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Curious to know what you all think of the 260AI. I have always been a 6.5 shooter 6.5x55, 260 Rem, 6.5-06 and 6.5x284. I have a 260 rem Sako 85 that has been become a bit of a safe queen it has lot's of room in the magazine and I'm thinking re-barrel or re-chamber.
With the 260 rem I believe that 24 is minimum bbl length with the AI I am not sure. I like the handling of the 85 as is but not sure about 22.5".
What's your opinion/s?
Thanks in advance.
Bob
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Joined: Oct 2006
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Campfire Ranger
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Campfire Ranger
Joined: Oct 2006
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It's a cool cartridge but I don't think I'd rechamber a rifle just to AI it . Fact I know I wouldn't .
Your FPS gain would probably be 100FPS - guessing/ballpark ..
I'd sure consider the 260AI for a build or rebarrel though .
Another guess.on barrel length - 20-25FPS per inch is a pretty good estimate .260R w/a 22.5'' barrel is perfectly fine , especially with heavier bullets .
An extreme velocity cartridge or what is considered an overbore cartridge will get far better velocity gains in a long barrel than a short barrel .
Example a 26'' barreled 22-250 shooting a 32gr. v-max bullet would lose a lot more velocity if you cut 4'' off the barrel compared to the same rifle shooting a 70gr. bullet load -then cut 4'' off barrel .
The 32gr. load might lose 75FPS per inch of cut off barrel . Guessing there again .
Of coarse do what you want and have fun with your Sako 260 .
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Joined: May 2003
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Campfire Ranger
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Campfire Ranger
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The 260 won’t benefit from it all that much.
I’m having a new barrel put on now and decided not to do it based on research and the advice of a very good gunsmith.
Now my 280 on the other hand....
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Campfire Outfitter
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Campfire Outfitter
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I think it's a waste of time. If you need a case fatter than the standard .260, go with 6.5x.284. That's like an AI and a half!
Anyone who thinks there's two sides to everything hasn't met a M�bius strip.
Here be dragons ...
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Campfire 'Bwana
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Campfire 'Bwana
Joined: Dec 2002
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I think that you could expect a maximum of 10% more case capacity and that would probably get you between 75 and 100 more fps of velocity.
I have bounce the idea of converting a 260 to 260AI multiple times over the past 20 years, but every time that I run the numbers, the cost to set the barrel back, cut a new chamber, and buy a set of dies make those additional 75 to 100 more fps less interesting.
If you want more velocity then you're getting from the 260, would your Sako be a good candidate for conversion to 6.5 SAUM?
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Joined: Sep 2007
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Campfire Tracker
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Campfire Tracker
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The 260 AI isn't a bad round by any means but the standard 260 Rem is just fine. Like was mentioned above the 6.5x284 on a different gun would be a great idea. In the end only you need to be happy with what you decide. If I ever thought my 260 wasn't enough the 6.5x284 or possibly the new 6.5 PRC would be intriguing.
Gerry.
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Campfire Outfitter
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Comparing case capacities and using Mule Deer's "Rules", the gain is likely to be maybe 50 fps depending on bass capacity, or the equivalent of around 2" of barrel length. So a 24" 260 should run with a 22" 260 AI, when loaded to similar pressures.
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Joined: Dec 2008
Posts: 21,157
Campfire Ranger
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Campfire Ranger
Joined: Dec 2008
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The 260 AI isn't a bad round by any means but the standard 260 Rem is just fine. Like was mentioned above the 6.5x284 on a different gun would be a great idea. In the end only you need to be happy with what you decide. If I ever thought my 260 wasn't enough the 6.5x284 or possibly the new 6.5 PRC would be intriguing. 260 AI oughtta be about equal to both of em huh?
Ping pong balls for the win.
Once you've wrestled everything else in life is easy. Dan Gable
I keep my circle small, I’d rather have 4 quarters than 100 pennies.
Ain’t easy havin pals.
