I got some decisions to make.. I searched the forums, but just seemed to come up with more doubts.. Specially when some folks mention head space issues after re-chambering..

Mike..the more you read and listen...the more confused you get!!..I'm considering a 280ai also

Had a 280al by big name maker, sold it after about 1 year, just not worth it. There have been about a dozen in my hunting club over the years but no one has 1 now.

I don't think that the gain is worth the effort.

The .280 AI is a great cartridge. These days where (Nosler) factory brass is available, there is strictly no need to go through the hassle of fireforming brass - with associated barrel wear etc. So, these days, the .280 AI is a much more sensible proposition.

If you have to rely on fireforming brass (which for me also included the necessity of annealing the brass to get hardening issues resolved), then you have to ask yourself whether a possible gain of about 100-150 fps is worth the extra work, barrel wear, added expense and decrease in resale value.

- mike

Well let me start by saying I have a 280 wildcat and it will be going with me to Africa in May. Then my second thought is if you want an AI then go for it. At equal pressure don't expect much of a gain.

Around 1980 I took a 280 to 280RCBS to 280AI to 7mmJRS and finally my 280PDK. I used a strain guage to allow me to keep equal pressure. In the 280 case as I increased the capacity at EQUAL pressure I got a 1% velocity for each 4% increase in capacity(assuming I could find a powder that allowed me to use it). So for the 280AI it was about a 1% velocity or 25-30FPS.

Most of the gain you see shown for an AI is pressure. Factory 280 is loaded to 60,000 at best compared to 65,000 for the 270. Increasing the pressure from 60to65,000 will give you 75-100fps. So added together its 30+100=130fps. To try and achieve some of the velocity gains I'd read about I was way past 70,000. Also often the "pressure signs" didn't show up to way past 70,000 as well.

As to the saving trmming. When you form an AI the case will shorten about .05" so you gain several firing before you must trim again. I shorten my factory case by that much to start during prep and get numerous firings before trimming again.

The 280 is a great underloaded factory round. Load it up. If you simply want a wildcat the the AI gives you something to talk about and looks great. If you want the max gain from a 280 case then consider the Hawke, Gibbs or AHR.

My case gives me an 11.4% volume increase over factory compared to a 4% from an AI. At equal pressure I gain between 80-100fps. Yep my case allowed me to match and beat some of the "factory" 7rem mag loading I tried. But not my handloaded 7mags. You simply have to burn a lot more poweder for small velocity gains. Check out a 6.5x55 to a 6.5-06 to a 264mag or a 308 to 30-06. Large increases in powder to achieve a small increase in velocity.

Very good analysis Paul.

IMO, not worth the cost of rechambering. If I were putting a new barrel on a rifle, why not. The only extra cost would be dies. There just isn't that much vel. gain. I can get 2850fps w/ 160gr bullets out of my 23" bbl. 280 w/o melting anything.
I've got about 700rds through a 260ai. I love the round but I am only getting about 75fps over the parent 260 case. If you just have to have one, go for it, just don't expect to be shooting a 7mag.

Whether or not an AI chambering is "worth it" is something that only the owner can say. The 280 is a fantastic cartridge on its own, the gains of going AI with one will vary from rifle to rifle.

These are some of the facts;

- Any AI chambering with "headspace issues" was not properly done by the gunsmith.

- There are typically some gains in velocity without increasing pressure because of the slightly larger case capacity, however the minimal taper reduces bolt thrust and does allow slightly higher pressures to be used safley. The maximum gains of an AI chambering are a culmination of both of these factors combined and as mentioned will vary with each rifle. Sometimes gains @ "safe pressures are only 50 fs or less, sometimes its much more. Know your gun and its limitations and always load safley..

- the sharp shoulder reduces brass flow and thus extends the life of your brass.

- Some chamberings respond better to the "improved" approach than others. Typically those with low case capacity and lots of taper gain the most.


