Home Forums Hunting & Shooting Custom Rifles & Wildcats great explanation of the Ackley Chamber

Sounds to me like Catshooter likes to use his chamber as a sizing die and his bolt as a press.

I've been doing that with a .280Rem die,then running the brass through the .25-06 die.A friend told me to start with .280 brass rather than .25-06,as the shoulder is farther forward.What I'd like to know is if there is a permanent fix for this,ie,setting the barrel back and recutting the chamber if neccesary? Monashee

Ramming hard into the lands helps much also.

without question a competent 'smith could set the barrel back and ream a proper AI chamber.

At least it did 40 years ago. Might not work anymore though... <G>

My point is some oldtimers are stuck on only old technology. Anything new is crap. Well they didn't offer heart stents 40 years.ago but the folks who live 20 extra years seem to think it's a pretty good idea. I have more respect for oldtimers than about anyone you'll ever meet....but this is how it is because someone did it for 40 years don't mean it's correct. To answer your question though ....I shoe a lot of performance horses he used to shoe and yes every single client say the performance increase is drastic. I am useing an oldtimers method just not the closed minded 40 years ago fella and I assure you he's more than wise enough to never bring out the 40 years ago crap. We use shet from 200 years ago...100 years ago...40 years ago...10 years ago... and 10 days ago.He's still open minded and learning everyday. Take it or leave it.

Shod

Catshooter also explained why this method does not work as well as most would think. I had been forewarned of the method of seating the bullets long into the lands, but was at the mercy of the gunsmith on my first AI. So, I did my own experiment to determine headspace growth. As the bullets are seated longer into the lands, upon firing, the firing pin drives the bullet deeper in the case allowing for various lengths of case stretch.

After fireforming 100 cases by using the Jamming the bullets against the lands, I measured the headspace of the cases in a 243 Ai and they were spread over .004, but there were no premature case head seperations that I can recall, some just chambered harder or looser than others. It seemed like the hard chambering rounds created flyers.

If the gun is set up for a crush fit, the "Crush fit" is achieved by running the new case in the full length sizer and bumping the shoulder back till you can feel the slightest resistance when the round is chambered. You can check firm contact by smoking the shoulder neck portion of the case, then chambering the round. If you have a proper fit, you will see a bright ring around the area just behind the shoulder neck junction. Chambers set up with the crush fit will fire form with a headspace length to the 0.001 on every piece of brass.

Customers of custom gun makers that have chambered the Ackley cartridges where you can also shoot a factory round have found problems with case head seperations if the headspace is not set up "tight". Since new brass will vary at least .006 in headspace length, chambering AI's has changed from P.O.'s way of chambering. Various manufacturers will have their own specs on how long the brass is headspaced and it does vary from lot to lot. Winchester brass runs on the short side along with PMC.

If a gun is set up to have the LONG headspace to be able to accept the factory rounds, then creating a false shoulder using long tapered expanders available from Kliendorst and Redding is good way to go, or to use a parent case such as a 7/08 for the 243 AI fire forming, etc.

The Ackley line of cartridges really took off after the invention of the 6PPC and the 22 PPC which shooters had to form a case from the 220 Russain. Gunsmiths had to learn to set this the PPC cases up on a crush fit to the Sako 220 Russain case which had .004-.005 variations in headspace length. Learning to use a set of go and no go gages is a science in an of it's self. Chambers that were not set up with the crush fit, had to have their necks expanded to form the false shoulder. Idiots that tried the jam the bullets into the lands to fire form got shock to see premature case head seperations as they found that their rifle liked the top end pressure node for extreme accuracy. They also had various lengths of brass to deal with which lead to some hard chambering and some loose chambering which really tears up a guys concentration when he is trying to remember the "flags" and hold off from his last shot.

From chambering the 6 and 22 PPC rounds, it got to be common knowledge that the "OLD" way of chambering Ackleys to be able to shoot factory rounds could leade to trouble with customers(depending on how much they shoot). Without the invent of the PPC cases, the Ackley chambering would have died off, due to brass problems with reloaders.

So, if you are considering having an Ackley cartrige of any caliber, chambered, the first question to the gunsmith should be, "will chamber the round with a crush fit". If he does not know what a crush fit is, you're in trouble.

"Without the invent of the of the PPC cases, the Ackley chambering would have died off........" REALLY? You surely need a smiley face after THAT stupid comment.

Those of us who shoot and enjoy the 22-250AI, 257AI, 280AI, 348AI etc. etc. would NOT have found these rounds interesting and chambered our rifles for them had it not been for THOSE two rounds which most of us have never touched or found of any interest to us? Wow...... just wow.

