Why is the .260 so dificult to tune?

[CanusLatransSnpr]

jcampbell, most Ackley Improved are of the 40 degree shoulder variety so I would assume that their's are 40 degree shoulders!

Mike

 

[arizonajake]

My Winchester Model 70 silhouette rifle would produce excellent groups with 36.0 grains of Varget with Sierra 120 grain bullets - just like my other rifles, but, unlike my other rifles, would shoot terrible groups with Sierra 142 grain bullets and 41.5 grains of H4350. I solved the problem by experimenting with seating depth. Seating the Sierra 142 grain bullets 0.030" from contact with the rifling solved the problem.

I have a similar issue with my .284 long range rifle. It loves Sierra 168 gr. bullets seated 0.010" into the rifling, but shoots terribly with Berger bullets of the same weight. I will be testing different seating depths this weekend.

My 25-06 Ackley Improved prefers the Nosler 110 AccuBond bullets seated 0.060" from contact with the rifling.

You might want to try experimenting with seating depth before declaring the barrel or cartridge bad.

 

[mysticplayer]

H4831SC is the best powder for this cartridge behind 130 to 142gr bullets. Seat just off the lands, CCI BR2 or Fed 210M in any properly sized and prepped brass. Very simple chamber to make work.

If using H4350 or faster powder, way too little load density and/or extra pressure.

I have shot the 6.5 Mystic/260 ai for years and all rifles shot more of less the same load (within 1/2 gr). That was 4 barrel makers too.

Super easy to work with.

Jerry

 

[.260 james]

I have only had one .260 in my life. It shoots the first bullet at 100yds. about an 1/8" high of rest of group at 100 yds. and if I do my part will send the rest of any number of shots through same .2-.3" group until I stop shooting. I started with reloder 17 and 130gr. berger hunting vlds and have not changed. I don't shoot matches and I have stopped praticing regularly with this barrel because IMHO this may be the smoothest ,fastest , easiest to clean barrel kreiger ever made. It puts single digit sd. up and at speeds I no longer mention to anyone who is not present to see the chronograph in person.
The reason I went for a .260 is because I seen some data an individual had with reloder 17 and the whole idea intrigued me at a time I was in need of a long range antelope rifle.

Remington brass un prepped , unsorted
Alliant Reloder 17
Federal 210 gold match primers
130 gr. Berger Hunting VLDS jammed .020 into lands ( 2.99" OAL)

I won't put the exact amount of powder but if you try this load out start at manuel recommendations and work up til the pressure is not hot ,but near max. Then check your numbers. You may be amazed or disappointed but I know from my experience it was jaw dropping. Almost wish I made the gun a .264 win or at least a 6.5-284. but still am a happy camper.

 

[arizonajake]

Just finished tuning my Berger 168 gr. .284 loads mentioned in my previous post. Seating the bullets 0.040" from the rifling produced a 1 inch. 5-shot group at 200 meters. Now it's on to confirm at 300 meters.

Did the same thing with Sierra 142s in my .260 when it would not group. Seating the bullets in that rifle 0.030" from contact with the rifling solved everything.

 

[jcampbellsmith]

.... and the medium weight bullets -- the 123s or the Berger 130. ..

I've had some success with my 260 Rem, using N160 and 123 gr A-Max recently at 580yds and I'm thinking about getting another 260 Rem built. Regards JCS

 

[bheadboy]

considering all the pros cons, stated here, and the inconsistancey encountered, some great, some moderate and some a disater,

WHY WITH ALL THE GOOD OUT OF THE GATE 6.5'S MESS WITH IT.

BOB

 

[GSPV]

My son's is a hammer. Took 30 mins to develop a 1/4" load. That's 3 shots. It's a hunting rifle.

 

[GSPV]

considering all the pros cons, stated here, and the inconsistancey encountered, some great, some moderate and some a disater,

WHY WITH ALL THE GOOD OUT OF THE GATE 6.5'S MESS WITH IT.

BOB

I've got a friend that feels the same way about a 6 PPC. To each his own.

 

[dryhumor]

I have 2. One is a 3 groove 27" Lilja 8 twist, the other is a 24" McGowan 8.5 twist. I shoot 120 through 139 grain with mostly 1/2 MOA or less. As long as I don't wiggle too much....

There is a significant difference that I see between the 2 in what shoots well in relation to seating depth, depending on make and weight. You could try to work the seating depth (more) and see what turns up.

H4831SC, RE15, RE19, and Fed GMM primers for the most part are what I use; but I have used different powder and primers from time to time. I just like to shoot, and spend a good bit of time just experimenting with different loads and calibers.

Maybe you should stick the .260 in the safe for awhile and get back to it in a few months. It may all fall into place next time around.

 

[Jay Christopherson]

I spent a year messing around with all kinds of loads with a .260. It all came together with H4350 and the Lapua Scenar 123 going at 2950 fps.

I think a lot of guys struggle because they insist on running the 140s-142s and try to get 6.5-284 velocities. Try H4350 and the medium weight bullets -- the 123s or the Berger 130.

