AI?

[Geezerbiker]

As interesting as the .30 ATK sounds, I don't think it offers enough performance increase over the 7.62x39 to justify the cost. There are now several bolt action rifles in this caliber to choose from and I'm thinking about a Ruger ranch rifle in 7.62x39 for my next gun purchase. The Howa is tempting too...

Tony

 

[stagpanther]

I don't know how the shoulder transition works out.

The redding die arrangement has what amounts to two bushings--the actual neck size change and one on top of it on the stem, there is a bit of a "float" to allow for self-centering concentricity--when you set the die you do a 1/16 turn out. My guess is that worse case scenario is that you might have to fire-form the brass once to "sharpen" the shoulder to neck transition. I'm thinking of eventually trying out a .257 in the grendel case (which is going the other way in a neck-down, but the .243 predator was pretty straight-forward so I don't see that being a problem).

 

[kraigwy]

Wouldnt a 7.62X39 AI be something along the lines of a 7.62X54R.

Or would that be a AI on steroids?

 

[Mobuck]

"Wouldnt a 7.62X39 AI be something along the lines of a 7.62X54R."
Basically completely different cartridges.
The thing with the 7.62x39 is the significant taper starting at the head of the case. The typical AI chamber is nearly cylindrical. Firing a standard case in the AI chamber would leave a large amount of the case unsupported during the fireforming process. This scenario would be less than optimum even if the case didn't just split. With so much room to expand , there would be a good chance the brass would come out lopsided or uneven (thick on one side/thin on the other).

 

[oldscot3]

Years ago my brother and I played around with Ackleys and Gibbs improved cartridges. My 6.5 Gibbs didn't pan out at all; when velocity gains over, say your basic 270 Winchester, were realized, they were accompanied by serious over-pressure symptoms like blown primers and sticky bolt lift. I had the rifle to the gunsmith several times and tried everything I could think of to get even a percentage of the benefits touted by the wildcat faithful. No dice; after much expense and frustration the LGS I acquired it from bought it back from me.
My brother still has a couple he had made, a 257 Roberts improved and a 6.5 Swede improved. Ackley never did the Swede but he had a custom reamer made following Ackley's principles. He gets a very modest gain, but I'm suspicious that he's exceeding prudent pressures a little bit.
My experiences changed my thinking from, "velocity is king" to, "there is nothing more effective than putting a good bullet were its supposed to go" (even if it's 100 fps slower when it arrives).

The 7.62x39 is such a small case with a 30 cal bullet, I doubt if anything measurable would result from "improvement".

 

[HiBC]

Mobuck,have you actually done any fireforming?

 

[stagpanther]

The 7.62x39 is such a small case with a 30 cal bullet, I doubt if anything measurable would result from "improvement".

Agreed--Inherent limitations. Might be worth it if there's an increase in consistent accuracy--maybe.

 

[HiBC]

Once again,I just don't have interest. I'm not building one. In post 10,there is a link to an article.
Take the article with skepticism if you choose.
Thearticle mentioned about 2500 fps with a150 gr Sierra. Military 7.62x39 is < 2400 fps with a 123 gr bullet.
Is 25 gr of bullet and 100 fps significant???
Its in the eye of the beholder.

A 150 gr 30 cal bullet at 2500 fps sounds like solid deer medicine to me.

 

[stagpanther]

Is 25 gr of bullet and 100 fps significant???

Agree with that too. Especially if you can get a sexy bullet that is more efficient.

 

[Scorch]

I doubt many of the cases would split during fire forming, people fire form cases all the time. Occasionally you lose one, but that is the exception rather than the norm.

The biggest question I would have is what would it be used for? Informal range time? Hunting? I know, "why do it?" isn't the question, the question is "why not?" The OP will have many opportunities to ask himself why, let's not try to discourage him. But it sounds like a fun exercise, nonetheless. About 35 years ago, a friend asked why I didn't turn my 22 Hornet into a K-Hornet, and I asked him why I should. He eventually bought the rifle from me and did the improving, learned a lot and had a good time doing it. This is about the same thing, improve the 7.62x39 and gain about 200 fps but have something unusual to show off. I say do it!