Rearwards Estimating My Bisley Load

[brown dog]

Trying to work out what the load that I fired at Bisley was. (Remember the rounds were loaded in field conditions in the back of a 4x4, but shot about 0.3MOA).

Thought we loaded them with 37.5gr RL15.

 

Just thinking about the elevation delta between the 500 yard 'zero' and then the elevation applied to be 'on' at 300yds.

 

If the round had an mv of c2880fps; I would have expected a delta of circa 14 x 0.1mRad clicks;

but I notice the actual delta was 20 clicks.

 

DEDUCTION - the MV was not as high as I thought.

 

Just fag-packet rearward calculated the mv from the observed delta; and get a likely actual mv of c2650fps -which made me go: hmmmm

 

 

So just weighed a bunch of things in order to calculate the actual charge weight in my remaining rounds:

 

It's c36gr -and not the 37.5 we thought we'd kicked off with (wind affecting the scale)

 

-now the low apparent mv makes sense.

 

Bugger! And there I was thinking I had to do no more fannying with the load

 

 

Out of interest, ran the low 36gr charge on quikload -not spot on my MV SWAG, but in the parish:

[oaken]

Sounds like you stumbled on an accuracy node....... just not the right one.  Seems to work OK at 300yds though!!! What made you decide on 37.5gr (or 36) as a starting point?

Rup

[brown dog]

Sounds like you stumbled on an accuracy node....... just not the right one.  Seems to work OK at 300yds though!!! What made you decide on 37.5gr (or 36) as a starting point?

Rup

 

Rup,

 

37.5 of RL15 is one of the fabled 'works in anything' charge weights for 6.5x47 - if you ask around it seems to be repeatedly recommended as the 'go to' charge weight. I buy-in to the OCW theory of load development; so it seems the best place to start. [but for those seeking 308 performance out of their 6.5x47, I now recommend 36.1gr as the goto load! )

[oaken]

Deary me, you will have to load test after all ;-P Sounds like a great excuse to get out and use that rather fine looking new rifle - what stock is that and did it come inletted for the Tikka?

As a matter of interest, I found several accuracy nodes when working up Varget loads for my .308. One at 40.6gr, one at 43.3 and another at 46. I only ever used to shoot the rifle at 600yds max and found the 40.6 (only 2500fps) load to be super accurate, but later found it was hopeless at anything longer. My brass used to last well too!

I use the 46gr load these days though.

[foxing2night]

37.5 is a good accurate load and not to hard on the brass,,

 

38.6 is one of the best loads that i have ever used in MY RIFLE,,

 

but can be i bit hard on cases!!!!

 

300 yrds = 3 moa

 

500 yrds = 7 moa

 

Sorry but i still work in old money

 

I have tried a lot of different powders and bullets,, and to be honest the cartridge is a jot to reload for and a joy to shoot,,

 

Matt, i am glad that you have come over to the dark side

 

Darrel