25-06 Ackley advice

I am no gunsmith, and I understand what you are saying. I also believe that your version of chambering is a better way of doing things[30-40 thou crush]. However explain how crushing a case .004 is any worse on brass growth in fire forming than factory brass fired in any custom chamber? The head space is still there. Oiling your brass before firing makes alot of sense.

The point to me about improved chambers is that you are blowing out the case, not lengthening it. So if we are starting with factory formed cases, and a tighter tolerance in our chamber by .004, how is this any worse in case growth than a factory fired in any chamber?

The only point to hold a parent case in an improved chamber for fire forming is the point of the neck and shoulder juncture. So the go gauge of the parent case becomes the no-go gauge of the improved case.

I still like what you are saying better, I am just trying to understand why Ackley's method is a wives tale.
 
Originally Posted By: SmokelessI am no gunsmith, and I understand what you are saying. I also believe that your version of chambering is a better way of doing things[30-40 thou crush]. However explain how crushing a case .004 is any worse on brass growth in fire forming than factory brass fired in any custom chamber? The head space is still there. Oiling your brass before firing makes alot of sense.

The point to me about improved chambers is that you are blowing out the case, not lengthening it. So if we are starting with factory formed cases, and a tighter tolerance in our chamber by .004, how is this any worse in case growth than a factory fired in any chamber?

The only point to hold a parent case in an improved chamber for fire forming is the point of the neck and shoulder juncture. So the go gauge of the parent case becomes the no-go gauge of the improved case.

I still like what you are saying better, I am just trying to understand why Ackley's method is a wives tale.

Well... lessee.

When you put a new case in a regular factory chamber, it doesn't fit (it is smaller) so, in effect, you are fireforming a new case when you fire it in a new chamber (or after you FL size it). Once fired, it will fill out the chamber spaces until it is within 1 or 2 thou, and now we (hand loaders) have the case as we like it.

In a regular chamber, the case and chamber may not be exactly the same, but they are close - the chamber shoulder is kinda the same shape and position as the case's shoulder... maybe 5 or 10 thou of space, but SAAMI allows a lot more.

The "Headspace" (capital "H") of the case and the chamber are close to each other. So we can fire it, and the shoulder, even though it is not a great fit, will keep the case in place, until the pressure causes it to fill out the chamber.

Say, for example, in a .280 Rem (the ol' 7mm Remington Express), you draw a circle that is 0.375" in diameter on the shoulder of a new case. That circle will wind up being ~2.105" from the case head.
Then we draw another circle that is 0.375" in the chamber shoulder. It will be ~2.100" from the bolt face, leaving 9,995" of "clearance".

These two circles are "The Headspace" datum lines, and when the case is chambered, they are supposed to be within 5 thou, but there are +/- tolerances, so the space can be more or less (even negative) - the rest of the shoulder can go to helll as far as "Headspace" goes.

If we want to "improve" his cartridge, we need to move the outer part of the shoulder forwards, and "theoretically" keep the inner part of the shoulder (the neck-shoulder junction) in the same place.

It would be easy to do, just run a new reamer into the existing chamber until the neck base of the reamer came to the existing neck base of the chamber, and, Voila, an improved chamber.

If we were going to form cases hydraulically, this would be fine - just pump the oil into the barrel & case, and the case would expand and fit perfectly... but we can't realistically do that.

So we "fire form" the case.

But the problem is... when the primer goes off, it is a true "explosive", just like TNT - and the primer acts like a "Ramset" and forces the case forward under a lot of pressure - upwards of 700 pounds (real pounds, not psi). So the case moves forwards, crushing that little neck base intersection and leaving the case with a lot of space between the bolt face and the case head - then the pressure builds up, the case body expands and grabs the chamber walls, then the case head goes back under pressure, while the case body is stuck in place, and we have just stretched the case and thinned the web - we already have a badly damaged case, and we have only fired it once. From that point on, we are loosing our case life cuz it is already weakened.

So what we do is, we cut the chamber shorter than the "perfect" chamber would be.

In the above case of the 280 Rem:

The outer shoulder is 1.992"
The headspace is 2.100"
The neck junction is 2.193"

For our improved version:

The outer shoulder is 2.097"
The headspace is 2.144"
The neck junction is 2.179"

Ok... lets see what we have done, by measuring the changes.

