Hi all

What does one actually gain by turning a .260 remington into a .260 remington improved?

I guess it is the angle of the shoulder. Does this give a greater case capacity and thus more velocity.

Jim

I second this question.

Jim B... if you owned both of those calibers you would probably be asking the same question.
Take care
smallfry

Jim,

There was a good article about the 260 Ackley Improved with 40 degree shoulder in the July 2001 edition of The Varmint Hunter (Issue #39). The article was written by Steve Timm. Timm has been experimenting with the 6.5-308 (wildcat version of the 260 Rem) in standard and improved versions since 1966 including three standard 6.5x308 barrels and four barrels chambered in the improved version. His "Improved" version sports a 40 deg shoulder and 0.007" total case body taper (roughly 0.018" taper on the 260 Rem).

In the article, Timm claims an increase in case capacity of about 8 percent in the Improved version. He also claims an additional 150 - 200 fps over the standard cartridge. He claims greatly reduced case stretching (due to the sharp shoulder). This allows 6 to 10 firings before trimming.

I have no experience with the 260 Imp (although I am having one built) but would guess the velocity increase would be closer to 60 - 100 fps over the 260 Rem.

Here a little data from the article for you to review. These loads are the highest velocity shown and, I assume, are at max pressure. Timm's rifle has a 23" stainless, Pac-Nor barrel with a 1:10" twist.

85g Sierra HP 45.5g Varget 3,443 fps

100g Sierra HP 49.0g H-4350 3,293 fps
100g Nosler BT 48.0g H-4350 3,239 fps

120g Sierra SP 47.0g WW-760 3,072 fps
120g Nosler BT 47.0g H-4350 3,090 fps

Velocities listed are the average of several 5 shot groups. The 1:10" twist will not stabilize bullets above 120g. I am having my rifle built with a 24" barrel with 1:9" twist where I will have the option of shooting 140g bullets. Be interesting to see how the two barrels compare.

Hope this gives you a little more info.

HogWild

Hogwild,

That does not seem like much of an improvement to me, in velocity anyway. I am getting 3100 from my 22" barrel Ruger in standard .260 with 50 grains of RL 19 and 120 Gr. BT. Rifle shoots about 1.5 " with load.

Taos,

I made no claims that the 260 Imp was better. I did guess that you can get 60-100 fps more velocity from the imp case with equal pressure (Timm claims more than that). Everything else was Timm's opinion from the article.

I went back and looked at the article again. It appears Timm was having a difficult time finding an accurate load with the 120g bullet. It looks like he listed the most accurate load for the 120g bullet, not the max load.

If Timm's statement is true that the Imp version has 8% more case capacity, then do you think the standard 260 Rem will achieve the same or higher velocity with equal pressure? The Imp case will either get a little more velocity at equal pressure or shoot the same velocity at lower pressure. Is the velocity increase (or pressure drop) worth the trouble? Everyone must make their own decision.

I chose the Imp version of the 260 Rem because my gunsmith had the reamer on hand and I didn't have to pay for one. That's as valid as any other reason! This will be my first Imp cartridge so I plan to have fun experimenting (another valid reason). The improved case life will be a nice side benefit.

HogWild

Let me know hoe that sucker shoots and what the velocities are. I may just have to have mine done. I think you will really like the improved case once you get them all fire formed. Good luck with it.

I had a reamer made for a 6.5/243 imp about 15 yrs ago. I love the round! It does 3140 fps with 49 grns of Re 19 and a 120 nosler solid base, in a 22" barrel. In a 16" Competitor pistol barrel, the same load does 2900 fps. It would be a great round for someone who wanted a flat shooting carbine.