What one bullet is most accurate in a .300 Win Mag?

I think the Weatherby Magnum calibers have a specified freebore in the chamber dimensions. That doesn't necessarily mean that Weatherby uses freebore in rifles built for Winchester Magnum ammo.

You could experiment with seating the bullets out a little more, though you may have to use it as a single shot if the overall length doesn't fit in the magazine.

B.L.E.
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I was going to say this same thing. The long freebore is for the higher pressures from the .300 Weatherby Mag vs. the .300 Win Mag. They would be making a giant mistake if they put that freebore on the Win Mag.

Just for the "heck" of it try a box of factory ammo. And 150 gr. should shoot fine in a .300 Win Mag.
 
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if i told you id have to kill you

Aha, so you REALLY don't know.... /QUOTE]

nope because ive never seen two differnt guns in the same caliber like exactly the same load best. Not that it couldnt happen but i wouldnt wager any of my money on it. How do you find out. You buy and shoot everything you can find until that majic load somehow appears.
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I got lucky. My Ruger 77 MkII all-weather .300 Win shoots any factory ammo (and bullet weight) to the same hole and groups with anything I run through it. I quit handloading when I couldn't beat it with my own loads. I'm talking sub-MOA with anything. That's why I kept the rifle for over 20 years. It's one in a million.
 
Have you measured the length of your chamber with those bullets? Bergers like to be set close to the lands or touching. My method of measuring uses two wooden dowels, one to press the bullet against or into the lands, the other used from the muzzle to measure the distance. Then use the muzzle dowel to measure the length of the empty barrel and chamber - the difference gives you your best OAL for Bergers.
I like the 210gr in 30, but they are making rather long cartridges when set to the right distance. They might not fit into the magazine in your gun.
 
Note that a 1:10 twist in a 300 Winny Maggie will spin bullets lighter than 200 grains much too fast for best accuracy. As 97% of all bullets are unbalanced to some tiny amount, it's enough that spinning them too fast creates enough centrifugal force to make 'em jump off the bore axis when they exit.

Which is why 1:12 twists were (and still are) popular for 30 caliber cartridges of that size with heavy bullets for long range matches. I've shot 180 HPMK's from my .300 Win Mag's 1:13 twist with excellent accuracy through 1000 yards.

So, for best accuracy with a 1:10 twist in one, I suggest a 220-gr. Sierra HPMK. But it'll only work well accuracy wise if the barrel's groove diameter is smaller than those bullets; they're typically about .3082". Lots of 30 caliber factory sporter barrels have larger groove diameters (Winchester was nororious for that and may still be). If the groove diameter's bigger than that, then I'd try to find some fatter bullets to use.

The 1:10 twist for so many 30 caliber magnum barrels came about when Winchester built their first Model 70's in .300 H&H Mag. They used the same twist as the .30-06 had, but even Harry Pope (famous barrel maker a century ago) said that was way too fast for best accuracy. Roy Weatherby used that twist for his .300 Wby. Mag. 'cause both he and his customers felt if the H&H version's twist was good enough, then so would his be. But Winchester and arsenal engineers were smart enough to make the 7.62 NATO's and .308 Win's twist 1:12 for 150-gr. to 200-gr. bullets leaving slower than the .30-06 shot them. They were more accurate with that slower twist.

Whatever bullet you choose to test, shoot enough shots per test group to be meaningful. At least 15 and 20 is better. Judge accuracy by the largest group for a given load as that's what you can count on all the time. Rarely does anybody shoot a group the size of the smallest one shot with a given load.
 
In my Winchester Ranger (plain jane Mod. 70) 30-06, I have beat expensive bench rifles using handloaded Sierra Matchkings.
Very accurate, I have no reason to consider anything else. But, top accuracy also requires proper loading techniques.
 
Note that a 1:10 twist in a 300 Winny Maggie will spin bullets lighter than 200 grains much too fast for best accuracy. As 97% of all bullets are unbalanced to some tiny amount, it's enough that spinning them too fast creates enough centrifugal force to make 'em jump off the bore axis when they exit.

Which is why 1:12 twists were (and still are) popular for 30 caliber cartridges of that size with heavy bullets for long range matches. I've shot 180 HPMK's from my .300 Win Mag's 1:13 twist with excellent accuracy through 1000 yards.

So, for best accuracy with a 1:10 twist in one, I suggest a 220-gr. Sierra HPMK. But it'll only work well accuracy wise if the barrel's groove diameter is smaller than those bullets; they're typically about .3082". Lots of 30 caliber factory sporter barrels have larger groove diameters (Winchester was nororious for that and may still be). If the groove diameter's bigger than that, then I'd try to find some fatter bullets to use.

The 1:10 twist for so many 30 caliber magnum barrels came about when Winchester built their first Model 70's in .300 H&H Mag. They used the same twist as the .30-06 had, but even Harry Pope (famous barrel maker a century ago) said that was way too fast for best accuracy. Roy Weatherby used that twist for his .300 Wby. Mag. 'cause both he and his customers felt if the H&H version's twist was good enough, then so would his be. But Winchester and arsenal engineers were smart enough to make the 7.62 NATO's and .308 Win's twist 1:12 for 150-gr. to 200-gr. bullets leaving slower than the .30-06 shot them. They were more accurate with that slower twist.
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OH no.. I really don't like to hear this. I don't like shooting big, heavy bullets because of the recoil. I choose the 300 Win Mag because it was at the top end of the acceptable recoil envelope for me for an elk gun. It replaced a .338 that I simply could not shoot because of the recoil. I've avoided muzzle breaks because of the noise and bother to nearby shooters at the range (where I probably shoot 200 rounds for every round in the field).

