Advanced Marksmanship T4A vs PRS2 recoil control

Subwrx300

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Minuteman
Jan 15, 2014
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Cedar Springs, MI
So background info: I've shot a T4A (fiberglass) with a 26"M24 6.5CM for the last 2 years or so. It has a flat bag rider with hand hook.

I just build a new rig which is also 6.5CM on a Manners PRS2 carbon stock with the sloped bag rider (no hook). The weight and feel between the two is very similar (18.7lbs vs 17.33 for the new build) and barrel length is identical.

However I've noticed that in the prone position, I'm struggling to manage the reticle vertical movement during and post recoil. On my old build it was pretty easy to keep reticle dead level and return directly to original POA. With this build, the reticle jumps about 1-1.5MOA straight upwards during recoil and will settle about .5-1MOA over target.

Groups are .25"-.5" with most misses high or high left (left is due to a body position issue I'm working on).

I'm using a pint size GC as a rear bag in the heavy fill configuration, which has been terrific as both a barricade bag and rear bag.

Has any one else made the jump from a T4 or T4A (flat bottom rear stock) to a sloped bottom rear stock found this issue during their learning period with the stock?

One of the only ways I've found to control/eliminate the issue is with pretty substantial bipod loading (much heavier than needed with a flat bottom) but it's not always practical or possible to use that much preload (ice, loose snow, thin sand, car hoods, etc). Any thoghts from those that have switched styles?
 
Here is an example of what I referring to. Point of aim is top edge of stickers (.75" stickers).

No sight adjustments between groups.

Left group: light rear bag squeeze/cheek pressure, medium bipod pressure. Impact .7" high, .4" left. Had one "oopsy" on the trigger though.

Middle group: medium rear bag/cheek pressure, lighter bipod load. Impact .25" high, .7" left.

Right group: medium rear bag/cheek pressure, heavy bipod load. Impact 0" high, .4" left.

20190225_195721.jpg


Bullet holes uncovered:
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I had the same issue. Changed to a new Manners T2AGAP from T4a and struggled in the prone. Was also using the smaller GC. I found adding a little no slip coating to the rear bag and/or getting more squared up behind the rifle helped. Using the bigger GC with less fill also helped.