Home Forums Hunting & Shooting Hunting Rifles Vertical stringing & barrel bedding

Is vertical stringing usually a sign of too much pressure in the barrel channel?

John,

Vertical stringing could come from a bedding problem, but I've noticed that bedding issues (even in the forearm) more often than not throw the shots "every which way."

Consistent vertical stringing is as likely to be a tang bedding issue as it is a barrel issue. If, per chance, you're talking about a Savage rifle the tang should be "free floated" just as the barrel. (There is no action screw in the tang on the Savage).

This all said, the most common thing I've seen cause vertical stringing is the position of the rifle on the rest. If the forearm is positioned over the bags in such a way as to allow the sling swivel to drag the bag on recoil, you can see this result in vertical stringing. The solution is to move the bag back, well away from the sling swivel and any other protrusion that might catch the bag on recoil.

If shooting from a bi-pod on the bench, folding a towel over a couple of times and placing it under the legs of the bi-pod will dampen the "bounce" of the rubber feet. Bi-pod bounce can also cause vertical stringing.

I had a rifle a while back that would vertical string on every attempt to group. I tore the whole thing down twice trying to find what was wrong. Then one day a friend asked to shoot it. 1/2 MOA group, instantly--with of course no vertical stringing. I had no technique problems with any of my other rifles, but for some reason--maybe the stock angle, the trigger, a combination--who knows?--I was causing this rifle to vertical string. With a slightly different bench position, I corrected the problem. I have now sold that rifle though, as I didn't like having to deliberately consider an other than natural position (for me) each time I shot it.

Dan

Wizard: The name suits you prefectly. I read your stringing theory with regards to the swivel and the sand bag and it works! thanks! jorge

PS: To those that claim you can't learn anything from reading, think again!

The one bugging me at the moment is a .375 H&H, Interarms Mauser action in a Boyd's laminate stock. Both recoil lugs and the tang are bedded with Steelbed.

The barrel is definitely in contact with the barrel channel, but was also that way in the original stock. Think I'll relieve it some more and see what happens, I can always add back a pressure pad.

John......

Many years ago, I "floated" the standard-weight 25� inch barrel on my "Alaskan" Model 70 .338 Win. mag. back to the front recoil lug and it made an immediate improvement in the size of the rifle's 3-shot groups.

Ron T.

Let's not forget the obvious. One of the most commonly-attributed causes of vertical stringing is barrel heating / stress relief. It most commonly shows up in rifles with flyweight barrels, but it can show up in any barrel that is not adequately stress relieved. As the barrel heats, it warps slightly or expands in such a way that bullets strike higher and higher. This is a very common problem.

True, but I figure it's not the issue here since it didn't string vertically in its factory stock, and I'm shooting a known accurate load.

John

Few things worse(to me),than a quirky rifle.

When I float,I really FLOAT.

I've found in many instances,that a full length bedded rifle is VERY forgiving(repeatable) and from all positions.

To eliminate variables,I'd suggest ascertaining all is tight,regarding optics platform and the stock. From there I'd experiment with bedding.

I've seen often,that full length bedding increases stock rigidity and "tricks" the barrel into thinking it is stiffer than it actually is. It might could be harmonic dampening or any one of a multitude of variables,but it takes but seconds to discern.

I confess to much of my favorite stuff being full length bedded,though that heavily bucks current thought.

Your mileage may vary..................

Are either of the two recoil lugs bottoming out in their mortises??

JimF

That was my first thought after one very high flyer on the 2nd group -- found a touch of looseness in the bottom screws on the Talley QDs. Next two groups were better but still 3 shots in a 1.5" vertical line each time (rather than the 1/2" cluster usually seen with this load).


JimF,

Shouldn't be bottoming out either recoil lug, they were electrical taped on all surfaces but the rear. I glassed the bottom metal as well and when I turn the screw, it has the correct feeling of a sudden stop when all is tight.

I suspect I have some uneven contact somewhere, probably because it's hard to tell a smudge of inletting black from the glue lines in this stock. Will take it apart tonight & look for any obvious rub marks.

Here is another thought - the rear of the magazine box is glassed solidly against a hidden second crossbolt, a la the advice of Jack Lott in the 1984 Gun Digest. Could this be a problem?

John

I don't have much experience with boomers but.......

My take is that on any vertical component of the action, (screws, mag box, trigger) there should be no contact with the stock. The exception being of course the vertical rearward surface of the recoil lug/s.

That means for one thing, be sure that the action screws do not bear against the holes. If the magazine is solidly fixed to the receiver, and is bearing against the rear of the well in the stock, that could possibly be an issue.