My AI is a 257 and it is a fantastic round, I get 25-06 velocities from it but I figure I have a "fast bbl". Not all of them gain that much. Ive considered the 280 AI as well but havent done it yet. If one gains only 100 fs then you will be kissing 7mm Mag territory with considerably less powder, not a bad proposition IMO.

Thanks Guy's.. Decision made.. Going to stay original 280.

Paul, you really out did yourself, Thanks for your detailed explanation..

Probably a good choice. I don't knock anyone's choice of chambering and actually think that all of them are quite interesting but, I just haven't ever been on the AI wagon I guess. The only actual advantages I personally feel they offer is slightly less triming. The velcoity gain is often small and can be closely matched in the originals when pressures are at the same level. Might as well get the 7RM if you want a little more gain and if you don't like the belt have a SAUM built....

Good Luck

Reloader

My dad built a 280AI on a Ruger M77, and it was the biggest pain in the ass for what amounted to no significant reward. Sure, the case holds more powder and gets better velocity, but 100fps is, IMO, not worth the hassle and $$ of fireforming brass, rechambering a rifle, and working up all the loads. Now, that process may have gotten a little easier with the invention of Nosler Custom brass already made, but the availability is still a problem.

I guess the claim to fame is that it produces near 7mm Remington mag performance with less powder, but you know what else gets that kind of performance...a 7mm Rem mag!

The extra effort and cost just doesn't do it for me on ANY AI caliber, not just the 280. Too many other cartridges do what they do but are readily available and less of a pain to load.

Personally i would not AI "this" case even though i own some imp rifles... I'm of the opinion if you really "think" you need more than a std. 280 then start out with a 7 Rem. mag. in the first place...

Just the option of NOT being able to get common factory loads would stop me, and i haven't fired a factory load for big game hunting in over 25 years... In fact 95% of the cartridges i hunt with are difficult at "best" to buy factory loads for, but i still think "that" option is more important than a bit more than 100 FPS...

DM

quote:

Thanks Guy's.. Decision made.. Going to stay original 280.

Paul, you really out did yourself, Thanks for your detailed explanation..

I've share my experience before. Just glad the brain was still working this morning. A 280 loaded to around 65,000 is just hard to beat.

Been there done that. Life is much simpliar with the original 280 Rem.

I started with a 257 AI. Then I got out of control with blowing out and improving carts! The craziest thing I've done was a 378 Improved. Then there was various 375 AI's. I still own the 257, but the rest are gone. If you need faster. Get a bigger case. However if you really want a lot faster then the 280, the STW or RUM are the speed demons. Everything else is within reach and not much flatter.

Ok... Not trying to kick a dead horse here, but would these same issues be the rule for the 6.5X55AI??.. The drawback for the 280 Rem is the obvious lack of "bang for the buck" or not worth the p.i.a for the minimum returns.. reason I ask is I have a push feed M70 that could use a new lease on life..

Thanks guy's

The 6.5x55 in a M70 would be a powerful little beast with judicious handloads. More oomph would be the 6.5-284 or the 6.5-06.

quote:

Originally posted by .366torque:
The 6.5x55 in a M70 would be a powerful little beast with judicious handloads. More oomph would be the 6.5-284 or the 6.5-06.

Hmmm.. No, I don't really want to step that deep onto the slippery slope.. I like the idea of being able to shoot factory ammo...

Should I bump this last question over to the Small Bore Forum??

Hey Mike

I just recently got a 280AI with a 26" barrel 1 in 9 twist from Hart on a Sako 75 action. I sent them a dummy case with a 160 gr Accubond seated to have a little clearance in the mag and asked them to make it kiss the lands. They hit it righ on the money. The action was squared and lugs lapped at Hart and the rifle came back ready to shoot



I have fired 125 rounds through as of yesterday. I have been shooting the 160 gr Accubond and RL22. This last session I was checking different seating depths so I shot 25 loads of 60.8 gr RL22 and the average was 2996 fps.

