Hi, I asked this question on another board and was directed to ask Barnes which was great advice. Thought folks might want to know as well. Here is the response.

"Chuck,

We test the .509cal 570gr TSX into our water tank at 1500fps.


Thanks, Josh

Josh Springer | Consumer Service
Barnes Bullets, LLC"

So at 2300 fps out of my 500 Jeffery sighted in at 180 yards (2.5" high at 100 yards, dead on at 25 yards with a scope) the velocity is still at 1882 fps at 200 yards and it's 1.5" low. At 2150 fps muzzle velocity sighted in 3" high at 100 yards it's dead on at 25 and 180 yards and 2" low at 200 yards still moving along at 1749 fps. This is tempting me to drop my powder down to 101g of H4895 to cut the recoil a bit and move down to 500 NE power levels. Food for thought ...

Chuck:

I talked to the Barnes people about this very same topic but with respect to a 9.3 286 grain bullet. I was afraid they would not expand properly in my 9,3X74R since muzzle velocity is only around 2250 fps. I was told that a Barnes TSX will "begin" to expand at around 1600 fps but reliable expansion really begins at an impact velocity around 1800 fps. As long as your impact velocity is +1800 you are good to go with a TSX. I just wish they would give us a 535 grain TSX because I think the shorter 535 is a lot less likely to "tumble" once it hits your animal.

Thanks Dave, I really appreciate and value your opinion. My 500 Jeff has a 1 in 10" twist so it should stabilize the longer bullet at 2300 fps better than a slower more traditional twist rate I think?

I've also got some 570g Swift A-Frames I haven't tried as well. After seeing how well a 300g A-Frame worked on my brown bear hunt out of a 375 Weatherby(broke the right front shoulder at 13 yards, tore through both lungs and ended up in the far hide weighing 299.5 grains) I was impressed. But the thought of more load development arrggh!

Chuck:

The faster twist in your 500 would probably help stability a great deal. In a rifle with a conventional 1:17 twist rate like my 500, I think they are just too long. For the most part, when I shoot a TSX, I usually drop down to the next bullet weight (i.e. a 350 TXS in my .416 Rigby as opposed to a 400). If you drop down a bit with a TSX they become similar in length to the heaver conventional bullet and they are a lot less likely to tumble once the open up, become shorter, and shed sectional density.

We have very good luck on bison with the Woodleigh 535 grain bullet and don't forget that Woodleigh also makes a 600 grain protected point as well as a 600 grain FMJ especially for the 500 Jeffery if you are so inclined.

Good hunting my friend and Merry Christmas.

Merry Christmas to you as well! Will you be at SCI Vegas this year? If so we should get together, I'm bringing my wife.

Chuck:

Can't make it this year but will be going to AZ later in the year to get away from the cold.