Im researching the cartridge and thinking about it being my next build. I have no experience with Ackley cartridges so I have some questions. Bob brass is difficult to find but factory ammo is fairly easy and 60 rounds is just a little more than brass cost anyway.

Can I use factory Hornady ammo to fire form the brass?

Ive read that you can but pull the bullets and re seat further out so they jam into the riflings. Others suggested using the COW method but that seems like a waste of time if the ammo is already loaded. Maybe I misunderstood? From what I understand Ackley chambers were designed to shoot its parent case to fire form brass. I would prefer to have 257 headstamp brass because I own a 7x57 and don't want brass mixed up so I am hoping the factory ammo would work

Thanks for any assistance

You should have no trouble shooting .257 Roberts ammo in your .257 Roberts AI. Your brass will then be fireformed for reloading.

Your understanding of Ackley chambers is correct.

I have done the same in my .280 AI with Norma .280 Remington Tip-strike ammo.

the Ackley rounds were designed to use normal ammo if necessary, and to fireform it when the trigger is pulled.

even if you do the bullet thing some brands of brass will still take a second firing to get them fully formed.

I would just use the standard 257 Robert chamber.

Then load the more modern +P 257 Robert's loadings.

In a good modern action.

The Ackley chamber has a shorter head space than its parent cartridge, The "GO" gage for the parent cartridge becomes the "NO-GO" for the Ackley. If chambered as P.O. intended, you should have a light crush as you close the bolt on a .257 Roberts cartridge in a .257 Ackley chamber. The cartridge is 'tapped' between the bolt face and the neck/shoulder junction. The misnomer of jamming the bullet only happens when a Roberts chamber is converted to Ackley without setting the barrel back. If done without setting the barrel back, the Ackley chamber is longer than intended. There used to be a good article on the Manson Precision web page,,,, or in Ackleys'
books.

FIRE AWAY!

I have also used 6mm Rem. to form .257AI brass.

You have a PM

Hip

I had a .257 Ackley barrel for my Encore for a while. To get fireformed brass I did just you are considering - fired "regular" .257 Roberts rounds. It worked fine, producing perfect AI brass ready for reloading.

I built my .257 Ackley in 1977. Back then new .257 roberts brass was easy to buy, so I never tried firing a standard Roberts cartridge in my Improved chamber.

Cream of wheat fireforming didn't completely form the new shoulders, so I went to forming them 75 gr bullets.

I've also formed some Ackley cases from 6mm Rem cases and even some from military M-14 (.308 Win) blank brass. The blank brass had to be cut to length, initally formed with cream of wheat, then the inside of the new case necks had to reamed thinner. I didn't do too many of them.

My ,257 Ackley has been my main deer and antelope rifle shooting mainly 117 gr Sierra GK bullets ever since, and it also made one shot kills on my 4 mountain sheep rams, a mountain caribou, and my 2nd best 6x6 bull elk.

quote:

Originally posted by slivers:
The Ackley chamber has a shorter head space than its parent cartridge, The "GO" gage for the parent cartridge becomes the "NO-GO" for the Ackley. If chambered as P.O. intended, you should have a light crush as you close the bolt on a .257 Roberts cartridge in a .257 Ackley chamber. The cartridge is 'tapped' between the bolt face and the neck/shoulder junction. The misnomer of jamming the bullet only happens when a Roberts chamber is converted to Ackley without setting the barrel back. If done without setting the barrel back, the Ackley chamber is longer than intended. There used to be a good article on the Manson Precision web page,,,, or in Ackleys'
books.

