I keep hearing that a normal hunting rifle can be made to shoot so accurately if the barrel "vibrations" were set up correctly.

Apparently, as the weight at the end of the barrel changes, it changes the barrel vibrations, which affects the accuracy.

Well, we have decided to do the experiment ourselves.

I have taken a brand new BRNO 550 rifle, in 308 Winchester, and installed a muzzle brake on it. I have also bedded the action, and free floated the barrel. I will install a high power scope on it - have not decided which one as yet. And try see how this works out.

My plan is to shoot 20 groups of 5 shots each with teh rifle as it is. Then take the muzzle brake off, and turn 0.010 off the end of the muzzle brake. Install it back, shoot another 20, 5 shot groups. I will continue this and see what results we might get.

I will use standard military ammo, made by FN.

I will keep you all informed of our progress.

yes... its the basis for the "Boss" system that is/was available on Browning/USRC Winchester rifles. You will also find that there are 'sweet' spots in velocity for a given bullet weight that will result in tighter groups. For my 22-250 Ackley the sweet spots were about 200fps apart with 55g bullets.

Saeed, when installing the brake back on make sure to torque it with a torque wrench to be consistant with tighting it. Just another variable that can be controlled.

And IHMSA is right about Browning's B.O.S.S. (Ballistic Optimized Shouting System). My Medallion in .22-250 shoots 5 shoots into one hole at 100yds with the BOSS tuned.

Saeed,

If you want to end up with a muzzle braked M550 308 then go ahead. Keep in mind that Browning went to the Boss after working on BAR's that did not group well.

The fix on the BAR's was to cut the barrel back a little at a time. This found a spot where that particular rifle shot much better.

Skip the brake, simply mount a tuning weight on the barrel. Dosen't need to be any fancier than a simple "worm drive" hose clamp (some of the Mini-14 guys have cut there groups in half by finding the right spot for the clamp), or it can be a steel weight with (brass) set screws to hold it in place.

My Gunsmith told me that this was the reason for the military step barrels, for tuning. Exactly how that is accomplished with such a barrel Im not sure, but there it is.

I would suggest chronographing all of the shots, as consistency of ammo quality will be an important factor in your testing.

Saeed,

What you are doing is basicly re-inventing the Browning BOSS system. Probably cheaper and easier to just buy a Browning with the BOSS system.

I have seen weight systems used on some hi tek
rigs and the owners were convinced they worked???
With the boss the weight stays the same with saeeds type of tuning the weight and length at the end of the barrel will change, depending how much he cuts off.
like tailgunner said, some of the tuning methods are pretty basic.

What, is in fact the principle behind the BOSS system-- as Hivelosity said the weight doesn't change, and the length of the 'system' can't change much, (maybe it doesn't take much) with the thread in /out of the BOSS attachment. I'm interested in the barrel tuning dynamics, do manufacturers make an estimate of cartridges that will be middle of the road in a specific caliber when designing a barrel for given models/calibers?

Just curious--Don.

Saeed, is the commercial ammo you are using extremely accurate? I would think you test would be best if you start with a baseline load of proven accuracy.
At the Silhouette matches I used to run, one of our best shooters won a number of matches with a beat up old rebarreled Model 70 that had lead Solder held on to the barrel with duct tape - it shot like a house a fire. It was fun to watch him spank some of the shooters with high-dollar silhouette barreled guns......DJ

i owned a browning w/boss i could shoot 1/2" groups with everything from 125 gr. to 210 match by tuning the boss

And I'm sure we all know, we are doing the same
thing when we adjust our handloads.
JL

If I remember correctly, I saw this exact experiement done with a bench rifle in Precision Shooting I believe. Don't remember how old the article was but the premise was the same. The author believed that every barrel has an ideal length for vibrations/harmonics. So he would shoot his groups, cut x amount off the crown, reinstall, shoot more groups, etc. The results were surprising and some lengths shot better than others. He did this a number of times. You might try finding the article before you start as it might be helpful.

