In reading about the AI cartriges it mentions longer case life. Is this a function of the straiter body or the sharp sholder? If it's the sholder, at what point do you get the positive effect on case life. ie miminum sholder angle without hampering feeding, but still limit case stretch?

Isn't it that the brass doesn't flow as easily?
Seems the beneficial effects would be on a curve, beginning immediately.

HI Lar45 sorry been off puter took a dump!! Ill take a stab at this.I origanally bult a 35whelen on a arg1909 m98 and it worked great till one day here in tx the temp was 104+ was useing it to cull some wild cattle(read that as never seen a human b4 and will stomp your ass)when my hot handloads seased the bolt(not a good thing!!)so I wanted a round that would develop the same fpenergy with less chamber psi.Found out about 35gibb(there is also an 8mmgibb) and decided to give it a try called don at clymer and got a great deal of insite and decided to go with it with some changes.I kept the 30-06 case lgth(however am useing 280rem or 9.3x62 brass for cases 280 being longer for longer neck)alsochanged from 35deg neck to 30deg to help feeding and changed dia at sholder to .455(from .465)to help extraction the side benifit is the action feeds flawsly without modification.I dont know exactly what vel is as i dont have a chrono but it really slaps them hard(and me)and no more stickey extraction

How is the case life? do they stretch much? I think the 8mm Gibbs is about what I'm looking for. I've got a couple of barrels to play with now, so I'll have to see what I can come up with.

I havent been playing with it very long so I dont know for sure how case life is,the hardest part is getting thru case forming.I started wrong with lots of used 35whelen cases(cause they were there and didnt need them anymore),lost about 30% in fireforming and have since changed fireforming methods and am useing new brass which is working much better,havent lost any new cases yet.

I have a 309JDJ barrel for my TC. I run 444 cases into a 308 die, then use a full load and fireform. I probably only lost about 2 out of 100. I put the barrel up for a couple of years and when I got the ammo back out, several of the necks had split and a bunch more split on fireing. I had to pull all of the loads and anneal. I wonder if annealing first would help the case to flow more easily and fill the chamber?

1st Cav said:

quote:

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35deg neck to 30deg to help feeding and changed dia at sholder to .455(from .465)to help extraction the side benifit is the action feeds flawsly without modification.

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The shoulder angle change might be OK, but according to a lot of people who have fired the Gibbs rounds, the Gibbs' minimum case taper is the reason why, per Jack O'Connor, "the bolt could literally be opened with the little finger", and extraction was exteremely easy with the Gibbs rifles.

There is also a .338 Gibbs, which should be the ultimate .338/'06! It gives velocities in the same range as the .338 Win. Mag (from 26" barrels) with a lot less powder!

[ 09-18-2003, 18:57: Message edited by: eldeguello ]

where would I find the data on the gibbs cartridges? thanks a lot

Red

Wolfes has a book on them Dago. I have a 7mm Gibbs and a 240. I quite like them. A little more juice then the Ackley versions, a little less then their belted mag counterparts. Cases are not difficult to form. Basically, an -06 (or family) case necked up or down, with minimum body taper and a very short neck (0.250" if I recall correctly). Gives you quite a bite more case capacity over the base -06 case, just about on a par with the Howell cases. - Dan

Lar45,
I'll try to answer your question. I have three rifles chambered for Ackley Improved cartridges(and one under construction) and I would say that in my experience it's the shoulder angle(40 degree) that minimizes case length growth. The mimimum taper reduces bolt thrust to a much lower level than a conventional case. Case trimming is seldom needed in Ackley type cases. I have a .17 Remington that when loaded to the max.cases grow .001-.002 each firing the same is true of the .220 Swift from what I hear. Parker Ackley and some of the other gunsmiths of his era were onto something, too bad they were limited by the available powders.
Stepchild

[ 09-23-2003, 01:51: Message edited by: stepchild 2 ]