Ackley kept the same shoulder. Gibbs moved the shoulder forward.
You can't fire form a gibbs. Once people found out the pressures he was running Gibbs lost popularity.
Don't know about the last sentence, but I'll take yur wurd fur it!
The Gibb's rounds as well as
classic Ackley-Improved cat-tri-ge's both use 40-degree shoulders in the nearly straight blown-out cases.
I suppose there's "value" in knowing how to stuff the brass with still-more powder, but in a .277 cartridge its seems the easier and more sensible [practicle] thing to do is either shoot the .270Win in a rifle with a 24 or 26in tube (vs. 22 inches) to gain extra velocity, or jump up to the .270 Weathherlie or 7mm Rem Mag.
Ken Waters ("Pet Loads" Wolfe Publishing fame) did four article on the .270WCF over his career. Last article specifically on 24-inch .270's as that was O'Connor's
bread n butter combo. Waters was quite surprised he gained over fifty feet-per-second per inch!! Going to a 24in tube! (but he only used two test rifles in that article too, the other 2nd rifle had a 22in bbl and was used in a previous article or two).
Shooting a .270Gibbs? One needs to ask whether all the hassle and extra risk (pushing the pressure envelope and that basic .270WCF case to
EXTREMES) is worth "maybe" an additional 200fps over the standard .270 Winchester?
Twas me I might choose a .270Win in a 24inch rifle (to gain up to 100fps velocity) if I was still shooting that particular round. The .270Win is indeed a great hunting round and it indeed kills very very well! Whether in a 22" rifle, 24" or even a carbine.
