Accuracy problem at distance?

[griffin ordway]

Hi All,
Curious on your thoughts about my problem. First, the particulars: trying to develop a load that is accurate out to about 400 yards in my newly built AR....17" Lilja match barrel, 1:8 twist. The problem is this: I was trying to develop a load based around the 60 gr. Nosler Ballistic Tip Varmint bullet. Found two powders that shoot 1/2 MOA or better at 100 yard, but when I get out to 300 things go to hell.....the spread is well over 10". My thought is that it ain't the powder, because I've found two that bring the same results/problem, so in my mind is has to be the bullet/barrel combo. I can't imagine that a lighter pill would actually be more accurate at distance, and I don't want to go too much heavier either (it's mostly for coyotes and bobs, and I do want to preserve the pelt...so no gaping exit holes). The powders that I used were H4198 and H322. Your thoughts and ideas are much appreciated. Thanks.

 

[L.Sherm]

It's your load out of tune at 300. Try seating depth changes and small powder charge changes.
I'm not sure your bullet choice is gonna be pelt friendly.

 

[RT2506]

Which direction is the spread of shots at 400? If vertical it is the load having a wide standard deviation between velocities of shots causing the shots to string vertical. Horizonal spread can be wind effect on bullet. At 400 yards it does not take much wind to move that little bullet a long ways. If your spread is all over the place it could be your shooting form mixed in with some of the other things. If you are not using a chrno to tell you what the load is doing it will be VERY HARD to cure your problem. You must know your standard deviation and extreme spread of velocities. With a max listed load of the powders you are using out of a 17" barrel and I assume this is a 223 Rem. your muzzle velocity should be around 2800 fps so at 400 yards it has slowed down a bunch and wind, even a little bit, can greatly effect point of impact.

 

[BallisticsGuy]

For it to not group farther out means either it's the shooter (possibly not using parallax setting or just not being very consistent) or precession is grabbing you by the short and curlies or you're actually doing just fine except for windage and you're counting windage dispersion.

Given a 60 grain bullet in a 7 twist, I'm calling it as likely precession. You're spinning the living hell out of that bullet and possibly a little cattywompous in alignment. What I would try are Barnes 50gn Varmint Grenade bullets (not the 36gn'ers). They're about as long as a 70gn bullet so your fast twist won't be such a handicap. They'll punch through the side of a yote and grenade in the pumping room. No good for quartering shots as they don't penetrate real deeply. Really want broadside.

By "don't penetrate deeply" I mean I once shot a jack rabbit at 15 yards with one and it didn't exit. It did gut the thing completely though. Weird from a broadside shot.

 

[L.Sherm]

It's a 8tw. Barrel and only 17" at that. I've had 100 yd.groups shot good at 100 and then fell apart at 300. I just tuned the load at 300

 

[griffin ordway]

Thanks for the get backs. I did a lot of research before choosing that bullet, and it seemed to have a stellar reputation liquefying internals with no exit. I come from reloading either big hunting guns (.30 cal mags) or long range .223 target guns (77's out to 600), so I kind of have an aversion to light-for-caliber pills. If you all with actual field experience have better recommendations as to bullet and weight, I'm all ears.

 

[BallisticsGuy]

Thanks for the get backs. I did a lot of research before choosing that bullet, and it seemed to have a stellar reputation liquefying internals with no exit. I come from reloading either big hunting guns (.30 cal mags) or long range .223 target guns (77's out to 600), so I kind of have an aversion to light-for-caliber pills. If you all with actual field experience have better recommendations as to bullet and weight, I'm all ears.

the 50gn varmint grenade would be the direction I'd try first. They're really long for caliber so they operate more like a 75gn bullet than a 50gn, at least until they hit and then they behave like a 40gn driven entirely fast enough