Muzzle Brake and Scope Movement

[royinidaho]

Just noticed that scope has moved ahead about 3/16th of an inch after 35 rounds and muzzle brake installation.

Scope had not moved w/more than 100 of same rounds prior to the brake?

What don't I know? /ubbthreads/images/graemlins/confused.gif Or should I chew out the fella that installed the scope (me) /ubbthreads/images/graemlins/blush.gif

 

[7Rumloader]

I'm no pro but it may be a ring issue.
I assume your talking about the 338 in some of you other posts.
I don't know what the recoil is like on it.
I have limited experience with brakes ( only one holland QD )but my scope has not moved and I have put 75 rounds down the tube since it was added. I mounted the scope on it new after brake installation with Burris signature rings with a 6X24X50 Burris Black Diamond in them( which is not a light scope )and no movement yet. Thats on a 7Rum but recoil is 243 level or less since brake job.
Thats all the help I can be but keep us posted on what you find out.

 

[Fiftydriver]

Roy,

Keep in mind that while you feel less "felt recoil", the scope and rifle are acutally having more stress and strain placed on them with a brake. Let me explain why before I am called a crazy loon!!

Recoil is the resulting force you feel from the bullet being forced down the barrel, that who opposite and equal action deal!!

Well, a rifle will gain teh exact same amount of recoil energy from firing a round with or without a brake. this is because the recoil energy is produced while the bullet is in the bore. From the time the bullet begins to move until it reached and is released by the muzzle, the rifle gains "X" amount of recoil energy.

This is true for a rifle with a brake on it as well. The only thing the brake does is try to fight the resulting effects of the recoil energy on the rifle. So we have two rifles, one with a brake one without. When the bullets leave the muzzle on each, both rifles have the same recoil energy in theory. Both rifles and scopes have experienced the same stress from the same recoil energy.

With the Non braked rifle this is the end of things as far as g-forces are concerned, not so with the braked rifle.

Now with a braked rifle, the rifle is in rearward motion and then the expanding forces of the gas escaping the muzzle hit the muzzle brake with tremendous energy which produces negative G-forces. SO not only does the scope have to handle the positive recoil forces generated by simply shooting a round, but it also, in a split second is hammered with negative forces generated by the brake.

This is why a top quality scope and mounting system are a nessesity with a large caliber rifle fitted with a brake. I recommend Burris Signature rings with all my brake fitted big game rifles at least.

That said, it may simply be a freak thing that just happened to occur. If your not using Burris Signatures, get some and your problem will go away. Also, if your using a standard base with windage adjustable rear screws make sure the rear screws are not slipping. Again, the Burris Signatures will generally solve this problem.

Have a good day,

Kirby Allen(50)

 

[royinidaho]

ah ha! Poop!

So that's why the recoil seems much "sharper" and "shorter" even though it is a bunch less than before the brake.

And that's why the windage mount screws looked off center.

Using Leupold 2 piece bases w/single allen (pun) screw rings. Guess they gotta go. /ubbthreads/images/graemlins/crazy.gif

Will switch to Sig rings. What base do I want? Shudda bot that IOR base for 80 bucks, huh? /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/grin.gif

Its just money /ubbthreads/images/graemlins/blush.gif No patience, SWH here I come... Gotta shoot Friday /ubbthreads/images/graemlins/tongue.gif

We'll see how the Alaskan Guide /ubbthreads/images/graemlins/frown.gif scope holds up. /ubbthreads/images/graemlins/confused.gif

 

[davewilson]

Fifty,
i'm certainly not gonna call you a crazy loon,but i am gonna disagree with you.you use the term recoil energy.i'm not sure what that means but i think you're trying to explain primary recoil.that is simply the bullet accellerating from zero fps to whatever.this accounts for maybe 5% of the felt recoil.secondary recoil is when the bullet exits the barrel and now you have 15K or whatever the pressure is on the inside pushing on the bolt.a brake is simply an extention of the barrel to "bleed off" the pressure from inside the barrel over a longer period of time so the felt recoil is less because much less pressure is pushing against the bolt.the escaping gases pushing against the diaphrams of the brake simply lessen the push against the bolt even more.in a nutshell, i simply do not believe that a scope has anywhere near the same amount of "felt recoil" with or without a brake! it's much less with a brake on.