The outer shoulder is 2.097" +0.105"
The headspace is 2.144" +0.044"
The neck junction is 2.179" -0.014"

So we have moved the outer shoulder forward 0.105, and the headspace line (in the middle of the shoulder) forwards 0.044", but we have moved the neck junction BACKWARDS 0.014"

Now, if we chamber a case, it doesn't want to go in - cuz the neck junction of the case is now too far forwards - we have to FORCE the case in the chamber, "crushing" the neck junction back 0.014"

That 14 thou is the "crush" that we talk about - and that is the crush you feel when you close the bolt on a new case in an improved chamber, and that is the crush that the primer would do if it had a chance in a chamber that was reamed with 0.000" neck junction setback.... it would blow the case forward and crush that junction of the neck.

Now... by going over these numbers, you an see there is no place that ANYTHING is 0.004" away, or close to, anything else... the headspace difference between the original, and the improved is 0.044" and that part of the case is not even involved in the "crush".

So that is why the old "0.004 of crush" is pure BS.

Most gunsmiths are not much more than highly skilled pipefitters - some are top grade engineers.

If this is not clear, lemme know and I'll try to fix it.

 
As I have said, I understand you'r method, and even like it more than Ackley's.

Having said that, you are trying to negate 60+ years of the the Ackley improved chamber.

Just because you disagree with it, does not change the fact that thousands upon thousands of Ackley improved chambers have been cut using the -.004 measurement, and they are all happy. So it does work. It is not a theory.

Ackley probably should have taken it further, as you have suggested, but the reason he stopped where he did, was so that it was easy for the gun smith in terms of the go, no-go gauges.

All I can say is Ackley's method is standardized, with many decades of proven results.

Can it be "improved"? I think you are articulating just that very thing.
 
Well, I sure have learned a lot in these posts, at the very least how to tell a go/no-go on the perspective smiff. Thanks to all for the input!
 
Originally Posted By: travjcWell, I sure have learned a lot in these posts, at the very least how to tell a go/no-go on the perspective smiff. Thanks to all for the input!

What did you want to know in the first place ? I'll have to go look .
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Originally Posted By: Tim NeitzkeOriginally Posted By: travjcWell, I sure have learned a lot in these posts, at the very least how to tell a go/no-go on the perspective smiff. Thanks to all for the input!

What did you want to know in the first place ? I'll have to go look .
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The name/number of a Gunsmith in the midwest that has done such work correctly.
 
The way catshooter explained it is the way the last gunsmith explained it as well, I've never read P.O. Ackley's books or anything so I have no bearing on his supposed method. Does Ackley specify for the 0.004" or is it just a common rumor or misconception of how things work?.
 
Originally Posted By: SmokelessAs I have said, I understand you'r method, and even like it more than Ackley's.

Having said that, you are trying to negate 60+ years of the the Ackley improved chamber.

Just because you disagree with it, does not change the fact that thousands upon thousands of Ackley improved chambers have been cut using the -.004 measurement, and they are all happy. So it does work. It is not a theory.

Ackley probably should have taken it further, as you have suggested, but the reason he stopped where he did, was so that it was easy for the gun smith in terms of the go, no-go gauges.

All I can say is Ackley's method is standardized, with many decades of proven results.

Can it be "improved"? I think you are articulating just that very thing.

(Wow, you guys get up early to give me a hard time)
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No!! I'm not negating anything - what I described above IS the Ackley chamber. Those measurements I gave were from the 280 Ackley Improved!!!!!

The point is that there is no 0.004" measurement anywhere - the guys that say that are just repeating what someone else said, who repeated what someone else said, who repeated what someone else said, who repeated what someone else said...

.. who repeated what some idiot said!

Of course, there are those "smiths" who just use a case and wing it ...

(With apologies to "The Treasure of Sierra Madre")...

"Gauges? What Gauges? We don' got no gauges. We don' need no steeenkin' gauges"
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Originally Posted By: nortexThe way catshooter explained it is the way the last gunsmith explained it as well, I've never read P.O. Ackley's books or anything so I have no bearing on his supposed method. Does Ackley specify for the 0.004" or is it just a common rumor or misconception of how things work?.