Thanks I just ordered some books today so I have an idea what I am doing when it comes time

Forget the AI! Remember where it came from; the original 257 R was a short, low pressure cartridge; hampered by that, so the AI was developed to get more performance.
All that is changed now, and here is my experience with the 257. I have a Ruger 77, Long action, with a long throat. I use 25-06 load data and get 25-06 velocities.
No need for anything exotic, or to form brass.
Or do what PDS said above; load your 257 to modern pressure; no need for the drama of an AI.
If you are using a short action; Why? Go to a 25-06.
And you can make 257 cases from 6mm; easy.

quote:

Originally posted by dpcd:
Forget the AI! Remember where it came from; the original 257 R was a short, low pressure cartridge; hampered by that, so the AI was developed to get more performance.
All that is changed now, and here is my experience with the 257. I have a Ruger 77, Long action, with a long throat. I use 25-06 load data and get 25-06 velocities.
No need for anything exotic, or to form brass.
Or do what PDS said above; load your 257 to modern pressure; no need for the drama of an AI.
If you are using a short action; Why? Go to a 25-06.
And you can make 257 cases from 6mm; easy.

I hear ya! I like to be not norm and have rifles not alot of others have. Built a 6.5-06 because of that when the 6.5x284 is virtually the same thing and easier to find brass for. I picked up a Howa Sako copy of the L61 action for a real bargain (under $350) that is virtually in new condition and trying to decide what to build with it. Won't be anytime soon. I don't have alot of Deer/Varmit calibers so I am exploring 257 257AI or I may go with a 6mm Rem. Its going to be a lightweight probably a Douglas #2 all my other rifles have heavier contours #4 and #5's. Its a long action so I could even go 25-06 but then I argue with myself that I already have a 6.5-06. I considered a 35 Whelen or 9.3x62 but I wouldn't really use it. I muzzleloader hunt Elk. Decisions Decisions

I definitely get having stuff no one else has; I never use anything common, nor do I take the same rifle twice.
So for that reason alone, go with the AI. Just because it is different, not practical.

This has got me wondering about the reason Roy Weatherby started using double-radius shoulders. Could it have allowed him to improve the 375 H&H magnum without blowing the shoulder-neck nexus forward in his prototypes? Obviously, some rifle makers don't care much about 'headspace' when chambering belted magnums but reloaders know it is still important.

If a standard .257 Roberts chamber is reamed to AI dimensions without setting the barrel back then it almost always results in greater than desired (erroneously called "excessive") headspace. A properly chambered AI will fire factory cartridges without creating a problematic pressure ring due to the rearward stretch of the case.

No, Weatherby designed the double radius shoulder to baffle and fascinate the average post WW2 hunter; the high gloss stock and the contrasting stock caps sealed the deal; it's all hype and marketing flair. Double radii were supposed to create a magic pressure wave effect, but we know that he used super long throats to reduce pressure.
Realize that belted mags do not use, nor do the drawings take into consideration, the shoulder, for any headspace dimensions. It is ALL in the belt, for belted mags. Only hand loaders who know that case life can be extended, like all AR members, use the shoulder as a headspace datum. Most hunters use factory ammo and do not care about brass stretch.
It ain't the rifle makers who "do not care"; it is the allowable manufacturing tolerances between brass, ammo, and chambers. A maker can chamber to a minimum belted headspace dimension, and the shooter will still have .018 of clearance. Not the makers fault.
Back to the AI rounds; anyone forming brass for an AI should always use one of two methods to be sure; 1: Bullet jammed into the rifling method.
2: Expand the neck and form a false shoulder so the case fits tightly.
Never just fire ammo without checking. You will get stretched inside, brass most of the time. IE, do not assume a "proper" AI chamber. Trust, but verify. Not my words.

Thanks dpcd, but do you deny that the shoulder-neck radius could perform the task I mentioned - allowing a case improvement without completely losing the original headspace or having to set the barrel back?

Yes it could do so but only if chambers and ammo were both designed to headspace on the shoulder instead of the belt, which they were not. Original 375 base to shoulder lengths varied; the shoulders just blew forward.
As stated; the best way to make an improved chamber is to make it fit on the shoulder of the original round. Not always/often done. Shoulder shape is immaterial.

my recommendations
1:Just build the rem-spec bob, not the AI - as the x57 cases that Ackley did showed HUGE velocity boosts in his version, people forget the pressure went WAY WAY WAY up - see below
2: use +p load data, as factory loads are neutured for the history of questionable actions being built into bobs
3:KNOW THAT winchester +p BRASS is thicker and heavier, resulting in less internal volume - which means higher pressure with same loads in other brass - i do NOT recommend using the win+p brass to form AI cases

here's the rule of thumb, you get 25% increase in vel of the % increase in volume, for the SAME pressure --

of you get a 10% increase in the AI volume, then at the same pressure, you should see a 2.5% increase in vel --

having done a "couple" wildcats, this is as good of a rule of thumb as many

anything past this is increased pressure --

Ackley proved that AI carts handle pressure better

A long throated chamber and a 06 length magazine works better than anything Ive tried, get Ackley ballistics and you have changed very little.