And those of us who have been forming our AI cartridges from firing factory ammo with NO problems all these many years have ALL been just lucky, maybe? Yeah, thousands of us firing hundreds of thousands of rounds of factory ammo or perfectly fitting easy chambering factory brass in our non crush fit (excepting for maybe a .04 crush if a new barrel fitted) AI chambers should have had our hands and eyes blown off by now. Interesting.....

And to think that in all these years of playing with AI'ed cartridges I have never had a case even begin to separate, and used the brass so formed many times over with no ill effect. I must be one lucky sonofagun. Or, maybe I read the damned BOOK and went forth accordingly.

The correct way to cut a chamber has been covered before. I've thrown this drawing out for a visual aid and have been told it's incorrect. I presonally drew it up in AutoCAD, so I know the dimensions are accurate. The .30-06 IMP dimensions are from Speer #4. It's 2.000" to start of shoulder from the cartridge base.

In the mid 1970's, the 6 and 22 PPC came out in 1975 and 1976 and immediatley the problem that there were few gunsmiths that could chamber the cartridge, all problems related to case stretching during fireforming.

Precision Shooting magazine did extensive articles on how gunsmiths should set up the PPC chamber with a "crush fit". There was extensive talk on the advantages of the "crush fit" on Wild Cat cartridges of all types along with a "tight" or "minimal" headspace on all regular calibers to eliminate stretching in the web. One article went as far as showing the length of the headspace on different pieces of brass within the same lot# along with various headspace lengths of new brass between different brands.

The "crush" fit on AI's is simply just a more advanced way to chamber a gun since there is at least .006 variation in the headspace length of brand new brass, and at times even more.

You can take an over size ogive gage and slip it over the neck to measure the length at the shoulder of new cases to get some idea of just how much your fired and unfired case lengths may vary. Using the shortest new case as a gage, a gunsmith set up the headspace for that brand of brass that you are using, on non AI cartridges. The long cases of that batch of brass would have to have their shoulders bumped ever so slightly with the full length sizing die...not a proposition for guys that want to shoot factory ammo.

Again, this just a more advanced way to set up chambers to eliminate case head stretching at the web to give longer case life. If a reloader is so inclined, you can set the headspace on your cases when setting your full length sizing die using the oversize ogive gage slipped over the neck.

Needless to say, there are various ways to use a headspace gage when setting up a chamber, and the gunsmith has to determine what the customer wants and set the headspace accordingly.

I guess its my own nieveity, but by the time a guy is proficient in chambering, he has long been using a depth mic. A tight fit on a go gauge in the parent cartridge is minimum size.....so minimum minus .004" is not be too hard to understand, in my simple head....and if a fella was mic poor, a simple feeler between the barrel & action could be used to show the crush.

If it won't close on a minimum gauge with .004" to spare, why does it need another .04" of crush?

High Country, you are right on the money! Brass can vary .006, but as you know when you fire the parent case in the AI chamber, the neck shrinks. When you are getting more crush on the case, you are actually making the neck longer...not sure if that is a good or bad thing based on what a guy wants.

High Country, what you are doing is the correct way to get the crush fit as you are well aware, some guys do not know what you have learned, thus you get stretching in the web as they expect guys to jam the lands with the bullet in an effort to keep the base of the case seated firmly against the bolt face. If the neck tension is tight enough to stop the firing pin from driving the bullet deeper in the case, then you will have reasonable success with the bullet jamming method. It will take about .004 undersize neck dia to give enough grip on the bullet to get good success with the bullet jamming method.

I just made 100 of the 6.5x47 Lapua's out of Rem 22/250 brass. I set the headspace on the die where there was slight contact on the shoulder. Accuracy is fantastic and after fire forming, the brass at the shoulder measures exactly the same on all rounds. Accuracy at 200 yards is in the .250 area for 3 shots fire forming with 130g Bergers. Large primers are not supposed to be that accurate in this case....OH WOOPS!

Muskeg Man,

Nice drawing! Does your drawing represent -.004" headspace?

Dale

Not in the case of the 30/06AI it doesn't. There was an error of roughly .031" on Ackley's drawing which has been perpetuated to this day. 30/06 AI gauges are made to -.004" while reamers are made to reflect the -.031" on the drawing. Ackley had made the drawing to show -.004" at the datum line rather than at the neck/shoulder juncture. This was, quite simply, a mistake as anyone might make. The strange thing is, it seems that nobody caught this until about five years ago.
Keith,
Back when the 6BR was new, we had to form our brass from what was, essentially, 308 brass with a small pocket. You had to WANT to shoot a BR when 220 Russian was available and easily formed to PPC. Anyway, a fellow competitor shot all through the 1979 season using one batch of brass with the small pocket and one batch formed from 22-250 with the large pocket. For the year, the agg difference was .002 or some like that; in favor of the large pocket. So I guess the small primer wasn't quite as critical as was claimed. In the case of the 6.5x47, I don't blame you for reforming the 22-250's. Not only is the Lapua brass expensive as heck, in the 6.5x47, it isn't even all that great. GD

Graydog,

Where is the .031" error? Body? Neck length?

