Strange thing happens with brake on Rem. 700. SPS Tactical AAC-SD

[Jerry45]

I have something very odd happening when I remove the muzzle brake from my Rem. 700 SPS Tactical AAC-SD .308. It has me baffled an I'm wondering if anyone can explain it.

First, I have a 700 BDL in 30-06. Shoots dead center without brake. Install brake and naturally the group shift but it groups to same POI. Pull brake group moves back to center.

The SPS AAC .308 shots center without brake. Install brake group moves but groups. Now here's the strange thing. Pull the brake and I have no idea where the next shot goes. Poof it gone somewhere off target. Second shot is a couple or 4" inches low and 1" off to the right. Then it groups center again. It has done the exact same thing three different times on two separate range trips. I can't figure out why it throws the first shot after the brake is removed so far off the mark the second closer but still way off then back to POA = POI.

Both the 30-06 BDL and .308 SPS AAC-SD are in Bell & Carlson M-40 stocks. Both are torqued to the same torque speck (55 in. pounds according to B & C instruction). Bed is clean, no obstructions under barrel. SPS action has been out of the stock and has been inspected and double checked. I'm positive nothing is touching the barrel an the action is tight.

PS, it's being shot off a Caldwell rest not the by-pod.

 

[Bart B.]

It's obvious that something changes. Without having the hardware to inspect and measure everything, I'd not make any assumptions about what's changing.

Contact the brake's maker or, if it came with the rifle, the rifle maker, then ask them about it. If they don't have any idea, then I'd take the hardware back to its seller and get a refund.

 

[Brian Pfleuger]

I'd be curious to know the results of an experiment...

Clean the bore, install the brake. Fire fouling shot, fire group.

Remove brake. Clean bore, fire fouling shot, fire group.

I theorize that the transition into the brake is having some sort of effect on the fouling.

 

[mapsjanhere]

Is your brake contacting over the whole muzzle area, or does it leave a ring of surface open around the actual muzzle? It might be depositing a ring of fouling on the muzzle surface that gets blown off by the follow on shots until you have a clean muzzle again.

 

[Jerry45]

Just for FYI, the brake was a JP Recoil Eliminator (Tank Brake).

Bart, the brake can't be the problem because the rifle shoot well with and without the brake. It only goes screwy for the first two shot "after" the brake is "removed".

Brian and mapsjanhere, I'm only firing 5 to 10 shot strings before removing the brake but crud on the muzzle is something for me to check. Thanks!

mapsjanhere, the muzzles is exposed inside the threaded section of the brake. The brake has a 5/8" threaded hole for the barrel to thread into. Muzzle falls about 1/4" or so short of exiting the threads into the brake's first chamber which is where JP recommends.

 

[Jerry45]

I picked up a JP Tactical Brake and ditched the Recoil Eliminator. I thought I'd be able to pull it at the range today but I put it on tighter than I thought. No vice at the range so I couldn't get it to budge. The way the rifle is shooting with this brake installed I think I'll leave well enough alone.

Five shots 100 yards.

 

[zplinker]

You might try putting the brake on 'just snug', tight enough to stay there, no more. Different brake manufacturers have pointed this out in the instructions I've seen. If you need a vice to remove it, its just got to be too tight, and who knows what sort of stresses you are inducing.

 

[Jerry45]

zplinker, thanks for the advice. I'm using shim washers to time it. No lathe here. I had to use a "short", 4", brass bar to get it timed. It's perfectly level with the horizontal line of the scope. It's not extremely tight but tight enough I couldn't brake it loose by holding the barrel with my hand. Next time I'll bring a pipe wrench with me. (joking)

Edit to add, I re-shimed it. It's now "hand tight", timed and location marked so I csn return it to same position.

 

[Dixie Gunsmithing]

I think that this has something to do with barrel resonance, where it is being re-seated, and it takes a couple of shots to get it settled to stop it. Any extra weight added to a barrel can cause a resonance, or start vibration into it, if it is designed a certain way, and placed at a certain spot on it.

 

[Jerry45]

Dixie, I agree. That was one of my thoughts. But what could be settling. Everything is tight. I know the action and bed are clean and tight. I'm wondering if the action is still trying to, for lack of better term, settle into the aluminum beading in the stock. I was beginning to wonder if there may be factory crud in the threads of the barrel and action but it "seem" to be tight and I believe it would cause a constant inconsistency in accuracy. In fact with 168 gr. SMK it was not grouping well. 175 gr. SMK took care of that concern.

 

[Dixie Gunsmithing]

Jerry,

It could be something to do with the threads themselves, and no matter what is done, it just wont cure it, but when shooting a couple of rounds, it forces the threads to seat, and the resonance is stopped. The only thing one might try, at first, would be to clamp an extra weight of some sort, close to the brake, and shoot it, to see what happens. It might be just something like removing a little metal, somewhere on the break, and it would stop it from doing it, like spin balancing something. That is, if this is what is causing it.

