trouble zeroing ne grendel build

[Superfly]

The gun is a brand new build, all quality stuff, 20 inch heavy barrel 6.5 grendel. Now I ran about 60 rounds through it just shooting it because I was told that it will take about 100 rounds through it before you will be able to zero it. so I have now spent 2 days at the range trying to dial it in. It has a 4x12 vortex scope on it with a aero precision mount so the gear is good, I am shooting 123 grain hornady sst match ammo and the thing is all over the paper. If anyone has any ideas or a protocal I should follow or anything like that I am all ears. First thing I am going to do is try some different ammo to start................. then what ????
help please

[Bigs28]

Check the scope is mounted and torqued to spec. Then try a different type of ammo. Sst is all over the place in my gun and hornady American gunner is fantastic.

[Superfly]

thanks, will start there.....
thanks Fly

[A5BLASTER]

Check the scope mount to scope and the scope mount to the rifle, try different ammo, check the gas block is lined up correctly, check the gas tube is free to move and not binding up in the barrel nut, check the muzzle device is not put on with heavy torque, check the muzzle device isn't having bullet strike.

Also if you haven't tear it down lapp the recover face and bed the barrel, bed the gas tube into the gas block if you can bed the gas block to the barrel then lock it down with locktite on the crews with bare min torque on the crews.

It very well may be the scope mount, I tryed them and they just broke and or wouldn't hold zero for me, I use leapold now and can't speak enough good about them.

Hope you get this figured out sir.

Also also check the muzzle for burrs.

[grayfox]

I have not used the Aero is it the ultralight?
Looking at its picture I don't really go for the interlocking top and screws as they are at the bottom... I would suggest definitely going with a more traditional cantilever mount, it would be more secure IMO.

Leupold, Nikon, Burris Pepr, heck I've even got a UTG one and they all stay nice and solid.
Tighten the mount-AR screws to torque, no loktite, install the scope level, with your desired eye-relief, and tighten the ring screws to torque, do them 1 at a time a bit by bit, do one pair on 1 ring first then a pair on the other ring, to keep it level... cross-tighten across the scope back and forth, like you would do for for a cylinder block, exhaust manifold or other multi-bolt sequence, then the others... get to torque then try it out. Don't over-torque these you don't need to!
Once satisfied then you can loosen and loktite/tighten one pair of screws at a time...
I also prefer the ones that have multiple ring screws on a side, like 2x2 or 3x3 for the rings.

Ammo, try the Hornady 123 Black, it is more consistent for my AR's. the 123 gunner is nice too.

It shouldn't take 60-100 rounds to zero, but it might take that many for the barrel's grouping to tighten up. I can usually get a zero in the first 4-5 rounds... then the others are for continued break-in.

Finally, who made the barrel? I don't think you mentioned. Several folks have had problems with BCA barrels, some seem to do fine others are a crap-shoot...

[rabiddawg]

Is the scope tracking properly? Do your adjustments move where you want them? If not, did you level the reticle to the gun when mounting your scope? And I don’t mean looking thru it and twisting the scope.

I put my gun in a cleaning vise to hold it. Place a bubble level on the receiver and get it level side to side. Then put another bubble level on the turret and level it. I hang a plum bob from my door and shine flashlight thru the scope from the objective end (backwards). This projects the reticle onto the wall. I line everything up and snug down the caps.

Be aware that some rings will tilt the scope as you tighten them. I use a torque screwdriver and walk up my torque.

[s3silver]

As others have mentioned, ensure all is tight and secure. Does the barrel crown look good? Even my 16" ar stoner barrel sighted in within 5 rounds.

Also, which model vortex scope do you have? If it's the crossfire model, that may be the culprit. My friend's brand new crossfire was all over the place. He no longer has it. Have not tried the diamondback, but most of the reviews on that has been pretty good. I have 4 of the regular viper line and all have not had any problems.

If other ammo doesn't work, then try some handloads.

[Klem]

Suoerfly,

Apart from the first couple of rounds you can start zeroing after that.

What sort of group sizes are we talking about? Some details would help.
What's your shooting platform?
Windy day?
How far to the target?
Were you shooting groups or doing gross adjustments with single rounds?

[Sticks]

Check the scope is mounted and torqued to spec. Then try a different type of ammo. Sst is all over the place in my gun and hornady American gunner is fantastic.

This.

SST is a picky bullet as to what barrel it will perform out of. Not brand specific at all.

Hornady Black, Hornady American Gunner, Federal/American Eagle 120 OTM.

[LR1955]

Guys:

When he is talking about shooting 100 rounds before zeroing, he was taking the advice of someone who is living in the past, or he misunderstood the advice. Most shooters tend to believe it takes about 100 rounds before the barrel 'settles down' and will shoot consistently. Maybe so with a barrel made thirty or more years ago but probably not as true today. If the barrel was made well, and the upper was put together well, there probably isn't a need to shoot a bunch of ammo for it to 'settle down'. Certainly there is no need to shoot a bunch of ammo before one can zero the rifle.

LR55

[Popeye212]

I would get a box of Hornady Black or something without the SST's American Gunner etc. As stated SST's are very picky.

[bj139]

Does that Aero Precision mount screw into aluminum threads in the base? That doesn't seem very secure.

[1Shot]

The question that no one has asked is who made the barrel? Sounds like exactly what my Bear Creek Arsenal shot like before I sent the upper back and they replaced the barrel. With the new barrel it took about 100 rounds down the tube before it would group consistently. My Oden works barrel grouped right out of the gate but averaged 1 1/2" with Hornady 123 SST but with hand loads shot sub MOA all day long.

[grayfox]

The question that no one has asked is who made the barrel? Sounds like exactly what my Bear Creek Arsenal shot like before I sent the upper back and they replaced the barrel. With the new barrel it took about 100 rounds down the tube before it would group consistently. My Oden works barrel grouped right out of the gate but averaged 1 1/2" with Hornady 123 SST but with hand loads shot sub MOA all day long.

My post #5 above... but it's buried down in the text.
but yeah, which barrel?

[drewthebrave]

Sounds like most everyone summed it up above. There are a lot of variables to consider, some of which are easier to fix than others. I have several Aero Precision mounts, and they're all rock solid - assuming they are installed properly. Here are some ideas to get you started:

1. Is the mount secured properly to the rail (correct torque)?
2. Is the scope secured properly in the mount (correct torque)?
3. Have you shot without a muzzle device attached?
4. Have you shot from a rest or a sled to stabilize the rifle?
5. Is the barrel secure in the receiver?
6. What brand of barrel is it?
7. Do you know an experienced shooter that can take a look at the gun & help you troubleshoot? Sometimes a second set of eyes is all you need.