7mm-06 Improved (Compiled Information and Drawings).

[offroadmatt]

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.

 

[offroadmatt]

Some more drawings

 

[Nathan]

So did you make him some ammo? If so, how?

 

[offroadmatt]

So did you make him some ammo? If so, how?

Working on that now. Having a custom set of dies made as we speak.

 

[F. Guffey]

Anyway, because the 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. Thus, Ackley’s method of using standard SAMMI gauges no longer works. And this cartridge becomes a true Wildcat.

Because smiths and reloaders believe 'the datum method' is a joke they make this stuff up.

If I was doing 'it' I would chamber the rifle to 7MM Gibbs. And while going it I would choose to use the 280 Remington case instead of the 30/06, as I have said 20 times there is something about forming cases reloaders and smiths do not understand the 30/06 case is not a good choice, I understand nothing has happened between the last time I said it an now to change anyone's mind just do the best you can.

the 300 win Mag is said to have a short neck. SO? I do not use tension because I do not have a gage that measure tensions; all of my gages measure bullet hold in pounds because the gage is marked off in pounds. I am the fan of bullet hold, I want all the hold I can get so right off I start by scheming how I can increase the length of the neck.

The 30 Gibbs has a neck that is shorter than the neck on the 300 Winchester Magnum meaning the 30 Gibbs has less bullet hold. the neck on the 30 Gibbs is .217" long from the shoulder/neck juncture to the end of the neck.

SO! I use the 280 Remington case. The case body on the 280 Remington is .051" longer from the case body/shoulder juncture to the case head than the 30/06 case when measured from the case body/shoulder juncture to the case head. And the 280 case length from the end of the neck to the case head is .041" longer than the case length of the 30/06 case.

And then there is the 270 Winchester case; it is longer than the 30/06 case and it is the same length as the 280 Remington case.

I have a friend that built 4 magnificent 7MM/06 rifles. It was impossible to improve on the accuracy of three of them, on the 4th rifle something went seriously wrong,. I checked the rifle with a few home made tools, after checking I told him what went wrong, he claimed that was impossible but in forensic there is something called 'chain of custody'. I did not have the opportunity to check the rifles after he built then. the rifle that was not accurate came back to him and then to me.

F. guffey

 

[Scorch]

If I was doing 'it' I would chamber the rifle to 7MM Gibbs.

I wouldn't. I would rechamber to a standard factory round, 280 Remington AI. @80 Remington is a slightly modified 7mm-06 (shoulder moved .050" forward), and since yours is improved, you would need to go with the AI version to clean up the chamber. That way you would have no special dies to get, you can shoot factory ammo, and if you ever try to resell it, it will sell a heck of a lot faster than an oddball wildcat. Nothing wrong with those other cartridges, just hard to buy ammo for a wildcat.

 

[offroadmatt]

These are the exact responses every thread I've ran across has. Why not .280? I would do 7mm Gibbs..... We are not here to pick another round to replace the 7mm-06. Simple sharing my hours of research in hopes that someday somebody stumbles across this thread looking for information on a 7mm-06. As i had little to luck in doing so myself.

That being said the responses do in a way help. As maybe, just maybe! Somebody has a 7mm-06 and is looking to have it modified to shoot off the shelf ammo.

 

[F. Guffey]

I wouldn't. I would rechamber to a standard factory round, 280 Remington AI. @80 Remington is a slightly modified 7mm-06 (shoulder moved .050" forward), and since yours is improved, you would need to go with the AI version to clean up the chamber

If I went with the 7mm Gibbs I would have to cut a new chamber' if I used a Mauser action I would have a difficult time with the long 280 Remington case. And then there is that part about cleaning the chamber, If I started with a 30/06 chamber and then used an Ackley chamber the only part of the chamber that would not clean up is the shoulder neck juncture. The shoulder/neck juncture is the part of the chamber that allows reloaders to fire form cases the Ackley way. I understand how confusing that is but; if the shoulder juncture is not cleaned up the clearance will not change. I know; it is almost impossible for smiths and reloaders to do the numbers. When using a 30/06 case the new chamber is required to form part of the shoulder at the shoulder neck juncture when the case is chambered and the case body/shoulder juncture and case body is formed when fired.

And then there is that part smiths and reloaders do not understand about forming cases.

If I was doing 'it' I would chamber the rifle to 7MM Gibbs.

And then I built a 338/280 Remington, I know there could be a struggle getting the bolt to close but I purchased 4 rifles that were sold to be as being suspect. the receivers were long for Mausers, the added length made it possible to fudge. When testing the receivers I tested all 4 receivers with one barrel and one bolt.

F. Guffey

 

[F. Guffey]

That being said the responses do in a way help. As maybe, just maybe! Somebody has a 7mm-06 and is looking to have it modified to shoot off the shelf ammo.

