.308 Norma Mag

W

wildfire

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good day to you all,
a newbie to our sport i must admit and a virgin poster on your forum so please bare with me if i make a few errors along the way.

I am about to take delivery of a .308 norma mag rifle built of an accurized m17 action and bull barrel, etc
I was hoping to start shooting 600m comps and was looking to improve the accuracy with a tight neck set up and was wondering about which dimensions for the case i should get the reamer and dies cut and hence the what neck thickness should i be aiming to achieve? also the standard case has a 25.5 degree shoulder. i was hoping to reduce creep in my cases by increasing the angle, has anyone done some experiementing with this and if so what angle should i use? (i am not looking to increase case capacity but like all shooters brass life and barrel life are something that is worth putting in the time and effort to keep.) i realise there may be better ways of tuning my rifle like a new action, etc but i have a strange attraction to ammunition so i thought this may be the place to start.

Thank you for your thoughts

Wildfire
 
OK, more than you probably wanted to know.

I, and the people I'll mention come from a benchrest background, with all the pluses and minuses that includes.

A number of us feel the the .308 Norma magnum is about the ideal size for a .30 caliber, 1,000 yard rifle. Case capacity is right at 88 grains water, full to overflow.

As far as the .308 Norma Magnum goes, Leonard Baity has chambered up a number of wining rifles with it -- including his own, and Kerry Vinson's. Kerry was IBS 1,000 yard Shooter of the Year not too long ago, using the .308 Norma Mag in both light & heavy guns. When Leonard first started using the case, he used an Ackley version (40-degree shoulder), but found no advantage to it.

Those of us who dislike the belt have taken a different approach: Dave Tooley's .30 BooBoo, my .30 chambering, and one of Jeff Rogers (fellow Australian) chamberings all use the RWS 8x68 case. Joel Pendergraft came up with a .300 JP -- .300 Ackley reamer run in short, then turn the belts off a .308 Norma case.

So I would say leave the shoulder angle alone. Changing it will increase your work, to no advantage.

As to the chamber reamer itself, I would get the brass and measure it. You want a certain amount of clearance -- I'd say .003 at the base and the shoulder; others might use slightly different numbers. A tight neck is fine, but there is no advantage to thin necks per se., only to even necks. I would imagine that a .013 neck wall would allow all the brass in the neck to clean up. That would give a .334 neck diameter, but there is no magic here; whatever results in even neck wall thickness.

The resize reamer is based on the chamber dimensions. You want the fired case .001 smaller, AFTER it is sized, which includes AFTER the case that is a bit work-hardened springs back after going through the sizing die. Oddly enough, this usually amounts to a resize reamer about .003 smaller than the chambering reamer, or one that matches the virgin brass.

Leonard Baity might be able to help you, but I don't know that he is back in his shop after his recent illness. I think his reamers, including the .308 Norma, have been ground by Pacific Tool & Gauge; you could send Dave Kiff an email & see if those prints are on file, and if you could have them copied.

The other way to specify a reamer is to work from an existing sizing die. It works, but is not ideal.

Finally, in the States, a .30 is usually considered a bit big for 600 yards. The 6mms are taking over. While the .30s work fine, you'll be bucking the trend.

Australian shooters I know of who might be able to help some would be Alan Peake, Jeff Rogers & Tony Z, & maybe Stuart Elliot, though I don't think he is shooting much long-range anymore.

Good luck with it.
 
thank you very much for your reply

you have answered many of my question and given me alot to think about and no you can never give this shooter too much information, any information you can give i will soak up..


Wildfire
 
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