Bipod/Hard Rest affect on POI?

[the444shooter]

My rig-
Rem 700 LSS 300RUM, Burris Fullfield II ballistic plex, Harris bipod.

When sighting the rifle in with factory 180gr Swift Sciroccos, I was 2.5-3" high at 100yds, and was hitting the 400yd gong with minimal holdover (second hash mark down from main crosshairs on B-plex), and 500yds no problem (third hash mark). That was shooting off of a bench, with a hard rest, and then from a bipod. I know that hard surfaces cause a rifle to jump and POI to shift a little higher, but I didn't think that a bipod would have an effect. Last day of season, I was shooting at a mule deer doe at ~400yds (at the moment, I can't remember what she lasered at) and so I held high in the vitals but was still hitting low. WAY LOW! When I eventually got one (a different one at no more than 350yds) I hit low in the brisket on a quartering towards me shot and disemboweled the deer. Not a pretty sight. I was shooting at both of these deer with a soft rest (left my bipod at home) and hit low every time. Aside from temperature affecting the ballistics of the rounds, the only thing I can think of is that my shooting off of a soft rest vs. a bipod made my POI shift lower. My question is this, Would fully floating the barrel remove the POI shift since it would allow the barrel to fluctuate naturally instead of having the contact point with the stock (and subsequently the rest/bipod, etc)? Or do I need to leave the bipod on all the time to get the same groups? This concerns me greatly since I had been consistent all summer long and all season long up until this point. And I was absolutely sure of my hold and my trigger pull. I've never experienced anything like this, and it's the only thing I can think would affect my POI, because I don't think the factory rounds would be THAT sensitive to temp.

 

[Charles A]

Free float your barrel. Thats the first to do when you get a new rifle. Could that have been your problem? Maybe. Shoot it and find out.

 

[Aussie]

Ben ,
Free floating your barrel is a good idea but won't make any difference in this case . I do lots of shooting off a bipod and find the only way I can get consistent small groups that impact at the same point as other holds is to hold firmly onto the forend as you would if shooting offhand . Do the same when shooting over a soft rest and your point of impact will be consistent . This is with a 12 pound rifle and no muzzle brake . Can't comment on 30 pound rifles with brakes as I have never fired one .
It's a well known fact that different holds result in different impact points . This is why it's not a good idea to get someone else to sight in your rifle .

 

[Shufisher]

I agree with Mr. Arbuckle, float it and put it to paper at distance and situation. Gongs are great noise makers, but not as good as groups on paper..

 

[RBrowning]

Ben,
I have noticed that I tend to group higher off of my bi-pods than off of a sand bag too. If I am shooting from a sitting position with them fully extended it is real bad. Now I use bi-pod off the bench or prone and a set of shooting sticks (3/4" diameter dowel rods) for sitting. They tend not to act like a spring board as much as the thin aluminum sticks do.

Best of luck sorting out the cause.

 

[wapiti13]

Ben,
Field positions will usually be different than off benches & bipods. Shooting with & without your sling varies. Anything that effects the way your forearm moves during recoil can change POI. Free floating helps take the "forearm" out of the calculation somewhat. But, field positions for checking your POI are very necessary. Paper groups fired in real world positions using exactly what equipment and set up you will hunt with are the real test.

 

[speedbump]

I agree with Wapiti on the field positions. Unless a person really trains in field positions, they'll likely have a larger spread than changing ammo. I've seen a trained sniper shoot 6" low at 100 yards just from shooting off a soft pack in heavy winter clothing. Speaking of which, if you zero your rifle in shirt sleeves, then switch to thick puffy winter clothing, you'll possibly have a shift of 2-3 MOA from the different recoil in lock time. /ubbthreads/images/graemlins/crazy.gif

The difference of bench to bipod to pack to field position varies completely from shooter to shooter. We had a discussion here a few months ago about whether or not to "load" the bipod tension forward. I prefer that method, but many others liked a more neutral tension, while a few preferred a little rearward pull. To each his own. In the end, making the shot consistently counts for far more than "pureness" of technique. /ubbthreads/images/graemlins/wink.gif