From P.O Ackley's Handbook For Shooters & Reloaders, Volume I, Headspace chapter, page 155:

Talking about the 30-06 chamber. "For example when chambering for the 30-06 we normally use a 1.940 gauge and get the bolt so that it will easily close with only a slight "feel" or close without any "feel" at all, but at the same time will absolutely refuse to close on a 1.946 gauge which means that the headspace of the chamber comes within the limits and somewhere between these two figures. Therefore, the 1.946 gauge becomes our "NO Go" gauge since the bolt refuses to close at all on this maximum gauge.

For the improved cartridge it is necessary to use the 1.940 gauge, as the "No Go" gauge, and our "Go" gauge must be approximately .004 shorter. There our "Go" gauge will become 1.936."


He goes on to list the measurements for the .257 Roberts.

"When considering the .257 as a further example the standard minimum headspace for this cartridge is 1.794 with a maximum headspace or "No Go" gauge measuring in the neighborhood of 1.800 or if the bolt will close on the 1.800 gauge the chamber is considered to have maximum headspace and should be corrected. The improved chamber then will require a gauge of 1.790 as the "Go" gauge and the standard gauge of 1.794 will become the "NO Go" gauge."
 
Interesting is it only those two chamberings? To me it would seem that with just the .004" one would be pushing close to case separation after forming the brass.
 
Originally Posted By: SmokelessOriginally Posted By: nortexThe way catshooter explained it is the way the last gunsmith explained it as well, I've never read P.O. Ackley's books or anything so I have no bearing on his supposed method. Does Ackley specify for the 0.004" or is it just a common rumor or misconception of how things work?.



From P.O Ackley's Handbook For Shooters & Reloaders, Volume I, Headspace chapter, page 155:

Talking about the 30-06 chamber. "For example when chambering for the 30-06 we normally use a 1.940 gauge and get the bolt so that it will easily close with only a slight "feel" or close without any "feel" at all, but at the same time will absolutely refuse to close on a 1.946 gauge which means that the headspace of the chamber comes within the limits and somewhere between these two figures. Therefore, the 1.946 gauge becomes our "NO Go" gauge since the bolt refuses to close at all on this maximum gauge.

For the improved cartridge it is necessary to use the 1.940 gauge, as the "No Go" gauge, and our "Go" gauge must be approximately .004 shorter. There our "Go" gauge will become 1.936."


He goes on to list the measurements for the .257 Roberts.

"When considering the .257 as a further example the standard minimum headspace for this cartridge is 1.794 with a maximum headspace or "No Go" gauge measuring in the neighborhood of 1.800 or if the bolt will close on the 1.800 gauge the chamber is considered to have maximum headspace and should be corrected. The improved chamber then will require a gauge of 1.790 as the "Go" gauge and the standard gauge of 1.794 will become the "NO Go" gauge."



That explains where the 0.004" comes from, but it does not explain how those measurements come about.

See, the headspace for the 30-06 chamber is 2.0487" to 2.587", (NOT 1.946"), which means that anything between 2.0487" and 2.0587" is within SAAMI headspace.

The only measurement that is close to the 1.946 is the 1.9399" measurement to the outside edge of the shoulder and this is NEVER used as a go/no go reference.

There is NO 1.946" or 1.940" go or no go headspace gauge. Headspace is measured part way up on the shoulder, NOT at the outside edge of the shoulder.

And... the "Crush" does NOT take place at the outside edge of the shoulder, it takes place at the neck/shoulder base junction.

(Here are the 30-06 SAAMI drawings)

http://www.saami.org/PubResources/CC_Drawings/Rifle/30-06%20Springfield.pdf

Plus... the measurements at shoulder for the 30-06 and the 30-06 AI are... 1.948" and 2.017" respectively... for a difference of, 0.069 - that's right, SIXTY NINE THOU - so how the h*ll do you use a 0.004" shorter gauge to set up a chamber where the shoulder has to move forwards 69 thou??

The other part of this is, if you understand how ANY rimless "improved case" is made (that includes Ackley, Mashburn, ICL, and all the others), they work by holding the case in place with the neck base junction, and blowing the outside of the shoulder FORWARDS...
... so you can't cut a chamber for an Ackley 30-06 with a shorter (1.936") shoulder length and have it move forwards at the same time.

