vertical stringing

[AKArcherdaddy]

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?

[pinehavensredrocket]

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!

[Murphy]

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.

[Murphy]

this is a general guideline. hope it helps!

I believe this cute little wheel just applies to handguns.

[BrownBear]

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.

[AKArcherdaddy]

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!

[MontanaRifleman]

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.

[pinehavensredrocket]

I believe this cute little wheel just applies to handguns.

i think it does too! (but it is cute)

[pinehavensredrocket]

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.

[beartooth]

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.

[Murphy]

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.

[H_I_L_L_B_I_L_L_Y]

vertical strays

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

[Murphy]

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.

[marshall]

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.

[AKArcherdaddy]

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.