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Joined: Jan 2010
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Campfire Tracker
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Campfire Tracker
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I have 2 very similar 260 AI's One with 22' Brux and one with a 23" Rock. They are a couple of my favorite rifles. I shoot the same load in each and shoot 123 Scenar's or 123 SST's at 3087 and 3090 fps.Great cartridge in my opinion.
I think goat called it pretty close but I have a standard 260 with a 24" barrel and about the best I can do with that rifle is 3K with a 120 BT. For the life of me I can't really tell ANY difference in the field but I like AI's and these were custom barrels, It cost no more to cut that chamber rather than Saami chambers.
On a positive note I have not had to trim a case fired out of either of the AI's yet
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Campfire Outfitter
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Campfire Outfitter
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I don't have an opinion, but I do have first hand experience with both the 260 Ackley and the 6.5x284. If you have the the magazine length I would go with the 284 case and depending on twist, 1/9 I am guessing, then shoot 130's. 140 VLD's didn't fly that great in the 1/9 twist but 140 Partitions did just fine. The Ackley will get you 3,000 with the 130 and the 284 case will get you 3,100 with 130's 140's at 2,900 and 3,000 mv. You can get those speeds with a 22" barrel in either cartridge if you decide to just re chamber. I think it's worth it to go with 284 case, going Ackley not so much unless you just have to have one. I personally would open up the bolt face and go 6.5 RPC and a 1/7 twist to shoot 147's at I would suspect 2,950. 24" barrel.
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Campfire Kahuna
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Campfire Kahuna
Joined: Jul 2001
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One of the problems with almost AI cases is there's no real pressure-tested data for any of them--except the .280 Ackley Improved, which was thoroughly tested when approved by SAAMI.
About half the reason for the .280 AI's velocity advantage over the standard .280 Remington is its higher SAAMI Maximum Average Pressure of 65,000 PSI, while the .280's MAP is 60,000 PSI. Higher pressure is also the reason for probably AT LEAST half of velocity gains in any Ackley Improved round. Since there isn't any pressure-tested data for most, handloaders primarily use the old stand-by method of adding powder until "pressure signs" appear, then backing off a little.
The trouble with this method is pressure signs often don't appear until around 70,000 PSI, and sometimes not even then. Now, many handloaders have used this method for decades without any problems, but SAAMI prefers to err on the safe side, the reason the highest MAP for any round they list if 65,000 PSI. This is because pressures are NOT constant; instead they can vary due to more than one factor, but most especially temperature.
Working up loads in an AI round without any real knowledge of what the pressure might be not only tends to result in much higher velocity gains than would result IF pressures were the same as the "parent" cartridge, but can result in surprises in warmer temperatures.
I know this partly through the help of a couple of piezo pressure labs (not some handloader who owns a strain-gauge set-up), and partly because I've owned a number of AI rifles. In every instance I was able to come within less than 100 fps of the velocities of the AI round when loading the standard round via "pressure signs"
The least amount of powder capacity gain in AI rounds is with cartridges that have little taper to the case body, because other than the shoulder there's no much to be blown out. Probably the most useless common Ackley Improved Round is the .35 Whelen AI, because the shoulder is so small it only gains about 6% in powder room--meaning about 1.5% in potential velocity when loaded to the same pressure. With 250-grain bullets this amount to less than 40 fps. Yet .35 Whelen AI fans often report gains of 100-150 fps. Guess why?
Back when I shot a .257 Roberts Ackley Improved for a few years, my standard loads got around 3300 fps with 100-grain bullets and 3100 with 115's, from a 24" barrel, both about 100 fps faster than the standard .257 loaded warmly in a 24" barrel. I couldn't notice any trajectory difference in the field over the standard .257, and of course none in "killing power." Now, this was back before we started twirling elevation knobs and all the associated stuff, so I rarely shot anything beyond 400 yards, but at 400 another 100 fps of muzzle velocity results in a trajectory 2 inches flatter at 400 with the 115 Partition.
The sharper shoulder did result in just about zero case-stretching, which is the only real advantage I've seen in any AI case. The biggest disadvantage was reduced resale value of rifles, partly because I usually had to throw in the dies, which sometimes (though not always) cost more than standard dies for the parent case.
