243 bullet weights

[Miseryguts]

Hi, a friend of mine has invested in a T3x in 243 calibre for deer shooting. He says that the twist rate is 1:10. He is working up loads on his 100yd range and has shot it with Sierra 70gn and Nosler 95gn with  good grouping. Today he tried some Sierra 90gn TGK bullets, and they appear to be unstable and going through the target sideways. Is this just a mismatch between his rifle and this bullet or is his twist rate unsuitable for bullets of this weight? To my simple mind, I would have thought that if a 95gn bullet is ok then the 90gn bullet should also be ok?

Powder loads are well below maximum, and there are no pressure signs whatsoever.

Any one else experienced anything similar?

M 

[banus02]

good evening my tikka t3 1in 10 twist would not group the sierra game changer 90gr so it may be the bullet length,try the 85gr game king at 2800fps for very accurate and minimal meat damage on roe,i of course load all mine to over 3000fps to make sure they reach the 1700 ft/lbs require in england.good luck with your choice

[Bangbangman]

My T3 groups well with Sierra Gameking, Prohunter and Speer BTSP 100gr bullets and Hornady 95gr SST.

 

However, the awful 90gr Sierra Gamechanger/Tipped Gameking were unstable at any velocity (within safe loadings).

 

Sierra screwed the pooch with the 6mm offering of this (over tough?) marketing dept bullet. They originally claimed it would stabilise in 1:10. That has quietly been revised after it became apparent it will not stabilise in many rifles with that twist (and is presumably marginal for many others, rather spoiling the high BC claims unless you have a fast twist barrel.)

 

I don't understand how Sierra got this so wrong.

[KABOOM]

4 hours ago, Bangbangman said:

My T3 groups well with Sierra Gameking, Prohunter and Speer BTSP 100gr bullets and Hornady 95gr SST.

 

However, the awful 90gr Sierra Gamechanger/Tipped Gameking were unstable at any velocity (within safe loadings).

 

Sierra screwed the pooch with the 6mm offering of this (over tough?) marketing dept bullet. They originally claimed it would stabilise in 1:10. That has quietly been revised after it became apparent it will not stabilise in many rifles with that twist (and is presumably marginal for many others, rather spoiling the high BC claims unless you have a fast twist barrel.)

 

I don't understand how Sierra got this so wrong.

I am glad to see the experiences with this projectile, will save me money not buying them. Altitude and assorted weather related things can enhance stability, but unless Im gifted some trying these wont happen.

[terryh]

As a passing note, stability and twist is, I believe, related to bullet length as opposed to weight. so not necessarily a lighter bullet will work where a heavier one had previously.

It did sort of apply when all you really had were SMK’s of different weights - they simply got longer with each increment in weight so a straight twist vs weight vs stability comparison worked.

You will see the Greenhill formula quoted, but this originated in the days of flat based bullets so needs a ‘tweak’ to work with modern bullets.

Now all this might be naff all to do with the TMK’s, just throwing it into the mix

T

[stephentri]

Stability has as much to do with length of bullet as well as weight, you should be able to shoot Sierra 100grain pro hunter through your  .243 as these are flat base and short.

[Miseryguts]

Hi, I have passed all your wise words on to my friend, who is not a happy bunny (he bought rather a lot of these bullets!)

Many Thanks for troubling to reply to all of you who did so

M