Posted by Michael Bell on
URL: http://oldforum.flyshooter.com.au/setting-up-loads-for-rifles-whats-your-story-tp5707370p5707375.html

G'day Les,
This is a pretty big subject and worthy of more contributions than it's getting....bit hard to keep it short though so I thought I might add just a few thoughts about some of the decisions needed when getting a rifle custom made ( as opposed to buying a second hand or pre made version).
I think I will also stay away from the quagmire of action & barrel selection which is probably a  topic in it's own right.

The obvious advantage to having a custom job is that you have total control over most elements of the build.

There are a few questions you must firstly ask yourself.
1; "What will I use it for?"  To use me as an example I wanted to mostly shoot the 500 fly but also needed it to be ok at  both shorter & longer distances with the possibility of also shooting F class. So it needed to weigh less than 22lb to be F class legal...might as well make it light gun legal for 500 fly, ie under 17 lb!

2; "What calibre will it be? ie, What case will I use?  I selected the 6 BRX because it was similar but not the same as the Dasher my mate Trevor Bent had.The Dasher , or anything built on or around the 6 BR, was clearly a very accurate round capable of everything I wanted it to do.

3; "What projectile will do the job?" Very important decision this ( some might say the most important decision of all) as it will have a significant bearing on the chambering of the barrel as well as the rifles ability to be competitive at the distances you wish to shoot! I chose Ken Melgaard's 103 grn copperheads.

Having decided on a case & projectile you then need to get to the specifics of the chamber. So..more questions!
How long will the chamber & what will the  neck diameter  be?  I knew the Dasher & BRX were very similar. Both are formed from 6 BR brass and have very similar powder capacities. I knew from discussions with Trevor that the 6 BR brass became shorter when fire forming to a Dasher so I obtained a Dasher case and measured it,- 1.545" (reduced from 1.555).
Next, seat a projectile and measure the neck diameter of the case, - .2675. I can now make decisions about chamber dimensions. A .269 neck will allow me to get away  (just) without turning necks and  a chamber length of 1.560" would allow cases to grow a little when fired without having a large carbon collecting area at the end of the chamber just before the start of the rifling- perfect.

It must be said that the neck diameter with a seated projectile can change from case brand to brand and also batch to batch within the same brand, so... take care  with this one!

We had one more decision to make! "What will the freebore be?"  This number is determined by the projectile selected. My instructions were to make sure the bearing surface / boat tail junction of the projectile sat just above the neck / shoulder junction of the case.
A reamer was purchased with the previously mentioned dimensions but with a deliberately short freebore ( to enable the reamer to be used for other, shorter bullets like the 87 grn V-Max) A separate throating reamer was then used to cut specifically for the 103 grn Copperheads!

With the benefit of hindsight I could probably have had a bit more free bore cut in to accommodate  longer projectiles like the Sierra 107 ( this is something I could still do ) but one downside to the BRX is that you end up with quite a short necked case which doesn't allow much flexibility in projectile selection like a standard 6 BR will with it's very long neck!

So there you have it, there a quite a few decisions to make & it might seem a bit back to front but I reckon working this way will give you the best chance of getting a good accurate rifle built.

 Then you go to load development which I think is another story!

Regards,
Belly