Boss setting inquiry, 150s in a .300 win mag model 70 supergrade. Anyone done this?

[Short Round]

I have a great shooting Winchester Model 70 supergrade stainless synthetic. I have it at the original OEM setting for 180 grain bullets. With Nosler 180 grain BT it shoots 1/2" groups at 100 y.

I have 400 150 grain Hornady GMX bullets I would like to try out but there is no recommended starting point for that weight.

All I can do is look at the othe calibers like .308 and see how much apart the settings are.

My best guess is around 8.

Anyone have experience or a starting point based, possible start on formulas for barrel timing? I am guessing Browning/Winchester had some modeling methods before field tests.

Yes I know the only sure way is putting rounds down range but I sure would like to get a jump.

No worries in rushing to the opener, this is like the third rifle in the rotation, not counting woods walking guns like Dad's Marlin 336 or my 6.8 build.

 

[SamuelBerryhill308]

Have you check on any powder company web sites? I know Hodges and vitavori has good load data also western powders

 

[david g ranes]

The best way I have found is turn it all the way down then you only have one way to go shoot a couple move a few marks shoot a couple you will find it will give you better groups then they will open up again doesn't take that long or that many supplies I started out using brownings sweet spot but by the time I figured out I was going the wrong direction I shot more shells than doing it one direction only. David

 

[Short Round]

The best way I have found is turn it all the way down then you only have one way to go shoot a couple move a few marks shoot a couple you will find it will give you better groups then they will open up again doesn't take that long or that many supplies I started out using brownings sweet spot but by the time I figured out I was going the wrong direction I shot more shells than doing it one direction only. David

That is certainly a direct and logical approach when one doesn't know where to begin.

Which hash marks are you talking about? The larger integer or the subtensions on the brake?

 

[asd9055]

Hey this is what I have. I would dare say 150 could be 0 or 0.1. You could give Winchester a call. Browning settings are totally different.

300 Win. Mag.	220	Winchester	3.6
300 Win. Mag.	200	Federal	2.8
300 Win. Mag.	180	Winchester	0.2

 

[Short Round]

Yes thats what my manual has too.

back up from say 1.2 to 8 or 9, in other words, to move to the right spot on the harmonic curve they came back in from the high end, it's circular more than linear. At least that is how I read the charts of other calibers.


ETA this is my project to make a long range zapper with an all copper alloy bullet, keep the speed up to ensure the GMX opens up.

I have had an interest in bonded bullets and all copper and to step away from shredded lead in my deer and after revovering a lot of Nosler Ballistic tips and Sierra game king jackets, and a tiny remnant of the core slug that flew off in another direction. (The deer were harvested though so I cannot whine too much.).


asd, I should at least send Winchester an email. Maybe they will give me a calculation to come up with a starting point. This is related to barrel time I would imagine.

 

[asd9055]

I have all but two calipers in M70 BOSS. Definitely NOT linear. More like a 2nd degree polynomial
Are you saying you are moving all the way to the other end? I am curious to see how it works out

 

[Baylor243]

I have a browning A-bolt 300 win mag and it shoots 5/8" or better groups (5 shots) with cheap-o Winchester factory power point 180's....and it's nowhere near the mfg recommended BOSS setting. I shoot it set at 9.6...factory BOSS setting chart says 0.5. Who knows why? Who cares? Not me. It shoots great.

I've filled the freezer quite a few times with those cheap rounds and I've never found a hand load that will out shoot it. I quit trying, bought a case of ammo and never looked back. Yes, I've had several bullets separate but it dang sure packs a whoopin on whatever I ask

I also had a 243 M1000 Eclipse A-bolt that shot lights out when set dead up on the factory settings. I shot the barrel out of it and gave it to my brother in law. He can't shoot for beans anyways.

Long story short, sometimes ithe BOSS just doesn't make sense with the factory charts. Good luck.

 

[Short Round]

This is from the Browning site with different guns, different barrel lengths etc.

I post it to illustrate what I am talking about, when one might expect to dial the weight in toward the chamber, after the zero you go to ten and start working back to the chamber again. Picture one of those osciliscope waves, you're just tuning toward a wave crossing the zero line instead of at the top or along the slope of the curve. At least that is the way I interpret it.


As Baylor says, at a certain point you have to shoot it and find it.

This gun was spot on for the 180s at the recommended starting point. 1/2 moa was good enough I didn't wander looking for better.


ETA.....Baylor I reread your post, my theory and belief is you are in reality close, not far away. Picture 0 to 10 on a 10 hour round clockface. 9.5 and 0.5 are 1.0 away.

 

[asd9055]

I am glad you pointed this out. I have both sets of data but never thought about it this way.
Thanks

 

[Short Round]

Glad to share my thoughts and theories.

If I used the Browning chart and looked at it, the 150 and 180 are 7 away from each other, dialing downward and coming back through ten. But I hardly know if that is accurate in the other barrel length. The Browning guide also throws in the variables of different numbers for different common brand loads. The winchester chart shows 180 at 0.2 and 200 at 2.8.

Somewhere I saw an optimal barrel length chart that were supposedly better for certain cartridges. Basically different lengths where the bullets should be exiting when the muzzle was near the centerline of the harmonic whip.


Great theories, but you still have to prove it on paper as my gunsmith Dennis would say.

 

[thwatson2]

Unfortunately sounds like most of us have the brownings. I have 6 brownings with BOSS. 5 of them shoot like a custom rifle with brownings "sweet spot" numbers. But the one in 7 mag isn't even close. Long story short, I started that rifle at 0.0 then started working up 1 full turn with 3 shot groups. Luckily at 4 I was getting a pretty decent group so I started increments back and up in 10ths and found 3.8 was perfect. I also was told,by browning years ago, that once you get your primary number, that for higher velocity rounds turn upward and for lower velocity rounds turn backwards. So far, that worked for me. regret to tell you but you are gonna be at the bench a little bit to figure it out. I also would note that the 300wm really shines at 180 and up so maybe try to sell the 150bullets to someone with a 308 or 30-06?

 

[Short Round]

You may be right. I originally bought these for a M700 Titanium Mountain rifle in .308 and never got to them. Reading up on the GMX I saw they need to be pretty **** fast to not act like a fmj. Thats where I had the thought of switching them over to the .300 WM where keeping plenty of speed is a no brainer. I read the copper penetrates like a heavier bullet but that will not do a thing accuracy wise if the rifling twist isn't happy with them. My 180 Nosler ballistic tip load is nice but I am now leading to bonded or copper.

I did shoot off an email to Winchester to see if they had the data and even asked about mathematical calculations they might be using to generate the sweet spot recommendations.


I figured now was the time for a rework as I rescoped with a leupold Vx-6HD.

Very likely not going to have this load for this year. No worries as I have enough clubs in the golf bag.