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Second stage of load testing today.
Rifle: Remington 700 sps 1-12 twist 26" barrel
Cartridges: Lapua brass, Lapua b476 170g lockbase bullets, vit N140 powder, Remington 9.5 primers.

The first run was to get a ballpark good load going running in .5 grain increments from 42g up to 45.5 (Max reccomended by Lapua). I found 43.5 - 45 grains to be the most accurate.
Today I load tested in .2grain increments from 43.4 - 45.6grains. Groups ranged from .5moa to 1.5moa. Charges above 45g began to open up the groups. After some quick measurements it looks like 44grains of n140 was the best giving just under .5moa..
Muzzle velocity was chrono'd and then double checked against ballistic software (strelok pro) to be 2658 with an error factor +/-15fps (due to my reloading imperfections and other variables such as powder temp).
A very productive and enjoyable day. Thanks to the BSRC for having me as a guest and special thanks to a chap there who let me have a shoot with his 375H&H.. Awesome noise!!!

At what distance ?.

@100yds. Next Sunday the chosen load will be used at 600 and then 900yds. The maths suggest it Will go transonic between 900-1000 which may cause issues. We will have to see...

paulbradley wrote:@100yds. Next Sunday the chosen load will be used at 600 and then 900yds. The maths suggest it Will go transonic between 900-1000 which may cause issues. We will have to see...

some bullets are more tolerant of the sonic transition than others so you might be lucky?

Yes. The Brian Litz book on applied ballistics has been a god send in terms of bullet selection and understanding. The Lapua B476s have a very high BC. I had the offer of several hundred of them at a great price which also helps!! The only downside is that they will be hard to source when I run out. I think I will then move over to one of Bergers long range offerings.

Have you also tried varying the seating depth? That can also make a difference to the groups.

Hello,
I like the Lapua 170 lockbase and found best results from my 26", 1 in 10 twist to be @ 45.4 grns Vit140 with Fed 210M's and they are seated 20 thou from the lands (what's left of them!)
I am not a comp shooter but this load is still capable of hitting a few V's @1000 yards (although I have to hold over as I run out of elevation at about 900 ish yards!)

I shot the 170 Lockbase for a couple of years with my AI then the supplies dried up. They rank as my all time favourite 1000 yard bullet and I have recently picked a few hundred up so I can always go back to them if needed.

What do you use now ovenpaa? By the way the .223 shot very well. Also got the .22 upper on there and sprayed some bullets down to the 100yd mark. Very good fun indeed. Unfortunately a small part of the .22 upper internals sheared off so I am off to the gunsmiths now for diagnosis. The good part about the AR platform... Parts are relatively cheap and easy to source...

I have exclusively used the 155 Scenar for many years however I have now fitted a 6,5x47 barrel to the AI and am feeding it 123 grain Scenar bullets which have been pointed. They work incredibly well to 1200 yards.

The upper is broken! What happened, we only shot it the one time however it was performing flawlessly for James and I. Can you ring me on this when you get a moment please?