What are you a fuckin' moron ? Any idiot can install a muzzlebrake. Geezes man, thanks for the totally awesome tip !

Buy something other than a gas ram while your at it. It'll make your collection interesting, not boring and redundant. LOL

10:28 AM  
Anonymous Anonymous said...

Great post Sonny. Thanks for the info.

10:46 PM  

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