Since my goal was to have a .284 caliber that would push the 160 gr Accubond at 3000 fps, I think I have arrived. I don't think I would have got there with the 280 rem. There are no pressure signs and I am on my 5th loading of that brass.

I am using the Nosler brass and it is no different than loading for any other caliber.

It shoots pretty good. Next I am going to try different primers

No! It is not worth it.

quote:

Ok... Not trying to kick a dead horse here, but would these same issues be the rule for the 6.5X55AI??..

I've done a lot of testing the various AIs over the years. The gains will be around 1 for 4. A little more for the greater taper a little less for the non tapered. Key thing is the max pressure for the 6.5x55 was around 48,000 I believe. Same reason the 257R shows hure gains factory is 51,000 handloaded 257RAI 60,000 plus If you load it to around 60,000 it gives up very little Example the Nosler #4 lists the follwoing max for the 120gr.
6.5x55 3002 using 48.5grs
6.5-06 3144 using 57.5grs
264mag 3202 using 62grs
Looking as similiar powders and not using the huge real slow load in the 264.

So between the first two that is 4.7% velocity gain for 18.5% increase in powder that is 1 for 3.9. Between the 06 & 264 it is 1.8% from a 7.8% or 1 for 4.33.

So assume the 6.5x55 is better than the jump from to 6.5-06 and call it a 1 for 3. The AI gain will be a little less than for the 257 since it has less taper so call it 6% that gives you 2% velocity or 60FPS.

In my opinion for the velocity gain the AI never makes sense. If you want one or are starting from scratch go for it. The actual velocity gains will never be much from capacity.

The 6.5X284 would be close to the 6.5-06 if the bullet can be seated out.

Paul,

Once again your voice of reason confirmed what I suspected based on your earlier post regarding the 280.. No free lunches.. Not even on the 6.5

Thanks All

Woods,

If it's the Hart Rifle barrel folks in upstate NY.....it ought to shoot.... as the .280 AI is what PJ Hart uses out here on deer and elk. They have them figured out pretty well.

He did a .257 Robt's AI for me a few years ago. Also have a 26" .280 AI on a Rem 700 action. Yeah a guy could just buy a .25-06 or a 7mm Mag....but those AI rds are SO sexy looking.

FN in MT

The improved cartridges are most definatly some sexy cases. They are cool to show off. Fun to put together too. In reality, almost any improved case can be replicated or even out performed with a standard chambering. When most of the improved cases were developed there was not much available that could match their performance. So they were filling a niche. Now that has changed so the niche has been filled with standard cases.

woods, try those accubonds seated just to touch the lands, by the looks of it, your rifle might like it like mine likes accubonds. seated to touch the lands is the only way to feed em

I own 3 7mm/08's, chrono 140gr at 2960 fps in a 21" bbl. That is all I want with that weight 7mm.

My first rifle in college, a Rem 700 adl Stainless barrel/iron coating, shot 160 Sierra's wonderfully at about 2860 or so, backed off a few grains off max, oh, it was 7mm MAGNUM, and I had no desire to push it more, due to recoil, bbl was 24" I believe.

I think a shooter with an accurate 280 has little to gain in actual PBR in the field by improving. It IS a good cartridge, but I might just do a 7mm WSM before improving a 280.

Really for me, beyond a 7mm/08 and 6.5x55, I would go up to a 338/06 because I would be wanting something for larger game, and preferring a larger bullet.

A 270 or 7mm WSM, 300 WSM, or 6.5/284 would appeal to me more, but its a preference thing.

Yes, the above will likely kick more, be louder, etc, but the gain in performance might be measurable in an accurate rifle fired by one who can do so w/o flinching, and in a decent rifle i.e. some heft, a good recoil pad, a little range time spread out should get one comfortable using a cartridge that I believe would give a noticable improvement over the 280. The AI seems like it gave a lot of work to custom gunbuilders, but back to the poster above, ask yourself, is 100-150fps really going to give you an incremental gain worth the hassle? An accurate 280, with 24-26" and the right powder/load combo is no slouch and I really doubt one would miss or wound an animal in the field vs not having an extra few fps.

