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5 x 5 at 200m groups in succession, .81 MOA best

Edit: I thought I had a bad flyer but rechecked and that hole was a tear in the cardboard that did not go through. So it was not a shot. I had counted out 5 slugs for each target, so I looked and found the extra shot on target #3. That eases my mind a little as I could not figure out why one would be so far off. Corrected below.

Winds were 3mph-11+mph on the meter. 3 sighter shots at a different target to establish the poi, and then 25 consecutive shots at the five targets shown below.

I shot from the bench using bags. 71.5gr 257420 slugs at 975fps. 5 shots per target.

wind-00.1621476244.jpg


#1) 23moa holdover from my 100yd zero, 2moa hold-off for left-to-right wind. All inside the 2.5 moa 7 ring:

target1.1621476255.jpg


#2) 23.5moa holdover, 2moa hold-off for wind. Wind must have picked up:

target2.1621476341.jpg


#3) 6 shots as one was intended for #4. 23.25moa holdover, 2.5moa hold-off for wind. Too much windage. All inside the 3 moa 8 ring +2X:

target3.1621476418.jpg


#4) Only 4 shots here. One of them went to #3 by mistake.

target4.1621480505.jpg


#5) 23.25moa holdover, 2.25moa hold-off for wind:

target5.1621476684.jpg


Finally - 5 shot sub moa group at 200m. And all 5 inside the 1.5 moa 9 ring +1X.
 
That is some really good shooting... 200 meters wow! So what PCP are you shooting those 71 grain slugs from? The last group was nuts...


The base gun was a Benjamin Armada.

Single shot cast breech (lost PLA process)

36" TJ liner in a 0.875" OD DOM tube

2000cc 300bar bottle, output currently regulated to 2300psi

Cothran Powerhouse valve

Armada-range-01.1621479299.jpg


I get over 100 shots at 150fpe on a 4300psi fill, but I usually only fill to about 3500psi. The Cothran valve needs a very stable psi in order to get a consistent velocity. There seems to be a little less creep if I keep the pressure between 2500psi-3500psi. At 200m, and 975fps, a 3fps velocity variation causes a 1/2" vertical dispersion. The velocities for those last five shots were 976, 976, 980, 975, 975.
 
Great groups. You have been busy with your rifle.

What did the Cothran valve do for the rifle?

The Cothran valve makes it easy to get big FPE numbers. But also easy to waste air. Tuning is different with this valve. Long dwell with little control over the dwell time. Best to use just enough hammer strike to open the valve reliably, and then adjust pressure to get desired FPE, and maybe transfer port restriction to fine tune it. My current tune is very efficient. About 1.3 to1.4 fpe/ci

Some info on the valve:

https://www.airgunnation.com/topic/big-new-valve-for-m-rod/

https://www.airgunnation.com/topic/another-custom-marauder-build-advice-needed/page/2/

Marauder version is not currently listed but the 22XX version is still listed on the website:

https://cothranmachine.com/powerhouse-valve-for-7-8-250-transfer/