My dad custom fabricates golf clubs. He has a device that electronicly measures the shaft stiffness by measuring the frequency the shaft oscilates at when it's 'twanged'. Shortening the length of the shaft raises the frequency showing that the shaft is stiffer. Shortening the barrel a bit at a time will increase it's frequency of vibration. With a rifle barrel, the timing of the exit of the bullet from the muzzle comes in to play. I would guess that you want the bullet to exit the muzzle while the barrel is a a node, or right in the middle of a cycle of vibration.

...or maybe not.

One thing that hasn't been stated is that in order to TRULY experiment with either barrel weighting or barrel length, the ammunition must be up to the task, ie... nearly 0 standard deviation. It would be a much easier task to tune the velocity to the existing barrel.

Check this out

http://www.rifle-accuracy.com/

Saeed,
I think the experiments have been done, ,
just pick a system and install.
Cheers,
R*2

quote:

---

I would guess that you want the bullet to exit the muzzle while the barrel is a a node, or right in the middle of a cycle of vibration.

---

It is my understanding that the preferred point in the oscilation cycle is actually at the bottom. Perhaps somebody knows something about this?

Try one of these, I believe it is exactly what you`re looking for........

http://www.benchrestspecialties.com/barrel_tuners.htm

There are several people offering after market barrel tuners, Harrell, Hoehn, Hamilton and others.

For some pictures:

http://benchrest.com/timeprecision/SUPERTUNER/supertuner.html


Pete

quote:

---

It is my understanding that the preferred point in the oscilation cycle is actually at the bottom. Perhaps somebody knows something about this?

---

assuming the oscillation is sinusoidal, any top or bottom point would be preferable. you want the part of the oscillation where the rate of change is least. that way, minor changes in the variable will have less effect on the result. the rate is 0 at the top, or bottom, if a sine curve.

if the oscillation is not sinusoidal, you would need to know its shape to determine where the best point is.

I would expect it is sinusoidal as there are simple 1st order accelerations involved.

or something like that.

Most benchrest 22 Rimfire shooters use tuners, because they work by tuning the barrel/ammo cobo so the bullet exits the barrel exactly the same every shot. I use a Hoehn tuner on my Suhl and like it very much. There has been much testingt done with tuners, which should be availabe on a search. If I remember correctly, Linwood Harrell makes the tuners that Ron Hoehn sells; both are identical. I do know from my own experimenting that changing the tuner settings sure changes group size; this with 22RF as I've never done any testing with CF rifles.
Don
Edit: I know that some guys use a piece of paper folded over and inserted into the barrel channel to find a node where the rifle shoots best. They start at the front of the receiver on a floated barrel and move the paper, which is fit tightly in the channel, one inch at a time forward shooting groups at each inch marker to find the most accurate group, and then leave the wad of paper at that place.

Well,

The rifle has been bedded, and a new Nikon 6.5-20 scope installed on it.

Tomorrow I will start shooting it.

The idea behind this test is to see if one can tune teh rifle to the ammo, and not the other way round.

I have a lot of FN military ammo, and that is what I am going to use.

Well, we have started our test, and some of the groups look like they have been shot with a shotgun!

So if this works on this rifle, it might make a tack driver out of a good shooting gun.

I will post the groups tomorrow for your entertainment.

Saeed,

Geez, you could have just bought my Browning 375 with Boss and saved yourself a lot of time.HI

Roger QSL

Here are the results so far.
0.993
3.146
1.599
2.428
2.154
1.494
1.717
2.538
1.346
1.917
1.054
1.435
1.404
1.529
1.629
1.930
1.044
1.415
1.497
1.315

Smallesty groups = 0.993
Largest group = 3.146
Average group = 1.679

I have removed 0.010" off the front of the muzzle brake, and will shoot another 20 groups of 5-shots each.

The geniuses we have here - yes, there are several of them, and I daresay their combined intelligence might not amount to much - think this is a lost cause.

