The Firing Line Forums

Go Back   The Firing Line Forums > The Skunkworks > The Smithy

Reply
 
Thread Tools
Old September 19, 2011, 10:09 AM   #1
Jerry45
Senior Member
 
Join Date: April 18, 2000
Location: Metairie, Louisiana
Posts: 890
Need something technical explained concerning muzzle brake/thread adaptor.

Bullets keyhole with brake and adaptor.

This may be a little long but I feel you need all the information. Rifle: Remington 700 BDL 30/06. Bullets 150 gr. JSPBT and 165 gr. LSPFB hand loaded.

Rifle shoots to POA without any brake. It shoots to POA with one of these
on it.


Barrel is threaded 9/16-24. I wanted to try a JP Recoil Eliminator.



Closest I could find, that didn’t require machining, was one threaded 5/8-24 bored for .308 billet so I purchased this adaptor.



The JP is timed correctly and bore alignment has been checked with a brass rod. The bullet IS NOT contacting the adaptor or brake. However, using two different weight bullets they keyhole only 20 feet out.

Rifle is sighted in and shots to POA with the first brake installed at 100 yards. Put the adaptor and JP on and wasn’t even on a 3’x6’ target at 100. Pulled target to 20’ and got two keyholes one inch apart 2’ low 6” right. I have many Ideas of what could cause this but I’ve shoot all of them down except one. There is approximately 1” of unrifled space (as bullet goes through the adaptor). Is that causing a shock wave traveling in front of the bullet to come back off the rear baffle plate of the brake and destabilize the bullet as it leaves the boor or the adaptor?
__________________
Guns are not dangerous! People are! RKBA!

Last edited by Jerry45; September 19, 2011 at 12:06 PM.
Jerry45 is offline  
Old September 19, 2011, 10:28 PM   #2
Ideal Tool
Junior member
 
Join Date: October 6, 2010
Location: Michigan
Posts: 1,080
Hello, jerry45. The gasses acting on the bullet going thru the adapter could be doing it. Years ago, a gunsmith friend wanted to make a "bloop-tube" for off hand shooting with a .22 rimfire. rifled brl. was 16.5" long.."bloop tube brought overall brl. length to 26". Originally he had used a 1/2" I.D., thinking this plenty for clearance..he ended up having to go to nearly 3/4" before gasses quit bouncing that bullet around.
Ideal Tool is offline  
Old September 20, 2011, 09:25 AM   #3
Jerry45
Senior Member
 
Join Date: April 18, 2000
Location: Metairie, Louisiana
Posts: 890
Thanks for the reply. Looks like time to file 13 this project. I wonder why JP doesn’t make a brake threaded 9/16-24. Couldn’t find a link on their site to ask.

This is the rifle with the brake that works.


This is what I can do with that brake on.



I still have some muzzle jump and that’s what I was trying to eliminate with the JP.
__________________
Guns are not dangerous! People are! RKBA!
Jerry45 is offline  
Old September 22, 2011, 10:35 AM   #4
triggerman770
Senior Member
 
Join Date: August 9, 2009
Location: Metro Atlanta Area
Posts: 125
Muzzle brake

It is most likely the difference in weight of the adaptor and the brake has changed the hamonics of the barrel thereby making the bullet exit at a different point in the harmonic cycle, say on the upswing. that could well inject an angle of attack on exit that would cause keyholong at such a close distance
__________________
Small Arms Restoration, Inc.
smallarmsrestoration.net
Proud member of Georgia Carry.org
www.georgiacarry.org
triggerman770 is offline  
Old September 24, 2011, 08:44 AM   #5
Harry Bonar
Senior Member
 
Join Date: December 5, 2004
Location: In the Vincent, Ohio general area.
Posts: 1,804
brake!

