Who's stretching it out with a 270 WSM?

[longarm]

First we need to know the length of the Berger 170 gr bullets to use a formula to figure out the stability of the bullet. The Greenhill formula is the best known but RSI says they have a nore accurate one.

Second, what kind of powder are you using and what charge. It sounds like you have a real impressive load. Remember that 140 Accubonds have a higher BC than the Bergers.

For 170gr bullets I would expect that VV N-570 would be your highest velocity powder.

Bob Beck says on this thread that the 170 grain Bergers will be 1.52 inches long. The temperature will be around 50 or more degrees, the height above sea level say 500 ft to 2000 ft.

I'm using 73 grains of H4831sc in the 270 Dakota behind 140 Accubond for 3,420 fps with 27 1/2 inch barrel and 67 grains H4831sc in 270 WSM behind 130 Accubond for 3,260 fps with 25 inch barrel.

As I use 1 in 10 twist barrels, I need to determine how fast the .277 170s need to go to stabilize, to work out if I can use them. I haven't used stability formulas before and not sure how reliable they are.

 

[bigngreen]

I would be surprised if they will stabilize consistently at that level even at 3100fps, your only at around a 1.1 stability factor and generally 1.4 is considered minimum. I can barely get above 1.3 during hunting season at 6000ft. This has been working for me with the Matrix but the Berger may or may not stabilize as well, shooting them is the only sure bet!

 

[TannerGun]

I really don't think pushing them fast is going to make up for a slow twist. Sure increased RPMs will make a difference, but only to a point...

 

[Bob Beck]

I may have already posted this. But if it will help, Bryan Litz has done all the calculations for the EOL/Berger Extreme Heavy Hybrid line of bullets that will be coming soon, including this one. He recommends a 1-8.5 twist minimum for these ultra long bullets.

I will post asap after our testing is complete, as well as when the bullets will be available.

Thanks guys.

 

[longarm]

Has anyone managed to solve the problem of how to successfully neck-size the thick 270 WSM brass to gain the utmost in accuracy for long distance work, or is everyone just full-length sizing or partial full-length sizing by bumping the shoulders back? Does the Norma brass neck-size better, or does outside neck-turning help by reducing the amount of brass in the neck? Although I now only full-length size my 270 WSM mountain rifle brass, if I build a long distance heavy barrelled 270 WSM using these Berger or Matrix projectiles, I will want to neck-size for best accuracy.

 

[TannerGun]

I use a Redding neck die and bump I shoulders when needed with a FL RCBS.

 

[lightflight]

Has anyone managed to solve the problem of how to successfully neck-size the thick 270 WSM brass to gain the utmost in accuracy for long distance work, or is everyone just full-length sizing or partial full-length sizing by bumping the shoulders back? Does the Norma brass neck-size better, or does outside neck-turning help by reducing the amount of brass in the neck? Although I now only full-length size my 270 WSM mountain rifle brass, if I build a long distance heavy barrelled 270 WSM using these Berger or Matrix projectiles, I will want to neck-size for best accuracy.

When i first started reloading for my 270 wsm I did have issues with neck sizing only. cleaned and adjusted my dies, bought some new lube FL sized once and neck sizing has work out just great since.

I use Redding for my WSM.

 

[bigngreen]

The Norma is .002 thinner at the neck than Rem brass. I have a reamer set up to turn .003 on Rem and skim the necks on Norma, Norma is also softer brass. I FL size everything and get much more consistency that way but I'm set up so it just bumps the shoulder and sizes just enough to chamber nice. Far sub MOA past a thousand so that good enough for me to hunt with.

 

[65WSM]

Nothing is softer than Remington brass. Remington is the cheapest brass they can put on the sale table in September just before hunting season. I works at the minimum level for handloading. Look at this metalurgy report. Remington is using the basic copper/zinc alloy it did a century ago. The handloaders market is dominated by alloys that contain iron or silicon or both to increase the case life and allow higher pressures. A friend of mine just went through a series of case separations with Remington brass in his .375 H&H on the second or third firing. This stuff was clearly not made for handloading.

X-Ray Spectrometry of Cartridge Brass within AccurateShooter.com

 

[jbird74]

I need a good load charge for a 270wsm shooting the 175 matrix bullet.

 

[TannerGun]

I'd start looking at around 63ish grains of Retumbo, and work up from there.