280 to 280 AI

[Newtire]

A man after my own heart, good for you!

Hi, I had the thought of trying out the .280 Improved. My trouble is that I have a .280 Handi-Rifle with a nice 26" barrel. I see I can get a 7mm-08 barrel for this thing but then those are only 22" long. So, the gain I got from the "Ackley-ization" would just be lost by the shorter tube. I can't set this barrel back as it's a single shot.

I am kind of getting the idea that I might be able to ream out this existing chamber but then would have to fireform the .280 cases to stretch them out to fit the overly long chamber and then just neck size my brass so that I won't set the shoulder back again. Is this the case? I have already successfully made up a bunch of .280 cases by creating a false shoulder (neck sizing the .30-06 brass in a Standard .280 die just enough to allow the case to fit). I fired these using a "start load" with a J-word and they turned out great. I'm thinking that this might be possible to do but wouldn't want to push a good thing too far. If I only end up gaining a hundred FPS or so, I would rather just leave it a standard .280.

I was thinking of using some 280 Nosler AI cases maybe so as to still have a neck left when I was all done.

So, would this be kind of a "Stretch-.280 AI" in the end? I have a .30-30 AI and a .257 AI and they are both really great cartridges.

Sorry so long of a post but seems this alteration takes a little more explaining since I can't turn the barrel back. In the end, this might just be more of a PITA than it would be worth! Any thoughts?

[swheeler]

You can form cases by creating a false shoulder, that way you insure that the case is stretching in the right place, the shoulder/body and not back near the head. That is why I don't use the jamb the bullet into the lands method for something like this, primer expolosion can move the case forward by seating the bullet deeper, then all the stretching is rearward. You would have to take the nosler 280AI brass and neck it up to create a false shoulder, then fireform and neck size only for the 280AI grande wildcat you made. The problem with a chamber like this is down the road someone else may end up with the rifle, could turn out bad.

[Newtire]

You would have to take the nosler 280AI brass and neck it up to create a false shoulder, then fireform and neck size only for the 280AI grande wildcat you made. The problem with a chamber like this is down the road someone else may end up with the rifle, could turn out bad.

I got thinking about the next person down the line getting ahold of this weird chambering like you said and decided that this would not be a good thing to do. Thanks for the great advice!

[leftiye]

I guess anything is "doable" the point I was trying to get across was without reaming to past existing headspace datum line(shoulder as BRS calls it?) you have NOT cleaned up the old chamber, at the very base of the neck you still have the original shoulder angle, now it may be small distance but its still there. You have created a wilcat that has a chamber with 2 shoulder angles, 40* most of the ways and the last bit before the neck/shoulder junction is still the original angle of parent cartridge. Then he says I reamed it this way and don't get any of the excess stretching you're talking about DUH, you never finished reaming the Ackley improved chamber! Ever wonder why Ackley him self set back one thread to ream?? I'd draw a picture BUT I DON'T THINK IT WOULD HELP! Crabo you want one have it done right, you won't be sorry

Nobody is arguing in favor of not setting back the shoulder. Do you have a need that people think like you do, or is it just that people should not disagree with you? By all means - "do it right" - unless as in the case of the break action, you can't. Then it will probly would function just as well (or better) with .017" of 30 degree neck left behind. You would think Ackley would have set the shoulder .017" further forward rather than setting barrels back.

[Newtire]

You would think Ackley would have set the shoulder .017" further forward rather than setting barrels back.

Didn't he do that so that you could shoot a factory cartridge in it to turn it into his Ackley version?

[swheeler]

Didn't he do that so that you could shoot a factory cartridge in it to turn it into his Ackley version?

Voila! Forget your AI handloads at home when you're a 1000 miles away on a once in a lifetime elk hunt, get by with a box of factory ammo. With a correctly reamed chamber(just like the OP Crabo asked about) you can safely shoot those factory rounds without having a head seperation, putting an eye out or injuring your guide.

[leftiye]

Didn't he do that so that you could shoot a factory cartridge in it to turn it into his Ackley version?

