223AI Chamber and Crush Fit

blopez50

blopez50

New member
I'm having a 223ai built and was talking crush fit "stuff" with my smith the other day. It got me interested so of course I had to start reading up on it. I feel comfortable about what it is and why it's needed but have one question that I can't seem to answer.

I've seen a lot of people write about crush fit but nobody seems to mention the Go-Gauge in the same paragraph. It seems to me like the crush fit would be a result of a gauge that is ~.004 shorter. So this is my question: If I were a smith and ordered a PT&G 223ai Go-Gauge and did everything the same as a "normal" chamber, would I have a crush fit? In other words, are the AI gauges made shorter?
 
The only thing that I can think of regarding the crush fit is that when you chamber a standard .223 round into a .223 AI chamber you have give the bolt a little extra "ooop" to get it to close because standard .223 brass is a tiny bit longer than .223 AI brass is. That's because when the round is fireformed the case is straightened out a bit causing the overall length to shrink because of it. Once the round has been fireformed after it is sized the next time that it is chambered it will load normally with normal effort.

When I had my .223 AI built I used a bunch of standard .223 ammo that I got on sale (remember those days?) and just fireformed it all out shooting rodents.

And I sure do like mine. That's what I am holding in my avatar. Cooler weather is coming soon and that's when you will find me in my heated garage loading for next year's varmint season.
 
New brass in an AI chamber headspaces on the neck/shoulder junction, that's the only place it hits. The chamber at that point needs to be shorter than the brass. The amount shorter is "crush", that's how far the case will be compressed at that spot. Thing is, that length can vary from case to cawse with different headstamps. And within the same headstamp it can vary several thousandths. Going by that .004" number and using a gauge can result in a chamber with no crush depending on which brass. And you want to set the chamber up with plenty of crush anyway. Don't mess with a headspace gauge........get your brass and have the chamber cut with at least .010" crush. Sounds like a lot but the brass is only hitting at that neck/shoulder junction, you'll feel only slight resistance when closing the bolt. And you will get a nice tight seal at that point. My 223AI chambers are set with .015" crush on IMI brass.
 
Originally Posted By: Rustydust

Cooler weather is coming soon and that's when you will find me in my heated garage loading for next year's varmint season.

It's still so hot here, that the idea of a heated garage is just something that i can't get my head wrapped around. lol

If you didn't have that rifle, and were going to get something would you get the 223ai or a 20 tactical or something else?
 
Hey, I rode my Honda Goldwing down to Glendale last October to visit my younger daughter. Was still way too hot for me that's for sure!

I really like the .223 AI chambering and now that I have had one for several years I can't see myself doing without one. Even though I have a really fine AR-15 varminter as well as a 527 CZ in regular .223 I prefer the AI for both ground squirrel and especially for prairie dogs. I take lots of guns with me to Wyoming every year for pasture pooch shooting but it is the AI that gets the most use.

But I do like my .204 Ruger a lot too. Even more so since I replaced the factory Savage barrel with a 1-11" twist CBI. But seeing that a .20 Tactical is 98% of what the .204 is then why not get one of those if you want? Wildcats are always cool and when they are easy to make like the Tactical is even more so.

All in all I think that the .223 AI makes more overall sense than a 20 caliber anything does simply because of the wider variety of bullets out there. But there are so many good 20 calibers out there nowadays then there is almost no reason to buy (or make) one more so than the other. If I was going after prairie dogs and rock chucks more so than the tiny ground squirrels then I would prefer the .224 bore for the more decisive tosses but here again, they are so close in performance that you can just pick the one you like the best.
 
It's a really versatile round.

I'm building this one as a "starter" LR rifle. I've never done the spinning turrets thing or shot much past 400 and want to learn the basics without spending a ton on bullets/powder/brass. I can shoot the 75amax and 25ish grains of powder for much less than even a 308.
 
Yup. And more comfortable too. And being able to see your hits (or in my case, misses
blush.gif
) at distant targets is ultra important to me. How can you correct if you can't see where it's hitting?

Like my other varminters, the barrel on my AI is treaded to accept my HTG suppressor. Makes a long day of shooting even that much more fun.
 
Originally Posted By: blopez50I'm having a 223ai built and was talking crush fit "stuff" with my smith the other day. It got me interested so of course I had to start reading up on it. I feel comfortable about what it is and why it's needed but have one question that I can't seem to answer.

I've seen a lot of people write about crush fit but nobody seems to mention the Go-Gauge in the same paragraph. It seems to me like the crush fit would be a result of a gauge that is ~.004 shorter. So this is my question: If I were a smith and ordered a PT&G 223ai Go-Gauge and did everything the same as a "normal" chamber, would I have a crush fit? In other words, are the AI gauges made shorter?




Short answer is yes.
Ackley set it up so that the parent case (223 Rem in this instance) would crush fit the ai chamber. The go-gauge for the 223 Rem would now be the no-go gauge for the ai chamber.

Trouble is that case lengths can vary a bunch and if your smith leaves a couple thousands long you get more than .004 variance. In a perfect world the .004 is just enough, but most things are less than perfect.

Have .015 to .025 crush plugged in if you are going to fire factory ammo for cases. Or have it all done as Ackley intended with .004 crush and size your cases with a false shoulder. The latter will ensure a crush fit and well formed case. If you fire factory stuff in the chamber it may stretch some on the first firing but will be fine there after if you neck size with a neck die.
 


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