1 in 9.5" twist 7mm-08, which bullet?

goldeneagle76

Trying to decide which bullet weight would be best for reloading my Tikka T3 7mm-08 with barrel twist of 1 in 9.5", 22" barrel. Is the 139 Hornady SST 139gr too light? I will most likely geta few different kinds to find a good load but don't want to waste my money on something I know won't work well.

JustC

140gr pills work very well in my 7-08. the 150gr pill will also be a hammer. The 160gr pills will offer the capability of dropping even the largest north american whitetail or mulie.

nononsense

goldeneagle76,

Those 139 gr. SST will work just fine in your rifle. So will most of the hunting style bullets up into the 160 grain weigh range. You have plenty of twist for stability and the barrel length will suffice.

I have used Re-17 for lighter bullets in the 130/140 gr. weights with excellent results.

For the heavier bullets I get better results from Accurate 4064 powder. I go for a full case and moderate pressures which for hunting seems to be the proper combination for all climates.

Best.

sandwarrior

175's Gk's or Nosler PT's will work just fine in that twist as well. In fact you can probably shoot 180 Berger match hunting bullets if you want in that twist. If you keep the load up high. You can expect around 2500 fps from them with a 24" barrel. So, depending on what you are hunting. You pretty much have the best twist for that caliber (7mm).

Remember though it's not so much weight of the bullets per twist but rather length of the bullet that determines stability. Most bullets in each caliber simply gain in length with more weight, and that is where the confusion comes in.

In your case, where you are using a light bullet for that twist, it may cause some slight accuracy issues. Usually, not ever enough to totally eliminate that bullet from selection though. What happens is the tiny imperfections in a bullets concentricity become exaggerated when over-rotated. At longer ranges gyroscope precession wants to direct the bullet on a lightly different path. Either of those should not be issues for you unless you plan on some extreme shooting.

nononsense

goldeneagle76,

From a ballistician/bullet maker friend of mine:

With twist rates there are some rules that hold true:

1. If a particular twist will stabilise a particular bullet length, it will stabilise anything that is shorter but not necessarily a longer bullet.
2. Twist rates only have an influence on accuracy if there are serious concentricity anomalies in the core or jacket of a bullet. Turned mono metallic bullets are exempt from this problem.
3. For a hunting rifle, a tighter twist than the CIP specification hurts absolutely nothing. Slower twist than specified will usually detract from terminal performance.

There are more but these are the broad strokes.

The 1:9.5" twist rate will stabilize nearly every hunting length bullet. The average weight for the 7mm hunting bullets is between 130 grains and 160 grains. The exceptions are the long for caliber VLD bullets in the heaviest weight which includes the 180 gr. Berger mentioned. Even at 2500 FPS the 180 VLD will show some signs of becoming unstable because it needs just a touch tighter twist. In a few environments or altitudes you might get away with it but for the most part they will not a be a great choice especially if you are only considering the lighter hunting weights anyway. We use the 1:8.7" or maybe a 1:9" twist for the 180 VLDs for our competition or hunting rifles for a slight amount of buffer.

The 1:9" twist has been a standard for the 7mm cartridges for quite a while so using the lighter weight bullets will not create any stability problems from the 'over-rotation' mentioned. Millions of rounds a year are fired from rifles with this twist and the accuracy has never suffered. The same can be said for the 25 caliber barrels with the standard 1:10" twist.

Best.

sandwarrior

goldeneagle76,

Sorry to have gone off on a tangent about stability and what can and cannot be stabilized. My intent was more about extreme shooting, not hunting within 300 yds.
I merely meant to express that if you choose the Sierra 175 Game kings or Nosler 175 partitions, they can be stabilized from that 1-9.5" twist. The 180 Berger is indeed, right on the edge. It needs a couple hundred more fps or a little bit tighter twist to stabilize properly. The 175's lend themselves better to that twist than the 180's, however. And, I know some people prefer weight over speed. Also, some people truly love the terminal ballistics of the partitions.

Another bullet that fits in here is the Hornady Interlock. Both the round nose and the spitzer. Again, weight vs. speed. I prefer speed.

Let us know how it comes out.

oneoldsap

I'd guess you can use any 7mm bullet that you want with the 1:9.5 twist . Nice rifle in a very useful and efficient caliber ! If I had to part with all but one of my center fire rifles , my 7mm-08 would be my keeper no doubt !