Berger VLD groups with different jumps

Attachment 7727

Interesting results today with the 168gr VLDs in the .280 Imp. All the rounds were the same except for the seating depth, 5-shot groups at 110m; jump was 0.010", 0.040", 0.070", 0.100", 0.130" left to right. For scale the circles are 1 moa in diameter. Close to the lands wasn't good but it came right with the 40-thou jump - nice and tight with one flier that could easily have been me and if we exclude that then the seating depth is changing the groups from 2moa down to half moa. Groups may also be trending back down again beyond .130" - I might look at this next time.

So jump alone is changing the group size with the VLDs from poor to quite acceptable, and by as much as I've seen with any other variable. As a follow-on from my last thread on this topic it looks like this may be the primary variable to nail down with these bullets - before powder type or charge weight.

good info puffin , cheers.

Im partial to a bit of a jump myself.

Iv found changing jump can change group shape too.
But not with bergers cos i haven't tried them

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A max did similar in my 7Mag. jam was shit, .020" went dead tight.

Yep that is what Eric Stecker from Berger bullets said would happen.

Why 110 metres?

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Originally Posted by Puffin

Attachment 7727

Interesting results today with the 168gr VLDs in the .280 Imp. All the rounds were the same except for the seating depth, 5-shot groups at 110m; jump was 0.010", 0.040", 0.070", 0.100", 0.130" left to right. For scale the circles are 1 moa in diameter. Close to the lands wasn't good but it came right with the 40-thou jump - nice and tight with one flier that could easily have been me and if we exclude that then the seating depth is changing the groups from 2moa down to half moa. Groups may also be trending back down again beyond .130" - I might look at this next time.

So jump alone is changing the group size with the VLDs from poor to quite acceptable, and by as much as I've seen with any other variable. As a follow-on from my last thread on this topic it looks like this may be the primary variable to nail down with these bullets - before powder type or charge weight.

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The berger VLDs can be very picky what they like when it comes to seating, did you try a just touch on the lands as well?
Your results clearly shows that just changing seating depth and nothing else can really make a big difference to how tight your groups can be.

Yes, confirms Stecker's methodology. For anyone interested there was a link to this article in the previous VLD thread from a couple of weeks back. Haven't tried touching. I'm very interested in going the other way with the possibility of a second "null" around 4mm off, then the rounds would fit the M98 magazine, otherwise it will be single loading.

110 metres is the spot for cardboard box targets - part way up the dirt back-stop behind the 100yd range above any obstructions.
The 100yd distance is set up for targets held up on frames.

Thanks Kiwijames for the report on the A-MAX - another >.6 G1BC secant ogive projectile that needs tweaking for jump. Longer was preferred in the .280 here but I still had the odd flyer. Maybe the composite ogive (classic hunting) will live up to the promise and be easier to load for. DDs in Levin said they were still months away with the situation in the US so I ended up buying a box of 500 of the std 168gr, so I need to make them work.

They all look pretty similar to me.

Do it again without the 'flyers' to check, should shoot better than that surely?

Chris