The official Mike Bellm's

Bellm TCs

TC Contender, G2, Encore/ProHunter Performance Center



Forming .25-06 Improved Brass


I recently found your site and have learned alot from it.  Thanks for all the info. I hope you can find the time to educate me a little more. Could you please provide me with the best method for forming .25-06 Improved brass from standard .25-06 brass in an Encore?  I have read several comments about doing this, but none were in reference to an Encore. 

Also, I am about to order your CD-ROM for Encore trigger jobs.  I will have three of these to do (myself and friends).  Thank you so much for providing products that are educational as well as economical.

Thanks again,
Kelly Ray
Cape Girardeau, MO

P.O. Ackley defined an improved cartridge to include the requirement that it fire factory ammo, or factory new brass necked up or down as the case may be, without stretching the case.  IF the person doing the chamber work cuts the chamber to the correct depth, which is by Ackley's definition at least .004" shorter than standard, then all you do is fire the standard ammo in the imp. chamber.  However, two things can occur to effect this.

1) The standard round headspaces on the neck shoulder junction in the imp. chamber.  The shape of this point varies on the brass case and also in the chamber.  Thus sometimes even the .004" shorter headspace is not short enough and will still stretch cases. 

2) Add to this the fact that when the firing pin drives the case forward in the chamber, the headspace point at the neck/shoulder junction sometimes collapses to varying degrees.

In either of the above situations, it is sometimes necessary to take additional steps to insure that no stretching of the case occurs during fire forming.  One method using a highly compressed charge of slow powder with the bullet jammed firmly into the rifling is described on the website.

One point is absolutely necessary to keep in mind.  If on any Improved cartridge, the primer protrudes from a fire formed case, then the case is too short from shoulder to head, and when it is loaded to full pressure, it will stretch.   I.e.. primers should NEVER protrude from fire formed cases.  If they do, you need to take additional measures to make sure your fire formed cases fill the space from the headspace point to breech face or bolt face completely.

Tip:  If you close the barrel in the frame with a standard round in the chamber, it should show a bright ring at the neck/shoulder junction when you remove it..... without firing it.  I.e.., there should be a tight fit at the neck/shoulder junction.

An important point to be made is that you cannot rechamber an existing .25/06 (or any standard chamber) to its improved counterpart without setting the barrel back. And with the lug welded on the barrel, this is not practical to do.  On a fixed barrel receiver where the barrel is threaded into the receiver, it is a simple matter to face off appropriate surfaces on the barrel and simply screw the barrel in further, thus moving the existing neck/shoulder junction back..... then rechamber.  Again, this cannot be done on these break open TC firearms.  You have to start with a shorter chamber such as .... .256  Win Mag, .25-35, .257 Roberts, etc. in order to rechamber to .25/06 Imp.

A final point.  You can rechamber the .25-06 chamber to the improved configuration, cutting the chamber deeper than normal, and take measures to fire form the shoulder forward correctly.  But since it will not fire the factory ammo without stretching cases, technically, it is not an improved, but something else.

Tip:  Neck down .30/06 brass leaving the neck and new shoulder junction on the case far enough up the .30/06 neck to get tight head-spacing on it.  It will be simply a step on the neck where you stopped necking it down to .25 cal.    This can be done with a standard .25/06 die backed off the appropriate amount.

Another tip:  Starting with the .25/06 chamber, you can cut a .25x.280 Rem. Imp. chamber, which is about .050" longer from head to neck/shoulder junction, and have a true improved chamber.

RE: the CD - You're welcome.  But also, you get the satisfaction of doing it yourself, and I get to spend more time doing machine work instead of bench work.  So we both win.

All the best,
Mike Bellm

<-- Back to the Table Of Contents


  eCommerce solution by
  Nibbles Knot Web Authoring

  Web Hosting by


All Images and information contained on this site are the intellectual property of Bellm TC's.