I guess I stumped 'em at Kimber

[back country]

On Monday I sent an email to the technical dept. at Kimber asking this question: "Understanding how an Ackley Improved cartridge is supposed to be fireformed from it's parent cartridge with the bullet making "hard" contact into the lands to prevent web stretch, are your .280 AI rifles chambered to accomodate this ? What I am wondering is, can factory .280 Remington ammo be fired and the brass still be safe to reload as .280 AI ?" Friday morning ... no answer as yet ......

 

[pinehavensredrocket]

one of the unique properties of the ackley improved cartridges is to be able to use standard caliber cartridges in the same chamber. of course it is understood that "fireformed" cases are then used for "improved reloads". i am currently shooting two remington AI rifles...30-06 AI & .280 AI and have never had any problem with cases in either rifle.
good luck.

 

[BrownBear]

...an Ackley Improved cartridge is supposed to be fireformed from it's parent cartridge with the bullet making "hard" contact into the lands to prevent web stretch....

So you're saying any time Ackley rechambered a rifle he also set back the barrel and rethroated it?

Didn't happen that way. I have several rifles he did for me back in the day and the correspondence to go with them. He also rebarreled one for me. None of them meet that criteria and he never discussed the point with me- in writing, on the phone, or in person. Most go the other way, in that wherever possible he actually lengthened the throats to provide the greatest possible OAL with a specific bullet. Any time he did work for me, he was always specific in asking me what bullets I'd be using.

His emphasis was on the junction of the neck and shoulder, which done right, would limit or prevent web stretch without regard for bullet seating depth.

Paper tiger.

 

[LuJon]

I guess I stumped 'em at Kimber

This info is readily available. Kimber chambers their rifles to the fairly new SAAMI spec.
Here is an article explaining the difference.
http://gunsmithtalk.wordpress.com/2010/01/13/280-ackley-improved-alert/

The only issue with the addition of this new SAAMI version is that the Nosler factory ammo and brass are designed for it with it's shorter headspace. Not a problem if you have a SAAMI spec chamber but if you have a 280 AI rifle chambered to the original 280 ackley specs then the new factory ammo/brass will have excess headspace in your chamber and should not be used.

In both cases using factory 280 brass to develops ammo for you rifle is fine. What you want to avoid is swapping ammo between the different chambers. Fire formed 280 done in an original spec chamber likely wont fit in a SAAMI spec chamber where as 280 brass fireformed in a SAAMI chamber would likely suffer case head separation if fired in an original spec Ackley.

Kimber will probably answer you but I get the impression that all involved with the SAAMI spec and its changes consider it to be the "real cartridge" and all the ones built to the wildcat specs to be exactly that "wildcats". Like any wildcat the expectation is for the owner to understand what they have and load for it properly.

 

[Vek]

To answer the OP's question to Kimber, there is no need to jam the bullet into the rifling lands in order to get standard 280 ammo to fire and fireform properly in an Ackley chamber that is cut properly. The entire first clause of your first sentence is completely and utterly wrong.

The Ackley chamber is cut so that the distance from bolt face to chamber's neck to shoulder junction is ever-so-slightly less than the distance from standard 280 case base to shoulder-neck junction. It makes for a very minor "crush fit" of standard brass in the Ackley chamber - it should take some effort to chamber a standard 280 in an Ackley chamber. In that fashion, headspace is positively controlled independently of bullet contact with lands.

If a standard 280 doesn't chamber with some effort, then you have an issue with Kimber. Otherwise you are just badgering them, and they owe you no answer for your incorrectly-framed question. It's not their responsibility to educate you on Ackley chambers; apparently it's ours.

For an improved chambering that doesn't provide the crush fit or otherwise positive headspace control of the Ackley, then you need to do one of two things: neck up then back down to establish a new shoulder for fireforming, or jam bullet in the lands and load it pretty hot. From experience with a 35 Gibbs, the neck up to .400 then back down method is superior and more reliable. This would be for the Gibbs, Hawk or Brown-Whelen improvements.

Belted mag Ackleys don't need a shoulder crush fit, neither do rimmed ackleys, since both the rimmed and belted cases manage headspace on the rim or belt rather than the shoulder. Reference Ackleys in 22 Hornet, 30-30, 348, 300 H&H, and 375 H&H for examples. There's probably lots of other rimmed examples.

 

[323]

As other said that was the benefit of the AI you could still use std ammo in them. Now getting off track here a 7mm Gibbs I had I just fireformed them and I got 3-4 firing out of them before tossing them... Anyhow come to find out the smith that did the chambering chattered the reamer anyhow no longer have it. As far as Beartooth wow whats up....

 

[TWB]

I guess I stumped 'em at Kimber

Tough crowd. Thank god I'm a weapons expert and rarely have to ask a question.

 

[stid2677]

Gentlemen,, please let us conduct ourselves as such,, PLEASE.

Steve

 

[Nitroman]

Gentlemen,, please let us conduct ourselves as such,, PLEASE.

Steve

Are you really serious? You think this thread is near-to-the-point of oblivion? I thought it quite interesting to this point.

Vek's answer is excellent. I was thinking of answering along those lines until I read his post. It is almost getting to the point where an intelligent response is considered inflammatory.

 

[LuJon]

I have been piecing together the needed tools to make modified cases for my Hornady COAL gauge and just got the correct drill bit yesterday. So after reading this I decided to take my lunch break and see if I could modify up one of my pieces of once fired 280 AI Nosler brass. I destroyed 2 in the process which sucks since this brass is B/O till next year but finally got one all threaded up that chambers properly! I ran it through a couple time really quick but need to do it about a dozen more times to get a sold average that I am comfortable reporting... Luckily the boogered up cases will make fine dummy rounds so I can test to find maximum magazine length and I will list that as well as the COAL for both 140 and 160 accubonds along with the COAL as measured to the ogive.

