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Thread: vertical stringing

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    Default vertical stringing

    I've been shooting several rifles lately, and my groups with one of them has little horizontal dispersion significantly more vertical dispersion. My groups are 2-3 times as high as they are wide.

    I've checked to make sure the action screws are tight, although I haven't torqued them. Same goes for the scope, which also seems to hold zero just fine.

    I'm chronographing everything, and my velocity numbers are pretty good. (ES 30fps, SD less than 10fps, MV about 3000fps) Besides, so far I've only been shooting at 100 yards so anything but major changes in velocity wouldn't show up.

    I'm shooting off of a lead sled, not offhand. I guess it could still be the "jerk behind the trigger", I make no claims of being an extraordinary rifle shot, but my groups with other rifles show no vertical stringing.

    What else might be the cause of vertical stringing? And what about the cure? Would a bedding job help?

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    Quote Originally Posted by AKArcherdaddy View Post
    I've been shooting several rifles lately, and my groups with one of them has little horizontal dispersion significantly more vertical dispersion. My groups are 2-3 times as high as they are wide.

    I've checked to make sure the action screws are tight, although I haven't torqued them. Same goes for the scope, which also seems to hold zero just fine.

    I'm chronographing everything, and my velocity numbers are pretty good. (ES 30fps, SD less than 10fps, MV about 3000fps) Besides, so far I've only been shooting at 100 yards so anything but major changes in velocity wouldn't show up.

    I'm shooting off of a lead sled, not offhand. I guess it could still be the "jerk behind the trigger", I make no claims of being an extraordinary rifle shot, but my groups with other rifles show no vertical stringing.

    What else might be the cause of vertical stringing? And what about the cure? Would a bedding job help?

    this is a general guideline. hope it helps!
    happy trails.
    jh

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    Have you shot good groups from this lead sled with other guns? Is this a heavy recoiler compared to your other good groups?


    It is necessary to determine if the first shot is low and the others go up or vice versa, starting high and working down.

    Vertical stringing from a rest is most commonly inconsistant pressure on the forend or barrel by the shooter. (never make contact with a barrel, with your hand or anything else) It could be as simple as holding the bottom of the forend in a different way each shot. The lead sled add another variable to this mix. Some shooters shoot well with the sled some do not. I have found that the greater the recoil the worse all these issue matter. Stock weld, as well as grip for and aft can effect grouping. These must be consistant. Poor trigger control is almost alwys a low shot or low left on an unsupported gun.

    Besides that there a few things that can cause the gun to string vertically. Generally these relate to forend pressure or lack of it. If the stock has an Aluminum rail even with bedding over it, it can absorb heat from the barrel and change forend pressure. I had one do this and another that was full contact bedded that heated up and pulled away from the barrel about 1/8". Its point of impact went down about 10" at 100 yards after about 4 shots but shots worked down an inch or so per shot for the first three or four.

    Good general shooting practices with a rifle apply here. Stock weld to the shoulder and face contact must be consistant. Also we need solid mounted scope that is trustworthy as well. The stock to action mounting must also be solid.
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    Quote Originally Posted by pinehavensredrocket View Post

    this is a general guideline. hope it helps!
    I believe this cute little wheel just applies to handguns.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  5. #5

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    Quote Originally Posted by AKArcherdaddy View Post
    I've been shooting several rifles lately, and my groups with one of them has little horizontal dispersion significantly more vertical dispersion. My groups are 2-3 times as high as they are wide.

    I've checked to make sure the action screws are tight, although I haven't torqued them. Same goes for the scope, which also seems to hold zero just fine.

    I'm chronographing everything, and my velocity numbers are pretty good. (ES 30fps, SD less than 10fps, MV about 3000fps) Besides, so far I've only been shooting at 100 yards so anything but major changes in velocity wouldn't show up.

    I'm shooting off of a lead sled, not offhand. I guess it could still be the "jerk behind the trigger", I make no claims of being an extraordinary rifle shot, but my groups with other rifles show no vertical stringing.

    What else might be the cause of vertical stringing? And what about the cure? Would a bedding job help?
    I've never used a lead sled, even for heavy boomers.

    But like Murphy, I find that vertical stringing usually boils down to rifle problems or shooter problems. If I understand how the sled works in isolating the shooter from the gun and recoil, then I have to guess it's gun problems.

