offroadmatt
New member
Alright guys, don't beat me up to bad here. I've spend HOURS over the last couple weeks compiling information about the 7mm-06. I had a customer come in looking to have his Enfield currently chambered in 7mm-06 IMP fixed and some loads made to shoot out of it. Believe it or not there isn't a lot of information floating around the internet about it and most threads that reference it quickly get off topic and the subject changed to the .280 Remington. Although similar they are different. And i'm sure if anybody was to have a rifle built today they would choose the .280 chambering over any variation of 7mm-06. But this isn't about what you would do new or which is better or why you just have it rechamber. This is about not changing a existing firearm already chambered and stamped in 7mm-06 and making it shoot as designed some 40 years ago.
So here is some excerpts from my letter to him:
"After extensive research it has been determined that your rifle chambered in 7MM-06 IMP is indeed a copied variation of P.O. Ackley’s design. Although slightly different in several regards.
Mr. Ackley used a parent case. In the case of say 30-06. He would have reamed the chamber to have straight walls, a 40-degree shoulder, and the new cartridge would have head-spaced off the forward case/neck junction, and not a datum point on the shoulder as traditional to SAMMI specs. In other words, a Go Gauge for the 30-06 would become the No-Go Gauge for a 30-06AI. And the proper Go Gauge would be .004" shorter then the standard cartridge GO Gauge. What made Ackley’s chambers unique was the ability to shoot either the standard parent case or his (Ackley Improved) case in a rifle rechambered to his new specs with the larger powder capacity. Making the availability of ammo less a problem. Should say someone traveling the country run out of thier special reloaded ammo they could buy factory ammo of the standard chambering and safely shoot it in thier rifle. Similar too how you can shoot .223 ammo from a 5.56 rifle but not the other way around. Poor comparison but you get the idea.
Anyway, because your 7mm-06 IMP uses a necked down 30-06 case, that shoulder/neck junction changes again. As the neck is smaller the shoulder becomes longer, and another issue is the varying lengths of chambers. Thus, Ackley’s method of using standard SAMMI gauges no longer works. And this cartridge becomes a true Wildcat.
The variations of 7mm-06 we have seen in our studies have for the most part been 40-degree shoulders with a couple exceptions. The location of the shoulder has varied by as much as .050” Actual shoulder location would depend on whether you change the shoulder angle before or after necking down to 7mm.
In should be noted that some firearm “enthusiast” would suggest that you have a .280AI. Ackley’s version of a .280 Remington or as earlier called the 7mm Express. Renamed the .280 to help prevent accidental chambering in 7mm Mag. The .280 is based off the 7mm-06 wildcat cartridge and is very similar. However the .280AI and .280 Remington are slightly longer then a 7mm-06 and this was by design of Remington to prevent accidental chambering of the 280 in the similar stamped and popular .270 Win.
There is no Standard cartridge round for your 7mm-06 IMP. And reloading for you rifle will require specialty made dies unique to it alone. We recommend using load data for the .280AI and a starting load 1 full grain less then printed to find a powder and charge weight to begin your load development. We also suggest using quality 30-06 brass necked down and then “fire formed” to fit your chamber".
The drawings were provided to me from CH4D. Along with the one we made for this particular rifle. Some of the drawings recommend the 25-06 as the parent case for fire forming as it is longer to aid in filling the chamber and not over stretching the brass.
So here is some excerpts from my letter to him:
"After extensive research it has been determined that your rifle chambered in 7MM-06 IMP is indeed a copied variation of P.O. Ackley’s design. Although slightly different in several regards.
Mr. Ackley used a parent case. In the case of say 30-06. He would have reamed the chamber to have straight walls, a 40-degree shoulder, and the new cartridge would have head-spaced off the forward case/neck junction, and not a datum point on the shoulder as traditional to SAMMI specs. In other words, a Go Gauge for the 30-06 would become the No-Go Gauge for a 30-06AI. And the proper Go Gauge would be .004" shorter then the standard cartridge GO Gauge. What made Ackley’s chambers unique was the ability to shoot either the standard parent case or his (Ackley Improved) case in a rifle rechambered to his new specs with the larger powder capacity. Making the availability of ammo less a problem. Should say someone traveling the country run out of thier special reloaded ammo they could buy factory ammo of the standard chambering and safely shoot it in thier rifle. Similar too how you can shoot .223 ammo from a 5.56 rifle but not the other way around. Poor comparison but you get the idea.
Anyway, because your 7mm-06 IMP uses a necked down 30-06 case, that shoulder/neck junction changes again. As the neck is smaller the shoulder becomes longer, and another issue is the varying lengths of chambers. Thus, Ackley’s method of using standard SAMMI gauges no longer works. And this cartridge becomes a true Wildcat.
The variations of 7mm-06 we have seen in our studies have for the most part been 40-degree shoulders with a couple exceptions. The location of the shoulder has varied by as much as .050” Actual shoulder location would depend on whether you change the shoulder angle before or after necking down to 7mm.
In should be noted that some firearm “enthusiast” would suggest that you have a .280AI. Ackley’s version of a .280 Remington or as earlier called the 7mm Express. Renamed the .280 to help prevent accidental chambering in 7mm Mag. The .280 is based off the 7mm-06 wildcat cartridge and is very similar. However the .280AI and .280 Remington are slightly longer then a 7mm-06 and this was by design of Remington to prevent accidental chambering of the 280 in the similar stamped and popular .270 Win.
There is no Standard cartridge round for your 7mm-06 IMP. And reloading for you rifle will require specialty made dies unique to it alone. We recommend using load data for the .280AI and a starting load 1 full grain less then printed to find a powder and charge weight to begin your load development. We also suggest using quality 30-06 brass necked down and then “fire formed” to fit your chamber".
The drawings were provided to me from CH4D. Along with the one we made for this particular rifle. Some of the drawings recommend the 25-06 as the parent case for fire forming as it is longer to aid in filling the chamber and not over stretching the brass.
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