 

[323]

Tough crowd. Thank god I'm a weapons expert and rarely have to ask a question.

Yes you are what gun did you build today on your lunch break?

 

[907pride]

Luckily the boogered up cases will make fine dummy rounds so I can test to find maximum magazine length and I will list that as well as the COAL for both 140 and 160 accubonds along with the COAL as measured to the ogive.

I don't want to sound like I'm a know-it-all, because I know nothing about gunsmithing and I am only a novice reloader. Having said that, I noticed that in your post you said that you have to find the maximum magazine length. I noticed that I don't have allot of issues with that when it comes to my Kimber .280 AI, but I do have issues with something similar. I have been doing some reloading and found that my most accurate load is while shooting Berger VLD 168gr. While shooting this bullet my lands on this rifle allows my max COAL to be 3.373" The load that my rifle liked most had a COAL of 3.36

These bullets chambered just fine and they even fit down into the magazine perfectly. The problem I have run into is that if I chamber a round and do not fire it, the bullet will not eject properly. It is too long. In other words, once the bolt face has grabbed the bullet and it is chambered, then I decide not to fire, I lift the bolt handle and slide the bolt backwards. Once the bolt is all the way back the bullet tips up and should eject but the length will no allow it to exit the chamber while the bolt is still grabbing the bullet. They get wedged into the bolt opening every time. I have never had this issue before with any other rifle. I just thought I might give this warning. I always measured the lands and the magazine but I never thought about measuring the bolt opening.

Lujon, I also wanted to let you know that if you are looking for .280 AI factory ammo they have some over at boondocks. I didn't know if you were just looking for factory brass or actual factory loads.

Ok, now that I've said my piece, I'm sure people are going to say that I have no clue what I am talking about, but just remember, I already admitted to that at the beginning of the post. haha

 

[LuJon]

I guess I stumped 'em at Kimber

Ok.... Micrometer is put back away and here are MY results in MY chamber in MY rifle.

MY as in mine the one I had on my bench today and may well not reflect what you find in YOUR rifle.

Measurements taken using the hornady LnL COAL gauge and the appropriate "#28"comparator.

COAL to ogive based on average of 5 closest measurements: 2.803"

COAL to tip of 160 accubond touching the lans: 3.383"

Max length to consistently extract: 3.345"

You may be able to sneak a 3.350" or possibly a tiny bit more but as was mentioned before 3.360" the tip of the round hits the front of the ejection port and is popped loose of the extractor and falls back into the action.

 

[Nitroman]

Ok.... Micrometer is put back away and here are MY results in MY chamber in MY rifle.

MY as in mine the one I had on my bench today and may well not reflect what you find in YOUR rifle.

Measurements taken using the hornady LnL COAL gauge and the appropriate "#28"comparator.

COAL to ogive based on average of 5 closest measurements: 2.803"

COAL to tip of 160 accubond touching the lans: 3.383"

Max length to consistently extract: 3.345"

You may be able to sneak a 3.350" or possibly a tiny bit more but as was mentioned before 3.360" the tip of the round hits the front of the ejection port and is popped loose of the extractor and falls back into the action.

If one needed the extra length you could have a gunsmith mill the receiver ring to gain that.

 

[back country]

BrownBear - I was not attempting to be (or sound) like a "knew what I was talking about" All I am attempting to ascertain is "can I safely shoot .280 Remington FACTORY ammo in a Kimber Montana .280 AI and have "safe" fireformed brass ? THAT is what I wanted to know ....... (I talk too darn much !!)

 

[Snowwolfe]

On Monday I sent an email to the technical dept. at Kimber asking this question: "Understanding how an Ackley Improved cartridge is supposed to be fireformed from it's parent cartridge with the bullet making "hard" contact into the lands to prevent web stretch, are your .280 AI rifles chambered to accomodate this ? What I am wondering is, can factory .280 Remington ammo be fired and the brass still be safe to reload as .280 AI ?" Friday morning ... no answer as yet ......

Your question would put Kimber on the spot if they answered it. Yes, factory 280 ammo can be fired and the brass "should" be safe to reload. This is assuming the chamber was not on the large size and that you adjusted your full length resizing die correctly to insure you were not sizing down the cases to much. Now, if your chamber was cut on the large size but still in spec, but your brass was a little undersized then there "might" be enough stretch to cause a problem.
As far as making hard contact with the bullet into the lands this is a common and easy way to help fire form cases. I'll toss out a couple of examples of how this helped me. One rifle was a .243 Improved and the other was a 35 Whelen. With the 243 I used factory brass and loaded them normally. About 10 out of 50 would have light primer strikes so I went home and pulled the bullets out and reset them so they engaged the lands. Then all 10 fired.
35 Whelen, used Remington 35 Whelen brass which has a habit of being made undersized. Same thing, about 10 out of 50 would not fire so pulled and reseated the bullets out further.

In a perfect world the brass would not be slightly undersized and would sit in the chamber in the proper position and fireform correctly. But this is not always the case going to an "Improved" version. So, it depends.....on the chamber size and on the brass size. Once the case if fire formed and then resized only enough to rechamber easily you should be good to go. The one thing I would never do and that is to use standard ammo in an improved chamber when hunting. Just to many misfires to worry about.

 

[LuJon]

I guess I stumped 'em at Kimber

The new SAAMI chamber is actually shorter than the original Ackley improved spec so should be less prone to soft primer strike FTF.

Looking real quick at the drawings the SAAMI 280 AI is 25 thousandths shorter to the the shoulded-neck junction than the factory 280 Rem.

The original Ackley drawing is about 14 thousandths shorter than the parent 280 Rem case as I recall.

 

[back country]

Thank you guys !!