7mmGibbs/280 AI

G

GRT338

New member
Have a 7mmGibbs built on Pre-64 Mod 70 w/26" Shilen #4. Work done years ago while residing in WA. state. Gunsmith was a neighbor to "Rocky Gibbs", Viola, Idaho. Gunsmith was Charlie Price. Now deceased. He initially stated that the Gibbs and the 280 AI were basically the same except for the use of 'o6 cases vs 280 cases. So he stated he chambered the Gibbs (headspace wise) to shoot factory 280's to fireform brass for the 7Gibbs. I never tried a 280 case or loaded round until last week. I removed the firing pin,etc from the bolt and only used the bare bolt to try a loaded 280 round in the chamber. It went with no resistance when closing the bolt. NONE!
I don't, in my opinion, think it would be safe to fire factory 280 loaded rounds in this chamber to make 7Gibbs brass. Would I not be correct? THe rifle will shoot reloaded 140/160 Partitions less then 3/4" inch at 100 yds. Now after all the hoopla over the 280 AI, I was just wondering if any of you gentlemen had any experience/advice/whatever to offer. Does anyone have any specs/drawings to compare the two?I do not know of anyone locally that might have headspace ga's. for the 280 AI. And the reason I ask is all the hassle to go through to fire form 06 brass to 7Gibbs. Any comments or help would be deeply appreciated. Thanks in advance. GRT
 
I believe the Gibbs rounds all had the shoulder of the case farther forward than any of the conventional rounds. Using 30-06 cases it should be a simple matter to size the neck down so the new shoulder has a crush fit in the chamber and then fireform... Only extra step would be in the initial sizing, and the fireform loads could be used just like any standard ammo is used in an Ackley chamber. You would need the proper die set for the Gibbs as I'm not sure a 280AI die set-up a little farther out would have the proper dimensions. Using 35 Whelen brass might be a better idea to provide more of a shoulder also.
 
As MSALM says, make a false shoulder to seat the brass and fireform with the bullet firmly into the lands. The original Gibbs cartridges were formed from 30-06 brass.
Butch
 
Ackley vs Gibbs

The cases do not use the same headspace. The Ackey cases are designed so one may shoot and form factory ammo ,not so with the Gibbs.Gibbs cases must be formed by a couple of various methods.They are both decent enough cartridges

Ackley cases can use the junction of the shoulder and neck to headspace when firing the mother case.

chris
 
GRT

What the other guys said.

The 280 Ackley is an Improved case. The 7mm Gibbs is a wildcat. Since it's a wildcat you need to make a few fire-formed cases (or a chamber cast) to determine exactly what your chamber looks like. Only then can you have dies made or decide if any existing dies can be used or modified to work.

Don't be surprised if your chamber is different than any drawings of the Gibbs that you may find. I could post photos of one, and even a drawing, but I don't want to possibly lead you down the wrong path.

Ray
 
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Wasn't the 280 Gibbs before the 280 Remington. I know that the Gibbs had the shoulder moved out from the original 30-06 shoulder and the 280 has it's shoulder moved out so it cannot be used in a 30-06. It might be very close.

Couldn't he have his gunsmith check some fired cases against some unfired 280 cases? It might work fine.

Concho Bill
 
Bill

Rocky Gibbs was experimenting with his wildcats just after WW II. The 280 Remington came out in 1957, I believe, although there were several very nearly identical 7mm/06 wildcats that preceeded it.

The 7mm Gibbs and the 280 Ackley may LOOK similar (as do several other wildcats) but the two cartridges are NOT the same. Headspace is significantly different. (P.O.Ackley had nothing whatsoever to do with developing the 280 Ackley, BTW. He never claimed that he did, either).

Ray
 
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Cheechako said:
Bill

Rocky Gibbs was experimenting with his wildcats just after WW II. The 280 Remington came out in 1957, I believe, although there were several very nearly identical 7mm/06 wildcats that preceeded it.

The 7mm Gibbs and the 280 Ackley may LOOK similar (as do several other wildcats) but the two cartridges are NOT the same. Headspace is significantly different. (P.O.Ackley had nothing whatsoever to do with developing the 280 Ackley, BTW. He never claimed that he did, either).

Ray
Click to expand...

