Better extraction with ackley improved?
I was just reading about ackley improved chambers/cartridges, and one of the claims made for their superiority is that because the walls are less tapered than a standard cartridge, that they extract easier. Can someone explain the physics of this to me? I would have thought a tapered shape would always be easier to extract due to the fact that moving it just a little bit out of the chamber results in very good wall clearance.
In a nutshell, think of the tapered cartridge as a wedge, when it fires, sets back and expands, it takes all of the available room and firmly snugs itself in place. The straighter body of an AI chambering tends to eliminate that and the additional benefits of greater powder capacity and a chamber cut to more exacting tolerances makes it a popular upgrade. Sorry that I don't have a fancy highly mathematical answer, but I would be generating more B.S than a politician. The earliest tapered cartridges were primarily due to the available black powder and manufacturing techniques. As both improved, we saw a transition to the straighter wall and more aggressive neck angles. It comes down to human nature always looking for a better mousetrap or "edge" over the next guy. Many cartridges see significant benefits such as the .218 Bee and the 30-30, to name a couple and note that they are seeing a more radical shape change than say, a 30-06 AI. The claim to fame of the design is that you can fire factory (unaltered) cases in the AI chamber with no risk, so if you run out of formed ammo, you can fire stuff available at any local store. Most all of the currently introduced cartridges now share the straight wall and aggressive taper because they reailize the benefits of these. I hope that helps out.
P.S. This is all based on the use of cartridge brass as opposed to steel (common in many foreign military cartridges). Steel changes the whole game and is virtually the opposite in behavior.
Doesn't a straight walled cartridge expand and set back too? I imagine with the steeper angle on the throat that you would have an easier time getting tighter tolerances in the headspace, which would seem good for brass life , but I still can't fathom how a straight walled cartridge does not also expand to fill the chamber. I can see how a straight walled cartridge would give less thrust against the bolt since it would hug the chamber walls better. Is that why extraction is easier, because the cartridge is not pressed tight against the bolt making it harder to rotate? Why would there be a difference between steel and brass?
You are reading it in Arabic my friend. Backwards. Ackley cases are almost always horrible for extraction. Especially with firearms that have short extraction cams. Heavily tapered case's are always easier to get out. If you look at any of the old British cases designed for double rifles they always have a horrific body taper. This outwardly seams incredibly inefficient as you are wasting a lot of potential case space. The truth of the matter is that double rifles have little or no extraction power so they give them heavy tapers to get them out. Also the case only has to move 1/64th to 1/32 of an inch before it is completely free of the chamber walls allowing it to be tossed out by the spring loaded ejectors. If you can't grasp it, imagine a CAT40 and a #3MT quill. Which one is easier to get out of the machine. Same principal. There are people who believe that heavy tapered cases create more bolt thrust. In theory, if you use Einsteins theory's, NO, this would not be the case at all. The piston or cartridge head remains the same size no matter what the chamber is shaped like. In fact there is a slight variance as the cartridge case does obdurate and grip the chamber walls and contribute slightly to strength. This gain in strength is very marginal though and should not be used to add strength to the system. Its like arguing about how much padding you should wear before jumping out in front of a bus traveling 60 miles an hour. Who cares, its a stupid argument, give me an address I'll send flowers to the funeral.
I was curious about this because I read some article that said extraction was easier, and this made no sense to me.
Well since the internet came out I don't believe to much of what I read anymore. Back when magazines looked after publications and had to be semi accountable for what they published it was bad enough. Now every armchair professional with a computer and internet access is free to put his or her opinion in print for the world to see. I'm pretty old and like many others I now understand that opinions are like assholes, we all have one and most of them stink! Its an overused cliche but its still the best one to describe it. I get good information from the net and magazines every day but most of the time I have to sit down after I read it and separate the facts from the BS. If it does not make sense when you read it or doesn't work when you try it there is probably a reason. The trick is to not wreak something while trying to learn and make stuff work.
One possible explanation is if the load used for the larger capacity "improved" case results in lower peak pressure.
When you fire, the case has to expand to fill the clearance between it and the chamber wall, then the chamber wall expands elastically, and springs back onto the plastically deformed case, clamping it.
During extraction, you have to drag that case back, until it is free of that clamping pressure. With equal firing pressures, you'd expect - as Speer Chucker says - that a steeper taper would result in the case coming free sooner.