In fact, one of them has bet one of his rifles, a Winchestre Model 70 in 7mm Remington Magnum that this is NOT going to work.

Saeed,

When your cutting gets your barrel down to 4", leave it. You will need this much to attach a "Boss".HI

Roger QSL

Saeed,..I took the top of a pack of marlboro's from the ground at the range,..folded it and placed it under the barrel at the end of the stock on a rem700 6.5x55 classic in a hogue stock with bedding block. In this stock,..the barrel is completely floated,..and obviously doesn't like it. So,..I increased the thickness of the paper 2 more times and each time,.the group got tighter. The load was the same (44.5gr IMR4350 with 120grNBT). This proves to me that YOU WILL find a combination that makes it a tack driver given the ammo you are using. The amount of barrel cutting and break cutting will be different with every similar barrel,..BUT you will find a spot in your rifle that goes .5moa and even better.

The Hick's accurizer for the Ruger No.1 is a set screw on the hanger that puts upward pressure on the barrel, and allows you to tune the barrel to the load.

I just put one on but have not shot it <dang this wind and rain>.

The vibration of a gun barrel is a three-dimensional sine wave. It has both rotational torque value as well as an x-y value.

The shortening of the barrel will both change the moment the bullet leaves the undulating barrel, as well as the stiffness of the barrel. Changing the stiffness will give it an entirely different frequency.

Should be an interesting test, Saeed. Looking forward to more data.

Jim

Um, just wondering about the large variation
in group size. If it's the "mil" quality ammo,
you may get a sweet spot for some random rounds and sortof not be able to reconise the position
due to ammo variations.
Best bet here I think is to rig the results and
grab the 7mm. :-)
John L.

quote:

---

Originally posted by JAL:
Um, just wondering about the large variation
in group size. If it's the "mil" quality ammo,
you may get a sweet spot for some random rounds and sortof not be able to reconise the position
due to ammo variations.
Best bet here I think is to rig the results and
grab the 7mm. :-)
John L.

---

It is already a forgone conclusion.

Hope you enjoy his rifles Saeed. !

Here is the Deal; every barrel has it’s own tensile strength, no two will be the same even if they are identical and when fired they vibrate like a tuning fork.

Depending on how well the barrel was stress relieved during manufacturing will determine how Accurate the barrel will fire a projectile. This is excluding other factors that may contribute to bad accuracy.

Sometime a dog barrel is just a dog! With proper evenly stress relieved barreling, the barrel Oscillation will be very even, Left and right and up and down.

Relieving weight or length, (both have a similar affect, but not exactly the same affect) you can sometimes change the Oscillation on bad stress relieved barreling and improve the accuracy for the barrel somewhat. Believe it or not, on a good barrel it has little affect.

Now as to your bet, snatch the Muzzle Brake OFF and start trimming the barrel 1/8-inch to ¼-inch at the time till the puppy will shoot right. You will find if it’s a dog barrel it will shoot better shorter and stiffer. By the way, a by product of this for your 308 is, if it has a 24 inch barrel, you will actually increase velocity as you whack it off till you pass 21¾.inches. After that the velocity will began to drop a couple of hundred feet per second for every inch you whack off. You may find that your shooting the same velocity at 21 inches that you were shooting at 24 inches with medium burn rate powders. You can use a little faster burn rate powder and sometimes pickup the speed you lost in cutting the Barrel shorter.

0.993
3.146
1.599
2.428
2.154
1.494
1.717
2.538
1.346
1.917
1.054
1.435
1.404
1.529
1.629
1.930
1.044
1.415
1.497
1.315

Smallesty groups = 0.993
Largest group = 3.146
Average group = 1.679


Second installment:

0.679
1.972
1.502
1.476
1.556
1.611
1.352
1.209
0.802
1.165
1.345
1.903
0.765
1.254
1.908
1.074
2.480
1.478
2.436
1.796

Smallest group = 0.765
Largest group = 2.480
Average = 1.488

So now we have the smallest group getting better by 22%, the largest group better by 21% and the average getting better by 11%.
Another 0.010" of an inch has been taken off the muzzle brake, and we will see if this improvement continues.

