Bullet bc 105 Amax V Lapua 105

[essexboy]

I was shooting at 600yds f class style yesterday fireforming cases my load was 31.5g n540 105g Amax just about holding v [x], i was getting near the end of the ammo and noticed that i had 3 rounds of formed ammo that i had seated the bullets the wrong depth 105g lapua so i thought i might as well fire them off, i shot the 1st round and wack 3.5 mins high thats 21" at 600yds hmm perhaps i miss aimed i thought but no the other 2 went exactly the same. Now i'm not sure what the load was but the highest it would of been was 33g of n540, as the bc for the lapua has been down graded to about .480 and the bc for the Amax is about .500 is it right that 1.5g of powder will give me that more elevation. All help and advice welcome.

Regards

Steve

 

[Terry]

A 100fps change in velocity at that range is about 6".

Terry

 

[essexboy]

Thanks for that, but the thing i cant work out is, as you say 100fps is 1 min/6" to strike 3.5min/21" high would mean a velo increase of 350fps. I have chrono'ed my fireform load at around 2780fps on that powder charge, the highest charge i've tried chrono'ed at around 2940fps leaving me 190 fps shy . The only thing i can think of is that some listed bc's are little more than, think of a number that will sell more bullets type of thing, but i may be 100% wrong [ not the 1st or last time].

Regards

Steve

 

[Erik Cortina]

Sounds like you are assuming that they both hit at the same POA at 100 yards. What I'm trying to say is that different bullets and different loads leave the barrel at a different place in the "barrel whip" cycle. Maybe the AMax is leaving at the bottom and the Scenars are leaving at the top, that's why there is such a high difference in POI at 600 yards.

Try both at 100 yards, I bet the Scenars are hitting higher on the target than the AMax. But regardless, the Scenars are very accurate and uniform bullets.

 

[essexboy]

Thanks Eric, i will give it a go next time i'm at the range.

Regards

Steve