With less taper, the only way you'd achieve less clamping, is if the elastic expansion of the chamber wall had been less, and the only way you'd achieve that, is with lower peak pressure.
I'll add one caveat:
If you have a very springy action which allows a tapered case to back out, expand, and then the spring of the action forces it forward again into the relaxed chamber...
Then you might get more trouble with a more tapered case, but the problem is with the springy action, and especially if it is allowing too much of the web at the head of the case to back out of the chamber, and in that situation, you don't want even more weight of hot powder gas infront of your face
I have no dog in this fight, but in Cartridges of the World by Frank Barnes, in the description of the 30-06 AI states; "As is typical of Ackely's improved series of cartridges, this design exhibits reduced case stretching and easier extraction, compared to the more tapered standard version."
I would credit Barnes as having a degree of knowledge greater than most in this area. I do seem to recall a discussion of this somewhere, but cannot locate it in my references, but Alpaca's reduced peak pressure seems to ring true.
Well, the 30-06 like all other high intensity or (magnum) cartridges operates at about 55,000 PSI. It is logical to assume that if one were to improve a 30-06 chamber and then shoot standard 30-06 loads through it the pressures would be less. They sort of have to. Your ratio of weight of powder per square inches of chamber goes down quite a bit. It would also logically give much lower velocities as well because of the drop in pressure. I think when Mr Ackley thought up this new cartridge he sort of felt that after he fire formed it to the new chamber he would utilize the new found space and he would put in more powder to fill the case back up and bring it back up to the 55,000 PSI and get a longer burn time and more velocity. As for less body taper being easier to extract, Mr Barnes can change the common laws of physics and mechanics as he see's fit.
Last edited by speerchucker30x3; 06-24-2012 at 08:49 PM.
Are we dealing with a relative statement?
Is extraction "easier" with an "improved" case
An "unimproved" case loaded to give the same performance?
If we are, then the statement would be true - in that very limited sense.
Barnes' COTW is one of the most annoying of the many highly annoying gun books which I own.
Barnes almost completely ignores operating pressures, and describes a smaller capacity case with a higher muzzle energy than a larger case as "efficient"
all other factors being kept constant, the difference is due to operating pressure. The information was out there for Barnes to find, and to point others to (most reloading manuals state max peak pressure for a given round), but he didn't.
His grasp of basic physics was questionable too, I can't remember which entry it was, but he'd clearly forgotten that Kinetic energy = 1/2 mass * velocity^2
Fortunately the succeeding editor(?s) has begun cleaning up the entries.
Although this has no bearing on the reliability of Ackley's claims about easier extraction, Take a look at his comments about the .223 Rem in his HBFS&RL. He beat Zumbo to that line by several decades.
I'm surprised that the antis don't chant a chorus of "Even P.O. Ackley wrote..."
I was wondering when anyone would get around to that passage on these forums. I am sure Ackley was a brilliant man, but I think he was like a lot of others, with a large ego and persona, and liked to see his name in print.
Originally Posted by Alpacca Fortyfive
Last edited by kendog; 06-27-2012 at 08:29 AM.
Brilliant? I don't know that I would go that far out on a limb. I think he was probably one hell of a salesman. He created a situation where by simply running a reamer in a short distance the could give people the next cartridge size up out of their old firearm and he could sell them a set of dies and often a full reloading set in the process. Rechambering was not done much in that time so he had a bit of a captive market and there was something a bit mystical about it which helped sell it. With the fuel components available at that time, the shorter barrels that were then standard and no chronographs to speak of I have often surmised that most of the people that were duped into improving their firearms gained little more than 100 FPS if that. On top of that none of his cartridges were ever adopted by the manufacturers which should say something about their design. Like Roy Weatherby, he did help force shooters and manufacturers to explore velocity and strive to produce practical cartridges and powders that could produce it. I suppose only arrogance would assume that he did not carve a tiny place for himself in firearms history. Everyone likes to see their name in print but to stand back at a distance and look at Ackley I kind of see a used car salesman. And, I guess there is nothing wrong with that.
