I've been doing some load development in my Custom FN M98 308 Norma Mag recently.
In Australia the most commonly available powder is produced by Australian Defence Industry (ADI). Many of these powders are exported to the US and repackage and sold as Hodgson powder (see http://www.adi-limited.com/handloade...quivalents.asp
). So US members won't be totally unfamiliar with these powders.
I settled on AR2213SC (equivalent to Hod 4831, see above link and http://www.adi-limited.com/handloaders-guide/powder.asp
) for a number of reasons. It seemed to give better shot-to-shot consistency in 308NM, gave equivalent velocity to AR2217 but with some fewer grains (my Scottish ancestry coming to the fore no doubt), at the time I had no AR2217 and finally a local (Oz) shooting writer (Nick Harvey) who had a 308NM listed loads with this powder that seemed replicate Norma factory ballistics (and I liked the numbers, 180 gr @ 3,100 fps).
I started well below the ADI book maximum of 73 grs (see http://www.adi-limited.com/handloaders-guide/rifle.asp
) and worked up to the maximum. Chronographing the 73 gr load I was disappointed to see that the average velocity was barely 3,000 fps but yet encouraged that there did not seem to be signs of excessive pressure. I then decided to work up (past the ADI maximum) to Nick Harvey's load pet load of 75grs in ½ gr increments, watching carefully for signs of pressure. I shot these a week ago last Friday with the following results:
73.0gr - ave 2,946 fps 2¼" 3 shot group @ 100 yds
73.5gr - ave 2,993 fps 3" 3 shot group @ 100 yds
74.0gr - ave 3,024 fps group too big
74.5gr - ave 3,078 fps 1¾" 3 shot group @ 100 yds
75.0gr - ave 3,105 fps 1½" 3 shot group @ 100 yds
The last load seemed warm but seemed safe enough in my rifle. I was happy with this as it gave the numbers I was looking for, at this stage I was loading to velocity not accuracy but I happy with the 1½" for a first try and felt that I could do better with practice. I even thought I could probably stoke another ½ or perhaps 1 gr of AR2213SC in this rifle to get even more velocity. By the performance of these loads, perhaps another 80 odd fps. That'll give around 3,180-3,200 fps (getting near 300 Wby velocities, see http://www.reloadersnest.com/query_b...t=180&offset=0
Yesterday, I had another range session. Rather upping the load I decided do some more work with the 75gr load. This produced a 3 shot group of just under 1" @ 100 yards and confirmed the velocity for the previous week by getting an ave of 3,103 fps. The bullets used throughout were Hornady 180gr SP BT with a BC 0.452 stock no 3072.
This is a real shooter and the load is a flat shooting, long range hard hitter. With a 300 yard zero it is 9" low @ 400 yds, 25" low @ 500 yards and on deer size animal a hold dead on out to 350 yds will secure the trophy. I think I'll stay with the 75gr load as another 100 fps (if that is achievable) will still be 23" low @ 500 yards and yield less than an additional 150flbs at that range.
I intend to do a lot more practice with this load/rifle and feel confident that, as I get used to it, smaller groups a quite achievable. I like all my hunting rifles to be tack drivers.
I know we all have our favourite big game rifles (for Elgin Gates it was his 300 Wby custom and he used it all over the world, in many cases where it was definitely too much gun for the animal but he still brought his trophy home) but I think this, now lamentably fairly obscure and almost wildcat, calibre has to be one the greatest general big game cartridges ever developed. And in my custom rifle even with full loads like these it is still a sweet thing to shoot