Ray,

Here in San Angelo, Texas we had a gunsmith in those days, who made quite a few rifles that were based on the Ackley improved type. He made something we called the .250 Curry Magnum which was a 25/06 with the shoulder pushed forward about .1250". It was a fine rifle for deer at 300 yards. The one problem, as you might expect, was that the barrel would not last very long. After the rifling was gone, he would send the barrel to P. O. Ackley and he would bore it out to a .270 or a .30 and we would go again.

Just to be different, I had mine bored out to a 7 mm. Today, I describe it as a .280 Ackley Improved because no one else would know what a .280 Curry Magnum was. I might should call it a 7 mm/ '06 Concho Bill.

Concho Bill
 
Charlie Price was well aware that the Gibbs and the 280AI were entirely different and more than just in the parent brass. However, this wouldn't be the first time someone was was in error.
If one chambered the Gibbs to allow the use of 280 ammunition, he would have to chamber the Gibbs short to allow headspacing on the neck/shoulder juncture, then cut the neck of the chamber long to allow for the longer 280 brass. I think it is unlikely Price did this but can't say exactly what he did do. If you take it to someone who knows, they could gauge the chamber for depth and overall case (trim to) length.
I knew both Rocky Gibbs and Charlie Price as I grew up in the Potlatch area. My uncle still has a 270 Gibbs built by Rocky Gibbs and reblued and the bolt jewelled by Charlie Price. Regards, Bill.
 
The fact that you felt no resistance when chambering a stock 280 round plus the fact that the 280 is .050" longer than the 30-06 case makes me wonder if he didn't chamber .050" deep to use the 280 brass. The Gibbs line moves the shoulder forward, sacrificing some neck length to get even more capacity from the case. If this is a 280 Gibbs you may have to expand the necks to 30 cal and then back down to 7mm to get a shoulder to support the case for fire forming. If you have a full length die that came with the rifle, you might run a piece of 30-06 brass through it to see where the shoulder is. I fireform for my 280 AI's using 16 grains of Unique and any old 140-154 gr bullets I have laying around, it leaves the shoulder a little soft, but headspace is good for full power loads. Bottom line, proceed with caution until you're sure what you have.
 
7Gibbs/280

My sincere thanks to everyone for each and every reply. I guess I should find someone that has both a set of go/no-go gauges for 280 and the 280 AI and try them in this chamber to find out for sure. Another thing that would be handy would be to have a cerrosafe cast for the chamber and throat area. Again my thanks to everyone of you.

GRT338
 
GRT338 said:
My sincere thanks to everyone for each and every reply. I guess I should find someone that has both a set of go/no-go gauges for 280 and the 280 AI and try them in this chamber to find out for sure. Another thing that would be handy would be to have a cerrosafe cast for the chamber and throat area. Again my thanks to everyone of you.

GRT338
Click to expand...

If the .280 AI is correctly chambered a factory .280 round should be firmly felt when closing the bolt... if you can not crush a factory round, it has excessive headspace as a .280 Improved.

... and I think Gibbs calibers were all on the 06 case with necks about .200" long and a 40 degree shoulder... they were not improved, they were wildcats...


.
 
GRT

This thread is getting a lot more complicated than it should be.

The single most important thing to keep in mind is that the Gibbs cartridges were wildcats. So there is no standard set of dimensions for them. Back in those days, reamers were made by gunsmiths, wildcatters, or just plain shooters. The chances of two of them being alike was remote. The original Gibbs cartridges as designed by Rocky had a 35 degree shoulder angle except for the 30 Gibbs which could be found with lesser angles. He used only 30-06 cases, mostly military.

The only way to tell what your particular rifle is chambered for is to fire-form a couple of cases, or make a chamber cast. You're only confusing things by bringing a 280 Ackley into the picture. They are not the same thing. And neither is the 7mm JRS or any of the other Gibbs look-a-likes.

The fact that your rifle is marked as a 7mm Gibbs is a good reason to assume that it is just that. The only thing left is to sort out the details.

JMHO

Ray
 
Sorry bout that

Ray, I do indeed thank everyone for their replys and concern to be correct. I thank you for your knowledge and conveying same to me. I never intended to create problems. Again I thank you.

GRT
 
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