Of course, some shooters just prefer having a rifle chambered for a non-standard round. If that, plus less case stretch, works for you, then by all means go for it. Hell, despite the unimpressive gains I've seen from improved cases, I still own two rifles chambered for improved rounds, a .22 K-Hornet and .280 AI. They go bang a kill stuff, but I do know the gains aren't significant over the parent rounds.
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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Campfire 'Bwana
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Campfire 'Bwana
Joined: Dec 2002
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Joined: Jun 2010
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Campfire Outfitter
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Campfire Outfitter
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One of the problems with almost AI cases is there's no real pressure-tested data for any of them--except the .280 Ackley Improved, which was thoroughly tested when approved by SAAMI.
About half the reason for the .280 AI's velocity advantage over the standard .280 Remington is its higher SAAMI Maximum Average Pressure of 65,000 PSI, while the .280's MAP is 60,000 PSI. Higher pressure is also the reason for probably AT LEAST half of velocity gains in any Ackley Improved round. Since there isn't any pressure-tested data for most, handloaders primarily use the old stand-by method of adding powder until "pressure signs" appear, then backing off a little.
The trouble with this method is pressure signs often don't appear until around 70,000 PSI, and sometimes not even then. Now, many handloaders have used this method for decades without any problems, but SAAMI prefers to err on the safe side, the reason the highest MAP for any round they list if 65,000 PSI. This is because pressures are NOT constant; instead they can vary due to more than one factor, but most especially temperature.
Working up loads in an AI round without any real knowledge of what the pressure might be not only tends to result in much higher velocity gains than would result IF pressures were the same as the "parent" cartridge, but can result in surprises in warmer temperatures.
I know this partly through the help of a couple of piezo pressure labs (not some handloader who owns a strain-gauge set-up), and partly because I've owned a number of AI rifles. In every instance I was able to come within less than 100 fps of the velocities of the AI round when loading the standard round via "pressure signs"
The least amount of powder capacity gain in AI rounds is with cartridges that have little taper to the case body, because other than the shoulder there's no much to be blown out. Probably the most useless common Ackley Improved Round is the .35 Whelen AI, because the shoulder is so small it only gains about 6% in powder room--meaning about 1.5% in potential velocity when loaded to the same pressure. With 250-grain bullets this amount to less than 40 fps. Yet .35 Whelen AI fans often report gains of 100-150 fps. Guess why?
Back when I shot a .257 Roberts Ackley Improved for a few years, my standard loads got around 3300 fps with 100-grain bullets and 3100 with 115's, from a 24" barrel, both about 100 fps faster than the standard .257 loaded warmly in a 24" barrel. I couldn't notice any trajectory difference in the field over the standard .257, and of course none in "killing power." Now, this was back before we started twirling elevation knobs and all the associated stuff, so I rarely shot anything beyond 400 yards, but at 400 another 100 fps of muzzle velocity results in a trajectory 2 inches flatter at 400 with the 115 Partition.
The sharper shoulder did result in just about zero case-stretching, which is the only real advantage I've seen in any AI case. The biggest disadvantage was reduced resale value of rifles, partly because I usually had to throw in the dies, which sometimes (though not always) cost more than standard dies for the parent case.
Of course, some shooters just prefer having a rifle chambered for a non-standard round. If that, plus less case stretch, works for you, then by all means go for it. Hell, despite the unimpressive gains I've seen from improved cases, I still own two rifles chambered for improved rounds, a .22 K-Hornet and .280 AI. They go bang a kill stuff, but I do know the gains aren't significant over the parent rounds. This answered all my questions about AI'd cartridges and in a few paragraphs to boot!
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Joined: Jan 2009
Posts: 8,891
Campfire Outfitter
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Campfire Outfitter
Joined: Jan 2009
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I've never really understood the "less trimming" argument. Some guys will spend weeks at their reloading bench, making the perfectly tuned load, and when they're not reloading they're talking about reloading, whether on the internet or in real life. Then when it comes time to trim brass and spend a little more time at a hobby they obviously enjoy, the task suddenly becomes a lot of work and they'd rather be anywhere else.
