What causes vertical stringing?

I was shooting some test reloads through a Savage 110fp, 308, at 200yds. last week. One 5 shot group came in at just under 2" but all vertical on the target. The rifle is the bull barrel, 24", I believe, with a thumbhole, laminated stock and a Timney trigger. I did a search on this subject but did not come up with much. Another 5 shot group was 1 7/8" and looked like a "typical" triangle. Is it me? the stock? the barrel heating up? The other 3 test loads weren't much to talk about. What do you think? ps. Sorry for the previous confusion.

What sort of ammo ??

Wind up and down the course, IE in your face/on your back can cause vertical stringing, but I would bet its barrel movement or variations in the load or something else.

This is a good read on stringing.

http://www.6mmbr.com/verticaltips.html

What sort of ammo? Handloads, OOPS! I goofed! :-[ It wasn't the 25-06, it was the 308. Shot from Savage 110fp. Load: Lapua brass, Fed GM 210M primer, 168 Berger VLD's. The vertical string was loaded with 45 grains Varget. The other group was 44.5 grains.

At longer ranges, you may find that a poorly tuned load, or one with high ES/SD may start showing some vertical stringing. At relatively close ranges like you describe... it may be a mechanical problem (loose actions screws, barrel contacting stock, other bedding problems, loose screws on scope rings or mount), or it may be shooter-induced. It is very easy with a bipod to inadvertently change your shoulder pressure against the stock and have shots go high or low. Same goes for cheek pressure, and grip on the stock, etc. Even sometimes with a front rest you may find that the gun doesn't like a particular setup in the bags - but thats usually when you are trying to really fine-tune things, not chasing 1 moa groups.

I'd check everything mechanical first - just put a wrench on every screw or bolt that matters and see if its at all loose. Then start working through your position on the gun very deliberately and methodically with a focus on consistency.

I checked out that link and I tend to believe the problem may be with me or the bags I was using. They were filled a bit hard. I checked the nuts and screws and all was OK. The concrete benches at the range are not ideal, especially if you're 6'4". Seating and posture and comfort are not to be had at the same time. Would a Lead Sled help for working up loads? I know I'm not the steadiest shooter because I see the crosshairs "dancing" on the target within a 1" diameter circle at 100yds. Tuning in to more consistent shoulder pressure is something I did not consider though I do try for consistent cheek and eye placement. I greatly appreciate all the comments and welcome any criticism that is constructive. :)

Excessive cheek pressure will cause it everytime and your grip or both.

Generally I'm not a big fan of the 'Lead Sled' and other rests of that type that hold the gun for the shooter, mainly because they are 'targeted' (forgive the pun ;) ) at shooters who are probably not going to go back and verify their zeroes from an actual position they might use in the field.

If your crosshairs are wobbling around a 1" circle @ 100yds, from a rest... assuming you don't just mean the normal respiratory movement, which can be coped with... is quite a lot. Are you gripping the rifle really firmly and/or pulling it back into your shoulder? That much movement almost sound indicative of muscle tremors from trying to hold *too* hard - which is really hard to do consistently, and most people start getting the wiggles like you describe.

Maybe you are far beyond this step but....

In the over 3k+ shooters I have trained, with all things being equal, it comes down to simple breathing control, and a stable firing position.

Go back to your fundamentals, make sure those are locked in, and then go from there with the more technical side of things. From experience, most issues lie between the rifle and the chair.

Horizontal stringing = trigger control
Vertical stringing = breathing

I have a Remington VS .308 with an HS Precision stock. Changing the front bag position, fore and aft, changes the shape of the group. If the front rest is under the scope bell the groups are round. Farther forward and the groups have vertical stringing but are very small side to side. The HS stock rings like a bell when struck. Cheeking or thumbing it will cause flyers. I'm new to Savages and don't know their characteristics yet.

MikeSSS,
Check your Remington and see if it has "pressure pads" inside the barrel channellat the front of the stock - I've seen several Remingtons that have them in the fore-end. These cause upward pressure on the barrel at the fore-end and can cause the effect you posted, especially if the stock isn't very rigid.

I generally am not a fan of pressure pads - they make return to zero difficult after you remove the action from the stock and also make action bolt torque really important. They can also cause quite a bit of stringing ("walking") on lighter weight barrels as the barrel heats up. I prefer to have my barrels free-float. You can sand the pressure pads out and make the gun a more stable shooting platform.
Elkbane