280 AI - Criterion Match Barrel - New

[Orezona]

I have been load developing for the new barrel. This is my first AI in any caliber. My experience through four firings is also new to me. The cases are not growing in over all length. The shoulder's are not growing (actually got smaller by .002 after first firing) and the cases are chambering and extracting smooth as butter. All I've done is collet neck size. The original plan was to go 2-3 firings with neck size only and then begin shoulder bumping with the Redding body die. My reasoning for this was to let the new brass stretch, not restart the 2-3 firings process all over again.

Questions:

Is this common in AI chambering?

Should I run them through the body die without bumping the shoulder back? Even though the junction between the case head and body look smoother than when the brass was new. The diameter of the body die is smaller than the fired brass.

Summary:

I'm not complaining at the simplicity and apparent limited need to work and resize the brass. It is new to me and I'm curious what other's reloading experiences are with the AI chamberings.



Thank you in advance.

[SageRat Shooter]

just tagging in... That is very interesting. My CBI .260 match barrel was kind of similar to what you are seeing. The brass just doesn't stretch in it... Even after 10 firings on the same pieces of brass, I think I had to trim about 3-4 cases, and even then it was about 2-3 spins of the case trimmer.

I just figured it was due to the tight tolerance in head spacing or something.

Glad to hear that your build has gone well and you don't have the feeding issues that have been reported by some. I hope it is a laser beam for you after you find your load.

[yobuck]

AI chambers tend to keep brass from growing less in length, so yes thats pretty normal with them.

[Orezona]

AI chambers tend to keep brass from growing less in length, so yes thats pretty normal with them.

Is there a need to run the cases through a body die and not bump? I ask because I'm not sure if it will some how improve case head to body integrity.

[yobuck]

Is there a need to run the cases through a body die and not bump? I ask because I'm not sure if it will some how improve case head to body integrity.
I cant answer that, in the 70 years ive been reloading ive only owned and used standard full length sizing dies.
I do check the trim length and trim when needed.
If a case wont chamber after full length resizing i dont change the die setting.
Instead i change the shell holder which serves to bump the shoulder.
As for case integrity i dont consider those things much. It does pay to examine the cases as you load, and there are signs you can look for such as bright colored rings around the case near the base. On smaller cases in 308 size and smaller, case integrity isnt much of an issue. I wouldnt be over thinking this stuff, if the loads you produce perform well enough to satisfy you for how you use them then leave it there and dont be concerned about how others think or do things.

[Orezona]

I cant answer that, in the 70 years ive been reloading ive only owned and used standard full length sizing dies.
I do check the trim length and trim when needed.
If a case wont chamber after full length resizing i dont change the die setting.
Instead i change the shell holder which serves to bump the shoulder.
As for case integrity i dont consider those things much. It does pay to examine the cases as you load, and there are signs you can look for such as bright colored rings around the case near the base. On smaller cases in 308 size and smaller, case integrity isnt much of an issue. I wouldnt be over thinking this stuff, if the loads you produce perform well enough to satisfy you for how you use them then leave it there and dont be concerned about how others think or do things.

Thank You Sir! I will take your 70 years of reloading and put it in the bank. My cases look great and the bright colored ring has actually smoothed out with each firing in the match chamber. I have been wet tumbling with SS so it isn't grime hiding the junction. What is funny, I purchased a set of Redding shell holders for the bump back. And this dang AI doesn't seem to need them.


Thank you again Sir.

[GaCop]

I cant answer that, in the 70 years i've been reloading i've only owned and used standard full length sizing dies.
I do check the trim length and trim when needed.
If a case wont chamber after full length resizing i don't change the die setting.
Instead i change the shell holder which serves to bump the shoulder.
As for case integrity i don't consider those things much. It does pay to examine the cases as you load, and there are signs you can look for such as bright colored rings around the case near the base. On smaller cases in 308 size and smaller, case integrity isn't much of an issue. I wouldn't be over thinking this stuff, if the loads you produce perform well enough to satisfy you for how you use them then leave it there and don't be concerned about how others think or do things.

Excellent advice. I rarely have to trim brass for my 223AI.

[charlie b]

If you go back and look at the history behind the AI shoulder you will find that one reason for it was to keep the shoulder and neck from increasing in thickness. It looks like you are proving that design factor as true.

One of the other design features is the ease of fire forming. A full factory load can be used to fireform and the accuracy of the fireformed shot will be as good as a factory chamber.

From all that I have read about all of the AI chamberings, the only downside is some of them have difficulty feeding from magazines. The same sharp angle that prevents brass flow will 'catch' on the chamber entrance. The lower angle necks of the original case slips into the chamber easier.

[Robinhood]

I never had any luck fire forming 280 AI brass out of anything(270, 280 or 30-06. It was always short. By something like .020". So I bought 280 AI brass and all is good.

[Orezona]

Thank you all for the replies.

[yobuck]

I never had any luck fire forming 280 AI brass out of anything(270, 280 or 30-06. It was always short. By something like .020". So I bought 280 AI brass and all is good.
About what you might expect from a machinist.
But the plus side is, you probably wont ever need to trim the cases.lol

[Robinhood]

About what you might expect from a machinist.
But the plus side is, you probably wont ever need to trim the cases.lol

You get me :)

[Orezona]

Robinhood, did did the short cases ever grow?

[Robinhood]

No, I was concerned that a carbon ring might develop so I went with the correct brass. Try it(the fire formed stuff). It may work fine. I was in a perfection mode at the time I switched to AI brass. It may be fine short. I know about better carbon removal now also. That is one fine round for everything southern 48

[yobuck]

Actually its a very fine cartridge even without the AI chamber.
I doubt very many load it to get the benefit from that anyway, so less case stretch would be the only real advantage for them.

[Orezona]

I received a Sinclair Concentricity Gauge today as a gift. I'm getting just under to maybe 1 Thou. Lee neck sized and Lee seated on Forster Coax using Forster lock rings. I think I'm happy with it.

[Orezona]

Actually its a very fine cartridge even without the AI chamber.
I doubt very many load it to get the benefit from that anyway, so less case stretch would be the only real advantage for them.

I'm going to load it to take advantage after I get my seating depth on this charge. Tug convinced me on the 24" barrel. So I'm going to burn the powder.

[Texas10]

Thinking about adding an AI to my collection this winter. Is the correct way to fire form the brass shoulder to AI accomplished by seating the bullet long so that it holds the cases rearward against the bolt head?

[Orezona]

Since it sounds like you will be reloading, I would just buy the brass. I wouldn't waste components to fire form. Especially in these time. I fire formed one box (20) of Nosler 280 140 grain BT's just to see how accurate the 280 would shoot in the 280 AI chamber.

[charlie b]

From what I have always understood about the AI design was the neck/shoulder location did not change. So, a factory round would head space as normal. The firing of the case would just blow the rest of the shoulder into the steeper angle.