POI change going from rest to bipod

[pmarauder]

I have a TRG-42 338LM that i have found a load which shoots very well @ 200 yds off my Caldwell BR rest. This load consistantly shoots in the .2-.3 moa @ 200. I wanted to check my data at 400 yards and so i shot (2) 4 shot groups at 400. Both groups were about 1.25" measured outside to outside. I was pretty happy with that concidering the wind was getting pretty choppy and the mirage was getting bad. I decided to shoot one more 4 shot group @ 400 off my TRG bi-pod this time. I still used my protektor rear bag though. After the 4 shots, i couldnt see any holes in the target through my spotting scope. I went down and pulled the target and was puzzled..... the 4 shots measured slightly under 1" outside to outside, but they impacted about 5" high at the top of the paper. Is this common? Seems like i need to go back and re-zero the TRG at 200 off the bi-pod instead of the front rest like i have been.
Any thoughts?
Thanks

 

[CatShooter]

I have a TRG-42 338LM that i have found a load which shoots very well @ 200 yds off my Caldwell BR rest. This load consistently shoots in the .2-.3 moa @ 200. I wanted to check my data at 400 yards and so i shot (2) 4 shot groups at 400. Both groups were about 1.25" measured outside to outside. I was pretty happy with that considering the wind was getting pretty choppy and the mirage was getting bad. I decided to shoot one more 4 shot group @ 400 off my TRG bi-pod this time. I still used my protektor rear bag though. After the 4 shots, i couldn't see any holes in the target through my spotting scope. I went down and pulled the target and was puzzled..... the 4 shots measured slightly under 1" outside to outside, but they impacted about 5" high at the top of the paper. Is this common? Seems like i need to go back and re-zero the TRG at 200 off the bi-pod instead of the front rest like i have been.
Any thoughts? Thanks

Somewhere in your "stuff" there is something wrong - typical, I built an M-24 and tested the loads on a rest, then put on a Harris BR-s bipod - nothing changed.

I have tested loads on many varmint rifles, and then went to Harris bipods, and nothing changed.

 

[CJ6]

Try using the bi-pod on the ground. The rubber feet tend to bounce when used on hard surfaces.

 

[pmarauder]

Try using the bi-pod on the ground. The rubber feet tend to bounce when used on hard surfaces.

It is a TRG-42 bi-pod.... no rubber feet. If i had to make a guess..... I would say that the rifle is recoiling differently from rest to bi-pod while the bullet is still traveling down the tube..... The groups are good both ways.... so i know its not the reloads or components. Im looking for anyone who may also have experienced this.
Thanks

 

[swampshooter]

My poi changes when going from a front rest to a harris bi-pod don't know about a trg but it stands to reason that it would change. For it to shoot the same, EVERYTHING must be the same.

 

[Minesweeper3433]

I get this with some of my light weight rifles. I use a rest I just put my left hand between the rest and rifle as if I was holding it off hand. I have a long harris bypod for shooting sitting and that one gets really bad POI shift even at 200. Only rifle I use with that is zeroed for using the bipod so it works.

 

[CJ6]

Metal (feet)will transmit vibration as well.

 

[jcampbellsmith]

My poi changes when going from a front rest to a harris bi-pod don't know about a trg but it stands to reason that it would change. For it to shoot the same, EVERYTHING must be the same.

+1 on that. I shot my 260 Rem from four different positions the other day and could see 4 distinct pairs of shots on the target. Zero it in the mode that you intend to use it in the field. Regards JCS

 

[Flouncer]

Size Matters

Just an observation. He is shooting .338 Lapua Magnum. Any effect of recoil on POI may be enhanced or magnified due to the energy released by this cartridge. It's not a 6mmBR or a .223. Is that plausible ?