One minor thing, we both know you cannot PROPERLY do an Ackley by just running a reamer in, not for a rimless round anyway. Gibbs or Mashburn, or rimmed ctg go for it :-). You have to set the bbl back for proper headspace on a rimless ctg.(unless you can somehow adjust it, like a savage action), and often that was done 1 full turn, which got the guy a sharper newer throat in the bargain.
Originally Posted by speerchucker30x3
And many modern ctg really use a lot of design attributes Ackley thought would be good ideas.
Donaldson shot at steel plates when he made up his ctg, including the 219 Donaldson wasp, with the same bullet he figured more penetration meant more velocity...and he did find the point where bigger was not better, he had a much more limited powder section than we do today. Donaldson had some neat ideas, another one being that a given VOLUME of powder, a given loading density would turn out to the most accurate. I loved reading his letters in the old Handloader magazines "yours truly Harvey Donaldson".
That whole powder selection but might be quite significant, "back in the day" the 222 was said to perform poorly in pistol length barrels, so much so that Remington thought the 221 fireball was "needed" but somehow today people seem to do just fine with 223 and even 22-250 in encore pistols ?
Well Bill 95% of the Ackley chambers I drop a GO in close on the GO just like they are NOT supposed to. The GO should become the NOGO and an unfired case in its original dimensions becomes the tight go. When faced with the extra $100 - $200 to set the barrel back one turn and re-index the sights most shooters will opt for .003 to much headspace. They are handloading anyway so headspace is irrelevant after first firing. In most case's you can long seat bullets to headspace on the lands during initial fire forming. Free bore is not needed in Ackley cases.
Do you think ole PO just ran the reamer in ?? Or did he consider setting back "part of the job" ?? I got an Ackley "go" gauge with my 22-250AI reamer. The SAAMI 22-250 chamber is a horribly sloppy thing compared to the brass, this reamer is a snug body and a .250 neck. Makes a nice chamber that can fire lots of factory brass (some brands are too thick), then turn them to .248 which cleans em up nice. One thing an Ackley will do for you, is if you care about your work, find a way to run the reamer in straight ;-).
Originally Posted by speerchucker30x3
I think Ackley probably just made his own gauge that left the ring where the shoulder joins the neck intact and ran the reamer straight in. I would be willing to bet the GO becoming the NOGO came about much later and was possibly not even started by Ackley himself. I have never seen anything in print in 31 years to support this but nothing to deny it either. Ackley was trying to make a living selling an idea to people who were to cheep or to poor to buy another rifle. His ideas were a shortcut or a POOR-MANS-MAGNUM as they have come to be called. The job had to be cheaper than a new rifle or people wouldn't have had it done.
As far as running reamers straight in rechambers it is virtually impossible. The squareness of the outer chamber area and thread extension are unknown and running a stick into the chamber on the broken interior of the barrel and dialing in on it 4 inches away is absurd. The only recourse is to float the barrel and let the reamer follow the existing chamber or use a floating reamer holder and again let the reamer follow the existing chamber. Besides, the rear dimensions of the chamber have already been established so you can't begin pushing the chamber from side to side unless you have enough material over the outer main chamber area to set it back an inch and create a new thread extension or silver solder a sleeve into the existing chamber. Soft soldered sleeves will often set back. After soldering in sleeves be sure to make a clean up cut with a boring bar. Driving the reamer over a spot of carbon will roll the cutting edge of the reamer over.
Actually I am not talking rechambers. The less taper a case has the more of an issue it is if the reamer is not going in parallel to the bore. It is never GOOD, but it will be a LOT more apparent when the case has very little taper. I really have no interest in rechambering factory barrels because for the most part they are poop anyway.
I have never experienced the problem you seam to be having. Something must be wrong with your chambering system or setup. If your chambers are coming out off center of the bore you might try using commercial chamber reamers with pilots on them so the reamer can follow the bore and cut the chamber between centers, or drive the reamer in a floating reamer holder. It should eliminate your problem.
It is actually a simple problem. And easily fixed. Picture the barrel on the steady, with the tailstock offset to the center of the bore, when you run the reamer in it the chamber is concentric to the bore, but larger in the rear than the reamer.
Originally Posted by speerchucker30x3
Simple solution, clamp an indicator the the barrel, adjust the steady until the tailstock center indicates 0.000 runout. Done deal.
I hate floating holders, have no need or want for one ;-).