If it did it every shot, I would think of something like the ports causing the gas to change or swirl behind the bullet somehow, and make the bullet travel abnormally. But this only happens for two shots.

Things like resonance and barrel whip are funny things to work with, since you can't really see it, and can be a pain to get rid of, if a barrel, or extension of it, has a problem.

 

[Jerry45]

It could be something to do with the threads themselves, and no matter what is done, it just wont cure it, but when shooting a couple of rounds, it forces the threads to seat, and the resonance is stopped.

That's something I didn't think of and could very well be what's happening. Thanks for the thought. I have some experimenting to do.

Things like resonance and barrel whip are funny things to work with, since you can't really see it, and can be a pain to get rid of, if a barrel, or extension of it, has a problem.

This rifle is a perfect example. Shoots POI = POA with the thread protector on, 2-3" high 1' right with the Recoil Eliminate (Tank brake) installed and 7-8" low 1/2" right with the Tactical brake installed. I was expecting the POI to change when installing and removing the brake(s) but the temporary change when removing the brake and reinstalling the thread protector really had me baffled.

Again thanks for the insight.

 

[Jerry45]

Well, I'm stumped. With the brake installed it groups 3/4" to 1/2" centered with the load it likes best with the brake and (with the brake installed) 1 to 1 1/2" close to center with the load it likes best without brake. All SMK 175 gr. bullets. Take brake off and adjust scope back to where it was zeroed without the brake and first shot is 4 1/2" low, second shot 2 1/2 " low, third shot 1 1/4" low then back to grouping. Did it with both loads several times several different ways every time the brake is removed, with and without the thread protector installed, clean or dirty muzzle and clean or dirty bore. Went through 100 rounds. Every time the brake is reinstalled and scope dialed to zero it goes right back to grouping POI = POA on the first shot.Take it off it's three shots back to POI = POA. I give up! Some sort of "CRAZY" harmonic going on when the brake is first removed. I've decided to just load for the brake and leave it on.

 

[JohnKSa]

Maybe it has nothing to do with the brake and you've got a scope that's a little flaky.

Scope adjustments typically are direct drive in one direction but rely on spring tension to return the adjustment in the opposite direction.

So when you dial it in one direction it takes a few shots for the reticle to settle because that's the direction in which the spring tension is driving the reticle and maybe the reticle is a little sticky. It might take the bump from a couple of shots to get it to move all the way. When you dial it in the other direction the turret is driving the reticle directly so the reticle moves exactly as it should.

Try tapping the scope after you make the adjustment and see if you can get the reticle to settle before shooting.

 

[Jerry45]

John, thanks for the suggestion but it's not the scope. When I dope my scope I dial well past the mark I want then dial slightly past in the opposite direction then one or to click back past the mark then to the mark. I've learned that works pretty much the same as taping does. The shot patters is pretty much identical every-time the brake is removed. I'm pretty sure a sticky scope would give a varying pattern the way I dial the scope up and down several times. I never use the same marks when dialing past and back and past an back so it would be virtually imposable for the scope to be settling on the same point for the first shot then drifting back to zero. Also I tried not re-zeroing the scope knowing POI will be off POA. I keep aiming for the same spot and the shots climb 1, 2, 3, then group. Good suggestion though.

 

[Mobuck]

My take is fairly simple. You're cranking on the barrel to remove/install the brake AND you're tinkering with the scope during the same operation.

 

[Jerry45]

My take is fairly simple. You're cranking on the barrel to remove/install the brake AND you're tinkering with the scope during the same operation.

I'm doing both whether installing or removing the brake. But the anomaly only occurs when "removing" the brake. Anomaly occurs even if scope isn't doped.

General info for everyone; I wrote about checking everything to make sure things were clean and tight a couple of rang trips back. Scope rail screws and holes were cleaned with Acetone and "Red" LocTite applied when rifle was first put together. Yes I use Red on my scope bases and will explain why in a minute. Ring screws had been Blue LocTit'ed. Action screws torque was checked (no LocTite on action screws). Rifle was shooting MOA or less both with and without brake.

Went to the range Wednesday and the rifle would put three shots in the same hole then throw a couple. Let rifle cool and it throw two then shoot one center than throw a couple more. Did similarly through 60 rounds. Now remember the week before it was shooting MOA and better all day. I was ready to throw it in the trash on the way home this week. When I got home I decided to check everything and pull it apart if necessary. Ended up doing just that. First thing I checked was the rail screws. One front was slightly loose and both rear were loose. I gave the holes and screws a VERY good cleaning with Action, Red LodTight and torqed to 20 in. # as per manufacture's instruction.... Again! I then checked the cap screws. Found three on the rear an one on the front 1/16 to 1/32 turn loose. Torqued to 15 in. #. Pulled action. Screws were tight. Pulled them anyway then Re-torqued to 55 Ft. # as per B&C instructions.

