Why is the 280AI almost revered?

[Dave Hoback]

I just ordered a new barrel. And I stuck to exactly what I said I would do. It’s getting chambered in 260AI with a .160” Freebore, what they call the “Match or VLD” chamber. This is so I can load them 2.900”+ COAL. Now I decided I would do this long ago. Probably a year AFTER getting my current Shilen barrel in standard 260Rem, & wishing I had done Ackley Improved from the beginning. Through these years, I never changed my mind. (I usually don’t, because my research is sound on what I want.), although I have taken note of many talking down the 260AI. Saying it’s not worth it..better to stick with the 260Rem. And the most popular rant, “switch to the 6.5 Creedmoor.” (Riiight… like that would ever happen! Right… switch to a LESS powerful cartridge. Although, somehow the Creedmoor has managed to “magically” increase velocity by doing absolutely nothing! Somehow loads that were doing around 2700fps 5 years ago, are now claimed to be going 2900fps+++ by on-liners..) So anyway, moving on. At the same time though, praise for the 280AI is everywhere! It’s almost heralded as a great upgrade to 280Rem. I’m just wondering why? Why does a person say “Yes! Absolutely switch from 280Rem to 280AI.”, but in the same breath will say, “NO! Forget the 260AI.. not worth it.” It doesn’t make sense to me. Obviously I know they are different calibers & cartridges. But the performance gains between the two are almost identical. So anyone feel only the one is worth it?

BTW: This is simply a talking point. Obviously I’m not changing my mind, and I’m certainly not trying to change anyone else’s. I genuinely would like to hear a credible reason for one being ok. Because it does seem like bias thinking; which is fine… we’re allowed to have biases towards THINGS. I certainly do.
So do some feel only the one is worth it?

[Txhillbilly]

Some cartridges really are better when Ackley Improved, and the 280 is one of them. Plus, You can buy factory ammo for the 280 AI, and most that shoot the cartridge are hunter's that may or may not reload.
Several years ago, I built a 260 AI with one of my Savage actions. I wasn't impressed with the small gains I had over what I get out of my 260 Remington LR 10. After a few range trips, I took the barrel off the action and sold the barrel, dies, and brass.
I know several guy's that swear by their Ackley Improved 223's & 7mm-08's as well as the 260 Remington, but to me it just isn't worth all the trouble for the small gains in velocity that you get.

Dave, there's a good reason that guy's like myself have gotten vast improvements in velocity with the 6.5 CM cartridge. It's called " Quality Brass"!
Hornady brass always sucked. The large primer pocket brass from Hornady usually wouldn't last past 2-3 mild loads before the primer pockets were shot, and the primers would fall out.
Now that we have Lapua, Starline, Peterson, and Alpha small primer brass, we can push the limit a lot easier, and get higher velocities while still being at safe pressure limits.
I have no problem hitting 2900+ fps using Lapua and Starline SRP brass, but the load that I stay with is the the 2880 fps range.

[charlie b]

The AI thing is cartridge dependent for a lot of reasons. Not sure what the case differences are from .280 and .260 (other than neck dia). Or what the AI dimension change is. Usually it means less taper and the 40deg shoulder, which means more case capacity and longer case life. Some cases are already 'overbore' a bit and the extra case volume results in little gain. The last may be the reason the 260AI is not as popular compared to the 280AI?

I think it depends more on what people do with it. Do they expect to make a sluggish cartridge a barn burner? Or maybe the factory twist won't let them 'use' the extra case capacity to it's full potential?

The CM is one of those interesting ones. Designed for short actions and then hyped up. But, it remains as a pretty efficient cartridge, which usually means better accuracy. Yes, the 260 and 6.5x55 work well for higher velocity and many accurate rifles were produced for them. I was considering a 6CM when I was looking for a 6mm cartridge. It is not too overbore to ruin barrel life, but, it has enough capacity to go over 3000fps with the heavy bullets. Interesting enough, I went the other way with a plain 6BR. The extra velocity made no difference for my use and the extra long barrel life appealed to me.

I do agree that many have a 6.5CM for very wrong reasons, expecting it to take down elk or moose with 'magical' performance. OTOH, there are those in the accuracy game who like the niche the 6.5CM fits in. And whatever you or I think about the cartridge, the various rifle manufacturers had stepped up with premium rifles in that caliber. Several folks at our long range shooting site like their 6.5CM's for the 1000yd performance out of factory rifles. For some it was the first time they moved from the .308 to something else.

[wbm]

The large primer pocket brass from Hornady usually wouldn't last past 2-3 mild loads before the primer pockets were shot, and the primers would fall out.

Has not been my experience at all. I am on 5-6 loads on Hornady brass. So far no issues.

[PhilC]

The 280AI very nearly replicates the 7RM with less powder, lower recoil, and negates the need for belted magnum brass. In most rilfes, the '06 size case nets an additional round in the magazine vs belted magnums too. What's not to like?

