Rechamber to Ackley? 223

dcloco

I have a new factory Rem barrel in 223 (new, takeoff). Is it possible to rent a 223 AI reamer and make it an AI or do I have to start from a non chambered barrel?

Hawk Carse

The usual procedure for rechambering to A.I. includes setting the barrel back a turn, including facing off the breech, and setting the shoulder back. This ensures minimum headspace so you can shoot factory loads to fireform to A.I.

bpost

I thought the AI rechamber if done correctly does not have any effect upon the headspace of the parent round....???? The idea of the AI is to change the shoulder angle and reduces body taper. This allows the shooting of the parent round to fireform brass.

Am I mistaken?

JustC

You have to set the barrel back to correctly do an AI chamber.

The datum line is moved rearward.

Hawk Carse

I looked it up in Ackley's book.
He says the standard Go headspace gauge becomes the No-go for the A.I. chamber; the A.I. Go is .004" less. You need a close chamber because the headspace surface shooting a standard cartridge in an A.I. chamber is just the junction of neck and shoulder, not the whole shoulder.

nononsense

dcloco,

"Is it possible to rent a 223 AI reamer and make it an AI or do I have to start from a non chambered barrel?"

Yes, you can rent an Ackley Improved reamer. Yes, you have to set the barrel back in order to cut a correct chamber. Here is a more detailed explanation:

Headspace is normally considered to be the distance from the face of the locked bolt to a point on the case shoulder called the datum line. This line is arbitrary to a great degree, being a point where the diameter of the case shoulder is .375" in most cases. Some use different diameters as datum points, and one in particular, the original Government .30 caliber (.30-06) does not use the datum point at all but uses the point where the shoulder joins the case body. Commercial .30-06 cases use the datum point. When we start changing things, such as forming the Ackley 40 degree Improved chamber and cases, we no longer can use this datum point for headspace, but must use the juncture point where the neck joins the shoulder. In standard chambers some part of the case shoulder, including the datum point, would contact the chamber to provide proper headspace. But when we cut out the chamber in the shoulder area, as well as some along the case body area, to change to the Improved configuration there is no longer any support for the shoulder of a standard case. Therefore, the datum point and shoulder area of the chamber no longer provides headspace. The only point of contact will be the neck-shoulder juncture. This is a very fine line. And headspace is now held between the bolt face and this neck-shoulder juncture point. The shoulder of the standard factory case is no longer supported by the chamber wall.
To assure that even the shortest standard cartridge brass will fit this Improved chamber snugly, without shoulder support, the standard headspace must be reduced by .004" from that of the factory, or SAAMI, specifications. This now causes the standard SAAMI headspace "GO" gauge to not fully enter the chamber. Thus, the standard "GO" gauge becomes the "NO-GO" gauge for use in Improved chambers! As an example, the standard .250 Savage "GO" headspace gauge in the .250 Ackley Improved chamber will not allow the bolt to close. This is required because the manufacture of pliable brass cartridge cases can not hold the neck-shoulder juncture point exact, and we do want the standard cartridge to fit rather snugly at this point in any Improved chamber.

Best.

dcloco

Thanks!

I am considering to add another 223AI to my lineup.

I have a new Rem varmint 223 barrel...

Also considering to chamber to 204 tactical...but I already own a 204 Ruger.