OzFclass

I have got a Vertical problem with one of my 6mm barrels at long range and would like to know if anyone has any suggestions. Rifle is a sleeved and Trued Rem 700 , Mcmilan F class stock and NF NXS. Gun was smithed by Dave Kerr.. barrell is Kreiger 1/8 30 inch 237 bore chambered in 243AI. I am confident it is not the rifle/rest setup as when i screw my 223 on it shoots extremely flat groups at the longs. I have tried numerous powders, 2209,2213,2217, R19,R22 and every available primer!!! Cases are lapua match prepped . Lapua and sierra bullets both jammed or jumped produce around 300mm or more elevation @ 900 with a 10 shot string. I have tried numerous neck tensions from 1-4 thou with no change in vertical. The weird thing is it shoots extremely tight 10 shot groups( 3/4 inch 10 shot) at 300 when testing with these components with no signs of vertical at 300 while testing. The only bullet i have had success with in terms of vertical was the Berger Hybrid which shot 95mm vert at 900m !! But i have to slow them down to 3100fps or the jackets start to shred and it fowls the barrell big time with copper!! i have confirmed this with a borescope and magnetospeed!! Lapua or sierra will not fowl when pushed to 3250 -3300 which is normal speed for a 243AI . Chrono ES was very good with around 25fps over 10 shots from the ADI powders and about 40 from the Reloader powders. Belive it or not though the Reloader powders had the least amount of Vert at the longs which makes it more confusing. This is the only 6mm 243AI barrel that has ever given me vertical problems!! all my others shot very flat at the longs with the same components . If anyone has any suggestions i would like to hear them !!!

Check out the info on the 6x47 subject on this same page but further down.
Sounds like a similar thing, but I guess you have checked the throat with the borescope??
cheers

Ive thought about it over the last few days since we shot on the weekend. And going by your description of yarloop mate, I would be seriously looking at running the bergers at the 3100 mark and be done with it until your 260 gets done up. I know the velocity is low but accuracy and no vertical is the name of the game.

Ive gone back to 2209 after the vert I got on the weekend and the chrono results showing weird velocity drops. The small primers just cant handle that slow burning powder consistently I reckon, where 2209 shot flat as you have previously seen.

Next weekend im grabbing the range on saturday morning for some 900m vertical checking if your interested.

Brad , im going to Greenough this weekend and am going to run the Bergers and see how they go over a whole prize meet!! You could be right with yours that the small primer might not have enough spark to light 13 in your case !!

Krakey , yes i have checked the throat and all is good!!

I reckon you will go fine mate. This weekend weather is looking pretty dodgy here so will just do 800m and have a play next saturday before sunday 900

Brett, good luck with it mate. Hope you get it sorted.