When the Brownings first came out I had the opportunutiy to play about with two of them, one a 270 and the other a varmint model in 22/250. One of our main barrel makers also made up a version of the Boss to try as well.

What we found with both sets of rifles is that you could make a load shoot but if it was a load that the barrel did not really like then the "good accuracy" you got was very touchy with with fouling and barrel temperature.

In other words loads that were worked up for accuracy without using the barrel tuning were much better in that they were more stable in their accuracy.

Mike

Fascinating...

0.993
3.146
1.599
2.428
2.154
1.494
1.717
2.538
1.346
1.917
1.054
1.435
1.404
1.529
1.629
1.930
1.044
1.415
1.497
1.315

Smallesty groups = 0.993
Largest group = 3.146
Average group = 1.679


Second installment:

0.679
1.972
1.502
1.476
1.556
1.611
1.352
1.209
0.802
1.165
1.345
1.903
0.765
1.254
1.908
1.074
2.480
1.478
2.436
1.796

Smallest group = 0.765
Largest group = 2.480
Average = 1.488

2.011
1.827
1.619
1.836
1.906
0.743
1.787
1.874
1.419
1.510
1.786
0.929
0.910
1.876
1.456
2.018
1.725
1.394
1.123
2.297

Smallest = 0.743
Largest = 2.297
Average = 1.602

Um, I'm not trying to be a smart butt, but isnt accuracy a very major part of the reason we "roll our own" ammunition. I have a factory REM 700 in a .270 with a 24" barrel and have found powder charge combinations with 130 and 140 grain bullets that will group under 1/2" @100yds. If you want to play with barrel vibrations I would suggest reading this article here http://home.earthlink.net/~dannewberry/dannewberrysoptimalchargeweightloaddevelopment/index.html I tried this method and found it works great. Better than I expected.

The SIMM Limbsaver folks are approaching this from another angle; they're now selling a doughnut of pad material that you slip over the muzzle and scoot down to the fore end tip. It seems to absorb or neutralize the barrel vibrations and increase accuracy considrably. Really crappy looking on the gun but a really interesting concept.

quote:

---

Originally posted by Russ Brumbelow:
Um, I'm not trying to be a smart butt, but isnt accuracy a very major part of the reason we "roll our own" ammunition. I have a factory REM 700 in a .270 with a 24" barrel and have found powder charge combinations with 130 and 140 grain bullets that will group under 1/2" @100yds. If you want to play with barrel vibrations I would suggest reading this article here http://home.earthlink.net/~dannewberry/dannewberrysoptimalchargeweightloaddevelopment/index.html I tried this method and found it works great. Better than I expected.

---

When we reload our own ammo, we tune the ammo to teh rifle.

I was told this is doing it the other way round.

Here we are tuning the rifle to the ammo.

Well, everybodys commenting...so will I. Do you remember the older idea when custom rifles were
made up in wooden stocks..like during the Trojan War Era? The practice that gunsmiths liked back then was for the wood stock to exert some pounds of forend pressure to attain the 'right' barrel vibration, and hence best accuracy. I remember this worked quite well. I knew an African Hunter friend of mine that had a Winchester Model 70 in .375 H&H...he had a plastic credit card jammed under his forend tip...said that was the only way the rifle shot accurately...it just applied pressure. I fixed it better for him, in case the credit card fell out & a Rhino was charging...with the applied forend pressure, the rifle was accurate. Now, everyone cries "free-
floating"...the rifle makers love it as it makes their job easier...and it works...but I'm not convinced the old forearm pressure idea doesn't work as well or better. I also understand that the experimentation isn't taking this in consideration...but just thought I'd throw this commentary in to see what the oldtimers might think. Tom