That is my .02

That said, I have nothing against those owning and enjoying 280 AI's. I just think one needs to give some thought to what they want to accomplish and the ease, or lack of in getting there.

I agree that AI ctg's do look good, no doubt, but I like the 6.5x55 also. Some former 6.5/284 users realize that their accuracy loads (at best velocity with given bullet) are not much more than a good load in a 6.5x55 in a say 26" barrel which is what many might use in a 6.5/284. Adding 4 inches bbl gives the velocity, w/o changing the case.

I spoke with a man once who used custom 26-28" bbls in std 270 and 280 rounds. Very happy, he had his gains by just adding a little barrel. Some don't mind it at all, others like me settle for a faster handling shorter bbl, but using a longer bbl is free gain and no hassle way to giving you that AI difference over std version in std length bbl.

Back to the 6.5x55, take it, run a 140 in a 24-26" with top loads and see what you get.......more than many think, just look at the charts. Oh, nice recoil and barrel life, heck a 270 and 280 standard are not too much more recoil with same wt. bullets.

If building a 280 is your choice, I'd go with a 26" if you are doing a long range deer rifle and use std chamber.

You mention rechamber, and I hear simply running the reamer in does not give you a 'crush fit' and causes problems. I was told, you must take barrel off, cut shank, then rechamber to proper headspace. If you have a 280 now, I would not rechamber it, for many reasons.

Good luck finding what you need.

Ya got to admit that having something differant than the other guys is kind of kool.Thats 75% of why I did it.

Update



I like mine!

If your looking for an excuse to own a Imp 280 then do it. The 280 Imp. is a nice caliber and case life may be an advantage.

As to the difference, not a lot and a deer, elk or whatever will not know the difference nor will you be able to hit them at longer range than you would with a std .280.

Is it worth the extra cost, not for a conversion in my opine, but if building a new rifle then maybe.

If you like to tinker, fireform and all that, then its fun to own.

Resale is less.

I sure like my ULA 280AI and here is another site http://www.jarrettrifles.com/280AckleyImproved.html

I am getting 3000fps with a 140gr pill through an 8 twist 26" PacNor in 6.5x55AI. My pockets last just fine and not even near a sticky bolt or cratered primers. I don't recall the gr. increase in H20, but it was significantly more than most AI's. It is something like only a few grains less than a 6.5x284 after forming.

I do notice one thing about ackleys, they allow the use of slower powders than the parent. I have succesfully gone with H1000 and RL25 in the 6.5-06AI and a 140gr a-max.

chamber your rig in whatever tickles your fancy,..but the barrel life issue has always been a mute point. The Ackley allows the load ladder to be run during fireforming, and has always come out very close to finished during forming for me. Maybe 3 loads need testing after that, and one is usually the accuracy node. Now Nosler makes brass,..so even more easy. No need to justify, just need to have fun with it.

FWIW, Nosler selling 280AI brass has eliminated all the "is it worth it arguments" for me.

Apparently ammo will be available next. The AI will be SAAMI speced to higher pressure than the standard 280--an issue that has always dogged an otherwise great cartridge.

If one of the larger rifle manufacturers starts chambering for it, I think the odds favor the 280AI at becoming THE 280 cartridge and the standard 280 will be a whole lot less popular than it is now. Guys like speed--like the WSM over the SAUM.

But you can always have your 280 set back and rechambered...

My AIs have picked up 75fps with a 175g Partition over my 280s loaded to about the same pressure--as evidenced by primer pocket life in Winchester brass. With a 200 yard zero that puts it just about the same spot at 300 yards as my 280 throws throws the 160 Partition.

Not much, but enough for me.