I think there's something to this... I had the same experience as the OP and rcw3, trying to run 140gn class bullets in a .260AI. One day it would shoot lights out, the next it might not hold in the .8's. Early on I shot a practice round that came up 200-16 @ 600. Never could reproduce that, although it seemed to shoot well enough at times. I took it to one match and it held fine for the first two relays and wigged out on the third, dropping 9's all over the place (like, well over a minute vertical). Finally, after 500 rounds, it decided it wouldn't shoot any better than the .8's and often much worse, no matter what I did. I spent 300 rounds worth of components trying to figure it out, using a half dozen different powders and load weights, different seating depths, even tried Moly coating when I got desperate. I seriously began to doubt myself as a shooter. Finally, I just pulled the barrel and switched calibers. Sanity has been restored.

 

[bdale]

I have a 260 also and in my opinion if you go much over 130gr. your wasting your time and money looking for a consistent load, especially in a 9 twist. Mine likes anything in the 120gr. territory, a 8 twist would be better but my 9 is shooting very well, gun also was throated for the longer bullets keep them above neck shoulder junction.

 

[M14AMU]

Possibly because it's not a 6.5x47L!

;D

 

[BradY]

Im running Roberts 30 degree improved version and its been a joy to use with H4350 and 140 hybrids. H4831sc not as good but I think thats my choice of case and primer combo. A mild load running 2890fps with 43.7gr of powder and CCI 450's in a 308 palma case. Going to test upwards of 44.5gr this weekend to get it into the area its designed to run with the 140's.

 

[stinnett1981]

The .260 is the same case as the .308 and .243 correct? The .308 and .243 for the most part is pretty easy to tune, inherently accurate and very popular? What would make that big of a difference in the .260? Or am I wrong and it is very popular? I just hear a lot more people talk about shooting the .308 and .243 than the .260. The more I ask the more I learn! Thanks.

 

[brian427cobra]

I have found my 260 very easy to tune, my target FPS is 2750-2810 with 139Scenar 140Amax 142SMK, H4350 and CCi primers, I only use Win 7-08 or Win 243 brass, resized to 260 with the neck turned to .0135, I have shot mine out to 1780 yards, 23.8-MRAD with a 2-MRAD wind hold with a 142SMK launched at 2790 and plenty of golfball hits at 600, my last Bartlein went 4068 rounds.

 

[JOHN708]

I've owned and shot out 5 260 barrels over the years from 3 different manufacturers. I generally agree with all of the above comments about them being finicky. One barrel didn't shoot anything well but I attributed that to the barrel being bad. The other 4 liked H4350 the best. I could get them to shoot consistently with 139-140 grain bullets but each one was very particular about with bullet it preferred. The bullets that worked best were the 139 Lapua and the 140 Serria. Dave Kiff at PT&G told me that that those two bullets seemed to shoot best with the reamer I was using. Go to load formulas that work for other cartridges don't seem to apply to the 260. It seems like you have to experiment with each new barrel.
It sounds like Robert may have found the solution by changing the cartridge geometry.
P.S. when I was using the cartridge in 2005-2006 the 139 Lapuas could be had for $18 per hundred! How times have changed.
John Skowron

 

[louielouie]

Like Forum Boss said, I've had more consistent results in my 1:8 twist Shilen using 123 A-Max's & H4350 at a less-than-max load - .4's is all I could manage with it. Nosler 140 CC may be 'blunt' but they weren't too bad at moderate loads either. The 260 has been dropped back to 'hunting' status now that I have something else to work on.
FWIW, I had QL tuned to be fairly close but the OBT's just didn't line up at all.

 

[mikecr]

Possibly because it's not a 6.5x47L

This is a good point actually.
The 260 capacity isn't ideal for 26 cal. It's too big for 123gr bullets and too small for 140gr bullets.

Step it up to 260AI and you hit the perfect capacity for 140gr bullets, as 123gr are perfect for the 6.5x47L. With enough barrel steel around the chamber(magnum action), you could push a 260AI like a 6.5x47L, and don't expect a match between these two unless you do just that.

The 6.5x284 is too big for 140gr bullets.

 

[Pablo]

Don't understand why they are so hard to tune. We have a Bryant built 260AI that I worked with of and on for a year before I figured it out. I was trying to develop a reduced load to shoot 120SMK for my 12 yr old. It never shot consistently or particularly well. I considered it a three quarter inch rifle and was pretty disappointed in it. I put it up for a while and thought about it and went back to square one. It has a 1 in 8 twist barrel and is throated to shoot bullets in the 130 to 140 class. So I went to 140's and my son didn't like the recoil, so we notched it back to the 130 Berger Hunting VLD's. About this time I discovered Terry Cross's article on the cartridge and his use of H4831SC. So that's what we did. I came up with a load that produced real consistent SD's with an ES that is very rarely ten feet either way from the center of the SD, then started playing with seating depth settling on .030". We now have a load that's 2930 with the 130's that is consistently in the .3s at a hundred yards. The earlier comment about shooting H4831 in this cartridge is, in my opinion, right on the nut. Varget and 4350 are too fast for this cartridge.