 

[Fiftydriver]

Dave,

I would respectfully disagree with your comments. Talk to anyone in the 50 cal shooting world and you will see what I am talking about. Most scopes are designed to withstand rapid acceleration in only one direction, from the scopes perspective, rearward very quickly. With a muzzle brake there is this initial reward movement but also a substantial forward force, or should I say a very quick Deceleration of the scope.

This is why all scopes designed for 50 BMG rifles and air rifles have lens locks on both sides of the scope lens, not just one like many scope designs.

This is also why a pneumatic air rifle is one of the best things to destroy a scope, negative g-forces.

Felt recoil is basically not recoil energy at all, its the momentum of the rifle that you have to physically stop with your shoulder.

If your theory were true, you could take say a 300 RUM loaded with a 125 gr Ballistic tip to 65,000 psi and a 250 gr ULD loaded to the same 65,000 psi and recoil would be basically the same because there is the same amount of pressure forcing its way back against the bolt face. This is not true.

The second the bullet breaks the seal of the muzzle the bore pressure drops to basically 0 psi extremely fast with or without a brake.

In fact depending on the brake design, a rifle with a brake fitted like a Vias or similiar brake will have a higher bore pressure reading, longer then a naked muzzle or a partition style brake.

This has been proven time and again and is the main reason why a Holland or similiar style brake reduces felt recoil more efficently then a Vias style. They allow the gas to vent quicker. Also why they are louder.

Still, a bare muzzle will reach 0 psi in the bore the fasted of all three. Now we are talking milli seconds here so keep that in mind.

On this one my friend I would again have to respectfully disagree with your theory.

What do some of the other guys think??

Kirby Allen(50)

 

[bailey1474]

Found this little tid bit on Lilja's website. Hope it helps. It is basically what Kirby is saying.


Eric Williams, the former editor of the Fifty Caliber Shooters Association's magazine VERY HIGH POWER, reports on another potential problem with scopes on muzzle braked rifles. According to Eric some of the brakes on today's fifties are so efficient that for a moment they are actually pulling the rifle forward. It is a very brief but forceful jolt and it seems as though it puts the scope into a kind of reverse recoil situation. Some of the target type scopes are not designed to take this forward thrust and soon develop loose parts inside. Eric did say that the Leupold Mark 4 seems to hold up, at least so far. It was Eric's fifty, with a Mark 4 on top, we used to shoot the tank hull at 2000 meters. This rifle had one of the type of brakes on it that can cause the forward thrust I mentioned. The scope seemed to be working just fine for me and it takes a lot of clicking to get on at 2000 meters.

 

[ss7mm]

Kirby:

I had responded to Roy off line via e-mail and basically told him the same thing you are saying. I didn't post it because I felt it would turn into an argument instead of a discussion because most people have never heard of this.

I have heard this for many, many years and have read many articles about it, and all said the same thing. Scopes can be damaged by a muzzle brake equipped rifle for the reasons you state. I wish now I had kept the info but I didn't.

Most people would also say you're crazy if you tell them an air rifle will damage a scope but it is a very serious problem. Maybe they need Nightforce scopes on their air rifles.

I have seen 2 scopes that were damaged because of this. Let me say that both were what I would call inferior scopes. Both scopes had been used on the guns prior to having the brakes installed with no problems. Both guns were in the 300 mag to 338 mag class. I have never known a high end, quality scope to be damaged and therein may be the problem. Most people that frequent this and other similar boards tend to gravitate towards the upper end equipment so would probably never have a similar problem. I suppose it could happen to a top end scope but not as likely.

I don't think Roy's scope is damaged, but it slipped. It hadn't slipped prior to the brake being installed so I would feel that the additional, increased forces created by the brake caused the ring to scope contact to go away and allow the scope to slip. I agree about trying different rings etc. I doubt he would want to try it, but he could remove the brake, make sure everything is tight and try it. Then re-install the brake and see if it happens again. Just my $ .02 worth.

 

[Shawn Carlock]

Roy,

I would concur with Kirby. The opposing shear forces produced by a brake are huge. Scope manufacturers ( I know a couple ) claim that a good brake on a large high preasure magnum rifle produces shear forces of double, or better, than the same rifle without a break. The rifle starts a recoil pulse the moment the ignition occurs. The rifle starts to move rearward only to be counter acted by gas preasures pushing forward in the break, This creats the same difference as a car running into a wall, or another car head on at near the same speed, the difference is huge. This is also the same reason that the recoil spring rates for a 38 super 1911 pistol with a break are half of one without a break. The bottom line is as Kirby has recommended, a stronger mounting platform is needed.