This may get me run off the board, but I kind of enjoy trimming brass. With a round I'm loading in low quantity, the twenty minutes once every two years I spend trimming brass isn't going to cut too heavily into my schedule. Sure it sucks when I've got 1000 cases to trim for a varmint rifle, but the rest of the steps to load 1000 cases get monotonous as well, not just trimming. So I break it down and do a percentage of the total at a time, and don't try to overwhelm myself by doing them all at once. Also with cartridges I load in bulk, a WFT Trimmer really cuts down on the time spent trimming.
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Joined: Jun 2006
Posts: 45,993
Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2006
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I've never really understood the "less trimming" argument. IMO it's less of an argument than an oft-repeated chestnut.
A wise man is frequently humbled.
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Joined: Jan 2001
Posts: 28,364
Campfire Ranger
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Campfire Ranger
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Posts: 28,364 |
...This may get me run off the board, but I kind of enjoy trimming brass... Get thee gone and never darken this forum again!  With new tools like the WFT trimming isn't quite the chore it used to be, but be that as it may the lack of trimming for AI rounds is a reality. I recently retired a batch of .243 AI brass which had been fired 25 times. I had trimmed them at 1X to .01" under max length and 24 firings later they had only stretched about .005" on average, about .004-.006 actual measurements. i.e. they never needed trimming over their useful life. OTOH I have some .25-06 brass trimmed to 2.484" after the first firing, but with that 17 degree shoulder after 9 more firings they had stretched to about 2.504 - 2.509", some .01 to .015" OVER the max length which was a real negligent boo-boo on my part. But interpolating from that one can assume they had stretched to max length in about 4-5 firings, and that was with neck-sizing only and bumping the shoulder .002" once.
Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
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Campfire Kahuna
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Campfire Kahuna
Joined: Jul 2001
Posts: 60,052 |
The less-trimming argument is often made by guys who use the .223 AI for prairie dog shooting.
The .17 Hornet and .204 Ruger are the two centerfires I so mostly of my PD shooting with anymore, though usually throw in several other rifles anyway, like my Ruger 1B .22 Hornet, a fast-twist .223, or whatever else needs shooting. (This year it was a heavyweight 6XC.) The .17 Hornet .204 don't stretch much either when neck-sized, and when they do need a little trim I used a Gracey power trimmer that trims and chamfers in one operation, at a rate of 15-20 cases a minute, depending on how much I want to hurry. Which means I can do 1000 in about an hour.
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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Campfire Outfitter
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Campfire Outfitter
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The less-trimming argument is often made by guys who use the .223 AI for prairie dog shooting.
I think it's most often used by guys on the internet to promote the church of the almighty Ackley Improved. "No trimming" is the AI church's mantra.
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Posts: 30,725
Campfire 'Bwana
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Campfire 'Bwana
Joined: Jan 2001
Posts: 30,725 |
built one about 14 yrs ago.....Pac Nor on a Salvage action...... dies then were a PIA.....had Lee build me a set then.......have since sold..... my LR is now a 6.5x55......Pac Nor/Salvage......the new Hornady 6.5PRC looks interesting....... http://bulletin.accurateshooter.com/2017/10/new-hornady-6-5-prc-precision-rifle-cartridge/
T R U M P W O N !
U L T R A M A G A !
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Campfire Tracker
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Campfire Tracker
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MD pretty well summed up the AI thing. I am still tempted to do a 6.5x55 AI as this is one that gains about 10-12 percent over the parent case but the 6.5x284 is more practical and there are many others in the mid to magnum range to consider too. Just did a 6mm AI because I was starting from scratch and it is another case with a fair amount of taper. But my loads are usually only one to three grains more powder than the standard for about 100-130 fps gains. Best reason to go AI is if you like to tinker with rifles and want to shoot more. Fire forming is just more practice to me so not a chore.
Last edited by Tejano; 01/13/18.
"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli
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