    Tell us more about the gun, and maybe we can help narrow it down.

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    Default additional info

    The rifle in question is a Kimber Montana in 7-08. As such it's not an especially heavy recoiler, although its 6 pound weight makes it kick a bit more than a heavier gun. The other rifles that I've been shooting (without vertical problems) off of the same rest include a 375 H&H (with a muzzle brake), a 6 pound custom .308, 22-250 with a varmint barrel, and a 257 Roberts.

    The Kimber, being a featherweight rifle, has a pretty thin barrel. It also has what I think is the nicest (read: light, tough, and stiff) factory standard synthetic stock that I have seen. I haven't pulled the stock, so I don't know how (or how well) it is bedded other than that it is factory pillar bedded and the barrel is free-floated. I checked the free-float of the barrel, and a piece of paper slid easily between the barrel and the stock all the way to the chamber. I intend to pull the stock tonight and look at how easy it would be to bed the Kimber action.

    I'm using the lead sled more as a rest than to tame recoil. I don't put any weight in the trays at all. I actually wanted to get set up with a nice front rest and rear bag, but the total for that came to about what the lead sled cost. I could only afford one set-up and I decided on the lead sled since my wife and young boys can and do benefit from some recoil absorbtion when they shoot.

    That said, this rifle has shot some very good groups (1/2") from the lead sled. However, whenever there is a flyer it seems to be high/low. Shooting this past Tuesday I was finalizing my load development with RL-17 in the 7-08. I had loaded 7 each with two different primers, as a final "shoot off" to see if primer selection made any difference. Both groups showed considerable vertical stringing, which prompted this question.

    During the same shooting session, in between 2 shot strings from the 7-08 (one of each primer), off the same lead sled, I was sighting in my wife's .308 at 200 yards. By the time I was done I was shooting 1" 3-shot groups at 200 yds. As far as I know I wasn't holding or shooting the .308 any differently. This is what made me think the problem was rifle related!

    Hope that helps! It's been an interesting discussion so far.

    Murphy, I have paid some attention to fore-end pressure, but I haven't obsessed on it. I definitely don't hold the fore-end though. Maybe the fact that this gun has such a light barrel would make it more sensitive to such things. I'll pay closer attention next time I shoot.

    I let the barrel cool for about five minutes between every 2-3 shots. Usually I just set it aside and shoot a group with another rifle. At less than 30 degrees, the barrels don't get too hot and cool pretty quickly, but they probably never get as cold again as before the first shot. This past Tuesday I was shooting one shot of each primer type, then letting it cool. Each time I switched off which set of bullets the first of the two shots came from, and both groups showed vertical stringing. As you can see I had barrel temperature as a factor in mind!

    As I think about it, the one thing I don't like about the Lead Sled is that the rear of the rifle rests on the bottom point of the recoil pad, instead of on the stock, as it would witth a rear bag. I'm wondering if maybe this might effect how different rifles react to being shot from the lead sled. In the meantime I have put together some shooting bags. I'll get to shoot with those in the next ten days, but I'd still love to hear what you all think!

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    I usually let a barrel cool 5-10 minutes between *each* shot until I cant detect warmth in the barrel.

    Have you tried slipping a dollar bill between the barrel and stock after each shot?

    The Kimber pillar bedded stock should be a fine platform. Badding might tweek an already tight group, but probably isn't the cause of your verticle stringing. By your description, tight groups with flyers, sounds like a barrel issue to me. If it were generally sporadic vertical grouping, it might be your rest, trigger control, bedding, scope, etc.

    Interesting.... let us know if you get it figured out.

