Load developement and range results

[Freestate101]

Took my new 6br sporter to the range yesterday for some load development. Started off with a mild load of 28gr. of R15, Fed. 205's and 107 smk's. Went up by .5gr incriments to 29.5grs. with lousy accuracy,re. all over the target). Tried 29,5 & 30 grs of Varget and BR4's with the 107's, the 30 gr load shot the best, 2', but all horizontal, vertical was around 1',wind 5-10 mph, L to R). Went to 105 A-Max with the same load, and again the 30 gr. load was the only one that would group under 1-1/2'. It wasn't untill I switched to Rem 7-1/2 primers and 30 grs. Varget under the 105 A-Max that the groups tightened up. I had 2 touching, and 3 clover-leafed about 3/4' low & right, but I attribute that to the nut behind the trigger and the sporter weight stock and barrel. Absolutely no primer cratering or piercing, but then these were mild loads. I'm not sure how much faster I can push the 105's without piercing the non-magnum primers. I am running a very tight headspace that leaves burnishing marks on the case head from closing the bolt, will that help with the increased pressures of hotter loads?

Rifle specs.
Savage Model 12 Varmint action, trued and timed by Fred @ SSS
SSS Competition recoil lug.
SSS Competition trigger set at 12 oz.
Savage Model 14 American Classic Stock,bedded with JB Weld)
Broughton #4.1 heavy sporter, 5C, 1x7.5 twist, finished off at 24' and chambered for a .272 neck by Dave Bruno.
Topper off with a Pentax 8.5x32x50 30mm scope in Lupy QRW rings on an EGW base.

Jim Berry

 

[Preacher]

Ease that RL15 load up a little at time and you may be surprised at the outcome.
Mine really started to close up after 30.5, and I ended up at 31.5 with the 105 Berger VLD's.. I also use the Russian Mag primers, the 6br is a little to hot where it likes to be with a standard primer in mine....
If your leaving marks on the case head from closing the bolt, you need to set the shoulder back just a tiny bit until it stops doing it.... you need to feel that there is a cartridge in the chamber but it shouldn't leave marks on the case head....

 

[Freestate101]

Thanks Preacher, I will try that. I may have to reset the head-space, as the sizing die is only a hair from bottoming out on the shell holder. I will also have to put a touch of locktite on my action screws, as I just discovered that they had backed out a full 1/2 turn during my time at the range. I will have to stay on the low side with my charges as I don't have any 450's or Russian mag primers.

Jim Berry

 

[niceone]

can you let me know how you get on with the 107smks and rl 15

 

[niceone]

have you tried the RL15 and 107 smks yet

 

[Freestate101]

niceone, due to my busy schedule and the weather I have not had a chance to do any more load development. I will most likely concentrate on the 105gr. A-Max and the 62gr. Varmint Grenade as I am not a competitive shooter. This is strictly a hunting rifle with a heavy sporter barrel in a sporter stock, mainly used as a walking varmint and deer rifle. I may try a few rounds using the 107 SMK just to satisfy my curiosity and will post my findings for you when I do. Thanks for your interest in my project and load development, and good luck with yours.

Jim Berry

 

[Ackman]

It wasn't untill I switched to Rem 7-1/2 primers and 30 grs. Varget under the 105 A-Max that the groups tightened up.Absolutely no primer cratering or piercing, but then these were mild loads. I'm not sure how much faster I can push the 105's without piercing the non-magnum primers.

The 7-1/2 is a magnum primer.