Stabilizing Berger VLD 115gr .243 bullets

[DrThunder88]

I made the schlep out to the "local" 200 yard range with my .243 Winchester Axis. It has a 26" 1-8 Shilen varmint barrel and has been a consistent 1/2 MOA shooter at 100 yards with no signs of bullet instability despite the Berger VLD bullets saying they require a 1-7" twist. My favorite load so far has been a 115gr Berger VLD hunting bullet seated touching the lands over 45.2gr of H1000 and a Federal LR primer in a Hornady case. My chronograph puts it at a fairly solid 2880-2900 fps at the muzzle.

Now, the problem. At 100 yards, the rifle and ammo is very predictable with five shot groups falling under half an inch. At 200, however, the groups grow to 4-6". The first time I shot at 200, I figured the problem was over-torquing the action screws. This time out, the action screws were still set the same as my last outing at 100 yards. This time I was about to write it off to visibility in the late-season flurry I was shooting in, but I feel pretty confident that I could see the target well enough to get a decent sight picture. Certainly I could see the 2" shapes on the target paper.

So, does it seem like I've got a mechanical problem, or is it just me choking at the increased distance? I realize 200 yards isn't a long shot by any means, and it seems like my load should have the legs to get there and my meager skills should be able to put it on target.

[LoneWolf]

I run 115DTACS in a 7 twist. They're a little shorter than the VLDs and David Tubb recommends at least a 7.5twist. I get 2950 with 40grs of H100V. My barrel is 27" long. If I had an 8 twist I would run the Berger 105 Hybrids, A MAX, or 107 Scenars.

[mike21]

You might run your parameters through here:

http://www.bergerbullets.com/twist-rate-calculator/

When I ran them, it showed "marginal stability". If you get the same results, scroll on down for other bullet recommandations. Might be worth a try.

[sharpshooter]

Why not just tune the load for 200 yds?

[stomp442]

I think I would switch bullets down to the 105 Hybrid. Almost Identical BC to the heavier 115 only with more velocity and is optimized for your 8 twist barrel.

[earl39]

If it is just bad groups the do like Fred said and tune it. If it is not cutting nice round holes then change bullets.

[Jamie]

^^^

What all three of those gents stated.

[DrThunder88]

Thank you for the suggestions. I will see what I can do. It just seems odd that the group size would more than quadruple when going from 100 to 200 yards. For a .22 LR: maybe. But I guess I've put together a dodo.

[stomp442]

Powder could be the culprit as well. I was playing with one of my 6.5-284s and testing with Reloader 17 and groups at 100 were outstanding I'm talking in the .2s-.3s for five shots. I shot in a 300 meter match with this load and could barely hold minute and a half groups. I was really stunned to see such poor grouping in relatively good conditions so I set up a box at 100 to shoot a nice tight clover leaf. Shot again at 300 meters and again poor grouping. I have since gone back to my H4831 Load that holds half MOA or a little less and holds it out to as far as I can shoot with it. Only thing different between the two loads is the powder. Same cases, same bullet, same primer and same jump off the lands everything. I still cant explain it.

[DrThunder88]

Maybe my gun just doesn't like Lapua brass. I found some loads I had prepared in Hornady shell casings and tried them at 200 yards and the grouping was closer to 100 yard groupings and almost directly on-center horizontally despite the gun being pretty hot throughout the string. The only change to the gun was setting the parallax to 200 on the scope, which I'd previously neglected to do, though I don't suspect that was the cause of my problems. Nor do I suspect the change in temperature (+45 degrees F) would have caused as much spread as I saw.

[LongRange]

did you start with hornady brass and work up loads at 100yds then change to lapua brass with the same load at 200yds?

[DrThunder88]

I started with Hornady when I worked up the load, but I thought I switched over to Lapua before hitting the 200 yard range. Maybe I didn't.

[barefooter56]

Drthunder88,
You do not have enough twist rate for those bullets. Drop back to the 105 VLD or 95 grain VLD . The loss of velocity at 200 yards is what your problem is. Not the rifle.
Take care,
Phil Hoham
Berger Bullet Tech

[stomp442]

I was under the impression stability increases with range as the rate of spin on the bullet decreases slower than the speed of the bullet thereby having more stability at longer distances. If the bullet shows no signs of instability at 100 it shouldn't have stability issues at 200. I agree that he should move down in bullet weight though as the 115s should be marginal at best and not maximizing the BC of the bullet anyways.

[darkker]

It does. Velocity decay happens quickly, but rotational decay is slow. So the rotational speed, relative to velocity will increase.
Also remember that it is "normal" for a barrel maker to be off by 1/2 twist from stated. Also barrel smoothness will play a larger than expected role in stability.
Don't use weight for stability, use length. THAT is the thing that needs considered.

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Look up the length and enter your particulars.
Some bullets that are "super-sexy" in the BC department have a center of gravity Vs Center of pressure issue. Typically this will rear it's head when crossing trans-sonic. But will be noticed when stabilizing RPM is marginal, as well.

[jonbearman]

Listen to the berger tech since they make them they know exactly where the problem lies.