Now..........how about this??

Stringing is often simply an issue of harmonics. The new stock would almost have to play a different harmonic tune than the prior one. Have you tried the same load but plus or minus say 1/2 gr. to see what happens?

JimF

Hey wizard, about the vertical stringing and sling swivel thingy. I have sorta gotten in a habit with my Rem 7mm where when shooting from a sandbagged rest, I grab the sling next to the sling swivel and pull it into my shoulder. It seems to be comfortable for me and almost natural.
You may remember a couple weeks ago I asked a question involving fliers opening up my groups. I was wondering if you think this could have anything to do with it?

The rifle is in factory original wood, unbedded (for at least a week or two more--I am really working in earnest to get it pillar bedded before I get some Brownells Acraglass Gel)--although I have freefloated it enough that I can fold a standard peice of paper in half length wise and run it to the recoil lug with no difficulty.

Bet your ass that grabbing/tweaking the forend AIN'T gonna help groups(on any rifle)................

JBelks bedding question tip,float the action on bleach bottle shims.It worked for me.

JimF,

I think I may have figured it out, in more ways than one.

I took it apart, coated the barrel with inletting black, put it back in and cranked all the screws down. Took it apart and found some smudges in the barrel channel. Repeated until no smudges appeared (except a few little ones right at the edges of the inletting.

Even after relieving the obvious pressure, I noticed that the last little turn of the front action screw causes a perceptible movement in the receiver ring area -- the stock flexing as torque is applied.

Then I compared all aspects to the factory stock, which is designed to provide some forend tip pressure but otherwise no significant contact other than the recoil lugs (also steelbedded). Not even the chamber area is bedded -- just the lugs.

There is a little bit of movement when tightening that screw on the factory stock, but definitely not as much. I don't think I inletted the bottom metal quite deep enough on the new stock -- there is still a little more gap between the top of the magazine box and the bottom of the feed ramp, which might explain some slight hitches I was having in that area at the range.

However, while I had the factory stock on, I realized how much better it looked than the laminate. And for some reason it seemed to fit a lot better, maybe partly because I mounted a new scope. The old scope was mounted just a touch too far forward, and I think I misinterpreted the fidgeting to get the eye relief right, as a stock fit problem.

So in the name of science, I'll take both stocks on my next trip to the range, and shoot some groups with each. But I think I'll make the original stock my "using" stock and keep the other in reserve as a spare. If the pretty one breaks I can have a serviceable replacement in action as quickly as the finish can dry ...

John

John,

I have an old Remington 788 in .308 that "lives" with my brother.

Its original stock is glass bedded, and the barrel free floated. Whoever did the bedding let the epoxy run over the sides of the stock, and the stock is goobered up in this area. (I bought if for less than 200 bucks).

I took it to the range and shot MOA group after MOA group, and with Federal Gold Medal it shot 1/2 MOA.

I said, "This little rifle deserves a better stock!"

I ordered a composite stock from some online company and put the action into it. I could not get the rifle to shoot in that stock no matter what I did. I bedded the stock, floated the barrel, tried pressure on the forearm--nothing... <img src="/ubbthreads/images/graemlins/frown.gif" alt="" />

I finally decided that "pretty is as pretty does," and put the rifle back into its original stock. I sanded down the overflow of the glass bedding, and got it to looking about half way decent. And that's as pretty as she's gonna get, but she sure does shoot. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

Dan

John, you mentioned that the original stock had some forend pressure. These days that is considered sort of sacreligious, because knowledgeable people KNOW that free-floating is better. And in theory, it is.

But I've experienced similar problems with a few .300 Winchester Magnums built on P-17s. In all cases I was able to solve the problem by putting a little pad of forend pressure. I accomplished this by putting a little rectangle of bedding compound directly under the barrel one inch back from the forend tip. When the compound dried, I just covered it with a layer of black electrician's tape to cushion the barrel from the bedding. It worked like a charm.

You might want to give this a try. The easiest way to test if this theory will work for you is to add business cards in increasing number between the barrel and the forend and note any changes. If you find a sweet spot, you know you're onto something and then you can replicate it with bedding compound and a layer of electrical tape.

Just a thought, but it's something I'd try if I experienced your problem.

John: Mauser actions have a lot of good points but they are not particularly rigid. I bed them with forend tip pressure - about 5 to 7 pounds of weight required to pull the tip away from the barrel. The previous suggestion to put some shims under the barrel at the tip in varying thicknesses is a good tip to see if it helps.

In a heavy caliber such as yours is long shot string groups aren't nearly as important as getting the first 2 or 3 in the right spot.

luck with it.