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    Quote Originally Posted by Murphy View Post
    I believe this cute little wheel just applies to handguns.
    i think it does too! (but it is cute)
    happy trails.
    jh

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    there were lots of great replies to your question, many of which that go to the bedding question. generally when a barrel "walks" it is because of uneven pressure, and barrel harmonics.

    lightweight rifles have their own mysteries, that run contrary to the standard norms of rifle marksmanship. the recoil momentum is so much faster that the rifle moves while the bullet is still in the barrel.

    not being familiar with your leadsled, perhaps it does not hold the stock AND forearm tightly. actually, some movement is necessary to keep your action in the stock.

    my solution is to retrain yourself to hold the stock, not cradle it (as with a heavier rifle) and put that bullet on target. this will force your trigger squeeze, and require a different (but easily mastered) skill. i own several kimbers' in the montana configuration, as well as a few remington titanium models. holding the rifle has worked for me, and has produced consistant groups.

    check my "pictures" showing a 7-08 titanium and it's group.
    happy trails.
    jh

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    Without letting the barrel get completely cold after each shot and you control shooter technique it will be hard to determine why. Do the two things above first letting the barrel come completely back to a cold barrel before you take the next shot and especially control your shooting technique and see what happens. Do this and let us know what happened but when I say let the barrel come back completely to cold, I mean completely.
    A GUN WRITER NEEDS:
    THE MIND OF A SCHOLAR
    THE HEART OF A CHILD
    THE HIDE OF A RHINOCEROS

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    A lot of good points here form others and I can't say I disagree with any of them. I have never used this sled and cannot commment on it good or bad except to say it is another variable. If you've shot well with it and other rifles, you've got the technique down.

    Light barrels are tougher for me to shoot well and some barrels are more responsive to heat, they need to be at 17 degrees celcius to shoot 18 or 16 won't cut it. And the lighter the barrel the worst it is. I don't think there is a particular problem with the kimbers but I did notice that with the light barrels they are very whipy in the 300 and 325 WSM calibers, (more ooomph!). The barrel seems to jump and twist with those (I call it torque) but the 7-08 shouldn't be nearly so bad. I would say shoot one shot then go shoot a couple hundred rounds through your 45 then come back to the kimber for another shot, etc. Lots of cool down and see how that groups. I would not consider it to be an ammo issue at this point. Keep us posted with the findings.
    Last edited by Murphy; 03-06-2009 at 00:15.
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    Default vertical strays

    i was always told that vertical was from not controlling your breathing. Is this not true? Hillbilly

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    Quote Originally Posted by H_I_L_L_B_I_L_L_Y View Post
    i was always told that vertical was from not controlling your breathing. Is this not true? Hillbilly

    Yes and no. Not very many people actually breathe while shooting but we're suppose to hold a half breath then break the shot. If we did a full breath then half then something else there would be a different chest for the rifle to recoil against each shot and that would string shots vertically. I have found this to make about 1 inch difference at 600 yards so rather disregard it. Good butt stock pressure by pulling it into the shoulder will out weigh any waxing or waning chest muscles. Certainly this stock weld at each of three points is important but from the bench less so.
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    Interesting information and comments here. I've been loading for a friends 300RUM made by Christensen Arms. It's a very nice rifle and certainly more money than I would ever consider for a hunting rifle, about $7500 with his choice of options and optics.

    http://www.christensenarms.com/rifles.html

    This rifle has a titanium action and a carbon fiber barrel with a stainless steel sleeve. I suspect it started out as a stainless steel barrel that was turned down and built back up with carbon fiber.

    The rifle is only good for three shots and it shoots them very well. After that it pulls 4" left every time and the shots go nuts after that. By letting this rifle completely cool you get three good shots again.

    I suspect the light weight thin barrel on the Kimber is telling you that it doesn't like heat. Let it cool between shots and come back to shot the same target and see how your group looks. If you get it to preform when cool it will preform as a hunter. Only the first shot will matter and perhaps a follow up.

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    Default good info!

    Great discussion guys! It sounds like the first thing I need to work on is my patience.

    I'll try letting the barrel cool and get back to you.

    By the way, I did as promised and pulled the stock on the Kimber last night. Wow, that really is a nice stock. Fit and finish, even inside the stock, are beautiful. Never the less, I'm kind of on a stock bedding kick so I think I might go ahead and bed it anyway. I think with such a light action and thin barrel it might make a significant difference.

    Another Wow was how small and light the Kimber Montana action and barrel are. Especially since I've been working on my 375 H&H (bedding it) lately, the barreled action of the Kimber felt like I had a large pen in my hand when compared to the 375.

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    Default Eye of the Beholder

    Eye of the Beholder - I'll add to this thread. It can be a real plus or minus using a lead-sled.

