Problem with the Barnes TSX in my 25-06

laurent · Member Joined: Sep 07, 2006 Posts: 65 Location: Quebec

I have just reload some 115grs TSX bullets in my model 70 in 25-06 (1-10 twist),and I am getting Keyhole.Had no problem before with 120grs.Grand Slam,or the 110grs ballistic tip and was getting less than one MOA.The groove and crown are OK.
Any idea what is causing this problem with the Barnes TSX.

Thank you

Handloader

It could be the longer bearing surface of the TSX. I suggest trying the 100gr TSX. In my 25-06, it has been accurate and has a MV of 3,475 fps. That load has taken two big bull elk and has totally penetrated the body, one after hitting the onside shoulder and exiting the offside ribcage. One black bear was shot with the same load @ 240 paces, a 380 lb male and , again, total pentration was observed. All were one shot kills.

Pumpkinslinger

Laurent, what is the length of that bullet? We can run it through the Greenhill formula to check for best twist rate. Roughly with a 1 in 10" twist you are looking at a maximum bullet length of around 0.99 to 1".

English Mike

When people talk about needing a certain twist rate to stabilise a certain weight of bullet they're incorrect to a degree, as it's the LENGTH of the bullet that matters.
A 115gr Barnes TSX is longer than the 120gr Grand Slam, so the twist rate necessary to stabilise it will be faster.
I'd think the 120gr is right on the edge for a 1:10 twist rate too.

Handloader

Minor point: too, keep in mind that velocity is a factor in determining twist rate. Bullets require a certain rpm to function optimally. IOW, a 180gr bullet from a 300 Savage and a 300 RUM don't require the same twist rate for stabilization.

wildlife

I would have to agree with everyone. The bullet is too long for the rate of twist in the barrel. I have seen this before. If the gun is an older model it was set up for the average lengths of that time, and may not stabilize the newer bullets.

laurent · Member Joined: Sep 07, 2006 Posts: 65 Location: Quebec

Pumpkinslinger wrote:

Laurent, what is the length of that bullet? We can run it through the Greenhill formula to check for best twist rate. Roughly with a 1 in 10" twist you are looking at a maximum bullet length of around 0.99 to 1".

Sorry for the delay, the length of the bullet his 1.223in.

I was in touch with the guys from Barnes and guess what:I will have to move if I want to hunt with that bullets,because it looks like an elevation issues. Here is a copy of that funny anwser from them:

I suspect the elevation is the issue, We are shooting them here and they are working fine at that velocity. You can try to get the speed up another 100 fps and it may help but I suspect you may not be able to get it to go even then. The 100 gr TSX may be a better bullet for you.

Dave Card

Barnes Bullets Inc.

Customer Service/Sales

800-574-9200 ex 103

Pumpkinslinger

Well... Barnes is in Lindon, UT, elevation 4600'. Near as I can tell the high points in Quebec are around 4000', low points around 1300'. Sorry, I can't see where elevation would be a problem. However, at 1.223" the bullet seems to be too long for the twist rate. I know that there is a fudge factor for velocities over 2000 ft/sec that allow a longer bullet but I can't remember what it is offhand.

laurent · Member Joined: Sep 07, 2006 Posts: 65 Location: Quebec

Pumpkinslinger wrote:

Well... Barnes is in Lindon, UT, elevation 4600'. Near as I can tell the high points in Quebec are around 4000', low points around 1300'. Sorry, I can't see where elevation would be a problem. However, at 1.223" the bullet seems to be too long for the twist rate. I know that there is a fudge factor for velocities over 2000 ft/sec that allow a longer bullet but I can't remember what it is offhand.

Thank you Pumpkinslinger,
I guess your are right this bullet is too long but if you look at Barnes #4 Data this bullets is listed for 1-10 twist and my rifle (win model 70) is 1-10 twist.
So the bullets is the problem,and I am stuck with half a box of no good bullets for my rifle,Anyway I still think that Barnes Bullets are good bullets

Thank you

chambered221

laurent, What has the temp been while doing your testing ?

Whenever your working with twist rates and bullet lengths that are on the edge of stability the climate or tempreture your in can have a huge effect on the outcome. The colder it is the harder it is to stabilize the bullet.

Slow twist rates ( 1-16, 1-18 ) seem to have a harder time overcomeing cooler temps.

Just food for thought and my 2 cents !!! Good luck !!!

laurent · Member Joined: Sep 07, 2006 Posts: 65 Location: Quebec

[quote="chambered221"]laurent, What has the temp been while doing your testing ?

It was last week and the temp. was around 80 F.
It is weird because since I post this topic I reload some 120 grs Hornady SP,
and those bullets are very similar to the TSX as the lenght is amost the same and both of them has hollow point and I end up with about the same velocity and none of the the 10 Hornady bullets I shot had keyhole.So maybe it is true that the twist is part of the issue but only with the TSX.

Thank you

Laurent

English Mike

"Nearly the same length" isn't close when it comes to ballistics.

Apart from the weight & length, there are aerodynamic differences that come into play & it is possible that the 120gr SP is at the edge of the stability envelope, whereas the TSX is just outside.