Like you couldn't safely fireform the shoulder seventeen THOU further forward? If you couldn't then you would lose many of your cases as it is also.

[GabbyM]

I could of set back a couple rifle barrels in half the time some of you have spent here typing arguments on why we don't need to do all that work. While we're at it and setting head space anyway. We could square up the Remington receiver face.

[B R Shooter]

You folks with your .017" plus or minus, don't make a lick of sense. With the shoulder angle aside, there is only .004" difference in headspace between a standard parent case and an Ackley chamber, .004" SHORT!

An excerpt from Manson Reamers:

Because the cartridge must be held secu
rely during fireforming, the dimension
between the breech face and the neck/shoul
der junction becomes critical. P.O.
Ackley, who popularized improved calibers,
recommended that this dimension be
reduced
by .004”/.006” from the standard minimum for a particular caliber.


Reducing this dimension compensates for
cartridge tolerances and ensures that
fireforming can be done safely.

This shorter chamber provides a crush of the brass. Some brass is thicker than others, and there is actually a .004" to .006" variance for this. You can talk all you want about .017" of something, but the bottom line is there is .004" of difference.

I started this out by saying, if you chambered UP TO the neck/shoulder junction, NOT PAST IT NOT BEFORE IT, you could fireform brass safely by standard methods of fireforming wildcat cases. This ca be done by a hard bullet jamb, a false shoulder, etc, either method works as long as you have a tight brass fit in your chamber. You need this so the firing pin hit doesn't move the brass forward.

I will also say, that it is not completely uncommon to see a factory chamber with .004" clearance. You can also do this in resizing if things are a little out of spec, a die a little too deep, or a shell holder a little less than the .125" depth it should have. Add those together and you ca push brass back far enough to create the exact .004" plus chamber.

If you have a notion that you may sell a gun in the future, then set the barrel back. If you're going to shoot it until it's a smoothbore like I do, I don't worry about that.

[swheeler]

I could of set back a couple rifle barrels in half the time some of you have spent here typing arguments on why we don't need to do all that work. While we're at it and setting head space anyway. We could square up the Remington receiver face.

Absolutely Gabby makes perfect sense

[leftiye]

Exactly - what BR shooter says. Boolit hard into rifling. light oil coating on case, mild load. It's over.

Actually, a standard case should headspace on the normal base of the shoulder/neck adequately to fireform. Regardless of how chamber is cut. Unless case has been sized, or sized too much.

[UBER7MM]

Crabo,

.
What's wrong with your 280?

[white eagle]

I picked up a Rem 700 7mm Rem. mag on Gunbroker for about 400. Gonna make a tight twist 264 mag out of it. Fills the same bill for me. I've got a 280, have liked them since I was in high school (early 60s). My first custom rifle was a 6mm AI which I designed the ctg myself, then found our that P.O. had already done. I've got nuthin' agin' wildcat or improved cartridges. But if you want a magnum, get one.

It aint about wanting a magnum its all about per for mance
if you end up stepping into magnum shoe's mo betta

[swheeler]

You folks with your .017" plus or minus, don't make a lick of sense. With the shoulder angle aside, there is only .004" difference in headspace between a standard parent case and an Ackley chamber, .004" SHORT!

An excerpt from Manson Reamers:

Because the cartridge must be held secu
rely during fireforming, the dimension
between the breech face and the neck/shoul
der junction becomes critical. P.O.
Ackley, who popularized improved calibers,
recommended that this dimension be
reduced
by .004”/.006” from the standard minimum for a particular caliber.


Reducing this dimension compensates for
cartridge tolerances and ensures that
fireforming can be done safely.

This shorter chamber provides a crush of the brass. Some brass is thicker than others, and there is actually a .004" to .006" variance for this. You can talk all you want about .017" of something, but the bottom line is there is .004" of difference.

I started this out by saying, if you chambered UP TO the neck/shoulder junction, NOT PAST IT NOT BEFORE IT, you could fireform brass safely by standard methods of fireforming wildcat cases. This ca be done by a hard bullet jamb, a false shoulder, etc, either method works as long as you have a tight brass fit in your chamber. You need this so the firing pin hit doesn't move the brass forward.

