Short barreled 223 AI

[Heavy4Cal]

Was thinking of building kind of a short handy varmint rifle in 223 AI, but the AI is new to me and I'm not sure what length of barrel to go with, was thinking maybe 18'' but not sure.

What kind of velocity could you expect out of a 223 AI with an 18'' barrel with 55gr bullets?

[handirifle]

Usually you lose about 25FPS per inch, as a general rule. But I have to ask, WHY? I mean, why bother with an AI when you are going to shorten the barrel that much. More powder needs more barrel to burn.

If I wanted a short barrel varmint barrel, I would load it with powder designed to burn fast, and get as much speed as possible from the short barrel. Just my $.02

[Heavy4Cal]

I want to replace the 22'' 223 rem sporter barrel with a varmint profile and was thinking a little shorter barrel would keep the weight down a little and be a handier rifle, but I don't want to give up velocity, the 22'' 223 rem on the rifle is running around 3300 with a 55gr Vmax and I would like to keep at least that velocity or better, maybe a 20'' would be better.

I'm not looking for a really long range rifle, just kind of a handy little ranch rifle.

[SavRimfire]

Kinda the whole point to "improving" a standard case is to burn more powder, by going to a barrel that short you're negating the benefit of being able to put more powder in the case. I know many will argue but ackley improving the 223 case, with pressures being equal, in a 26in barrel is usually only about 100 fps gain over a standard 223. Some will argue they're getting 150 or even 200+ fps more out of their 223ai's and I'm sure they are but I can promise you it's not at equal pressure/s.

I have a 223ai with a 22 inch barrel and for the most part, I'm only getting about 50 fps more from it than I am some of my other 223's, in fact I have a standard 223 with a 26 inch barrel that shoots the same bullet a little bit faster. I can load my 223ai hotter and make it shoot faster than the others but it will be the result of higher pressure and I could easily do the same with my 26 in. 223 as well.

If a 223ai is what you want, by all means have one built, I love mine and shoot it as much as any gun I own, just be careful listening to people talk about fps numbers and how much faster a 223ai shoots over a standard 223 because, again pressures being equal, it's really not that much of a gain and with a barrel as short as you're talking about, it would be minimal. I hunt coyotes with my fireforming loads because they shoot so well but they shoot slower, because the larger ai chamber lowers pressure, than the exact same loads do in my standard 223's. When I think about it it's actually quite ironic, my first round of loading for my 223ai shoot slower than they do in my standard 223's then the second round of loading only shoots about 50-60 fps faster than my standard 223's. As much as I like my 223ai to do all over again with only using a 22 in. barrel I'm pretty sure I'd save the expense of another set of dies and go straight 223 and if I was going shorter than 20, there is no way I'd go AI.

[Stork]

Kinda the whole point to "improving" a standard case is to burn more powder, by going to a barrel that short you're negating the benefit of being able to put more powder in the case. I know many will argue but ackley improving the 223 case, with pressures being equal, in a 26in barrel is usually only about 100 fps gain over a standard 223. Some will argue they're getting 150 or even 200+ fps more out of their 223ai's and I'm sure they are but I can promise you it's not at equal pressure/s.

I have a 223ai with a 22 inch barrel and for the most part, I'm only getting about 50 fps more from it than I am some of my other 223's, in fact I have a standard 223 with a 26 inch barrel that shoots the same bullet a little bit faster. I can load my 223ai hotter and make it shoot faster than the others but it will be the result of higher pressure and I could easily do the same with my 26 in. 223 as well.

If a 223ai is what you want, by all means have one built, I love mine and shoot it as much as any gun I own, just be careful listening to people talk about fps numbers and how much faster a 223ai shoots over a standard 223 because, again pressures being equal, it's really not that much of a gain and with a barrel as short as you're talking about, it would be minimal. I hunt coyotes with my fireforming loads because they shoot so well but they shoot slower, because the larger ai chamber lowers pressure, than the exact same loads do in my standard 223's. When I think about it it's actually quite ironic, my first round of loading for my 223ai shoot slower than they do in my standard 223's then the second round of loading only shoots about 50-60 fps faster than my standard 223's. As much as I like my 223ai to do all over again with only using a 22 in. barrel I'm pretty sure I'd save the expense of another set of dies and go straight 223 and if I was going shorter than 20, there is no way I'd go AI.

Sorry to quote the whole post, but I've been down the same road and couldn't disagree with one word. Mine happens to be a xp100 with a 27 1/2" 223 AI. My results were the same. If I had the chance to do it over, I wouldn't bother, not enough of a difference to change any results downrange. I had the xp converted to a 223 AI/6 dasher switch barrel & haven't touched the 223AI for nearly 15 years.

Save your money & buy components.
Al

[Damon555]

The main advantage of going with the AI is that you get standard 223 velocities with a shorter barrel.......that's the way I'd look at it. I have a 223 AI with a 26" barrel and it is a very fun cartridge to mess around with and components are easy to find.

[Scott Evans]

If you increased your case size by 3g (nearly 10%) and you're only seeing 60fps better velocity same 50g class bullet same barrel, you aren't trying very hard.

[handirifle]

He could get the same gain with a std case, and varying types and burn rates of powders. The rate of burn will be even more important on a short barrel.

As for the varmint weight barrel, measure the diameter of the barrel, where the new muzzle will be, and most likely it will be a varmint weight, for all intents and purposes. In my thinking, if it's what you WANT to do, go for it, but I doubt it will gain enough to make it a cost effective change.

[SavRimfire]

If you increased your case size by 3g (nearly 10%) and you're only seeing 60fps better velocity same 50g class bullet same barrel, you aren't trying very hard.

No, it's really not anymore than that. If there actually was a 10% gain by improving the case that would certainly help but unfortunately it doesn't increase that much it's only a 7.6% increase over the parent case.

There's this misconception a 223ai shoots 150-200 fps faster than a standard 223, but again, pressure being equal, it's just not there. You can't load up one and not the other then compare velocity, which often happens.

If someone wants to build a 223ai, by all means, do it! Like I said before, I have one and it shoots some of the smallest groups of any rifle I own and I hardly ever have to trim the brass so there are definite gains to be had by going 223ai, unfortunately, big increases in velocity just isn't one of them.

[Scott Evans]

I'm not comparing apples to oranges, been there, done that, 223 to 223AI, 6x45 to 6TCU, in each finding minimal case life, and acceptable case life.

[Heavy4Cal]

Thanks for replies guys it give me some things to think about.

I might just leave it the way it is for now and work on finding a more accurate load and see what it will do before I decide what to do with it.