    I'll take another stab at the seemingly problematic situation of vertical stringing. Like Murphy and others have said, "more info" from first shot, to second, to third, and so on would help us better interpret the variety of possibilities that you are experiencing.

    I think it may be the shooter here... if it is only vertical strings, particularly if the horizontal grouping never shifts <1/2". If all things are solid, I'll be willing to bet it involves 'inconsistent eye positioning' relative to the ocular and field of view on your rifle scope. This may be caused by winter clothing, the lead-sled itself, and the rest moving rearward on the bench (combo of the entire rest moving back and repositioning it or the rifle settling into the rest's padding).

    Try these few things before getting too technical or more expensive.

    #1 does this happen regularly day after day when you shoot this gun and loading? In other words don't change a thing yet and keep on shooting... ya may be sweating the small stuff.

    #2 try to keep everything as far as equipment, clothing, and technique plus conditions all the way down-range consistent.

    #2 Does this occur if you hand the gun off to another trusted shooter (appearing to be shooting well) that very day next to you on the range? See if your problem is mostly similar on paper that may be evidenced by another reasonably good shooter.

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    Default shot yesterday

    Here's some more input.

    Yesterday I shot some more, and this time I placed a small shot bag filled with rice in the stock holder of the lead sled. The idea was to keep the stock from resting on the tip of the recoil pad.

    I also shot no more than one shot every three minutes.

    The results? No more vertical stringing. My groups were not my best ever but they were right at 1" at 100 yards, with one 3 shot group going 1.5" at 200 yards.

    I think that much of the input people made was very good, and all these factors come together and are made more noticeable with a very light rifle. In this case I think that the rifle sitting on the "nose" of the recoil pad in the lead sled makes a difference, especially since the recoil is quick enough to make changes before the bullet completely exits the barrel. Barrel heating seems to matter too, although in this case I don't think it matters as much, based on the fact that in the past I shot three shot groups within about two minutes, and most of those never strung out vertically.

    Once again, fantastic discussion. No need to end it here. If anyone else has more input, I'm still interested.

    Thanks to all!

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    Default that was an interesting discussion !!

    I was putting my money on the barrel heating as being the root cause ! thanks to all for sharing ! Kevin

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    Default This is the same as the Shoulder/Cheek/Stock "weld"

    Quote Originally Posted by AKArcherdaddy View Post
    As I think about it, the one thing I don't like about the Lead Sled is that the rear of the rifle rests on the bottom point of the recoil pad, instead of on the stock, as it would witth a rear bag. I'm wondering if maybe this might effect how different rifles react to being shot from the lead sled. In the meantime I have put together some shooting bags. I'll get to shoot with those in the next ten days, but I'd still love to hear what you all think!
    If the butt of the rifle stock is not secure (and consistent) where it is supported by the sled, I would expect vertical stringing as you have experienced. A bag of dried beans, hard plastic beads, BBs or some such incompressible media that would form a "pocket" for the rifle to be secure in would go a long way toward locking in your groups.

    A consistent hold, either in your hands and shoulder or on the sled might just be your only problem, to be solved, as you suggest, with some shooting bags.

    Is there any way you could bed the action directly to the sled or to an inletted rectangular wood block that you could just clamp in place. Talk about free-floated barrel. No fore-end at all and 100% consistent contact. That would certainly make diagnosing groups simpler.

    Lost Sheep

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    Your experiences with your Kimber Montana are very similar to those I had with my 30-06 M-700 Remington Titanium Mountain rifle last year.

    The super thin barrels heat up and warp. Cooling periods are a must.
    Plus these rifles have pressure points built into the barrel channels due to the soda straw barrels.

    I removed mine (the pressure points) and it changed the grouping dramatically. But it was still prone to heat warping.

    Eventually my continued use of a Lead Sled with this super light weight caused the stock to break from a small internal flaw. Luckily Remington replaced it at no cost. These lightweight rifles were not made for continual pounding were the recoil cannot be absorbed by the shooter's body moving backwards. There are old threads here with photos....

    I am back to a regular stock and this rifle will give me 0.75 inch groups as long as I let it cool and give it ammo it likes.
    Floatplane,Tailwheel and Firearms Instructor- Dragonfly Aero
    Experimental Hand-Loader, NRA Life Member
    http://site.dragonflyaero.com

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