Maybe I need to start a new thread on the best way to rebarrel my gun... :mad
 
I really don't like to hear this. I don't like shooting big, heavy bullets because of the recoil.
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Then don't worry about it. The lighter bullets 150 and heavier will shoot just fine out of your 1:10 barrel.

Look at the recommendations bullet makers put on their bullets, "X twist of faster".................Meaning, you can use faster twist but not slower twist.

Hunting bullets, (not varmint but hunting bullets) made for the 300 jackets heavy enough to take the fast 1:10 twist.

Heavier bullets work better at long range because of the weight (wind bucking ablities) and better BC (Longer compared to the cal), not the twist.

Next time you go to the gun store, look at the bullets that list the recommended twist. its X or faster, not X or slower.

Or go to the Berger website, they list the recommended twist for their rifles. I've never seen anyone say X is too fast except for light jacketed bullets such as made for the Hornet or small varmits.
 
Max-pressure loads and a long barrel let my '06 do pretty well in the velocity department. 150-grain bullets somewhere near 3,150. Way back when, (okay, 60 years ago) I loaded 80-grain .32-20 bullets ahead of some 54 grains of 3031, which would be up near 4,000. (Ruinacious on jackrabbits).

I've never had any problems for accuracy with the 1:10 twist.

I tend to think that folks worry too much.
 
I agree with the last couple post on the 1/10 twist barrel for the 300mag. I think Wby found that out when they changed over to a 1/10 twist for the 300WbyMag vs using the 1/12 twist. Wby only has one load for a 200gr bullet but 6 loads for the 180gr and 4 loads 165gr and 2 load 150gr bullets for their mag.

If your going to build something maybe use 1 or two bullets you might do better with different twist but you sure want to talk to the barrel guys and get feedback from them also talk to the bullet guys. Nothing wrong with getting education from the guys who build them.

I tend to build around certain bullets.
 
For those who think a twist too fast won't impair accuracy may want to investigate the following.

When the Brits finally decided to do something about their .303 SMLE's not-so-great accuracy at long range, something had to be different. They already knew that the barrel whip properties of the SMLE let their cordite-loaded ammo's huge velocity spread compensate and made accuracy better past 500 yards. But the M1903 Springfield's out shot them handily with their 1:12 twist custom barrels and the new 172-gr. FMJBT machine gun bullet was used.

Finally, a smart Brit said the 1:10 twist in those SMLE's spun the 174-gr. bullets about perfect for decent accuracy leaving at 2500 fps, but the 150-gr. ones used later were spun too fast leaving at 2800 fps. He tried 1:11, 1:12 but finally settled on 1:13 twist barrels for the 150's leaving at 2800 fps. The Commonwealth's been using that for their fullbore medium and long range matches ever since with both the .303 Brit. and 7.62 NATO round. A 1:13 twist (and even 1:14) are now popular in Palma rifles shootng 150 to 155 grain bullets out at 2900 to 3100 fps. Faster twists start causing accuracy problems.

However, if you and your stuff can't shoot under 1/4 MOA at 100 yards or 3/4 MOA at 1000, you probably won't be able to tell the difference. For those who can, spinning bullets too fast matters. Best examples are the short range benchrest crowd shooting 22 and 24 caliber bullets; folks make tiny changes in charge weight as ambient temperatures change. They use twists just slow enough to stabilize the bullet and if it gets a few degrees cooler, the gotta add 1 or 2 tenths of a grain of powder to raise muzzle velocity just enough to increase the bullet's rpm's leaving the muzzle to stabilize it as it goes through thicker air. If a bullet's rpm rate didn't matter, they would not do it.

What about the .30BR round used in benchrest? Their 110 to 125 grain 30 caliber bullets leave at 2900 to 3000 fps. Best accuracy's with 1:16 to 1:18 twist barrels.

And yes, Weatherby did make lots of .300 Wby Mag's with 1:12 twist barrels.
 
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Old Roper, I got similar results Salazar did when I shot 168's, 180's, and 190's from a 1:12.7 twist 29 inch barrel chambered for the .308 Win. cartridge. Did just fine in 75 degrees and higher temperatures. With temperatures in the 30's and 40's, accuracy suffered with the 180's and 190's but the 168's still did pretty good.
 
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Since you have the rifle and are probably not looking to rebarrel for competition, but to simply tighten your groups, then you should try something in a spbt or hpbt. 150 to 180 gr should do fine with your current twist. You really cant expect 1/4 MOA 5 shot groups with a factory rifle even with custom reloads. Just remember, each rifle is different. You can have 2 identical rifles 1 serial number apart and they shoot differently. For accuracy, my old M77R likes the Sierra Matchkings the best.
 
One interesting thing I learned years ago was Sierra Bullets tended to get best accuracy in factory sporter barrels with flat based bullets. Their boattail ones shot better in high quality match barrels.
 
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