As I understand it, if a gun has too much headspace the the firing pin can move the case forward before it discharges and the case then slams back against the bolt creating an extremly dangerous set of cirumstances. What is to keep this same thing from happening while fireforming an AI case?

Seat the bullets way out, so that they are jammed hard into the lands. This will keep the case flush against the boltface.

Wstnhntr---

EVERY fireforming round should have *feel* in the bolt when closing. There should be NO slack, NO excess headspace, NO slack.

This applies to rimless cartridges only.

All you need to do it is an expander plug of one larger caliber.

If you're fireforming 257 AI, for instance, and you can't feel the slight crush of the shoulder with a factory round there's two things to do.

First take it back to whoever did the work and tell him to fix it....

Second (if the first can't be done) is to replace the .257 expander plug with a .264. Then adjust the FL die until it creates a case that contacts the chamber at the neck-shoulder junction enough to make a mark and feel on the bolt.
(Please disassemble the bolt before try this. You can't believe how many accidents happen with a rifle in the reloading area....several deaths, in fact.)

Be sure to use a FULL load when fireforming. You have to have full pressure to properly form the case. If you have a case with a protruding primer, DESTROY that case!!. It has excess headspace built into it.

wstrnhntr,

I live on the east side of the valley from you. If you need, email me your phone number and I will check out the weapon for you. I do a lot of the P.O.Ackley stuff here in the valley...

The correct way to headspace for the AI cartridges, is to set the barrel back enough to allow approximately a -.004 crush on a factory case. This will assure a proper hold on the case while fireforming. To check this out in an AI chambered weapon, first remove the bolt nose ejector as in the Remington 700's and those that are likewise equipped with them. This can push a case forward and give you an false reading. Remove the firing pin while you are at it so you feel nothing when you close the bolt except the contact of the case head and the bolt face. Insert a factory round and close the bolt. Remove the case and examine it. If the chamber is properly set up, you should see a bright ring at the neck/shoulder junction indicating positive contact.

Some folks wish to leave the bolt nose ejectors out while they fireform just as an added precaution.

Conventional headspace (rimless) is based on the gap between the boltface and the datum line on the shoulder of the chamber. Gunsmiths not familiar with the AI chamber, simply run the AI reamer in, to straighten the body and form the shoulder giving no thought to the excess headspace they just created by moving the shoulder forward.

If you have a weapon with such problems, I would highly suggest having it repaired rather than trying to make it work by adjusting the brass to fit the chamber. Some unsuspecting soul may end up with such a weapon and injure himself or others. Get it repaired right.

Malm

If an "Ackley Improved" chamber has been reamed correctly, the neck/shoulder junction is set back .040". This allows the "crush fit" that JBelk spoke of. Supposidly, one of the advantages of Ackley Improved chamberings (when done properly) as opposed to some of the other wildcat chamberings is that this "crush fit" will allow the use of "standard" ammunution in a pinch.

Problems can arise when using Ackley Improved dies for necking up.

For example, if you are necking up 30-06 brass to form an Ackley Improved case such as 8mm-06, 338-06 or 35 Whelen, (improved) and are using the Ackley Improved resizing die to expand the neck, you must back off the die so that the neck is not "set back" before fireforming. I use a .060" shim under the locknut when necking up for 8mm-06 A.I.. I then remove the shim when resizing the already fireformed cases.

I no longer concern myself with "long seated" bullets when fireforming. I do as JBelk advises, make sure I feel the crush fit resistance when I close the bolt handle.

As Malm mentioned, some 'smiths just run an AI reamer in w/o setting the barrel back, often creating a dangerous situation. This can be compounded by the rifle owner shooting non-AI reloaded cartridges that have had the shoulder set-back with a short die. The only good thing that can happen is the excessive h'space keeps the firing pin from adequately impacting the primer. Some shade tree 'smiths are working in areas that they should never get near. I'm not a gunsmith, just do my own things.

