300 Win Mag Build and Loading Questions.

[bigngreen]

Just trying to help, consider this, long range rifles generally are considered capable to 1000 yards, kind of a bench mark distance. Let's load a 215 Berger and a 180 Accubonds since those best represent what your looking at and what is the norm on any long range hunting forum. With any 300 win mag i built this year I hit a bull at 1000 yards with a 215 at 1980 fps and 1.9 moa of wind drift per 5 mph and 1870 ft lbs of energy, your going to hit him with the wind Accubonds at 1721 fps and 2.8 moa of wind drift per 5 mph full value wind and 1184 fr lbs of energy.

I have those kind of guys in my life also but now that their hunting at long range also the bullets their shooting also changed for the reasons you see above. You want the best with what you have but you still have the opportunity to get the best you can for a long range hunting situation.
It mayball be a mut point if all your wanting is 6-700 yards but if your wanting to push it please consider the numbers above!!

 

[barefooter56]

So what your saying is that as long as the SG is 1.5 minimum it will shoot just fine.

Yes sir.

 

[barefooter56]

I did that. It's not easy to define best when your temps range from 30° - 70° and the altitude changes from 700 ft to 7000 ft. The minimum twist recommendation ranges from 12" to 10.3".

Edd,
In situations like this the 1-10.3 would be the best compromise. You could try the 1-10.5 and probably still have a stability factor (SG) above 1.4 which would work just fine. BC would be compromised a bit but nothing that would make the bullet become unstable and not fly point forward out to 1000 yards. It would just mean that external conditions like wind would have a little bigger effect on the bullet than it would at the 1.5 SG. Its when you get down to 1.2 SG or so that the chance of the bullet being unstable to the point of not flying point forward increase in possibility.

 

[barefooter56]

By the way, Bryan Litz is tearing it up with a 9 twist 308 shooting a 215 Berger.

bigngreen,
Bryan also does most of his shooting in the Midwest where we are about 800 feet above sea level on average at most and have to deal with high humidity, sometimes cooler temperatures , hordes of mosquito's and lower velocity due to using a .308 Winchester cartridge. The 1-9 twist is optimum for the 215 target hybrid at sea level and 59 degrees which is the "worst case scenario" we use . Not to mention hes a real hard holder can read conditions like they are a comic book and is a nice guy.

 

[Edd]

Edd,
In situations like this the 1-10.3 would be the best compromise. You could try the 1-10.5 and probably still have a stability factor (SG) above 1.4 which would work just fine. BC would be compromised a bit but nothing that would make the bullet become unstable and not fly point forward out to 1000 yards. It would just mean that external conditions like wind would have a little bigger effect on the bullet than it would at the 1.5 SG. Its when you get down to 1.2 SG or so that the chance of the bullet being unstable to the point of not flying point forward increase in possibility.

I don't mind trying some things to see if it will work but barrel twist isn't one of them. I expect it to be right the first time. The basis of my question was, I already have a barrel with a 9" twist. I bought that barrel with the intention of using it for a 308 Norma Mag and 215 gr bullets. That project may not happen so I was thinking of using it for a different project. If I need to to get a different barrel I can do that.

 

[barefooter56]

If I build a 30 caliber, 300 RCM, to shoot the new Hornady 178 gr ELD-X at 2850 fps and use a 9" twist barrel, is it not going to be accurate?

Edd & Wisner74,
What Bart B says about twisting an out of balance bullet faster is correct. BUT it depends on how much if at all the bullet is out of balance . Don't go down the rabbit hole and think that 1.5 SG is the holy grail of accuracy and anything else is bad juju. Its all a compromise because unless we all have a range out back that is the only place we shoot the SG, velocity, altitude, ETC,ETC, changes when we go to other ranges or hunting areas. This is a tool to use to help you make good decisions with what bullet to use or what twist rate barrel to buy so you wont have to deal with bullet instability from sea level on up.

 

[Bart B]

Don't go down the rabbit hole and think that 1.5 SG is the holy grail of accuracy and anything else is bad juju.

