Rifle Re-Barrelled

[Orka Akinse]

Gents

 

My old load for my 6.5x55 Swede was 37g Varget behind a 140g Sierra SBT.

 

Whilst v. accurate, the 37g did not fill the case and so looking round [before I start load development in earnest] VVN160 seems to be a popular choice and round the 46g would I think, almost fill the case.

 

This got me wondering, should I be looking for a powder to "fill" the case [assuming all other safety parameters remain within limits] or is it the case the priority is an accurate load no matter how much it fills the case [Again assuming the parameters remain in safe limits]?

 

Whats your thoughts?

[pat]

Running the numbers through QL suggests that....

 

37gn of Varget is barely an 80% fill ratio for a 6.5x55 Swedish case with a 140gn SPBT seated 195 thou. It predicts pretty low pressure and velocities, I imagine it isn't telling the whole story...

 

As for powders that appear to be suitable, Vit N570, Retumbo, MRP 2 and RL-25 look promising, but of those RL25 looks the most promising, not because it achieves the best velocity, but because it seems to yield the most complete burn, and lowest muzzle pressure. All of those run at over 100% fill ratio, but RL25 is only at 102.6%, a very mildly compressed load and should be nice and stable.

 

Accepted wisdom has it that running less than 80% capacity can have odd side effects and therefore not the first option to explore (perhaps a last resort when all else fails). As such, whilst the Varget may have worked I would only suggest that better results may be possible with a different powder. None of the above are fast powders so they will be heavily coated and require a good kick up the backside to get them going, definitely magnum primer territory.

 

For reference, this is what QL spat out... 54.7gn N570, 53.7gn Retumbo, 51.3gn MRP 2, 49.7gn RL-25.

 

Hope this helps,

 

Pat.