280 AI case head seperation

[vanhornsky]

Ok so I have a brand new 280AI that I am trying to fire form brand new 280 remington Hornady loaded ammo and it blows the case head off. 2 out if 10 rounds survived. Go guage closes tight. No go will not close. Measuring the fired cases it measures to sammi spec. I even took it to another smith to look at and he couldn't see a problem. Anybody else had this happen to them? I am ordering nosler loaded ammo 280 ai to see if that helps. But I have a bunch of 280 Rem. Any ideas?

 

[bigedp51]

For some reason you have excessive headspace, the original Ackley Improved chamber was designed so a standard .280 case could be fired without headspace issues.

You could try to buy new brass and fire form the cases by seating the bullet long and jamming the bullet into the lands. This will hold the case against the bolt face and the case should not stretch and separate.

"BUT" it sounds like your rifle might be chambered properly.

Fireforming Brass

https://gunsmagazine.com/fireforming-brass/


280 Ackley Improved Alert

https://gunsmithtalk.wordpress.com/2010/01/13/280-ackley-improved-alert/


280 Ackley Improved Emperical Headspace Test

https://gunsmithtalk.wordpress.com/2012/07/17/280-ackley-improved-emperical-headspace-test/

 

[velvetant]

When you try to fire form does your bolt close harder then normal? It should, at least on my AI it did. If not you can seat long like bigedp51 suggested or you can neck up your case then neck back down but not all the way. You want to create a false shoulder to headspace on. Is your bunch of 280 already loaded?

 

[dok7mm]

When you try to fire form does your bolt close harder then normal? It should, at least on my AI it did. If not you can seat long like bigedp51 suggested or you can neck up your case then neck back down but not all the way. You want to create a false shoulder to headspace on. Is your bunch of 280 already loaded?

Exactly right. I prefer the false shoulder over the jam, when fire forming. Just set the false shoulder, so you get a crush fit where the bolt will close with pressure, it's kind of a feel thing.

 

[Edd]

If your chamber is the correct size and your new ammo is the correct length, your brass is probably too hard to form the new shoulder.

 

[J E Custom]

Ok so I have a brand new 280AI that I am trying to fire form brand new 280 remington Hornady loaded ammo and it blows the case head off. 2 out if 10 rounds survived. Go guage closes tight. No go will not close. Measuring the fired cases it measures to sammi spec. I even took it to another smith to look at and he couldn't see a problem. Anybody else had this happen to them? I am ordering nosler loaded ammo 280 ai to see if that helps. But I have a bunch of 280 Rem. Any ideas?

The new SAMME 280 AI chamber is to long for standard 280 ammo by .014 to .018. the only ammo that truly fits the "New" 280 AI is the Nosler 280 AI. all other ammo should be fire formed to chamber dimensions.

There have been many conversations on this and most smiths still chamber using a 280 head space gauge so that all ammo except Nosler can be used. The reamer is essentially the same on both versions of the 280 AI but the head space gauges used are different. If you can get a 280 rem head space gauge and test the chamber, you will se the difference. You can add shims the 280 gauge to find out how much head space you have. You should be able to get a 280 head space gauge for under $50.00.

I would not recommend shooting the rifle any more until the problem is solved.

J E CUSTOM

 

[vanhornsky]

Thanks for the links. The ammo is brand new loaded 280 rem from the hornady factory. The bolt may have just a little bit if resistance right towards the end. I colored the entire loaded round with a sharpie bullet and brass, put it in the chamber. The only signs of contact are right at the base of the shoulder that is is headspacing off of. Everything seems right but the case head wont stay together. One of my friends has a 280 ai also and says he cant shoot hornady because of the same issue

 

[Edd]

I think your brass is too hard, brittle, Instead of it stretching into it's new size and shape, it is breaking. If you have the new 280AI SAAMI chamber, it is actually shorter than the original, not longer.

 

[vanhornsky]

What brass do you guys use?

 

[Edd]

I don't have a 280 AI but if I had one and was buying brass to fire form, I would probably buy Norma. I expect Hornady brass would work fine if you annealed it. I would sell the loaded ammo and get a fresh start.

 

[vanhornsky]

That may be the way I need to go.

 

[Pdvdh]

If you have the new 280AI SAAMI chamber, it is actually shorter than the original, not longer.

I concur. Which makes the case head separations even more of a puzzler.

Are the Hornady cases separating near the case head? Or near the case shoulder?

 

[vanhornsky]

Near the case head.

 

[Pdvdh]

With normal tempered cases, it requires a lot of excess headspace to separate near the case head on a single firing.

I think the Hornady casings may be excessively brittle, and I'd try some different cases. Norma would be a good option.