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Thread: Vertical stringing

  1. #1
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    Post Vertical stringing

    Has anyone experienced vertical shot stringing? What seems to be the most common cause? I suspect the stock or stock fit to be the problem area but would like to touch bases with those who have seen this before.

    This is on my initial sighting in of my Rem 700, 338-06 AI using 53 grs of RL-15 and 250 gr Swift A-Frames at 100 yards. Temp was 66 degrees, a slight breeze from head-on, less than 2 mph.

    Any input would be appreciated.

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    Default Stringy groups

    Your load is good, you might also try 58.0 grains of RL-19 with the 250 grain.

    Vertical stringing is typically barrel heat up or bedding problem. If the forend is touching the barrel that is the most likely culprit. Or, a big thing, (and I could just assume that you are doing everything correctly) if the forend rest on a solid or semi-solid rest it will bounce the rifle slightly and vertically strings, if the group is more than 2 inches long this is probably it. Of course the barrel should never touch anything.

    All bedding screws must be tight, but you know all this right. Nice caliber, by the way, I've got a couple of them, good shootin'.

    Murphy

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    Murphy is right, in my experinence three causes, bedding problems, barrel temp or shooter breathing problems. Assuming you have breathing under control, watch for the barrel getting hot and check bedding. The barrel heating up, especially a light weight barrel will definitely do it. After three shots with my light barrel on my 7mm, you can start to see stringing. I had McMillian put a new synthetic stock on it so the problem is very small now but its still there.

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    One other thing to look for - when using the front rest, be sure to place the stock in the same position every time. If the stock doesn't sit in the same place for each shot, pressure on the fore end changes and can cause stringing. I have experienced the same problem before.

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    What others have said makes a lot of sense. Move the rifle forward on the support so that the area of the stock nearest the magazine, not the tip is supported. Try that and see how it goes.

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    Could be your load is on the mild side and your simply getting some deviance in velocities, which can cause stringing.

    How much is the group strung, ie how wide vs how high? Is this a 3 shot group, if so it's easy to pull one and make the group look like a string, but pulled shots usually go right/left. Differences in how you hold the rifle can cause stringing. Is the barrel a very light contour?

    Since this is an AI, is it fireformed brass, or unformed brass?

    I really wouldn't be concerned at this point, I'd fireform some brass, then work up by 1 gr increments to max and see what the spot is in your rifle. Once you've done that, if it's still stringing, I'd suspect the action isn't well bedded in the stock.

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    I concur with the other writer’s analysis…
    But, I do want to throw in this one instance I experienced with an 8mm06 I purchased w/scope years back.

    It would string shot groups on a 45 degree line going high and left - long story short - It was the scope. It would not hold zero and would walk up and left about 1 MOA after each shot. It was a Tasco Silver Antler. After a new scope was mounted, the problem went away.
    God, Guns and Guts is what made America Great

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    Cool Move target to 50 yards

    I'd try a better sight picture at a confidence building 50 yards using a rock solid consistent bench rest. No more than three shots – keeping the bbl cool.

    Try two more to see what happens to determine some level of heat sensitivity

    I'd then let ‘er cool down & try some other precise loading for comparison at 50 (also 100).

    Could be to the tune of the gun, mounts, scope, load, or just the weather ---- However….

    I differ with most of the others here and feel that vertical stringing is more frequently the case of shooter error… visual preparation or perception, inconsistent practice, and misinterpreting conditions.

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    New member George's Avatar
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    Default vertical strings

    Can be several causes. The most common is action/barrel shift because of heating/bedding shift at recoil, etc. Less common is inconsistant load pressure/velocity. Less common also could be changing rest location on forearm or shooter error. There's something to be said for shooting at 50 yards when load testing- it eliminates some of the other variables. I've found that fairly large amounts of vertical stringing is usually the barrel/action bedding thing, particularly if the barrel touches the forearm. Have solved that problem with several Winchester lever guns that have the mag plug screw protruding too far into its blind hole in the barrel and putting a tad too much pressure on the barrel. The difference was so obvious after tinkering with that, that there is little doubt that any variable forearm pressure on the barrel will/can cause stringing or other accuracy problems.

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    Default Vertical Stringing

    Some years back,15 or so, i picked up a nice Savage 99 but when i took it to the range to see how she looked on paper i was shocked at how bad this thing grouped or as it turned out, how bad the vertical string was.
    Thinking the worst ( i just got taken to the cleaners) i put that puppy in my closet(aka....gun safe) for further review. I cleaned it but it was a closet queen for a couple of years till one day i read in a sporting magazine where some pros where testing rifles amoung them a Sav 99. They also reported the same problem i had, vertical stringing.
    Their conclusion along with tech help from Savage was that if the forearm screw is to tight it puts undue pressure on the barrel resulting in VS.
    After reading that i took the 99 back to the range, backed off on the said mentioned screw and what do you know? That puppy was/is a shooter.
    Since that day it`s been my side kick on many a happy hunt. Live and learn.