One of the best comments on in this thread. Accuracy doesn't fall off the SG cliff when the number goes below 1.5. That point was picked as the limit of accuracy degradation that's on a gradual downward slope based on the developers objectives, standards and conditions. Someone else may have picked 1.6 or even 1.4.

I doubt anyone could see a difference in long range accuracy with any bullet and velocity whose SG went from 1.55 down to 1.45. They may if they shot the load from a machine rested rifle inside a building with perfectly stable atmospheric conditions and shot at least 20 shots per test group and both were well under 1 MOA.

And the OP will shoot 180-gr. bullets more precisely than heavier ones which typically masks a small loss of accuracy due to its lower BC. Picking the right powder and charge weight coupled with a good primer (Tulammo LR) and the muzzle velocity spread will also drop increasing accuracy.

 

[bigngreen]

So given the number from the ballistics I posted above whats your predicted out come of a hunting shot at 1000 yards with a 215 vs a 180 gr bullet?

 

[Bart B]

So given the number from the ballistics I posted above whats your predicted out come of a hunting shot at 1000 yards with a 215 vs a 180 gr bullet?

With both bullets striking the same place and axis on a given animal, only the difference between wound cavities.
Neither would survive.

 

[bigngreen]

With both bullets striking the same place and axis on a given animal, only the difference between wound cavities.
Neither would survive.

You don't think you owe an animal at least the cleanest kill possible, the difference between hitting them with a bullet that is penciling and a bullet that is fully open can be very dramatic, not to mention a sad thing to watch.
Were not trying to print a group on the side of an animal here, if we were I'd be totally in agreement that go ahead and rock a 180 and 12 twist but things change dramatically when you push the range on bullets when it comes to terminal performance, terminal performance is the end game here not group size!

 

[brentc]

All this talk about what happened in the 60's is driving me nuts. It's still relevant and it's proven to work, however, I look at it this way. Using 180s is like the old saying "This is what I'll use until something better comes along". Well, something far better came along several times in the past 55 years. If you want to ignore all the good information that's been posted here (not what happened in 60's) that's fine. It's your thousands of dollars going into a neutered win mag.

 

[FEENIX]

All this talk about what happened in the 60's is driving me nuts. It's still relevant and it's proven to work, however, I look at it this way. Using 180s is like the old saying "This is what I'll use until something better comes along". Well, something far better came along several times in the past 55 years. If you want to ignore all the good information that's been posted here (not what happened in 60's) that's fine. It's your thousands of dollars going into a neutered win mag.

lightbulbIt don't get no simpler than that.lightbulb

 

[BEEMAN]

All this talk about what happened in the 60's is driving me nuts. It's still relevant and it's proven to work, however, I look at it this way. Using 180s is like the old saying "This is what I'll use until something better comes along". Well, something far better came along several times in the past 55 years. If you want to ignore all the good information that's been posted here (not what happened in 60's) that's fine. It's your thousands of dollars going into a neutered win mag.

Couldn't agree more!

 

[TOM H]

One of the best comments on in this thread. Accuracy doesn't fall off the SG cliff when the number goes below 1.5. That point was picked as the limit of accuracy degradation that's on a gradual downward slope based on the developers objectives, standards and conditions. Someone else may have picked 1.6 or even 1.4.

I doubt anyone could see a difference in long range accuracy with any bullet and velocity whose SG went from 1.55 down to 1.45. They may if they shot the load from a machine rested rifle inside a building with perfectly stable atmospheric conditions and shot at least 20 shots per test group and both were well under 1 MOA.

And the OP will shoot 180-gr. bullets more precisely than heavier ones which typically masks a small loss of accuracy due to its lower BC. Picking the right powder and charge weight coupled with a good primer (Tulammo LR) and the muzzle velocity spread will also drop increasing accuracy.

Bart, Your on the target side of shooting and I think most hunters look at more things when selecting a bullet than what you may do. Tells us how you know what bullet OP will hunt with?