[Txhillbilly]

Has not been my experience at all. I am on 5-6 loads on Hornady brass. So far no issues.

I built my first 6.5 CM back in 2009. The only brass available back then was Hornady, and it was horrible when it came to the primer pockets expanding with anything loaded near the top of the powder charge range. There was also the same problem for guy's that bought Hornady factory ammo, and many complained to Hornady about not being able to reload once fired cases because they wouldn't hold a primer.

If you like it, good for you. I'll stick with loading quality brass that I know will give me longevity.

[Robinhood]

I like cartridges that serve a purpose. if you want to shoot prs, go to a prs match and see what the top guys are running and determine if that fits your budget and needs. Want to shoot belly benchrest? Go to a match and observe what is winning. Go to a RMEF Convention and ask someone what they would consider a good rifle for the type of hunt you are going on. The rifle makers and the experts don't choose a cartridge for cool factor. They choose what works.

The current top 7 pro PRS shooters utilize a 6 Dasher. Number 8 uses a 6.5 Creedmoor.

The 280 is a great round as is the 284. Loaded heavy is good medicine. The 280 AI is just better, for reasons mentioned. It is a lot of energy in a smaller package.


As for the 260 AI

You will rarely see ten 260 AI's at a match. You will see many 6BR's or their variants. You will see a variety of 6's and 6.5's. 260's or 260 AI's....not often. You will see guys shooting 6 and 6.5 Creedmoors.

I like the 260. I like the sound of a 260AI. I just don't need it. It fits a niche that does not exist in my life. It obviously suits your needs. I say perfect choice.

But so is the Sweede or the 280.

[wbm]

As for the 260. AI I like the 260. I like the sound of a 260AI. I just don't need it.

A lot of us felt the same way about the 260 when it first came out...after a while people started thinking 260AI...then the CM came out and as one gun guru said "ah the 260 done right"...bought my first CM in 2010 and have built a few since. But ya know I really wish I had done at least one 260.

[Robinhood]

A lot of us felt the same way about the 260 when it first came out...after a while people started thinking 260AI...then the CM came out and as one gun guru said "ah the 260 done right"...bought my first CM in 2010 and have built a few since. But ya know I really wish I had done at least one 260.

I was in the same boat. I kept blowing out the primer pockets with mild loads in my 260. Got more speed out of a properly chambered 6.5 Creedmoor barrel.

[Whynot]

The 30-06 family of cases have features that make them a good choice for improving- and the 280 does it nicely- and comes out with a very good end product. It is the only improved cartridge (that I am aware of) you can buy off the shelf and locally has many more ammo choices that the regular 280.

As far as the sudden found speed of the 6.5 CM..... it is over pressure-- WAY overpressure. Quality brass came out that was able to handle/hide the results of that pressure- some powder developments as well-

A company with the equipment to test pressure tested the loads they found on the internet -- duplicating the brass/primer/powder/bullet and found that many of the "safe" loads are well in the 70,000 psi (and higher).

[Dave Hoback]

Sorry, I didn’t mean for this to go into the 6.5 CM, but yes Whynot, it’s overpressure. The thing with overpressure and everything looking “good”, is it can fire time after time with no problems. And then, without any warning… KABOOM! Just nature of the beast. This is why just about every manufacturer loading 6.5CM has 140 class weight bullets, the bulk of which at 2650-2710fps. With a few lower & few higher.

My intention was understanding the thinking which makes 280AI great & 260AI not. They are both in that area of only like 4.5-6% performance increase over their standard counterpart. (280 being slightly better) I can understand that simply having some factory loadings in 280AI is pretty huge. I guess I’m more wondering why that was decided. Really over any other AI’s. Why was only 280AI chosen by several manufacturers to load for?

[wbm]

As far as the sudden found speed of the 6.5 CM..... it is over pressure-- WAY overpressure. Quality brass came out that was able to handle/hide the results of that pressure- some powder developments as well

Exactly! +1

My intention was understanding the thinking which makes 280AI great & 260AI not. They are both in that area of only like 4.5-6% performance increase over their standard counterpart. (280 being slightly better) I can understand that simply having some factory loadings in 280AI is pretty huge.

I think over the decades that AI became synonymous with "always better" rather than look and see.

[Robinhood]

SAAMI suggested pressure for the 260 Rem is 60,000 psi with a 6 grove barrel and a 1-9 twist
SAAMI suggested pressure for the 6.5 Creedmoor is 62,000 psi with a 6 groove barrel and a 1-8 twist.

Like I have said before. Chambers, freebore etc can effect pressure. The 260 I had spun was a Sammi spec reamer(probably designed for a 120 bullet.) therefore the 140's I shot where smoking primer pockets at a low velocity. The first 6.5 creedmoor I had, shot/shoots faster with less pressure. Both barrels were chambered by the same smith. So there is sudden found speed if you have and understand the data. This is where been there done that pays off.