I will also say, that it is not completely uncommon to see a factory chamber with .004" clearance. You can also do this in resizing if things are a little out of spec, a die a little too deep, or a shell holder a little less than the .125" depth it should have. Add those together and you ca push brass back far enough to create the exact .004" plus chamber.

If you have a notion that you may sell a gun in the future, then set the barrel back. If you're going to shoot it until it's a smoothbore like I do, I don't worry about that.

Glad you posted that! .017+.004=.021 or .017+.006=.023" sure helps confirm what I said I think if you stop and think about it you will see exactly why PO wanted set back before reaming to AI chamber, well maybe not

[B R Shooter]

Read my first line, the .017" don't make a lick of sense. I have no idea why you are hung up on something that is non-existant.

[swheeler]

I'll try one more time in a different form;

1 EXISTING 280 CHAMBER length from head to shoulder/neck junction 2.199
2- 280AI CHAMBER length from head to shoulder/neck junction 2.182
______
.017
3 You say ream to shoulder/neck junction with AI reamer, THE ORIGINAL CHAMBER IS ALREADY LONGER AT SHOULDER/NECK JUNCTION THAN THE ACKLEY CHAMBER BY .017". You know 2.199 minus2.182 = .017"By reaming to this position you just ADDED .017" to existing headspace(which can be from 0-.005 and still be in spec)

You are misconstuing what is said above- they want a crush fit of .004-.006

in Ackleys own words- THE GO GAUGE NOW BECOMES THE NO-GO GAUGE


Say you are a right handed shooter and fire a round in a chamber done your way, have a case head seperation, hot powder gases carrying shards of gilding metal follow the firing pin back and escape around the shroud putting your right eye out, you have now beco
me lefteye

I do not know how I could explain it any clearer? I think 99.9% of the people here get it, some just like to argue I have done my best to keep you safe and it's up to you to learn now. For that reason I'm out of here.

[crabo]

Crabo,

.
What's wrong with your 280?

Nothin', but as we all know, what's that got to do with anything? Sometimes we just got to fix what ain't broke... Actually, I will probably leave it the way it is. I am enjoying the discussion.

[B R Shooter]

I will check my reamer drawings when I get home. I do know there are SEVERAL DIFFERENT 280AI prints and reamers being used, the original Ackley is different than the SAAMI. So first off you need to decide what you start with. I would expect, if you started with a SAAMI 280, and used a SAAMI 280AI, there would be the .004" shorter difference in the later, at the neck/shoulder. I have a full set of JGS prints at home, I'll check those.

Regardless, let's assume you have a rifle with a standard 280 chamber, you have fired brass in the gun without issue. Your brass is already a fit to that chamber. Unless you pushed the bajeebers back on the shoulder while resizing, the brass will be a decent fit. If you ran a AI reamer just to the N/S, no more, no less, there would be minimal issue if any when that brass is fired. You certainly wouldn't experience ahead separation.

This .017" is in the differences of reamers/chambers. Do a search, do some reading. There are indeed differences with this "improved" cartridge. I will bring my prints into work on Monday, scan them, and post them both for all to see.

[kywoodwrkr]

Friendly Google:
http://gunsmithtalk.wordpress.com/20...eadspace-test/

[B R Shooter]

Yes, I saw that same website.

So I checked my JGS prints. The standard 280 Rem print, #3118, shows a dimension to the N/S as 2.1924". The 280 AI print, #3056, shows a dimension as 2.1884". Exactly .004" short! Imagine that!

Look, this whole discussion was about fire forming. There are so many variables/tolerances to deal with, some common sense has to prevail. Even setting back a barrel takes special care. The short AI go gauge has the parent case shoulder angle, and it takes a close feel, because you will be using that same sharp angle that is shown in the sketch of the chambers I posted above, not a full contact shoulder fit. Don't be surprised if you feel some brass closing fine, some loose, and some very tight while fire forming. Brass thickness varies, and that crush ASSUMES .004" is the thickness.