.284 Win neck diameter dimension

[giuliano]

I'd like to build a 7mm rifle so I'm considering very interesting the .284win.

In order to build a "right" finisher chamber reamer I'd like to know which is the neck

diameter dimension of the (6.5-)284Lapua brass with a sierra 175smk bullets seated ?
(without lathe turning).


Thanks in advance

 

[rcw3]

That's a loaded question for sure, since if you neck up Lapua 6.5 x 284 brass you will have a heck of a bulge/donut at the base of the neck and shoulder and you really have to neck turn the brass to get rid of it. Lapua 6.5 x 284 brass has thicker shoulder metal than the neck metal and when you do a neck up, some of that thicker shoulder metal becomes part of the neck (at the base of the neck).

If you are not going to neck turn use Winchester brand .284 Win brass and you will need about a .317" neck for a "no neck turn" set up and a free bore on the reamer of about .185" will be perfect for the 175 Sierras (assuming a one and a half degree throat angle) if you want the junction of the boat tail and bearing surface of the bullet just ahead of the neck and shoulder of the case.

Robert Whitley

 

[FilippoMo]

I can help Giuliano with the neck turning business.
I also plan a 7 mm but will use the 7.5x55 Swiss case necked down and blown out.
I have the reamer though in .224 caliber.When possible I prefer to neck down than the other way round.
Sincerely
Filippo