The 7MM06 was never a good ideal. Again, a friend build 4 magnificent rifles chambered to 7MM06/Gibbs version, the first thing he asked me about was the case head separations; he had 5 of the first 10 rounds fired separate. I told him I could have determined if that would happen before I left the shop: I told him I could have fixed the problem after I got to the range. I told him I could have fixed the problem before I left the shop.

I also told him I could have formed the cases to fit before I left the shop. I am a case former most are fire formers.

F. Guffey

 

[F. Guffey]

That being said the responses do in a way help. As maybe, just maybe! Somebody has a 7mm-06 and is looking to have it modified to shoot off the shelf ammo.

that would not require over the counter ammo; I have no ideal what all other reloaders would do, I would neck the 30/06 case down to 7MM and then start loading. But before: I would determine the length of the chamber from the shoulder to the bolt face and knowing necking a case down increases the length of the neck I would check the case length from the mouth of the case to the head of the case.

And then there are among mistakes made by reloaders/smith; Among us are those that chambered 7MM57 chambers to 280 Remington. After firing and checking the cases they thought it strange the neck of the chamber had two diameters. they forgot the 7MM57 military chamber had a 'generous' chamber.

And then it did not get better when smiths and reloaders decided they would move up from the 7.62 NATO/308W to 30/06. The 30/06 chamber reamer will not clean up the case body/shoulder juncture in the 7.62 chamber. When finished the juncture becomes an artifact of the old chamber.

Shooters have fired 308 W in 30/06 chambers without knowing the forcing of the 308 W into the 30/06 chamber wedged the 308W into the chamber without case head separation when fired. Cases are ejected looking like a 30/06 case with very short necks meaning?

Yes, what does that mean?

F. Guffey

 

[old roper]

offroadmatt, Ackley book has loading data for 7mm/06 Improved (Ackley). Speer Wildcat manual 1956 has load data for 7mm/06 and they used Speer bullet. 280 became spec 1957

In Ackley book on the 280 Rem Improved they mention it had little more case capacity than the 7mm/06 improved.

I think there was some interest in 7/06 at one time but 1957 you had 280.

This is one of the newer Ackley/Gibbs

https://shermanwildcatcartridges.com/280-sherman

 

[offroadmatt]

I have a ackley book on order, should be here any day now. But I think its safe to say the 280 load data can be safely used if slightly backed off as a starting point. Yes the case has more capacity. But any sensible reloader can understand that. To often we get caught up in doing just as the book says. This powder, this charge, this length. And if you don't have a lot of experience you probably should do just as printed. But if you take a step back and really look at things. You can really improve on whats printed. Things like distance to the lands. Understand powder burn rates and case capacity to choose a powder. Or powders designed to push heavier bullets and why. There is a lot to learn and the more you learn the more there is to learn. I was at the rang the other day doing load development and using a chrono. Guy next to me wanted to see the speeds of his reloads. He claimed "By the Book" it should be pushing X amount of FPS. My experience said he would be well under the as printed. He didn't believe me. But the numbers dont lie.

 

[offroadmatt]

offroadmatt, Ackley book has loading data for 7mm/06 Improved (Ackley). Speer Wildcat manual 1956 has load data for 7mm/06 and they used Speer bullet. 280 became spec 1957

In Ackley book on the 280 Rem Improved they mention it had little more case capacity than the 7mm/06 improved.

I think there was some interest in 7/06 at one time but 1957 you had 280.

This is one of the newer Ackley/Gibbs

https://shermanwildcatcartridges.com/280-sherman

Cant say ive heard of the sherman. But its hard to keep up with all the wildcats. Doesn't look to be much differnt for the advancements they claim.

 

[old roper]

offroadmatt, I'm not going to disagree with but I do things little different on the AI. First, I have to shoot parent case, next new barrel. Couple of my AI are 280AI wildcat build before spec, and Spec 280AI and it's long throated with 27" barrel. When I had Spec build I also had 284 on long action long throated 3.250" also 27" barrel. I got 27" on a 243AI, 26" on tight neck 222AI and 35 WhelenAI had just 24" but long throated 3.500".

 

[std7mag]

Offroad,
I'm noticing different dimensions for the body length, and the neck junction length.
Have you done a casting of the actual chamber?
With this, you could have a reamer made, and buy a blank die to make your own.
Reamers typically in the $150 range, blank die in the $20 range.
I looked at this method for creating my own wildcat.
Do note that the dimensions for a die reamer, and a chamber reamer are slightly different.

While 280 Rem load data may be a good starting point for load development, with the case dimensions, and volume, you could run that data through Quickload.
Might give you somewhat of an indication of where to start.