Does anyone know if the 1 in 9 twist rate of 260 rem barrels will stabilize the 160 grain roundnose "moose killer" bullet that performs so well in 6.5 x 55 swede mausers (1in 7.5" rate)

Should be alright if you adjust the powder loads until you get the accuracy you find acceptable. It is a long bearing bullet, so will have quite a bit more friction pressure than the standard 140 grainers. This bullet isn't for long range shooting anyway, so you should be able to develop a satisfactory loading for "moose" work.

The Hornady 160 grain round nose bullet is 1.124" in length with a BC of .283. Optimum twist rate is 1 turn in 10" (or less).

The Hornady 140 grain pointed spire point is longer at 1.201" in length and a BC of .465. Optimum twist rate is 1 turn in 9" (or less).

This weight was one of the favorite bullets in the old 6.5 by 54 MS rifles. It worked all out of proportion for big game. It should work in a 1 in 9 twist, but only shooting it in your rifle will tell for sure.

Haven't found a 1:9 that wouldn't stabilize the Hornady 160gr. Have found some that don't care for it accuracy wise, but the bullet holes were nice and round....have found other guns that shot them exceptionally welll; like any bullet, some b arrels like them and others don't.

Might be becasue of their two diameter nature...most of that long nose is sub diameter, made to lower pressure/eaqse engravment. The part BELOW the cannelue is full sized. Two-daimeter bullets just seem "picky" about what barrels will shot them well.

The Remington Model 7 will stabilize the Hornady and the Sierra 160 grain bullets. You can push these to 2,450 fps or so but best accuracy will be found between 2,350 and 2,400 fps.

IMR 4350 does well with the Sierra RN loaded to 2.620” ahead of 38.0 grains giving 2,296 fps from the short Model 7.

A good full power load is 42.5 grains of IMR 4831 for 2,465 fps at a COAL of 2.450”.

Hodgdon 4831SC works well with the heavy bullets.

The Remington Model 7 magazine restricts COAL to about 2.825” Dads rifle has been shot a lot and the throat has washed out to where a COAL of 2.885” puts the bullet into the rifling. With the round nose bullets a COAL of 2.829” works best.
The Remington had a short throat when new and this gave some fouling problems. As the rifle broke in and the throat smoothed up these problems went away.

Barnes X is the way to go.

Will say this about those 160gr. Hornady's...they certainly weren't lacking in meat-penetration.

Thanks to everyone..great info here .....just got back to the board....now to the bench...thanks again

Most of the Ruger M77 rifles that I have worked with in 260 Remington had a 1-8" twist and most 160 gr. round nose bullets would shoot better than most other bullet weights and types.

A

Most of the Ruger M77 rifles that I have worked with in 260 Remington had a 1-8" twist and most 160 gr. round nose bullets would shoot better than most other bullet weights and types.

A
Keep in mind, those 160 RN bulelts are shorter than the 140gr. HPBT bullets...lenght has more to do with barrel twsit than just weight.