FNG intro and horizontal POI issue maybe

[worthen86ford]

So i put me together a Grendel because for some reason i'm big on the one rifle/general purpose rifle concept. My first rifle was a ruger scout and tbh it is my go to confident rifle. I then figured i needed a semi auto so i got a M1A scout squad and that has been more of a disappointment than anything unfortunately yet its so sexy that it will never be sold. I first put together a 5.56 ar and after carrying it around at the deer lease i realized i needed to make this my hunting rifle hence the transformation to Grendel. Lightweight, short, and easy to sling ready with two free hands is nice.

Here's the basic build list:
Anderson upper and lower
Arms buis
AA 16" barrel
Spikes T2
MI 15" lightweight handguard
JP bolt
Standard Cmmg lpk
Areo scope mount
Vxr patrol 3-9x40 leupold
FZ bcg
Yada yada what ever...

Since i see that it comes up on a lot of forums; the purpose of the rifle will be considered a handy rifle. Normally keep it unscoped (since it does get banged around) and with the buis deployed with a weapon mounted light. Keep it somewhat ready for any coyotes or coons that might try to get at my chickens. Also plan to use it for deer and hog hunting likely never further than 250-300yards. Most current shots on animals are less than 100 in east texas but might have opportunities in west texas or kansas that will require longer shots. Possibly night hogs which is why i went vxr. Obviously it meets the $h!tty day gun pou as well.

Took it to the range today to sight in the scope. Have only plinked with it using irons and wolf steel cased. Kind of time crunched so couldn't work out everything, but at the 100 i was pretty impressed with hornady sst. Put six shots within an inch and a half to 2 inches. Two were fliers but 4 were close. I think it was the shooter and not the gun. Never had a 9 power so all that zoom was new to me. The GSR wears a 1-4x leupold scout scope.

Anyway, i decided to take it to the 200 and to my surprise i was grouping low and right about 3" right and 2-3 low. Good enough for government work but a little concerning with the horizontal shift in poi. Should i be worried about this? Havent had a problem with the gsr doing that and at a lower mag. Only thing i can figure is either the barrel is slightly not square with the flat top, or the scope is torqued over at a slight angle, basically either way i'm thinking the scope and barrel bore are not parallel.

Any thoughts on the horizontal poi or maybe a critique of the build. Some days i feel like i ought to have a rifle for every purpose rather than an all purpose rifle, but i just dont have time to get proficient with that many arms.

[worthen86ford]

Some pictures

[worthen86ford]

[Klem]

Past 100 you have to take into account environmental conditions. Most barrels are right-hand twist which means that any wind blowing from left to right will not only print right but low. Winds blowing right to left print left and high.

Your group at 100 looks good. Your right/low group at 200 doesn't mean your zero is out. It just means that on that day the wind caused it to print right and low (can you remember which way the wind was blowing?).

[LR1955]

So i put me together a Grendel because for some reason i'm big on the one rifle/general purpose rifle concept. My first rifle was a ruger scout and tbh it is my go to confident rifle. I then figured i needed a semi auto so i got a M1A scout squad and that has been more of a disappointment than anything unfortunately yet its so sexy that it will never be sold. I first put together a 5.56 ar and after carrying it around at the deer lease i realized i needed to make this my hunting rifle hence the transformation to Grendel. Lightweight, short, and easy to sling ready with two free hands is nice.

Here's the basic build list:
Anderson upper and lower
Arms buis
AA 16" barrel
Spikes T2
MI 15" lightweight handguard
JP bolt
Standard Cmmg lpk
Areo scope mount
Vxr patrol 3-9x40 leupold
FZ bcg
Yada yada what ever...

Since i see that it comes up on a lot of forums; the purpose of the rifle will be considered a handy rifle. Normally keep it unscoped (since it does get banged around) and with the buis deployed with a weapon mounted light. Keep it somewhat ready for any coyotes or coons that might try to get at my chickens. Also plan to use it for deer and hog hunting likely never further than 250-300yards. Most current shots on animals are less than 100 in east texas but might have opportunities in west texas or kansas that will require longer shots. Possibly night hogs which is why i went vxr. Obviously it meets the $h!tty day gun pou as well.

Took it to the range today to sight in the scope. Have only plinked with it using irons and wolf steel cased. Kind of time crunched so couldn't work out everything, but at the 100 i was pretty impressed with hornady sst. Put six shots within an inch and a half to 2 inches. Two were fliers but 4 were close. I think it was the shooter and not the gun. Never had a 9 power so all that zoom was new to me. The GSR wears a 1-4x leupold scout scope.

Anyway, i decided to take it to the 200 and to my surprise i was grouping low and right about 3" right and 2-3 low. Good enough for government work but a little concerning with the horizontal shift in poi. Should i be worried about this? Havent had a problem with the gsr doing that and at a lower mag. Only thing i can figure is either the barrel is slightly not square with the flat top, or the scope is torqued over at a slight angle, basically either way i'm thinking the scope and barrel bore are not parallel.