And, you can't have the improved shoulder be within 0.004" of the original outer shoulder measurement - it is just physically not possible.

Ackley's book is filled with this kind of stuff.

And what has happened is that people that don't understand what is going on in the chamber of an improved cartridge, have grabbed that 0.004" figure, and just throw it out to sound like they know something.

I read P.O. Ackleys books many many years ago, mostly for the historical aspects. While he did do a lot to promote the world of wildcats, he was a pipefitter, and not an engineer.

Where these figures he has, came from I can't say - poor writing, or poor proof reading? But there is no way that they are accurate.

What is in the book, is NOT what is happening in the chamber.


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Yes, you are correct about the 30-06 measurements. Seems he was using an "old" method that is measured from the face of the locked bolt face to the start of the shoulder or the point where the shoulder angle starts. Maybe from 1906?
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He does mention the standard measurement to the datum point [.375] as being 2.0479 as a minimum and that that is in contrast to the figure commonly used of 1.940 at the time.

He also mentions the juncture point of the neck and shoulder, and says that it is "critical" for the fire forming process. However he lists no measurement for that juncture point.

In my thinking of the .004 "crush" I was thinking of the juncture point of the neck and shoulder. If that point is .004 shorter than the parent chamber, won't the cases fire form at least as well as the parent case in the parent chamber? The case would not not be able to grow in length, would it? Growth in length is the cause of incipient separations. Maybe a better way to put it, is 30-40 thousandths needed, or can you get away with less "crush"? We are trying to stop the case from growing in length while it fills out to the new body taper and shoulder angle.
 
How would one even go about measuring from closed bolt face to shoulder start? Maybe chamber cast, but that seems like a lot of extra work.
 
Originally Posted By: Smokeless

"In my thinking of the .004 "crush" I was thinking of the juncture point of the neck and shoulder. If that point is .004 shorter than the parent chamber, won't the cases fire form at least as well as the parent case in the parent chamber?"

No - because the "'ramset" force of the primer will shove the case forward, and crush the neck base junction - now the case has lots of headspace - then, when the powder burns, you will get a case stretch of 20-30 thou, and then the case is going to fail soon.

Quote: The case would not not be able to grow in length, would it?

Yes it will - see above!

Quote: Growth in length is the cause of incipient separations. Maybe a better way to put it, is 30-40 thousandths needed, or can you get away with less "crush"? We are trying to stop the case from growing in length while it fills out to the new body taper and shoulder angle.

Well, the amount of crush is already determined by the design specifications of the improved cartridge - the 30-06 AI has it's amount of crush - you don't want to do anything to lessen it by sloppy chambering it without setback, or using a hand reamer like PCAMMO described - practices that are still done on a daily bases today.
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Ideally, the amount of crush should such that you need to really lean on the bolt handle to close it on a new, unfired case - it guarantees that you will have a case with 0.000" head space and 0.000" stretch.

At that point, if you manage the case condition well, you can get 40 to 50 loadings from it.


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Originally Posted By: nortexHow would one even go about measuring from closed bolt face to shoulder start? Maybe chamber cast, but that seems like a lot of extra work.

A chamber case does not measure anything from the bolt face - it only gives you measurements of the chamber from the web forwards.

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Originally Posted By: SmokelessCatShooter. You make a lot of sense.

Very well explained.

Thanks for your time, and patience.

I need a nap!

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Catshooter, say hypothetically I had a lathe and had the barrel out of the action, how much approximately would I need as a minimum to set the barrel back in order to be able to follow up with a reamer? I do realize that variations in the existing chamber tolerances make that an impossible dimension to derive, but as an estimate what would be commonplace? I'm not sure of the thread pitch on a ruger M77 barrel, but would like it to index the same as original. So would one full rotation so to speak be enough set back to allow the proper chambering job to be accomplished, I'm thinking it would be more than needed. I have looked on the internet and all I have found is indicating 16 tpi, which should work out to .0625" setback for one exact revolution.
 
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Originally Posted By: CatShooterOriginally Posted By: nortexHow would one even go about measuring from closed bolt face to shoulder start? Maybe chamber cast, but that seems like a lot of extra work.

A chamber case does not measure anything from the bolt face - it only gives you measurements of the chamber from the web forwards.

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That's what I thought, so why even give a measurement of bolt face to shoulder.
 
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