Actually there wildcat junkie, on the Ackley Improved design, the neck/shoulder junction remains the same. By going to the 40 degree shoulder angle of the Ackley Improved design, the shoulder is actually moved forward with this change in angle, and it is this angle change that is the cause of the excess headspace. That is why the barrel needs to be set back.

Malm

Just a little confusion there on the junkie's part I think. Or probably just a typo. He meant to say the shoulder junction is set back .004" which is another way of saying the chamber is cut .004" below minimum HS in a std chamber. .040" crush is just a little more than one wants to attempt!
One other thing that should be mentioned is, when you are fire forming your brass, use a good, snappy load. Do not use a reduced load. To do so will produce brass with excess headspace. Regards, Bill

It was my understanding that the dim. from bolt face to datum line (at some point on the shoulder) remained the same. If the shoulder angle changes but the dim. remains the same there CANNOT be enough material to ream the new shoulder completely to the neck. In my mind I see a possible double shoulder angle. Is this right? I wish I could find the drawings from Clymer that I had that showed all of this, from about 1996?

Jay,

The datum line is erased with the chutting of the new shoulder. The only thing that remains the same is the neck/shoulder junction which must be tight enough to hold the round in place while fireforming with a snappy load (thanks Bill).

Yes, .040 would be a bit much to ask of the brass...

Malm

Concerning the 338-06AI I once had, I used 270 Win brass, and necked-up to 338. This allowed for a snug feel when closing the bolt.
On my current 375 WhnAI, I use necked-up 35 Whn brass, but the 'feel' on closing the bolt is slightly less. ~~~Suluuq

Wildcat junkie,

I don't have the Nosler #4 book, But it sounds to me like you need to find another source for your information. I have the drawings, reamers and over 20 years of experience chambering for these cartridges but, you go ahead and believe what you want... and while you're at it, lighten up a little or you'll have a stroke, or, prematurely wear out your exclamation key.

Malm

I fear that you guys are splitting hairs.

First of all, factory chambers are typically notoriously oversized. The factory starts with a chambering reamer which is at the very maximum diminsion so that they can get the most chambers out of it before it wears below minimum dimension. And factories are much more fearful of someone complaining that ammunition was hard to chamber than someone complaining that their chamber stretched the devil out of fired brass (which is thrown away 90% of the time).

Second, starting with an oversized (or too long) chamber is the reason the barrel would need to be set back for an A.I. rechamber. If the original chamber were of the proper length to allow the A.I. reamer to clean it up without moving the neck-shoulder junction forward, then there would be no need to set back the barrel (at least in theory).

Third, we're talking about wildcats here, so it should be of little consequence whether the chamber is too long for factory loads, anyway. In my opinion, even the A.I.'s should be considered wildcats and the brass tailored to the specific chamber. If the chamber is too long to headspace properly with new brass or a factory cartridge, then use the methods outlined in previous posts to make it headspace properly before the initial firing.

I treat all of my rifles (at least the bottlenecked ones) as if they were wildcats and tailor the brass to fit the chamber. That way, it is irrelavent whether they are belted, beltless, rebated, rimmed, or whatever.

Just thought I'd thow in my 2 cents on this discussion. I'm going to add an image of all the Standard, AI, Gibbs and Hawk based wildcats. This image was draw up in AutoCAD with each overlaid on top of each other. The drawing was converted to a JPG for universal viewing. The image could be clearer, but I think it's worth a thousand words as-is.

You must set the barrel back to properly rechamber to the AI version. This distance is 0.040" for the .30-06 ONLY!!! This distance is different for the .338-06 and 35 Whelen! Just look at the drawing. The distance for the 338-06 is 0.01" and once you get to the 35 Whelen, there is no need to set the barrel back.

I have seen a "double shoulder" chamber job on a barrel made for me. We were taking a 375 H&H barrel and rechambering to 338-375. I think it was set back one barrel turn, but that wasn't enough. Had to send to back to get the H&H shoulder "cleaned out" all the way.