But the beauty of the 257 R0berts like the 250-3000 is how well they perform on any game without all the fuss and recoil..If you think you need more then go to the 25-06 or a caliber like a 7x57 or a 280.

I agree with Atkinson-my .257 R is built on a 1909 Argentine Mauser, and throated so OAL length with a Sierra 100 gr spitzer is 3.00". I got excellent accuracy at 2900 fps and never felt that combo is inadequate for antelope or mule deer (or whitetails, for that matter).

ClaMar

If you want a 257 Roberts AI build one.

"What the hell?" is a perfect reason to do something. I have a 22.250AI and love shooting the 36 grain bullets at 4300+ fps and the 68 grain SMKs out to 1,000 yards.

quote:

Originally posted by jeffeosso:

Ackley proved that AI carts handle pressure better

Ackley didn't prove any such thing, because it simply isn't true. Changing the shape of a cartridge does not make it stronger. Even the amount of measurable breech thrust is more dependent on chamber finish and chamber pressure than it is on case shape and taper. Regards, Bill

Well yes and no Bill, the wildcats on the 7x57 case have proven themselves with 300 FPS improvement give or take a tad..No other comes as close that I know of as proven, I recall even Ackley seemed to agree with that..

I see little use for wildcats these days and particularly, the wonderful 257 Roberts and 250-3000. That, of course, is my personal opinion only, and probably based somewhat on my early use on deer, antelope and elk with the mild but effective 25-35 Winchester 94 carbine.

If PO A didn't prove that a straight case design could handle pressure better than a tapered one (when he removed the locking lug from the 94 Win), then I have been suffering under a delusion for the past 60 years. And so have many others.
You are now saying that the only reason his experiment got the results it did, was that his chamber walls were rough on the straight one and smooth on the tapered one?

quote:

Originally posted by Bill Leeper:

quote:

Originally posted by jeffeosso:

Ackley proved that AI carts handle pressure better

Ackley didn't prove any such thing, because it simply isn't true. Changing the shape of a cartridge does not make it stronger. Even the amount of measurable breech thrust is more dependent on chamber finish and chamber pressure than it is on case shape and taper. Regards, Bill

While i rarely disagree with you, Bill, you are incorrect on this one

heck, i even proved it with my 458 AR -- more or less identical to the 458 lott/ackley in case capacity, then used indentical bullets and powders, and got higher FPS, over several chronos, than EXACTlY the same load, thrown on the same scales, from the same box of bullets and from the same powder can, than the straight walled cases ... case shape (we are getting into actual rocket science) DOES have a larger effect on performance than would seem obvious

Sory buddy, i think you are barking up the wrong tree on this one

quote:

Originally posted by dpcd:
If PO A didn't prove that a straight case design could handle pressure better than a tapered one (when he removed the locking lug from the 94 Win), then I have been suffering under a delusion for the past 60 years. And so have many others.
You are now saying that the only reason his experiment got the results it did, was that his chamber walls were rough on the straight one and smooth on the tapered one?

While I didn't know Parker, his guns aren't known for rough chambers --

you know how many women he had working for him?
ain't no way a rough chamber was coming out of that shop.


the answer is he had ~7 out of 10 that were women building his rifles.
seen it in person

anyway the angled shoulder will slightly speed up the powders burn rate.
that's one of the reasons why the slower powders tend to be a better choice in the Ackley shouldered rifles.

That's the whole idea behind the sharp shoulder, to help the powder burn and also keep the hot flame away from the throat with the long neck. The Creedmoor's are examples.