Does anyone have any experience with this round? I figure it will outrun a 270 AI a little. I am trying to compare the two to see which is more desirable for me. The AI is the way I think I am now leaning because it has a longer neck for me to chase the lands as the erode. That is the only advantage I can think of. This will not be a BR gun, but rather a 600ish yard deer/paper puncher. What say you?
As I understand, AI's maintain the neck for the most part and blow out a 40 degree shoulder. Gibbs have a .250" neck and 35 degree shoulder. That is all I have been "told"! Thats why I am asking for more info.
You are right the gibbs shortens the neck and because of this you will gain a little over the AI with the Gibbs. I have a 30 gibbs so I cannot say exactly how much the 270 gibbs will gain you but I am getting 3090fps with 190's out of a 30in tube, so compared to the standard 30-06 that is a big improvment. The gibbs is not that much more difficult to load for than the AI so if you want to go with more of a wildcat then go for it. In the grand scheem of things, a deer and especially paper won't know the difference at 600yards.
I also have the .30 Gibbs...getting 3100 w/ 165gr Hornady IL's from a 25.5" tube. Dropped a deer at 445yds a couple years ago....bang---FLOP! Been thinking about the .270 Gibbs...as I have an AMPLE supply for 140gr BTSP in .277" and my 'smith has all the Gibbs reamers. Best way to form cases is neck up then size in the Gibbs die to form a secondary shoulder to headspace against. I neck my .30-06 cases to .338 then size in the .30 die. For the .270 you could use .280 brass...I would use good 30-06 brass and just size in the .270 Gibbs die.
the real "major" difference between any of the rounds created by rocky gibbs and those of po ackley, besides geometry, is the ignition system. all of rocky gibbs' round were centered around "frontal ignition." rocky would put a tube from the flash-hole to about 3/4 of the way up the hull to dispatch the spark to the front end of the round. this proved to induce a more complete burn of the powder and in turn more performance. one can still alter gibbs hulls in such a manor (as nothing like that is avialable anywhere). but none the less, gibbs rounds still perform and outperfom just with the traditional form of ignition as we know today, but just to inform, the frontal ignition system put rocky's round even more out in front of all other conventional designs.
I have all the giibs between 240 and 338 except the 270. I like the 264 and 7mm better than the 270 so didn't do the 270. You are right about the neck differences. And take the advice of using 30-06 brass and necking down to form a good headspace off the shoulder. The gibbs will be faster than the 270 AI. I have both in all those calibers and in every case the gibbs is faster than the AI. Gibbs cartridges never really took off because of the short neck many don't like. Mine have done well even up to 338 caliber and the short neck has not been a concern with me. Basically all my gibbs are the virtual equivalent of the standard magnum counterparts. The 7mm gibbs same as the 7mm rem mag, 264 gibbs same as the 264 win mag, 338 gibbs same as the 338 win mag, 240 gibbs faster than 240 wby mag. 30 gibbs equals 300 wsm. The gibbs will be slightly slower in those cases but they are so close you would not notice the difference in a hunting situation. I also have some calibers on the JRS design which uses the slightly longer 280 case and I like those because you can do the gibbs case capacity and it still leaves a longer neck.
Predictions are difficult, especially when they involve the future