Dale

Keith shot benchrest for years with 7.62x39 brass, large primer. Maybe he'll tell you about it.

Against my better judgement I'll venture into this pit of quicksand. Wait a second, I gotta get my safety line snapped on - okay.

Having fooled around with Ackley cartridges for about 40 years of fun and excitement I decided to try something different this time. So, I had Pac-Nor make up a barrel for a Remington 700 short action chambered for the .22-250 Ackley. Only this time I ordered it with the Pac-Nor Rem Nut so the barrel would screw on like a Savage. I set the barrel up with a .22-250 Ackley PT&G headspace gauge, and fired formed an initial batch of brass. Chris at Pac-Nor emailed me the chamber reamer drawing (the JGS drawing called for a .004" crush fit) and I sent it off with three fired cases to Hornady to have a custom hydraulic forming die and F.L. die set made.

So first thing I did when everything came together was form up a batch of 100 cases with the hydraulic die. They fit the chamber perfectly with just a kiss of resistence. So they were loaded with a few test loads which worked perfectly. No primers backing out because the case was too short or the load to light, the shoulders finished forming up with sharp corners, and accuracy was between .5" and 1" for 10 shots. Cases did not stretch much, and because the cases had already been formed in the die, they did not shorten. After the second firing the cases were trimmed back to 2.885", a few had lengthened by up to .004".

When I checked concentricity, bullet runout was from .000" to .0005", with one or two going to .001", not bad for hydraulically formed and full length sized fired cases that had not been neck turned. Even better considering it is Winchester brass. Accuracy with the Barnes 50 grain Varmint Grenade ran a tad under .4" for 10 shots at 3,706 fps.

Setting the barrel up with a nut allows me to set the headspace as needed, but with the forming and sizing dies set for the chambering headspaced with the PT&G gauge it works fine. Had there been a problem the nut would have let me adjust the headspace as needed. If a tighter headspace was needed I would have ordered a custom JGS gauge to return the barrel consistently to provide a bit more crush.

All this rigamarole was necessary because I must use a lead free bullet and they do not shoot well jammed in the rifling. With the hydraulic forming die I can load and shoot knowing the first firing will be as accurate as subsequent firings.

Because there was no problem with standard .22-250 brass fired initially it should function with factory ammo, although I do not use factory loadings.

Even when I had an earlier rifle set up for a .257 Roberts A.I. the smith required three dummy cases made on the brass I use loaded with my preferred bullet to set the headspace. That also worked.

In the past, I used the false shoulder technique to get a crush fit when the brass and chamber disagreed. This is a hassle, but it worked well for forming wildcat cases.

I must be one of the lucky "Idiots". I used that system to make brass for the .220 Extremist; based on a .220 Swift with 17% increased capacity. A sharpened bent wire was used to check for incipient head separation, none was found.

I discovered if I used a full case of slow powder the neck did not get shorter. That means there must be brass flowing in the shoulder or body but not just in front of the head.

Edited to add: The loads worked fine when laying in the hot sun on a 100* day. For me that is not a "top end pressure node".

The error is in the length of the body (too short)and the neck (too long). If a chamber is cut using the -.004" rule or by using a commercial AI headspace gauge, the neck and, therefor, the chamber length, will be too long by approx. .031". If the chamber is cut so the chamber length is as drawn, the juncture of the neck and shoulder will be too short by approx.031". As I said, the error was made in labeling the AI chamber as being .004" short at the 30/06 (.375" dia.)datum line rather than at the neck/shoulder as it should have been.
Now, when a chamber is cut at the traditional -.004 headspace measurment, the fact the the chamber, overall, is too long is of no real consequence. The brass will certainly never need trimming! So, from a functional standpoint, the chamber works out fine but it is dimensionally incorrect. Cases fired in this chamber will be as Ackley intended for them to be but they will not be as depicted by the drawings because the drawings are incorrect.
Over the years, I have chambered a bunch of various AI chambers at -.004 on a gauge. When that did not provide sufficient "crush" I chambered to -.004 on a piece of new brass. This did work better and did allow the use of factory ammo with no problems while -.004 on a gauge often resulted in short cases when factory ammo was fired. It turned out that -.004 on a piece of new brass was as much as -.010 on a gauge.
One point that is also often missed is that manufacturers of rimless cartridges are more concerned with the headspace measurement at the datum line than with the measurment to the neck/shoulder juncture and this is as it should be. It does create a bit of a problem for those cutting AI chambers though.
When Muskegman posts his drawing, he is not incorrect; he is accurately reproducing a drawing which is based on data which is incorrect. Reamer makers and the publishers of reloading manuals have been doing the same thing for years. GD