A while back I acquired a beautiful custom rifle that had not been fired except to fire form some cases. It's a 7mm with CBM Mk I stamped on the barrel. I was told it was built in the late 70's by a gunsmith in Oregon by the name of Gene Colton (hence the Colton Belted Magnum "CBM" moniker). He apparently created a wildcat based on the 7MM Rem Mag cartridge. Besides the MK I he also designed the MK II which I was told is a longer case variant of the same caliber. The rifle has a 24 in. Shillen barrel, Winchester action, and this firearm was supposedly tested by Guns and Ammo Magazine and appeared in one of their issues. I have spent countless hours trying to find some reference material on the cartridge design and struck out. I want to have some reloading dies created for the gun but really need the cartridge specs first. If any one out there has any knowledge of this cartridge or a copy of Guns and Ammo magazine featuring the firearm testing I would be most grateful hearing from you. I tried to get an old copy from Guns and Ammo but they were not helpful ............. actually, they blew me off. Thanks in advance if anyone has any data on the cartridge.
Need help with a wildcat cartridge
- Thread starter CSM19Z5M
- Start date
BigDMT
Probably should have done your research BEFORE buying the rifle. But that's just hindsight and does you no good now.
Anyhow. You could have a chamber mold made by a gunsmith and then get all the chamber dimensions from it.
OR if the rifle is not too old, perhaps you could call Dave Kiff at PT&G to see if he has any records of a reamer in that caliber. If that rifle was made since PT&G has been making reamers, there's a pretty good chance they made the chamber finish reamer for it.
Good Luck!
Anyhow. You could have a chamber mold made by a gunsmith and then get all the chamber dimensions from it.
OR if the rifle is not too old, perhaps you could call Dave Kiff at PT&G to see if he has any records of a reamer in that caliber. If that rifle was made since PT&G has been making reamers, there's a pretty good chance they made the chamber finish reamer for it.
Good Luck!
Darn, thanks for all the quick replies from everyone. I should have noted that I have some fire formed brass as well as some loaded cases that I assume were also for fire forming. I acquired the rifle with eyes wide open and for a great price and, since it is basically new, and assuming I could eventually strike out looking for data on the cartridge, I figured I could just have it rechambered to 7MM Rem Mag, one of my all time favorite calibers, or have a chamber casting made and then a set of dies and start working up loads for it. It never occurred to me that I might find a vendor who had a reamer for it as BigDMT advised. Thanks again to everyone for your advise.
BigDMT
GSPV said:
I'd have to disagree completely with that statement. You have no idea how well the brass fireformed to the chamber. To make dies off of fireformed brass is a HUGE gamble with an unknown wildcat cartridge.
Have a chamber cast made like I stated before. Do not use that brass to make dies or you'll probably end up with a bad set of dies that size the case too much and make it unsafe.
jonbearman
I live in new york state,how unfortunate !
Could he use the cow method to make sure the cases are formed or why not have a good smith figure out how close the brass is to the chamber cast. Do the original cartridge's fit the gun and does the bolt close on them,if they do you could try scotch tape 1 layer at a time to see if the shoulder is close to the headspace.In another words if one piece of tape stops the bolt from closing I would think the cartridge was fired in that gun,also ink the body and shoulder and neck with sharpie to see if there are rub marks on the shoulder,that would at least confirm they were shot out of this rifle.You could put a sheetmatal screw in the flash hole and rotate it around and see where the rub marks are.You could call sammi to see if it was listed on their database.Google wildcat collectors and see if you can contact some of the people that collect and they may have imfo too.
Ah the joy of acquiring a true wildcat-chambered rifle.
Yes it's fairly easy to make a chamber casting but reading the resulting dimensions can be a challenge. Too, with the usual casting metal there's a fairly short window of time after casting when those dimensions will be 'true'... about 30 minutes as I remember it, so maybe best left to a gunsmith familiar with the practice.
Fired cases - usually at least three times fired and unsized each time - can and are used for 'dimensioning' fully suitable sets of reloading dies. Still a pricey option; a sizing die with three neck bushings cost me ~ $250 back about 2005 for a then-new 6.5 Grendel spacegun.
I'd probably just buy & chamber a new barrel for something suitable & save the custom barrel for later on....
Yes it's fairly easy to make a chamber casting but reading the resulting dimensions can be a challenge. Too, with the usual casting metal there's a fairly short window of time after casting when those dimensions will be 'true'... about 30 minutes as I remember it, so maybe best left to a gunsmith familiar with the practice.
Fired cases - usually at least three times fired and unsized each time - can and are used for 'dimensioning' fully suitable sets of reloading dies. Still a pricey option; a sizing die with three neck bushings cost me ~ $250 back about 2005 for a then-new 6.5 Grendel spacegun.
I'd probably just buy & chamber a new barrel for something suitable & save the custom barrel for later on....