I use Red LocTite on the rail because I had my 06 rail shake loose twice when using Blue and I've never had a problem getting the Red to break loose when I've wanted to remove the rail. If the .308 rail shakes loose again I may just take a chance and use Green (bearing retaining) LocTite on it. I don't understand why it shook loose when I was very diligent about cleaning the screw holes and screws with Acetone before mounting the rail. I may have broken the LiocTite on the cap screws loose when checking the torque so I'm not that concerned, right now, with them becoming loose. If they loosen up again it's clean and Red LocTite time.

We'll see what happens next range trip.

 

[Jerry45]

Went to the range yesterday and spent the whole day shooting it. 100 rounds.

Just to make sure it wasn't me I shot my 06 that I put together. It's the SPS Tactical not me. Skinney barrel 30-06 shot center center. Very discurigerin since the SPS Tactical is in the same stock, has the same trigger and same scope as the 06.

It would not group consistently with or without the brake. And evey time I took the brake off I got a string befor coming back to POI was close to POA.

I called my smith on the way home. He can look at it in a couple of weeks.

 

[Dixie Gunsmithing]

Jerry,

If it's what I think it may be, there's a test that might determine it. However, you'll have to shoot the gun with the brake on and off. If it was to be barrel resonance, adding a weight of some sort off the bottom of the barrel, toward the muzzle, will tend to cancel it. If it does cancel it, then there might be a chance to just set the brake about 1/4" to 1/2" back from where it is now, of course you'll lose a little in barrel length to do it.

Sometimes, its a combination of things, from the barrel length, rifling twist, type of steel, and the load, that can cause this, and changing one can nullify it. Adding a clamp-on test weight just lets you know you're looking in the right direction. There are adjustable muzzle dampeners for this too, that attach on the end of a barrel like a brake, but don't do the same thing.

A good way to explain resonance, is an automobile on an interstate, that has the sleep-bumps on the berm of the road. If you hit there, with your tire, at the right speed, and then pull off them, the resonance thats set up in the spring will cause the wheel to keep on hoping for a bit. Another example is like when a wheel weight falls off, and the tire will vibrate at a certain speed. Its funny that barrels can do this too, for some reason.

I don't think the action is shifting in the bedding causing this, as once it shifted, you would have a problem all the time. I take it you keep the torque off the action when removing the brake? If so, and you hold the barrel, as you unscrew the brake, then I think it has something to do with stressing the barrel, and its sensitive to about anything done to it in the way its made, especially when its fired.

 

[Jerry45]

Dixie, I agree with all you have said. I feel like I'm going to shoot the barrel out before I get the darn thing to shoot right. I'm just disgusted because after reading about this rifle I though putting the action and barrel in a good stock would make it a sub MOA shooter. The harmonic issue with the brake on and off has turned out to be the least of this rifle's problem. The harmonic thing aside what has me thoroughly disgusted is the way this rifle is shooting. Here's the rundown. Worked up a load using Varget and 168 gr. SMK. Couldn't get it to shoot less than 1 1/2". Worked up loads with Varget and 175 SMK. Wound up with a load for brake on and another for brake off. The one that shot well with brake on didn't shoot well without the brake and vise verse. Without the brake it would shoot 1" with the load it liked and with the brake on it shot 1/2" or less. At least that's the way it seemed while working up the loads and until yesterday.

Started the day without the brake and the load it liked. I knew I would have to be re-zeroed since I had "everything" apart. First shot center 4" high. I though great. Things are going to work out. Cranked the scope down 4" and hit 2" low 1" left. Cranked scope up 2" hit 1" high 1" right. Next two went side by side center. Let the rifle cool. 1 1/2" high 1/2" right, 1 1/2 high 1" left then dead center. Decided to let it heat up. Center 1" left, center 1" right. Though damn it has to be me. Pulled the 06 out. Two shots dead center. Since the .308 had shot better with the brake on I put in on. First shot 8" low 1" left second 8" low 1/2" left. Thought well it just likes have the brake on. Adjusted scope. Couple more shots adjusted scope. Shot several hot and cold strings. One high right, one high left next is same hole high right then two in the same hole dead center then center left, low left round and round. Pulled the scope off the .308 and off the 06, checked the torque on the on the rail on the .308 and installed the 06 scope on it. Of course it was way off but I fired 5 shots and got a 1 1/2 group. Not good! Put the .308 scope the 06. Three shot group could be covered with a nickel. Two holes touching.

Put scope back on respective rifles. 06 (me) shot first shot 1/2 left center then two touching taking out the right corner of the 1/2 diamond.

Pulled the brake and shot 20 shots hot and cold barrel with the two different loads and could not get a group under 1 1/2". Put the brake back on and did the same. Best group was 1". Only got one 1" group all the others were well over 1".

I started the day with a dirty bore, 100 rounds down the tube. Cleaned after about 25 rounds and finished the day without cleaning again until I finished shooting. I want the smith to have a clean rifle to look at / work on.

I'm going to bring it to Don Gracie. He'll get it to shoot.