Sir;
First of all I don't like muzzle-brakes.I have alway said that if the recoil is too great to handle go to a lighter caliber!
However, you have a problem.
Your problem is the adapter AND the brake! When you install a brake on a rifle you never assume that the exit holes are lined up. They can't be! After I install the brake, while it is in the lathe I make sure the bore is concentric with the outside of the barrel! Then after you screw all the stuff on you have I select the proper drill or carbide small cutter and bore SLOWLY with no wobble the exit openings on the brake and in your case the brake and adapter!
I also agree with the gentleman who told you about the "gas" upsetting factor.
There are three aspects to velosity: 1. Translational velocity - forward movement of the bullet - 2. Rotational velocity: the rotational velocity imparted by the rifling - 3: Processional velocity - the wobble of the bullet around its intended path.
Now, by using a brake you have "upset" these velocities! L say go to a lighter caliber or install a Limbsaver pad!
Harry B.
Harry Bonar is offline  
Old September 24, 2011, 10:51 AM   #6
Jerry45
Senior Member
 
Join Date: April 18, 2000
Location: Metairie, Louisiana
Posts: 890
Sir, I appreciate your reply. However, let me explain a couple of things. First, I’m not a novice. Second, the first brake was installed by a competent guns smith. I’ve been shooting through it for some time and I’m positive the bore and treading for the brake are true. Third, if you read my first post I stated that I used a brass rod (that fit snuggly in the bore) to assure the bullet would not contact the adaptor or the JP brake before I ever attempted to shoot it.

There are good reasons I installed a brake on the 06 one of which is… When I was a young man I broke my collar-bone (it has a stainless steel rod in it). Now that I’m getting older the 06 is starting to sting. I’ve had it and shot it on and off for over 35 years, I’m sure as hell not going to stop shooting it if I can mellow it out. And yes it has a LimbSavor on it. You did look at the pictures right?

If you would also note in my original post, I stated that my guess was that the adaptor was causing a turbulence problem. I posted because I was looking for confirmation of that or suggestions of other things that could factor in. Ideal Tool conformed that my assumption was probably correct and Triggerman has given me something I know about but hadn’t thought of, harmonics. While I don’t believe harmonics is the root cause I could very well be a contributing factor.

I do like muzzle brakes! They give the shooter several advantages. The most important to me is I like my wife to come shoot with me. She doesn’t like recoil. She won’t shoot the 06 even with the brake and LimbSavor. She’ll shoot the .223 bolt gun I bought for her but loves the AR (less recoil). She is going to love it even more with new brake that I’ve installed. She’ll probably love the bench rest AR I’m planning on building and yes it will have a brake on it. Another thing I like about brakes is they allow one to either stay on target or achieve a quick site recovery.

I’m old! I don’t need to play macho-man look how much recoil I can take. If I could find a way to achieve zero recoil on every rifle I own I’d do it (even my .22 LRs). I shoot for the enjoyment of shooting. I tinker with my firearms because I enjoy it and have the mechanical and technical background that allows me to do it safely. I’ve found a way to make it more enjoyable and still shoot my favorite rifle. Muzzle brakes!

Again thanks for your reply.

Jerry
__________________
Guns are not dangerous! People are! RKBA!

Last edited by Jerry45; September 24, 2011 at 05:25 PM.
Jerry45 is offline  
Old September 24, 2011, 11:55 AM   #7
guncrank
Senior Member
 
Join Date: July 15, 2006
Location: Fern Creek ,KY and Metro Louisville at large
Posts: 318
Do you think holes drilled in the adopter could allow the gas to escape or reduce the interference?
__________________
CW Shooters Supply Inc
1-866-217-5990
Machine Shop and Finishing Services to the trade and public
guncrank is offline  
Old September 24, 2011, 05:21 PM   #8
Jerry45
Senior Member
 
Join Date: April 18, 2000
Location: Metairie, Louisiana
Posts: 890
Hummmm! Now that’s something I hadn’t thought of. Have to give it some thought. First thing that comes to mind though is it will reduce the effectiveness of the brake. I’d have to study where/how large and at what angle to drill the holes. Something to think about! Thanks.
__________________
Guns are not dangerous! People are! RKBA!
Jerry45 is offline  
Old September 24, 2011, 05:50 PM   #9
mapsjanhere
Senior Member
 
Join Date: August 6, 2009
Location: Albuquerque
Posts: 2,352
Don't know how much material you have in that JP brake, but I'd drill out the 5/8 thread, fill with a piece of tube, tag weld in place, and tap for 9/16.
__________________
F 135 - the right choice
mapsjanhere is offline  
Old September 24, 2011, 07:54 PM   #10
James K
Staff
 
Join Date: March 17, 1999
Posts: 19,445
Just FWIW, but folks who fool around with suppressors know all about a precursor wave. This is a blast of gas and air that precedes the bullet out of the barrel. It is comprised of the air in the barrel, plus any gas that has leaked around the bullet in the leade or on its way up the barrel. Normally, it doesn't affect the bullet since it is ahead of the bullet and is out of the way by bullet exit. But it seems to me that if anything attached to the muzzle allows that gas to bounce around instead of escaping, it could interfere with the bullet as it exits and that could be bad for accuracy. I don't think the propellant gases would be much of a problem as they are behind the bullet, but I wonder about that precursor wave.