If anyone wan't to AutoCAD source drawing, just drop me a line.

Thanks guys,

I havent got my AI back from the smith yet but I was curious. It'll be my first wildcat and Im looking forward to it. I was assuming that the reason the barrel was set back was to compensate for material removed from the chamber, but now I understand. Ill make certian that Im getting a crush at the junction.

Malm,

I appreciate the offer and will keep it mind. Are you by chance related to the Malmborgs from Kearns?

Lars
G: Thank you very much! Oops there goes that exclamation key again. Indeed your picture was worth a thousand words.

It looks to me that to some extent we are all correct. The "set back" depends on the caliber.

I checked my Nosler #5 manual for all of the Ackley Improved variants listed. here are the "set backs" (neck/shoulder trasition)

• 22-250 Rem. A.I. = .020"
• 257 Roberts A.I. = .006"
• 280 Rem. A.I. = .024"
• 30-06 springfield = .040"

My 8mm-06 A.I. cases measure approximately .040" shorter to the neck/shoulder transition. This data is taken from actual cases measured with a dial caliper as I have no published data for this round. The chamber was cut with a 30-06 A.I reamer with a pilot and then the neck/throat was cut per my sample "dummy" round.
Thank you again Lars G for clarifying the issue.

Jay,
Dace Kiffs drawings show a difference for the 30/06 AI of .001 for the datum line with the AI being the shorter of the two. Interestinly enough the 280 AI shows the datum line moving forward by .054 which is what I would expect. The datum line on the 30/06 class of cartridges is .375 dia by the way. On the 243 AI the datum line (.400"dia)moves forward by .090. So it seems that the 30/06 AI is the exception when it comes to the retention of the original datum measurement. It would appear that headspace guages are not interchangable between the 25/06 AI and the 30/06 AI while they are the same for the standard cartridges. This seemed strange to me so I went down and measured my 30/06 AI reamer and compared it to my 30/06 match grade reamer and sure enough, the AI neck is longer by nearly forty thousandths. In the other cases the juncture of the neck and shoulder is moved back by .004 to .007 while the datum line moves forward. So there is a real lack of standardization among the AI cartridges! I notice that the datum line location (same dia)for the 6.5/06 is .006 further ahead than that for the 25/06 AI. Chambered using these specs the 6.5/06 AI chamber would be too long and would not support the brass while fireforming unless the brass were necked down and left with a secondary shoulder to provide a headspacing point. All in all it shows there is more to the Ackley Improved mystery than meets the eye! I've been chambering Ackley improved cartridges with .004 to .006 negative headspace for 25 years and have been happy with it. The cases fit with a light "crush" and fireform nicely. Factory loads are fired with no problem (where factory loads exist).
I could see the point in retaining the same datum point on the 243AI for instance, since it would yield a longer neck. This would be a benefit with the 243 since the neck is short. But on the 243AI the juncture of the neck and shoulder is moved back the usual .004 and the short neck is retained. On the 30/06 with it's long neck, the datum measurement is retained and the neck lengthened. The question this raises in my mind (such as it is) is, Why? Where did these specs come from originally? Did Ackley make the original guages and screw up on one set? Did he start out one way then change his mind? I'll admit to being baffled by this. It's worth pursuing further. My apologies to the Wildcat Junkie! Regards, Bill.

Bill Leeper: Your apology is graciously accepted, although I don't feel that it is neccesary as your responses to my post were quite civil even though we didn't agree. (at the time)

This has been a most enlightening thread for me. One of the reasons I participate in this forum is to learn. It seems that perhaps we all have learned quite a lot from this discussion.

As I said, it seems we were all correct to some degree.

I wish that ole P. O. was alive so that he could solve some of the mystery involving the various A.I. variants. Perhaps he did it just to perplex us!

Regards: Wj

[ 10-30-2002, 17:10: Message edited by: wildcat junkie ]