GSPV
A failure to plan is a plan for failure.
Let me restate: With reasonable care that the brass is well formed to the chamber, it can be used to make dies.
If you contact any of the custom die makers, they are going to ask for a reamer print, if available, and several pieces of brass that have been shot in the chamber three times with neck sizing only.
I have several custom dies and have had exactly that experience. I and hundreds of others are happily shooting on dies made that way.
With that said, mistakes are always possible. I have a FL die from one of the best custom die makers that sets the shoulder back excessively...like just over 70 thousandths.
If you contact any of the custom die makers, they are going to ask for a reamer print, if available, and several pieces of brass that have been shot in the chamber three times with neck sizing only.
I have several custom dies and have had exactly that experience. I and hundreds of others are happily shooting on dies made that way.
With that said, mistakes are always possible. I have a FL die from one of the best custom die makers that sets the shoulder back excessively...like just over 70 thousandths.
BigDMT
GSPV said:
That's exatcly what I mean. It's a gamble. The brass might make a good set of dies, might not. If he wants to gamble with spending $250-$300+ set of dies and a 4-6 month wait only to end up with a bad set of dies, then I suppose he could use the fired brass.
The big problem is that NOBODY has chamber dimensions, so even if he sent 3 cases to a die builder, there's still no guarantee that the headspacing is correct. Plus who knows if the brass was annealed to give a truer chamber form. Just too many unknowns that make it a risk that's not worth taking IMO.
GSPV
A failure to plan is a plan for failure.
Let me restate again.
I have a whole shelf full of custom dies, all for wildcat cases of one stripe or another, all made from brass, and all but one work better than the off the shelf dies for standard chambers. Many, many people have the same experience. After all, there is no standard PPC chamber, just to start.
How many custom dies do you have, BigDMT? How many have been good, how many bad?
I have a whole shelf full of custom dies, all for wildcat cases of one stripe or another, all made from brass, and all but one work better than the off the shelf dies for standard chambers. Many, many people have the same experience. After all, there is no standard PPC chamber, just to start.
How many custom dies do you have, BigDMT? How many have been good, how many bad?
jpretle
Gold $$ Contributor
If those fired brass came from that chamber, load them up and shoot them. I have 6 sets of dies for wildcat chamberings, made from fired cases. Have never had a problem w/ any of them.
You should be able to get enough of the neck sized w/ any one of several sets of 7mm dies, enough to hold a bullet for developing pressure. Done it many times.
You should be able to get enough of the neck sized w/ any one of several sets of 7mm dies, enough to hold a bullet for developing pressure. Done it many times.
BigDMT
I'd still have a chamber casting made to be sure since it is a caliber with "unkown" chamber dimensions.
I suppose then that custom dies could be made from the fired cases. A gunsmith should have a set of shims he could use to check headspacing on the fired cases as a cheaper and quicker alternative to a chamber casting. A couple minutes using shims on the shoulder of a fired case should be able to determine whether or not headspacing is acceptable.
I've had custom dies made, but I had them made before the barrel was chambered using reamer prints. I then formed cases with them and had the chamber headspaced off the full-sized/formed case. That has always produced very accurate barrels with chambers that are "catered" to the dies, rather than the other way around. Another advantage to this method is that the dies are already set up to your press with proper headspacing and ready to load rounds before the rifle is complete. You could even go as far as loading rounds for testing before the rifle is complete, but I don't because I like to find "jam" on the lands for reference to bullet seating.
Of course that would be more difficult with an Ackley shoulder wildcat, but I did use a necked down 221 Fireball case with the factory 23 degree shoulder to headspace the chamber on a 20 VarTarg. It shot nearly as accurately with unfired brass as when rounds were loaded with the fired brass having an extra 7 degrees on the shoulder.
I suppose then that custom dies could be made from the fired cases. A gunsmith should have a set of shims he could use to check headspacing on the fired cases as a cheaper and quicker alternative to a chamber casting. A couple minutes using shims on the shoulder of a fired case should be able to determine whether or not headspacing is acceptable.
I've had custom dies made, but I had them made before the barrel was chambered using reamer prints. I then formed cases with them and had the chamber headspaced off the full-sized/formed case. That has always produced very accurate barrels with chambers that are "catered" to the dies, rather than the other way around. Another advantage to this method is that the dies are already set up to your press with proper headspacing and ready to load rounds before the rifle is complete. You could even go as far as loading rounds for testing before the rifle is complete, but I don't because I like to find "jam" on the lands for reference to bullet seating.
Of course that would be more difficult with an Ackley shoulder wildcat, but I did use a necked down 221 Fireball case with the factory 23 degree shoulder to headspace the chamber on a 20 VarTarg. It shot nearly as accurately with unfired brass as when rounds were loaded with the fired brass having an extra 7 degrees on the shoulder.
A friend said to check with RCBS he thinks they made the dies. Larry
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