Hunting Rifle Tuner

I have also observed that group size varies with amount of jump, but most of the time, with factory chambers, due to their generous dimensions, I have gotten my smallest groups with bullets seated longer than "touch", somewhere between .006 and .010. This is not to say that the accuracy that is obtainable (jumping) is not usable in the field, just that I have gotten better results, with these sort of chambers, seated into the rifling. It has also been my observation that many reloaders do not necessarily bother to record the length of loaded ammunition measured off of the ogive, or work to a thousandth of an inch for seating depth. IMO once a reasonable powder charge has been determined, that there is much more to be gained by close adjustment of seating depth than by fiddling with powder charge by tenths of a grain. This has also been true with my tight necked 6PPC making the difference between good and great accuracy. I should also mention that with tight, target chambers, some excellent accuracy has been obtained with loads that have the bullet jumping to the rifling, by shooters that have had great success at matches.
 
Back at the Range

March 6 & 7, 2010. I was back at the range with the short light weight barrel. Additional testing, 80+ rounds with 87 gr BIB bullets and 75 gr VMax bullets. Very windy conditions made testing difficult. Best case was ½” group, mostly horizontal. Most groups were ¾ to 1”. The tune on this barrel is very sharp. “Peaky”. Tighter neck tension may be required. I was not able to duplicate the smaller groups shot earlier. Barrel set aside for now.

March 13 & 14 At the range again. 25 BR Barrel #2. Installed 25”+ Montana Barrel with #6 contour. This is a longer heavier barrel. Barrel muzzle is threaded 5/8-32 for use with either the Varis or Harrell muzzle brakes. The muzzle brake is installed with a brass Jam Nut behind the brake. Brake and Jam Nut work just like the Browning Boss. Screw them out slightly to change the barrel harmonics.

Barrel was shot 80 rounds with N-133 under BIBs and V max bullets. Bullets were set just lightly touching the lands, .003 into the lands, .006 into the lands and .009 into the lands. Best groups with the tuner adjusted was 1/4 to 3/8” mostly horizontal. Neck tension was too light; bullets only hand tight in the neck. (Using 281 Neck Bushing.) The light neck tension may be causing the horizontal spread. The tune using the setting depth, using the powder charge and using the brake-tuner all worked and still only got down to a ¼” group at best. (Out of tune the groups were 1/2" with this load. Both bullets shot the same load and to about the same point of aim. The VMax bullet was shot with a jump as it does not reach the lands.)

With the lighter Varis Brake the barrel went "out"to "in" tune in about 45 degrees rotation, or less. Very sensitive. A lighter tuner is indicated.

The plan now is to machine off as much weight as practical from the Harrell Brake and to machine a brass Jam Nut style 4 Oz tuner without the brake feature. Additional shooting is scheduled March 19, 20 & 21.
 
To Octopus.

Am following your thread with a great deal of interest but just a couple of questions. How many shots are in your test groups, three of five and what sort of scope are you using? If you are shooting in less than ideal conditions this is bound to effect your group size. When I used to shoot on a public range, I tried to arrange my shedule so that I could shoot very late in the afternoon when the wind had died down. Now I have my own range so I am a bit spoiled. You certainly are not afraid to burn a few components to achieve your goals, generally after about 20 rounds I find I can't give it my best and a bit of human error creeps into my groups.:eek:
 
Don't underestimate the BOSS Fred. It's as good as any other built to date.
And likely better than most...

Read Browning's patent sometime
 
Murphy,

I shoot both 3 and 5 shot groups. Use 3 for starters and when groups get better I double check with 5 shot groups. These 25 BR barrels are on a Rem 40X action pillar block bedded into an Edge Stock. Scope is a 12X42 NightForce. Rife is correct. I shoot at a private range in Indian Hammock (Fort Drum, FL). Benches are premium concrete. Most days I shoot over 4 of Smilies Flags. With a good 6 PPC barrel the rifle will agg below 0.2. Only change is a switch to the 25 BR barrels with the tuners I have been testing.

I try to get to the Range as early as practical. Usually I load at the range. My typical range day is 4 to 5 hours. I usually fire 80 to 100 rounds. With naked bullets I usually clean after 25 shots using JB borepaste and Koil.

Mikecr,

I think you are correct about the BOSS tuners. With the barrel on a correct rifle you can see that they do make a difference. However, many of the BOSS tuners have been delivered on rifles that had other error factors that swamped the tuner's action. If you have a rifle that is shooting two inches or more the tuner's improvement on accuracy is near impossible to detect.
 
To Octopus

Thanks for the information on your shooting arrangements. Sounds to me like you have most of your bases covered and if anyone can wring the accuracy out of that 25BR you will.:cool:
 
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