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    Smile Thanks

    I appreciate all the good advice. I never ran into the vertical stringing problem before, but I also had never owned a plastic stock either. I believe the Remingtom stock was way too flimsy for the recoil of the 338-06 AI.

    I received my McMillan hunter stock the day before yesterday and then went back to the range. (It took about 100 days for the order to be filled) I also used a small roll of carpet padding as a forearm rest instead of my sand bag. Now I have no VS!! The group tightned up considerably and it now is beginning to look, feel and shoot like a good hunting weapon should.

    I have always glass bedded and free floated the barrels on my hunting guns in the past. I see that McMillan feels that glass bedding their stock for a hunting rifle may be unnessary. Has anyone glass bedded a McMillan? And what were the results as compared to no glass bedding?

    Again thanks for all the good advice and for responding. Getting a different slant on the subject was most helpful.

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    Default McMillan Stocks

    Peter,

    Yes I have several McMillan I have glass bedded and that never makes them worse. I have gained ground with them by bedding, however. I will say that McMillans fit better than every other stock I ever used. I have talked to them about bedding and they say it won't hurt but just don't feel it is necessary. If it shoots to you liking without bedding, save the money. I have a 338-06 AI in a Sako action and a McMillan stock, it is bedded and has shot several 3/4" groups at 200 yards. I think it would shoot very well with or with bedding.

    You're right about the flexible flyer stocks, they are a problem. They are injection molded, the question is what, exactly, did they inject into the mold?
    Good shootin'.

    Murphy

  13. #13

    Default vertical stringing

    A benchrest shooting friend has said, and I find it to be true, that most of the time vertical stringing is caused by the load. Beef up the load a little. See you are using an AI and I use a regular 338/06, and load it with 56grs 4064 or RL-15 with the 250s. Get a solid 2500fps, and shoots in an inch. If barrel is any good, shooting 5 or even 10 shot strings won't effect it. In high power shooting, we have to shoot 10 shots in one minute through our rifles, and it better still stay accurate. Some matches, you shoot TWO strings of 10 shots in 1 minute each, (with only enough time between the strings to stand back up, and load it again) and this is at 300 yds (normal group will be 3-4" at 300 yds, rapid fire). Any barrel that won't hold it's accuracy would be replaced. I think the old barrel heating up stuff went out years ago, when better barrels came along. Also, if free floated, would not effect the barrel with tension. You should be able to shoot 10 shots in a row, reasonably quick, and keep them all in a reasonable group. I've seen barrels so hot you WOULD burn your hand on them, and they still shot accurately. I'd up your load a 1/2 grain at a time, and see if it settles down. I have gotten excellent SDs (under 10) using RL15. Since your case blown out some, you might go up to 57 grs or so, as when case is blown out like that, you lose some of the velocity you had, due to expansion area of case. Usually you need to go a grain higher in load to get back to what velocity you got out of the un-improved case.

  14. #14

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    What a vexing problem!

    If you are an experienced reloader you should know what you are about. Yet, Sinclair International has an in-house book on accuracy reloading that may offer some real tips for you. No need to buy Wilson dies and go to extremes, but the more perfect your ammunition, the more confidently you shoot and the better your results can be. There is also a paperback about Varmint hunting that has some great reloading tips in it. Boyd somebody is the author, blue book with a grinning boy behind a varmint gun on the cover. A great read for any accuracy shooter.

    Are you using Bsquare stock bolts? The allen head bolts are great for uniforming your stock tension. If you have another Remington like a Sendero with an HS Precision stock, try switching them at the range. If you have and inch pound torque wrench set the stock bolts at 65 INCH Pounds, not foot lbs!!

    You might also try some Sierra spitzer boat tail bullets, just to be sure. Sierras have always been the more accurate bullet for me. As was said before, work up your test ctgs using brass fireformed to your chamber. You might also want to only necksize about halfway down the neck. Not like you are going to be hunting big game with these, you are trying to establish that the gun will shoot consistently to point of aim.

    What kind of rest are you shooting off of? Pretty tough to free recoil shoot a 338-06, but if you can borrow a hart or other quality rest and bag setup it might help your results so you know the rifle is okay.

    I have a varmint special with HS stock and Mark 4 scope. Bought a Badger scope base and the retailer, Premier Reticles, was out of Badger rings, but sold me Leupold mk4s, saying they were just as good. Uh uh. The Leupold rings were junk. I couldn't get the results I expected. The first day shooting same loads with the Badger rings I got 5 shot groups under .40 at 100 yds and 5 shot grps of under .8 at 200 yds. It was a windy day. The gun was one I assembled from a used barrel and action.

    You might also try shooting prone and sitting with a good sling. It may be you will see different group patterns if you shoot without a bench.

    Another thing to try is centering your crosshair on a drawn "L" or the same intersecting grid mark on your target.

    Finally, it is very likely your gunsmith adjusted your trigger to a good smooth, non-creeping trigger pull under 4 lbs. If not, that is another variable.

    Hope you get this straightened out soon!

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