Home Forums Hunting & Shooting Custom Rifles & Wildcats .270AI question

I had thoughts of converting my .270W to .270AI. I only have a 22" barrel. Would the performance increase warrant changing?
Approximately what velocities with a 130 gr. bullet could I expect? Also, with a 150 gr.? Would appreciate comments from anyone with firsthand experience/knowledge.

Not much of a gain for anything. If you realy want a AI, rebarrel it to .280 AI for better bullet selections. 270 is great, even guys who shoot the short fats are coming back to the classic.

270 AI is not as popular as the 280 because the 270 has always been loaded to higher pressures than the 280.

I like the 270 WSM but go back and forth on if it is that much of a step up from the .270 Winchester. It is but not sure if it is more psychological than real? The 270 AI is even less of a step up to the point I don't think you could tell the difference.

A 270 with a longer barrel is really a belt less magnum. A 26 inch barrel will get you up to 270AI speed with the standard cartridge.

No first hand experience but I think the velocity increase would be 50-75 fps or possibly up to 100 fps with the 150s and 160s. You will see higher velocities listed but people expect higher velocity so tip the jug pretty heavily. Powder Jug that is.

Thanks for the info guys. I was thinking I might get the answers you gave, however I just wanted to confirm my suspicions. Two of my friends
have 280 AI's, but, they are single shots with 26" barrels. I guess I just saved myself some money which I can put toward a different firearm!
75 +/- fps would come at a high premium, as well as possibly showing no accuracy improvement over my current barrel. (That being said, the cartridge does look pretty cool.)

Yes it is cool but the only plus you can bank on is less case trimming. As a project go for it but if you want to see demonstrable improvement go 270 Wby.

If you want to see more bullet choices go 280 AI. If you just want to kill some stuff efficiently go 270 Win.

Had a 270 Win Encore 15" barrel rechambered to 270 AI. The change added 150 fps. Went from 2700 fps to 2850 with 130's.

Yeah my 6.5-06 went from 2950 (standard) to 3150 (AI) with 140s. H4831sc in both loads, but I also gained 2" of barrel, so that accounts for some of it.

You can AI it, but the question to ask is why?

I have friends that were intrigued about the 270 AI a few years back so I chambered a few rifles for them. They are primarily Long Range enthusiasts and were running loads in the 270 AI up to 250 fps over the standard chamber in much longer barrels and using VLD bullets at reasonable pressure, but you can't come close to that in a standard length barrel. They liked the round but are now using the 270 WSM which is a much better platform.

In standard length barrels the standard 270 Win has enough case capacity to drive normal hunting bullets to mag velocity. Within normal hunting ranges an extra 50-100 fps won't make any difference on any target, and that faster bullet will be traveling slower at the actual target impact range by at least half of the difference. So at best you may only realize an additional 25 yards benefit...in my mind that's hardly worth any expense or effort.

There is nothing wrong with the 270 Win in capable hands. The standard 270 chamber will reliably get you to 1000yds supersonic with a decent bullet. If you are after more range a higher BC bullet is an easy option. I'd just shoot the 270 Win as is and if I thought I needed better performance I'd buy better bullets. Really, performance is all about the bullet.

The same time and money that would be spent on chambering, fire-forming and expensive dies could be invested in a new rifle in a more capable caliber, like 270 WSM, 7WSM, or several dozen others.

Slightly (ever so much) less gay . . .

Read Parker Ackley's book.

He stated that .270 Winchester was one of the very few cartridges that did not "improve".

How much case capacity do you gain by going from 270 to 270AI?

Mule Deer's 4 to 1 rule of thumb says that you get 1% more velocity for every 4% of increased case capacity, assuming all other factors remain constant. If you believe in Mule Deer's ROT, you'd need a 20% increase in case capacity to get a 5% increase in velocity. I don't know how many AI applications increase case capacity by 20%, but I doubt that there are many.

And, even if you gain 5% in velocity, how much practical value does that increased speed really get you? If you're getting 3,000 fps now, how much practical value is another 150 fps going to add?

Forty years ago I drank the AI cool-aid and convinced myself that Ackley's numbers were real. Then, advancements in technology provided shooters with affordable chronographs and we were able to see the actual velocity numbers for ourselves.

There are a few cartridges that are worth AIing for increased velocity, the 250-3000 and 300 H&H being prime examples, and the sharper shoulders reduce case stretching, increase case life, a benefit for high volume shooters.

If you do a cost/benefit analysis, the costs associated with changing a 270 to 270AI are likely to outweigh the benefits of a small increase in velocity and increased case life.

Or so it seems to me.