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270 WBY vs 270 WSM ballistics

EROY

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270 WBY vs 270 WSM ballistics
« on: October 30, 2010, 05:48:04 PM »
Just curious. Since 270 WBY is measured in a 26 inch barrel and 270 WSM is measured in a 24 inch barrel, would they be basically identical performance wise in the same length barrel? Let's say both in a 24 inch barrel?

dubyam

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Re: 270 WBY vs 270 WSM ballistics
« Reply #1 on: November 03, 2010, 11:39:14 AM »
Nope.  The case volume is still about 5-6gr lower for the WSM versus the 'bee, and contrary to what some gunwriters will tell you, there is no magic "efficiency" that allows the WSM to produce the same velocity with that much less powder.  I can get 3450-3500fps from a 130gr bullet out of a 26" barreled 270Wby, using current published data - and the velocities are right in line with what was achieved in testing during the load development for these data by the powder or bullet manufacturers.  A 270WSM is going to run in the high 3200's with 130gr bullets, and adding 2" of barrel isn't going to give you 200fps.  The real world difference is only about 150fps in the same length of barrel, but the advantage does go to the 'bee.

For reference, Hornady used to test all their 'bee data in 24" barrels from the Japanese-made Mark V era, when 24" #1 contour barrels were common, and they were still getting 3400fps and above for the 270Wby, even then.  Some of that data is in line with current published data, but some of it is not.
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Re: 270 WBY vs 270 WSM ballistics
« Reply #2 on: November 07, 2010, 05:55:07 PM »
A friend of mine has a 270 WSM and he has a hard time reaching the advertised velocities without running into pressure signs.
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tclark

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Re: 270 WBY vs 270 WSM ballistics
« Reply #3 on: November 07, 2010, 07:22:04 PM »
I am with dubyman on this.  I have both calibers and handload; for my rifles the 270 wby is about 150 fps faster with weights up to 130,  above that the wby realy shines and is closer to 200 faster with 150s.  I bought 100 old round nose 150s at a sale for 3 bucks and they are bad news on whitetails up close and cheap for blasting with friends.  heavy damage but I use the wby for a field stand so I pick my shot on the lungs. the low BC of the round nose does not hurt inside 300 yds and when the flat meplat hits them it looks like I shot my 338 win.  btw in my experiance the wsm cartridges all flatten primers including factory stuff.
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EROY

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Re: 270 WBY vs 270 WSM ballistics
« Reply #4 on: November 08, 2010, 04:13:11 AM »
Thanks for that info guys. I would really like a 270 WBY. I was disappointed when I found out it wasn't made in the Vanguard. I would have chosen it over the standard 270 WIN just because of the significant increase in performance but I do love my 270 WIN in the Vanguard. That thing can shoot! Anyway, I've been contemplating either a custom barrel on a TC Encore Pro Hunter or something else. The TC is not inherently accurate and I don't know if I will be disappointed with the work it takes to make it so. Thanks for the "real world numbers" on the 270 Bee.

Re: 270 WBY vs 270 WSM ballistics
« Reply #5 on: December 21, 2010, 09:55:09 PM »
There is something else to consider besides muzzle velocities: I have a Remington 700 CDL in 270WSM, and the feeding of rounds out of the magazine & up the feed ramp into the breech is just a bit sticky. My Weatherby Mk V (in 300 Wby Mag) feeds smooth as silk. The longer cartridges just slide more easily in the movement magazine-breech. So if I had my "druthers" I would go for the 270 Wby next time and carry a few extra ounces of long action!

dubyam

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Re: 270 WBY vs 270 WSM ballistics
« Reply #6 on: December 22, 2010, 06:34:34 AM »
EROY, if you're in the market and just want a 270Wby, there are plenty of good used guns out there.  I can turn you on to a good source for used Mark V's and they happen to have several 270Wby's in stock right now.  These are mostly synthetics, and they're running around $750-800, for the most part.  They sometimes have some better deals than that, and I have seen a number of used synthetics for under $500 at this shop and one more.  If you're interested, PM me.

Oh, and I don't work at these shops.  I just spend all my money there.
I believe this is a practical world, and in it I can count only on what I can earn.  Therefore I believe in work, hard work. - The Auburn Creed
The older I get, the less stock I place in what men say, and the more I place in what men do. - Andrew Carnegie

Chip

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Re: 270 WBY vs 270 WSM ballistics
« Reply #7 on: December 22, 2010, 07:47:12 AM »
I agree that the heavy bullet performance of the Weatherby should be better than the short mag. With the 130 gr bullets it's a different story from what my actual load data and chronographs indicate.  My five shot string average with a 24 inch using RL-17 and 130 gr Accubonds was 3420 at 10 feet off the muzzle.  Turn that load loose in a 26 inch tube and it's 75 to 100 fps faster.  I ended up using RL-22 this year for my hunting loads as it had less extreme velocity spread. I will get back to the RL-17 though as it showed some good potential while  I was playing around with it.   The RL-22 is a 3200 ish powder.  Not sure how smooth the short mag feeds in a Weatherby, but in a Tikka  with a inline 3 shot magazine they feed like buttah.  Really a guy should have every sort of 270 ever made I think. You can't really go too wrong.

Chip