I just aquired a new toy a few days ago. It's a browning a-bolt with boss chambered for 300 win mag. I plan on reloading 180 gr. partitions for it. However, there is no recommended boss setting in the manual for the a-bolt, only the BAR. Just wondering if anybody out there could give me some suggestions on where to start. You sure would save me alot of range time.

from the Browning website:

300 Win. Mag. 180 Winchester 4
300 Win. Mag.
(for A-Bolt II M1000 only) 180 Winchester 9
300 Win. Mag. 180 Federal 8.5 3

http://www.browning.com/faq/detail.asp?ID=109

Crank it back to 0.0 and forget it.

Terry I'm not sure why "cranking it to 0 and forgetting it" would do any good?

There is a whole chart thing on the Winchester website for various bullet weights and I'm sure Browning has one too. I've found the information to be pretty much right on for my .338. With factory loads I've got this gun shooting sub MOA and best 3 shot group is .264". Not bad for a factory loaded .338 Win Mag!
Definitely take the time to get it dialed in, it could be the most accurate rifle you will ever own. In my opinion the biggest downfall of the BOSS is the muzzlebrake. I bought the "CR" or brake eliminator for mine, more recoil but at least no ear piercing brake in field shooting situations.

I've only worked w/ a few BOSS Equiped rifles and they didn't shoot by the settings Browning advertises. They all shot great but, it was sort of a trial and error thing w/ the setting of the BOSS.

Had great luck w/ a 300 set at 0.0 when shooting 150s ontop of 66 grns of H4895. One of the other 300s was a BAR and the setting was different w/ the same loads. I've only tried 180s through one of the bolt 300s w/ a BOSS. Sorry, cant remeber where I found the sweet spot.

I think powder selection will have an effect on your setting as well. I think I'd do like Terry said, start at 0 and shoot the thing. If it doesn't shoot try 1, when you find a sweet spot then you can fine tune. It may very well be a shooter at 0. I've seen some BOSS equiped abolts that were just plain accurate.

I wouldn't have one simply because of the noise , be sure you have some darn fine hearing protection on and be kind to the other shooters at the range by finding a bench away from anyone.

Good Luck w/ your new toy

Reloader

molar1 ----- Start at the setting reccomended by Winchester and go from there. A considerable amount of shooting by testers determined that setting with several bullets in that weight. It will tell you fairly quickly which direction from the start it likes. When you find the spot, it will work but you need patience and consider yourself in the equation when a good group turns bad suddenly. Good luck and good shooting.

Are you using this link:

http://www.browning.com/faq/detail.asp?ID=109

I see a setting for the A-bolt under 180gr Federal of 8.5. Federal does use the partitions in their premium loads.

My A-Bolt was very good at the factory recommended BOSS settings on factory ammo. Usually 1" or less at 100 yds. If you are using reloads, all bets are off. Now if you can chrono the factory load, and build your load to match the factory load speed, the BOSS starting point should be in the right range and you will just have to fine tune. The dampening factors will shift with bullet weight and muzzle velocity.

Personally, it was too much trouble for too little benefit to reload for my BOSS rifle. I didn't shoot it that often and the factory loads were plenty accurate for what I was using it for.

Loading with a BOSS equiped rifle can be a real challenge, infinite possibilities of powders, grains, bullets, primers, seating depths etc. etc. and then throw in the BOSS adjusting, it can make you crazy.
The best way I have found to load for a BOSS is to pick a bullet ( type, weight etc.) and the desired velocity. Set the BOSS where ever the hell you want. Load several rounds with different powder and primer combo's until you reach the velocity you desire with somewhat acceptable accuracy. Now, make a shit load of this round and go to the range and work on BOSS adjustments.
The BOSS adjustments listed by Browning and Win. will not help the handloader in any way. It is all trial and error.

quote:

Originally posted by Snellstrom:
..... In my opinion the biggest downfall of the BOSS is the muzzlebrake. I bought the "CR" or brake eliminator for mine, more recoil but at least no ear piercing brake in field shooting situations.

Snell,
I would never put a muzzle brake on a rifle that I would even possibly use for hunting. Just believe my hearing and that of hunting buddies, guides and PH is more important that some additional felt recoil!

Now, a nob to dial accuracy into a rifle does interest me! But I've never heard of a "CR". What's a "CR" and can I get one for a rifle other than a Browning?

Hey Ray,

The cr is essentially an adjustable barrel weight without porting, thus you don't get a reduction in recoil, but you also don't get an increase in muzzle blast. CR comes standard with all boss equipped rifles. I have seen adjustable muzzle brakes for use with other rifles. They are made by QUE industries and can be found at brownells. However, the sell only ported brakes. It might be possible to use the browning cr with this system if the threads are the same. Brownells says they are licensed under the browning patent, so there is a good shot it might work.

The "CR" stands for "Conventional Recoil".
That's the part I put on my Browning BAR MkII in 7mm Rem.Mag.
I didn't notice much difference in recoil, but there was a bit less noise.