Any thoughts on the horizontal poi or maybe a critique of the build. Some days i feel like i ought to have a rifle for every purpose rather than an all purpose rifle, but i just dont have time to get proficient with that many arms.

WF:

You shot it at 100 and did not come up for 200. That explains it shooting low at 200.

You aren't used to the optic and apparently don't have a lot of time to get proficient with 'that many arms'.

The elevation issue is one of gravity.

Displacement to the right that much could well be that the optic is not aligned with the axis of the bore. More common than you may think.

The displacement to the low right could also be a classic case of trigger control problem. Very common for someone who is not used to an optic like you say is your situation.

LR55

[Klem]

WF:

You shot it at 100 and did not come up for 200. That explains it shooting low at 200.

You aren't used to the optic and apparently don't have a lot of time to get proficient with 'that many arms'.

The elevation issue is one of gravity.

Displacement to the right that much could well be that the optic is not aligned with the axis of the bore. More common than you may think.

The displacement to the low right could also be a classic case of trigger control problem. Very common for someone who is not used to an optic like you say is your situation.

LR55

That could also be the case and looking forward to WF's response.

The drop from a 100yd zero at 200 using a 16" Grendel is about 4.1 inches. If the ranges are in metres then its even more at 5.5". WF claims a 2-3" drop (assuming this is precise) so on face value it does not appear related to failure to account for elevation.

(using the trajectory of a 120NBT @ 2480fps)

[JASmith]

In this instance, every shot, save one, in the image above was to the right of center at 100 yards. The center was at least a half inch to the right. That group would have printed low and a bit more than an inch to the right at 100 yards.

My experience has been that one needs to shoot several 5-shot groups on different days at the desired sight in distance to be confident that the 100 yard zero is within about a half-inch of being on.

Shooting groups on several different days and noting the center of the aggregate will help work the wind challenge Klem notes unless the wind is consistently from the same direction at your range.

More on the topic of hunting zero is here: http://shootersnotes.com/articles/zero-for-hunting/

[worthen86ford]

Wind was blowing some. Can't recall direction. i really need to work with the gun and see if i feel there is really a problem. Vertical drop was about where i expected it at 200.

Do any of y'all have RTZ issues when removing and reinstalling scopes. My gsr does it just fine but its only a 4 power and has leupold qrw steel rings. Not too sure how this aluminum mount will do. If it doesn't RTZ within 1moa or so i'll put out for a larue or something.

[LR1955]

Wind was blowing some. Can't recall direction. i really need to work with the gun and see if i feel there is really a problem. Vertical drop was about where i expected it at 200.

Do any of y'all have RTZ issues when removing and reinstalling scopes. My gsr does it just fine but its only a 4 power and has leupold qrw steel rings. Not too sure how this aluminum mount will do. If it doesn't RTZ within 1moa or so i'll put out for a larue or something.

WF:

I have about everything from a thirty dollar set of Weaver QD to expensive LaRue QD mounts. Both return to zero within a half minute. I have seen guys use the torque wrenches on the Leupold mounts for the M-24 rifle for a number of years and have also simply tightened up the same mounts using a wrench by hand and have never seen a shift in zero.

LR55

[Klem]

JA is right, your group is a little off to the right by half an inch. If you shot at 100yds that will be 1/2MOA.

1/2" will of course be double that at 200 and so on. In your shoes I would fire a few groups to get the average MPI (Mean Point of Impact) and don't discount the flyers. You can download OnTarget which is a free program if you want to precisely calculate your groups.


Return-to-zero is never perfect however you should expect 0.1mil if you torque the screws to exactly the same as previous. If you don't have a torque screwdriver you can put a mark on the screw and later when you take the mount on and off just screw it back up to the marks.


What did you do to offset bullet drop at 200?

[worthen86ford]

What did you do to offset bullet drop at 200?[/QUOTE]
at 200 i could see i was hitting in the lower right quadrant when aiming at the center of the target. I just held high and left in the top left hand quadrant to mark the center. Only had 2 boxes of sst and used most of it at the 50 and 100 getting sighted in and playing around. Didn't walk down to take pictures of the target at 200.

Targets are 8x8 5 diamond shootnsees btw

[Klem]

That sounds about right. There's a 4" drop between 100 and 200yds. The squares on those 8*8 are 1inch. The right-hand bias on the group you posted will be 1" right at 200 and any wind left-to-right will shift it further right. I don't think there's anything wrong with your gear.

[worthen86ford]

Sweet. Gives me enough confidence in not buying more stuff. Just ammo to go shoot. Thanks for the responses guys. Lots of good help and info for me.