torquing mount above barrel nut

[corey4]

i bought a warne xskel mount for my pst gen1 1-4. per the instructions, i mounted it as far forward on the upper receiver as possible. the rifle shot ok with a few different brands and weights, but i will be using fiocchi 55gr mostly (the "better" ammo i had on hand only shot marginally better than the fiocchi at all distances). zeroed at 50 yards, about a 1" group. 100 yards averaged between 2.5-3. not too bad for a ddmk18 10.3" sbr. after i figured out my come up for 300, i was hitting the 8" plate damn near every time. when i was packing up to leave i realized my scope was loose. my dumb ass never torqued it down (65in/lb)! i figured it wouldn't take long to confirm so i went back to 50 to check the zero. everything seemed ok. when i went to 100, i was getting 4-5" groups with all the different ammo. so yes, the groups doubled in size with the proper torque setting vs hand tight. WTF??? so i backed the torque setting to 45in/lb. same 4-5" groups with all of the different ammo. so for shits and giggles, i torqued the mount to finger tight. i was back to 2.5-3" groups at 100 and smacking the 300yd 8" plate. i thought that maybe the dd upper just doesn't like the mount in general. the next day, i took my ddmk18 and my RRA 16" upper to see how that did and to get dope on the RRA upper as well. same F-ing thing. i torqued the RRA upper to 65 with the mount all of the way forward and was all over the place. so i tried hand tight, and i was getting .5" groups at 50, and 1.5-2" groups at 100. WTF?

i ended up moving the mount back on both rifles about an 1" or so and torqued it to 65 to see if that would work and am able to get good groups, but now the rear of the scope is over the charging handle and the scope gets in the way.

all shots were taken off an atlas bipod and rear bag. i'd rather run the scope mount all the way forward so i have room to reach the charging handle, but don't trust it to hold up during a 2 gun match.

does anyone have any insight?

223 ammo:
fiocchi 55
hornady american gunner 55
hornady balck 62
hornady match 75 bthp

rifles:
ddmk18 10.3" 1:9 twist 5.56 chamber
rra 16" 1:7 twist 5.56 chamber

[GH41]

Dumb questions first... Is the mount 100% on the receiver? Are the cap screws in the rings torqued to Warne's 26 "# spec? If answers are yes and yes it could only be one of three things. There is something wrong with the scope or the ability of the shooter to consistently run the gun. 3rd... Tell me you are NOT mixing 5 different loads in the magazine because because they all perform about the same.

[hk_shootr]

Assuming the mount it ONLY mounted on the receiver, it sounds as if it or the receiver is warped. I’ve never see either of those though. Torquing the mount could be tweaking the scope body, producing the MOA shift

[bamashooter]

Regarding only the optic, you should use the values from Vortex. Here's what I learned from them: "Vortex Viper PST Torque Specs (Rings)
Thought I'd pass this on to those who use torque specs when mounting scopes.

ME: I recently ordered a Vortex Viper PST 1-4x24 and ADM Recon mount from OpticsPlanet. I had found conflicting values for the scope hold-down screws. I contacted ADM and they suggested 20-25 inch pounds. However, they told me that it's best to contact the scope manufacturer due to different housing thicknesses, etc. What do you recommend?

Thank you

Vortex Rep: Thank you for contacting Vortex Optics. Congratulations on your new Viper PST 1-4x24 scope! We recommend using 15-18 in/lbs for ring to scope. If you exceed this, you risk damaging the internal erector tube on your scope. Thank you for the inquiry! Thank you for choosing Vortex!!

Complete thread: https://www.m4carbine.net/showthread.php?189941-Vortex-Viper-PST-Torque-Specs-(Rings)

[corey4]

Dumb questions first... Is the mount 100% on the receiver? Are the cap screws in the rings torqued to Warne's 26 "# spec? If answers are yes and yes it could only be one of three things. There is something wrong with the scope or the ability of the shooter to consistently run the gun. 3rd... Tell me you are NOT mixing 5 different loads in the magazine because because they all perform about the same.

come on...give me some credit lol. i am not using all of the different ammo in the same mag on the same group. it's not my inability to run the gun either. i'm not the best shooter, but i'm a fairly competent shooter. below in an 8" circle, 7 out of 8 (i forgot to dial on the first shot...oops. a buddy was "spotting" for me and when i shot the first round he said i was way low.). the head on the silhouette is 6", 7 for 7. not super impressive, but capable. yes i know the group is a little low. it was part of getting my dope. i was aiming at the center of the "body". both of these groups were shot with the mount finger tight. both are 300 yds. both were shot with my sbr and fiocchi. i'm not one to really run around and take pics of groups and post them, but there is a fudd at work who thinks it's impossible to hit a plate at 300yds with an sbr, so that's why i took the pics.

50129

50130


Assuming the mount it ONLY mounted on the receiver, it sounds as if it or the receiver is warped. I’ve never see either of those though. Torquing the mount could be tweaking the scope body, producing the MOA shift

it is only mounted on the receiver, not the rail. it can't be the mount is warpped, because i have the mount sitting with the first screw 4 rail sections back from the front of the receiver. i had it mounted fully forward, shot a "group", moved it back one rail section at a time until i got normal groups again. this was done with both uppers.


Regarding only the optic, you should use the values from Vortex. Here's what I learned from them: "Vortex Viper PST Torque Specs (Rings)
Thought I'd pass this on to those who use torque specs when mounting scopes.

ME: I recently ordered a Vortex Viper PST 1-4x24 and ADM Recon mount from OpticsPlanet. I had found conflicting values for the scope hold-down screws. I contacted ADM and they suggested 20-25 inch pounds. However, they told me that it's best to contact the scope manufacturer due to different housing thicknesses, etc. What do you recommend?

Thank you

Vortex Rep: Thank you for contacting Vortex Optics. Congratulations on your new Viper PST 1-4x24 scope! We recommend using 15-18 in/lbs for ring to scope. If you exceed this, you risk damaging the internal erector tube on your scope. Thank you for the inquiry! Thank you for choosing Vortex!!

Complete thread: https://www.m4carbine.net/showthread.php?189941-Vortex-Viper-PST-Torque-Specs-(Rings)

i torque all of my vortex scopes to 20 on my fat wrench. i have a few pst gen1s, a pst gen2, a few razor gen2s (all are the bigger bolt gun scopes). this is my first and only little scope.