I'm purchasing a Ruger 77 in 6.5x55. I have a Remington Mountain rifle in 260 Remington. I noticed in Quick Load that the pressure that the 260 is loaded for is 60,000 psi and the 6.5x55 is 54,000. Can the 6.5x55 be loaded to higher pressure in the Ruger? I should get velocity that is about equal to the 260, right?

Bob257

variations in loads, guns and loading manuals show overlapping max speed for either one in almost any bullet weight. The differences have got to be very small. 6.5 uses more powder in a bigger case at lower pressures. I have both but never chronoed my swedish.

Dang if Seafire/B17G didn't hit on something I have been saying for awhile. While do you need a Magnum anything?? let alone an Ultra Magnum or Super Magnum?? 6.5 Swede and .260 are great rounds with less noise and recoil. Also, longer barrel life. I've also got a .280/7mm Rem. Express instead of a 7mm Magnum. We're re-inventing the wheel and overlooking some great old rounds for something that takes a mouth full of words to mention the caliber and doesn't out perform the old one by any great amount.

Yup. That's a big difference. Wonder if Marge Inovera came to work today, or if it's from a difference in standards? ANSI/SAAMI takes pressure readings in the middle of the casing. CIP in Europe takes their readings at the mouth of the cartridge. Correlation between the two methods is less perfect than you'd hope.



The only solution is to buy a 260, a modern 6.5x55, and a 6.5-284, and instrument them. If you guys will chip in for the guns, I'll furnish the ammo and instrumentation, and promise to report the results.

Something's still not adding up for me. Norma's loading data for the 6.5-284 shows a MV with 120gr and 140gr bullets some 300fps faster than you do. That is with MRP, a powder with a burning rate between the 4831 and H1000 you used. I'd expect use of a more appropriate powder to make up some of the difference (4831 being too fast, H1000 too slow, MRP being Goldilocks' choice), but even so, 300fps seems a bit much...

Slightly OT, but does anybody have a trim-to length number handy for the .260...?

Thanks,

Monte

Denton

The data released by Lapua and Norma show a significant difference between the cartridges were the 260 has to work under much higher pressures to get the same velocity.
The 6,5X55, 6,5-284 and 6,5-06 will work best with Norma MRP, Vithavouri N-160 and N-165 and the slower RL powders.

260's main problem is that if it's used in a short action the 140 gain bullets must be seated down in the case which results give less powder capacity.

Some claim that everything larger than 6,5 BR is over bore, it is a debate with no end

/ JOHAN

I had the same question a few days ago, and did a little research. The result may be helpful.

Using data from the Hodgdon site, I compared max loads for the Swede, the 260, and 6.5-284, and their resulting muzzle velocities.

For my Swede, I know that a grain of H4350 produces about 50 fps of muzzle velocity. In my 30-06 and 7.62x54R, which are instrumented, and have a similar size case, a grain of H4350 produces about 2,000 PSI. So, ROUGHLY 3-4 additional grains are PROBABLY allowable in a 6.5x55 of modern design and dimensions. I added 3 grains and 150 fps to each of the Swede loads.

The result: All three calibers produced nearly identical maximum muzzle velocities. The bigger case capacity guns used more powder, but produced no additional MV.

Use load data from european ammo makers and 6,5*55 is faster than 260r. The long troat can be used to seat the bullet near the lands so you can fill more powder with the same pressure.

Say "grass pants" ten times, and then try to say Grant's Pass.

Absolutely: Sven and Ole came up with a cartridge DANG hard to improve on. My Swedish Mauser seems to always find some way to delight me. The only problem with it is that it works so well I don't need a 243, I don't need a 7mm-08, I don't need 257, .... It just seems to take away justification for a whole lot of mid-capacity rifles.

Just like Denton indicated, it all boils down to efficiency.

I shoot several 6.5 x 55s, several 260s, and a 6.5 x57.

I laid off building a 6.5 x 284, or a 6.5/06, or a 264 Mag.

Throat erosion can be caused with all the excess powder blowing out the barrel because it was not efficiently burned.

Shoot a 264 with an old sheet or pillow case, or T shirt about 12 inches from the muzzle and see how much powder residue is on the cloth. Then try it with a 260, or 6.5 x 55.

That is indicative or why you have throat erosion on the bigger bores.

One a 260, 6.5 x 55, or 6.5 x 57 or any of the smaller case, try using mid range powders ( 4064, IMR4895, RL 15, RL 7, or 3031 ). You will get as much velocity, more efficient burning of the powder etc.

Also pay attention to the ballistic charts. Pick any 6.5 mm bullet and then see how the trajectory is not that much flatter for a couple of hundred Fps, at say 300 yds, or 600 yds. 6.5 bore is very efficient., the bullets are very aerodynamic.

260 reload data is a good starting point for a 6.5 x 55 or 6.5 x 57.

Anyone who has worked with them can verify they perform a lot better than anyone would think, but in accuracy, trajectory and on game performance, low recoil ( making it very shootable)

Sven and Ole had their shit together when they came up with the 6.5 x 55 back in the 1890s. to me not much has improved on it, at all.

Yup. Isn't that a kick in the head? In a couple of cases, H1000 produced very slightly higher MV than these numbers. I was mainly interested in H4350 and H4831, and the best of those two was always quite close to the maximum. Data are from the Hodgdon reloading data site.







Rem 260

120...2960

140...2686



6.5x55, + 3 grains and 150 fps

120...2942

140...2736



6.5-284

120...2897

140...2720



The 270 is slightly overbore. A .277 bullet on a 308 case will produce very nearly the same MV as a 270 does, with less powder. 6.5x55 is even more overbore. As you add powder, efficiency falls. You end up with little or no gain, but the gun becomes more finicky, and the barrel doesn't last as long.



The thing that puzzles me is that the 264 Win Mag does get higher MV, and generally at lower pressure than the 260. And it has a reputation as a major barrel burner.



I can't say I've figured the whole thing out, but that's Hodgdon's data. A fine budding scientist, such as yourself might figure out why that happens! It has always bothered me that you for a given gun, you can reach a point that the MV vs charge curve smacks into a glass ceiling. Sort of excites your cognitive dissonance, doesn't it?

Huh? You're saying that you are getting the same MV out of a 260 as you do out of a 6.5-284? That doesn't make any sense to me.