6,5x47 - VV N550

[honzaaa.cz]

Do you know, what is the best distance of the bullet from bore at caliber 6,5x47? Barrel LOTHAR WALTHER 28" - 8",used bullet LAPUA SCENAR 123 and 139 gr. Thanks for info.

[DaveT]

There is no absolute answer to how much Jump or Jam (relationship to the start of the rifling) a given bullet requires to give best performance in a specific rifle.... just like load development to find the optimum powder charge you will need to experiment with Cartridge overall length.

 

Get yourself a Hornady OAl gauge and see at what length these bullets actually just barely touch the rifling.... that gives you an absolute maximum cartridge length for your chamber.

 

This may not fit into your magazine (and if you need to use a magazine you will have to shorten your OAL) ...but I usually start at that max length if I can as the minimum jump to the rifling will often give the best accuracy....Beware that this also implies higher startup pressures than a 'jumped' bullet will produce so start with even lower powder charges than you otherwise might have done.

 

I have not looked up the ogive design of the two bullets that you mention but I belive they are what is called TANGENT which means that there is a smooth transition from the point of the bullet to the main diameter ...in turn this means that it is likely to maintain accuracy with a shorter OAL. Conversely, a bullet with a SECANT ogive design (sharp transition from point to main diameter) is likely to produce best accuracy if set at an OAL where it touches the rifling.

 

There are no fixed absolutes ... you will need to run tests but starting at the maximum (close to or touching the rifling) is a good starting point.

 

You should be able to read MUCH more on this subject on the web....advise that you research before starting.... and beb careful of the powder charges!