 

[arthurj]

Hey guys, sorry to hijack but I am about to put a leupold long range target on a braked 300 RUM that kirby is finishing for me. What base and rings would you suggest that would be substantial enough for this beast?

 

[davewilson]

Fifty,
my understanding of why a heavier bullet kicks more is because of more primary recoil, that being more energy to get it up to speed. and second,the chamber pressure is higher when the bullet exits due to more barrel time and generally speaking,slower burning powders.i knew there was a forward push on a gun using a baffle style brake,but i will admit i didn't realize it was enough to actually move the gun forward.i understand now what you mean by more stress put on the scope because of getting smacked in both directions.as far as the rearward movement of the scope,it comes back with less force using a brake.

 

[davewilson]

Arthur, beginning to sound like you might just have to weld that puppy!

 

[Fiftydriver]

Arthurj,

I will be range testing your rifle with a Burris one piece standard base with a set of Burris Signature rings and a Weaver Tactical 4.5-14 scope.

The reason the windage adjustible base with standard screws often fails under heavy recoil or with a muzzle brake equip rifle is very simple.

When you have a mounting system like this you basically have the front ring doing the work and the rear ring being the pilot.

By that I mean that the front dovetail ring has about 80% of the work involved in keeping the scope sitting still under the strains of recoil. The rear ring which is clamped between the windage adjustment screws does very little as far as keeping the scope from slipping and the grip of the windage screws is totally inadiquate for this purpose.

They are there to offer you windage adjustment and thats about it.

When the front ring looses its grip, the rear ring will do very little to keep the scope from slipping. Often the rear ring does not loose grip on the scope body but instead it slips out from between the windage base screws.

The same system using the Burris signature rings is no differnet in that the front ring does 80% of the holding work keeping the scope from slipping. The only difference is that when fitted correctly, the Burris Signature rings are said to have 200% more gripping strength then a standard ring. As such that front rings just simply grips the hell out of the scope body and does not let go!!

At least not nearly as easily as a conventional ring.

If you want even more stability, go with a double dovetail base with a set of signature ring or a weaver style base with a set of Z-rings.

These systems are what I recommend as minimum for the type of rifle you will be using. I have yet to see a properly fitted set of Burris signature rings fail to hold a scope securely. Only one I did see fail was on a rifle where the left windage screw literally broke in half from being over tightened.

The key here is degreasing everything on the base and ring system except the dovetail contact surfaces where a quality moly grease should be used.

Everything else should be oil free and dry.

Above this you can get into the tactical style rings and bases and they certainly have the gripping strength to easily cover your needs.

Remember Alot of the stress on the scope is a result of the weight of the scope itself and the height above the axis of the bore at which it is mounted. The heavier the scope, the more serious a base and ring you need to keep it still. Also, the higher it is mounted, the more stress the scope endures under recoil and the effects of the brake under recoil.

Good Shooting!!

Kirby Allen(50)

 

[royinidaho]

I'm certainly getting an education with this one. Good posts fellas. /ubbthreads/images/graemlins/grin.gif

ss7MM, Thanks for the post. Points are spot on and well taken. No the scope isn't ruined but I sure can't say "only slight" ring marks any longer on that one. /ubbthreads/images/graemlins/blush.gif

The front schooched ahead nicely. The rear ring gouged a bit on the bottom. /ubbthreads/images/graemlins/frown.gif But I doubt I'll ever get rid of it anyway. Who would want a used cabela's scope anyway.

Also Kirby seems to be spot on regarding the rear ring and windage screws. I was real careful to get them centered on both sides. That didn't last long. /ubbthreads/images/graemlins/grin.gif

Kirby, I like the twin dove tail idea. Remember us talking building something that max weight is less than 16#. That's still on my burner, which is y I'm messing with the 250 gr bullets and muzzle brake. Besides being fun I'm getting the feel for the larger caliburs.

The 338 Win now sports a set of Burris Sigs. So far 9 full power shots and things look good.

Thanks again guys