Removed recoil pad, strange result????

[oldracer]

My Rolling Block had a recoil pad on it when I bought it, the original owner/builder did not like recoil it seems. While shooting on a rest the total stock length was not a big issue but last week I started trying my ability with off-hand shooting. I quickly found the stock was too long with the pad and also with the lead plate I made for the end so yesterday I shot without anything after trying both pads and having trouble holding the gun. The original owner is about 6ft 6in and has longer arms than I do.

I shot several shots and did not see a hit anywhere on the target off-hand so I thought that is strange as I should at least hit the backer??!! I put the gun on the rest and the same thing and the shooter beside me said the dust kicked up looked very low. So I raised the tang sight and full hash mark and hit the bottom of the backer. I raised it another (which now equaled the 200yd setting from my dope book) and bingo, right in the center! I fired a couple more and they hit together so I tried several off hand and they were now on target?!

I asked a couple of long range competitors that were there and they said that the recoil pad was causing what was known as "barrel whip" due to the rearward movement from recoil and the barrel was also trying to rotate so the shots were artificially high as to the tang sight setting. Thay also noted the gun would be more accurate WITH OUT the recoil pad so I made a new temporary butt plate while I sort things out.

Does this sound reasonable to those with lots of experience as it does to me especially about the part about the barrel trying to rotate?

[405]

Short answer is yes. Upon recoil the whole gun rotates around both a resistance pivot (how it is held) and a center of gravity. The first part of this rotation begins when the bullet is still in the barrel. The effect is especially large in handguns and to a lesser degree in long guns. The other things that determine how much it affects POI is the velocity of the bullet, length of barrel and the amount of drop in the buttstock. This "rotation effect" shouldn't be confused with barrel harmonics, the sine wave and angle of departure of the bullet when it leaves the muzzle.... a completely different thing from this recoil/rotation effect. I really don't like the term "barrel whip" because it confuses the two different issues. The extra weight of the recoil pad would cause some effect but I've never seen such a large one.... could have to do with the lead weight added exaggerating the rotation effect (higher POI).

[scrapcan]

One other item that could cause issues is where your head sets in relation to a slope on the but stock. If the slope is lower at length and you shorten the length you may end up higher on the comb, or vice versa if the stock slopes the other way.

just something else to think about if you have a sloping comb on the stock. If the stock comb is parallel to the obre this woudl not be an issue.

[onondaga]

Sounds reasonable to me too. Strange things can happen changing the resonance of a rifle or the angle of the butt to the bore centerline. An extreme example happens to me with my .458 Win Mag Colt Sauer Rifle and hot loads. After sight in sitting and shouldering for a nice Zero, I tried the Lead Sled of the guy next to me at his invitation. My rifle point of impact instantly dropped 18 inches!!! I went back to my shoulder and all was fine.

Gary

[oldracer]

Thanks for the input guys. I expected some change due to the difference when I put some lead in the stock to move the balance point towards the trigger(see you slightly earlier post). I did try the gun with shotgun recoil pad after adding the lead and the POI on the bench did not change and was also the same when shooting off-hand. The big surprise came when I took the pad off and now all was solid and the POI dropped dramatically both on the bench and off-hand and as 405 said it is "rotation" which I agree sounds better than barrel whip. I have already figured out the resonance of the barrel and I leave the coating of oil on it when I start to shoot and the first several rounds make the oil actually form a sine wave and I check it to see it it has the same distance between the peaks. I did find that the measurement changes from 70gn to 68gn to 64gn loads, but only by a few thousands of an inch!

As noted, the top of the stock is parallel with the barrel so my cheek weld is the same. The gun does have a pistol grip (pics in the gunsmithing forum) and since I checkered the forend and stock there is no slippage. Again thanks for the input and I am finding this much more fun (learning stuff) than just banging away with my ARs or even the pistols!!!

[bearcove]

The recoil pad is probably letting the gun move sooner. To compress the pad is much easier than moving your upper body.