Jim
__________________
Jim K
James K is offline  
Old September 24, 2011, 09:04 PM   #11
Jerry45
Senior Member
 
Join Date: April 18, 2000
Location: Metairie, Louisiana
Posts: 890
James, that was exactly what I was thinking. The adapter is a nice space/pocket for all that air being pushed in front of the bullet to get swirling around really well before entering the brake. With the brake screwed up to the end of the barrel that air/gas being pushed in front would immediately exit the brake. With the adaptor there is a place for it to buildup and swirl around.

I wrote JP asking about a 9/16-24 threaded brake last week. No reply. Great customer service.
__________________
Guns are not dangerous! People are! RKBA!
Jerry45 is offline  
Old September 24, 2011, 10:03 PM   #12
modgodcom
Junior Member
 
Join Date: September 24, 2011
Posts: 5
Muzzle Brakes will always operate poorly with adapters

If you want a brake to operate properly you need to cut new threads and fit to the muzzle brake, after which you take a finish pass on the interior diameter of the brake to ensure concentricity. Generally, if you buy a brake that fits the threads already cut on your barrel you should be ok. I'd still reccomend chucking up the barrel, indicating on the bore and taking a finish pass on the ID, but it might not be necessary if you're not looking for 2MOA accuracy or better.

I will say this once just to clarify, you cannot expect a brake to operate properly on a thread adapter unless it is a very mild expansion chamber (read:birdcage flash hider).
modgodcom is offline  
Old September 25, 2011, 07:16 PM   #13
Harry Bonar
Senior Member
 
Join Date: December 5, 2004
Location: In the Vincent, Ohio general area.
Posts: 1,804
brake

Sirs;
James K has an excellent point and I suspect he is correct!
Harry B.
Harry Bonar is offline  
Old September 26, 2011, 02:19 PM   #14
guncrank
Senior Member
 
Join Date: July 15, 2006
Location: Fern Creek ,KY and Metro Louisville at large
Posts: 318
Good point about the precusser wave.
I think 1911 need that space so the gun can cycle the slide back

Sorry if that was a dumb idea about venting the space in adaptor but two .250 opposite each other ninety degree from TDC should not interfer with brake preformace.
I just thought it could help
__________________
CW Shooters Supply Inc
1-866-217-5990
Machine Shop and Finishing Services to the trade and public
guncrank is offline  
Old September 26, 2011, 03:37 PM   #15
zippy13
Senior Member
 
Join Date: August 23, 2008
Location: SoCal
Posts: 6,405
Isn't there a Murphy's Law about adapters being the root of many an evil? I don't know how many times I've added an adapter, to make things fit that normally don't, with miserable results.
zippy13 is offline  
Old September 26, 2011, 08:53 PM   #16
Jerry45
Senior Member
 
Join Date: April 18, 2000
Location: Metairie, Louisiana
Posts: 890
Guncrank, not a dumb idea. I just hate to ruin a $45.00 adaptor experimenting. The right size hole(s) drilled on the right angle would probably work. But that would render the JP less efficient and I can accomplish the same thing by using the comp with all the holes in it. It actuall works pretty well. I was just looking for more.

What has me POed right now is I just spent over $375.00 on JP products and they don’t have the decency to respond to my e-mail. I guess after dealing with companies like Dillon, Midway and Powder Valley I’ve come to expect too much from OTHERS. JP sure doesn’t care about customers after the sale. And I "would have" bought an unthreaded comp if they would have sold me one or paid them to thread one for my barrel.
__________________
Guns are not dangerous! People are! RKBA!
Jerry45 is offline  
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:44 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2014 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.09598 seconds with 7 queries