Plenty of guys are running 175 or 185 class 308 Bullets with 43.5 grains of varget, 4064 or VV powders. Way over book loads. How many FTR guns have you heard of going KABOOM! The safety margin is designed in and target shooters push the limits all the time.

[Reloder 43]

Dave Hoback, you have asked an interesting question about the "why the 280 Rem AI gets more praise than the 260 Rem AI", or words to that effect. I don't have solid answers, but a couple of ideas to kick around and maybe one of them may sound plausible. Maybe not, but food for thought.

Are you shooting targets or hunting with your rifle?

You have avoided some problems for your 260 AI by loading a heavy-for-caliber (better sectional density) streamlined VLD bullet. You have a magazine long enough to seat it out to 2.90" and more, and you probably specified a faster twist rate than the original Rem M 700's 1/9 to stabilize the VLD. The long-seated bullets gives you more usable powder space, so slower powders can be efficiently used and I imagine that a longer barrel was chosen to allow for a generous expansion ratio. Lots of good things going on in your design unless my understanding of ballistics is not valid after all these years.

Remington made the 260 in their M 700 with a 24" barrel and then the Model 7, with a short 18.5" barrel that seemed to handicap the cartridge from the start. The 260 AI makes sense with longer COAL loads in longer actions and longer barrels, but would not in the Model 7. The same thing happened with the 6 mm Rem when they stuck it in the Mohawk, but that didn't stop me from buying one for my petite wife. It is still light weight, handy, has low recoil and enough energy for our deer and antelope hunts. The 260 has just about been benched by the 6.5 CM; the 260 broke the ice for the American 6.5 developments, but didn't get the popularity crown it deserved.

The 280 Remington AI gets about 7.7% more velocity with the 140 g bullet than the regular 280 according to a a comparison chart I found, author unknown. (Stats for the 260 AI were not mentioned). I was interested in splitting the difference between my 30-06 with 180s and a 7 X 57 with 140s. Both rifles have killed elk for me, but I thought about it long enough that a M 700 25-06 showed up in a local gun store rack and followed me home. The 30-06 brass was the parent case for the 280 and the AI version, but really good brass was being produced with the 280 head stamp, so it was an easy conversion. Feeding from the magazine was the same for the 30-6, the 25-06 and the 280 AI (originally called the 7 mm-06) because the cases were the same, just necked differently. I don't think it is prudent to push limits of velocity or pressure, so I don't pretend that it is almost a 7 mm Rem Magnum. I think the 280 AI is more appropriately compared to the 30-06, and the major improvement over that century-plus-old cartridge is that the SAAMI specifications allow for higher pressure levels in newer rifles, with a slight additional advantage of higher BC for 7 mm bullets in the same weight class. The choices of longer barrels, slower powders and better brass are here. The 7 mm Rem Magnum is the winner for those same reasons, also.

Why the 280 AI became popular probably includes some marketing hustle and the appeal of having something different that is easily obtained. Nosler jumped right in early, including load data in their manuals and producing quality brass with the correct head stamp, rejuvenating the old 280 Rem round. Remington provided gun writers and magazine publishers with fresh products, and the timing seemed to be about right for a "new" cartridge. Die makers didn't have to do much to retool and add this to their catalog, good bullets and powders were plentiful. . . Ah, yes, the good old days, almost like when the 270 Winchester was introduced, or when the Varminter went public as the 22-250. Timing seemed to favor innovation when the 280 AI came along.

Recently, with the economic damage done by Covid (and our responses to it), the introduction of a new cartridge (anyone for the 30 Super Carry?) may be met with more skepticism and hesitation. Reloading supplies are sparse and expensive and commercial ammunition for even common cartridges is often difficult to find. The innovators and early adopters are similarly more scarce, or possibly less noticeable; we are waiting for the unforeseen and the little cash stash we had in 2019 evaporated. The shooting fraternity is more cautious. "Ackleyerizing" and wildcatting are not as practical or as necessary, since we have such a wide range of choices, and the frontiers have been pushed back quite a bit.

Not enough, say I, from my hiding place in the mountains, cradling my 280 AI.

[Dave Hoback]

Good points. And I agree with your last sentiment. Not for me either. I’m sold on AI rounds. I’m quite happy with the choice of my new barrel on the way. I just wish I had gone Improved from the get go. I’ll take another 100fps+ & be quite happy. Not to mention still having the ability to fire standard, non AI version of the cartridge with nil accuracy loss. Actually how I plan to fire form. I won’t waste powder & primers. I’ll simply do mild 260 Rem loads.

[J.Baker]

Here's some good reading for you Dave - it will take you well down the P.O. Ackley rabbit hole.

http://www.gundigest.com/wp-content/...stPOAckley.pdf