Sako accuracy problem

MFH · September 8, 2002, 10:27 PM

I have a Sako AVL61 in 338 win that I can't figure out. It is in a mcmillan fibergrain stock, is free floated and is wearing a varix-3 scope. So far, about the best accuracy I have been able to obtain is 1.5" @100yds. Occasional handloads will do better but none consistantly. The thing I don't understand is the group distribution. This thing insists on throwing vertical groups. The most dramatic is with 210XLC's. Using either RL-22 or H-414, groups will range from 4-10". These groups will never be more than 1.5-2" in horizontal spread and will frequently be under an inch. The last group this evening was with factory failsafes. It put 3 into about 1.5"; 1.5" high and .3"wide. Does anyone have any suggestions? I know it just may not like x bullets, but why a constant vertical string?

Thanks!

MFH

DeBee · September 9, 2002, 12:02 AM

Your forend could be 'bouncing' off the rest in recoil. The sandbag could be too hard or overstuffed and .338 is no treat to shoot off the bench...

I occasionally get vertical stringing with a known accurate rifle when I install a bipod and shoot of the bench.

Have you ever tried the Lahti Rifle Evaluator?

Anyone else?

MFH · September 9, 2002, 07:08 AM

I wondered about recoil inducing the strings, so I have tried both with and without a sling, as well as forearm loose on the bag or using a shooting glove and holding on to it. The barrel has also been magnaported. Any possibility this could be involved?

MFH

kurt IA. · September 9, 2002, 08:04 AM

I had a Ruger in that cal that did the same thing, never did fuger it out. It could be your load, some times a little more power will stop this, unless your at the top all ready. Next it could be stress in the barrel, letting it bend as it warms up.

George Stringer · September 9, 2002, 08:31 AM

MFH you might try the old "business card under the barrel" trick and see if that helps. Put the card in about an inch or so back form the forend tip. If that helps you might consider a permanent glass pad at that point. Vertical stringing can also be a result of inconsistent velocity. You might load a few rounds as carefully as possilbe and see if there's a difference. George

Art Eatman · September 10, 2002, 12:56 PM

I don't particularly believe in "always", but vertical stringing is usually due to some sort of bedding problem, and commonly with the forearm. I've always had good luck with a free-floated barrel if I shim out at the tip of the forearm.

Gale McMillan commented that the shim is a Good Thing for a less-than-perfect barrel.

Knowing nothing about your sensitivity or lack of it, to recoil, there is always a possibility that there might be varying degrees of "hunch", of anticipation of recoil, from shot to shot. This would surely affect vertical dispersion.

Art

MFH · September 10, 2002, 05:44 PM

Thanks for all the information! I am assuming that a properly bedded action should remain solidly in the stock even if the rear action screw should become loose. I tried loosening the rear screw and found that the action would move about 1/16th of an inch up and down. There appears to be a high spot in the bedding material at the front of the action. After finding this, I tried shimming the barrel and fired one shot. Then removed and replaced the stock and fired again. Repeated for a third. Total vertical string of less than 1/2 inch. It's going in for a glass bedding tomorrow.

MFH

September 8, 2002, 10:27 PM	#1
MFH Senior Member Join Date: February 13, 2000 Posts: 122	Sako accuracy problem I have a Sako AVL61 in 338 win that I can't figure out. It is in a mcmillan fibergrain stock, is free floated and is wearing a varix-3 scope. So far, about the best accuracy I have been able to obtain is 1.5" @100yds. Occasional handloads will do better but none consistantly. The thing I don't understand is the group distribution. This thing insists on throwing vertical groups. The most dramatic is with 210XLC's. Using either RL-22 or H-414, groups will range from 4-10". These groups will never be more than 1.5-2" in horizontal spread and will frequently be under an inch. The last group this evening was with factory failsafes. It put 3 into about 1.5"; 1.5" high and .3"wide. Does anyone have any suggestions? I know it just may not like x bullets, but why a constant vertical string? Thanks! MFH

September 9, 2002, 12:02 AM	#2
DeBee Senior Member Join Date: October 5, 1999 Posts: 408	Your forend could be 'bouncing' off the rest in recoil. The sandbag could be too hard or overstuffed and .338 is no treat to shoot off the bench... I occasionally get vertical stringing with a known accurate rifle when I install a bipod and shoot of the bench. Have you ever tried the Lahti Rifle Evaluator? Anyone else?

September 9, 2002, 07:08 AM	#3
MFH Senior Member Join Date: February 13, 2000 Posts: 122	I wondered about recoil inducing the strings, so I have tried both with and without a sling, as well as forearm loose on the bag or using a shooting glove and holding on to it. The barrel has also been magnaported. Any possibility this could be involved? MFH

September 9, 2002, 08:04 AM	#4
kurt IA. Senior Member Join Date: February 19, 2001 Location: Iowa Posts: 141	I had a Ruger in that cal that did the same thing, never did fuger it out. It could be your load, some times a little more power will stop this, unless your at the top all ready. Next it could be stress in the barrel, letting it bend as it warms up.

September 9, 2002, 08:31 AM	#5
George Stringer Staff Alumnus Join Date: October 12, 1998 Location: Earlington KY Posts: 2,299	MFH you might try the old "business card under the barrel" trick and see if that helps. Put the card in about an inch or so back form the forend tip. If that helps you might consider a permanent glass pad at that point. Vertical stringing can also be a result of inconsistent velocity. You might load a few rounds as carefully as possilbe and see if there's a difference. George

September 10, 2002, 12:56 PM	#6
Art Eatman Staff in Memoriam Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 24,798	I don't particularly believe in "always", but vertical stringing is usually due to some sort of bedding problem, and commonly with the forearm. I've always had good luck with a free-floated barrel if I shim out at the tip of the forearm. Gale McMillan commented that the shim is a Good Thing for a less-than-perfect barrel. Knowing nothing about your sensitivity or lack of it, to recoil, there is always a possibility that there might be varying degrees of "hunch", of anticipation of recoil, from shot to shot. This would surely affect vertical dispersion. Art

September 10, 2002, 05:44 PM	#7
MFH Senior Member Join Date: February 13, 2000 Posts: 122	Thanks for all the information! I am assuming that a properly bedded action should remain solidly in the stock even if the rear action screw should become loose. I tried loosening the rear screw and found that the action would move about 1/16th of an inch up and down. There appears to be a high spot in the bedding material at the front of the action. After finding this, I tried shimming the barrel and fired one shot. Then removed and replaced the stock and fired again. Repeated for a third. Total vertical string of less than 1/2 inch. It's going in for a glass bedding tomorrow. MFH