You might even want to look at a 7mm RUM or 7mm STW if you are looking at going with a 28inch barrel. I am pushing a 180 berger out of my STW at 3125fps with ease I am sure a RUM would add another 100fps or more with ease as well. Mine has a 28inch Broughton 5c 9 twist on it and if you run the numbers on the berger it has the energy to kill an elk at 1500 yards. My rifle weighs just about 12lbs scoped and it will shoot 7inch groups at 875 yards off the bipod. I am not trying to take anything away from any cartridge but you mention a 28inch pipe and your concern about forming brass with either of these you just load and go.
Well, If you look at my current big game hunting arsenal, it consists of two rifles, a 9.5 lb 7mm AM for anything out to 1/2 mile and a 15.5 lb 7mm AM for anything out to 1300 yards or so.
That said, the only reason my heavy rifle is a 7mm AM is because my BAT receiver did not get here in time to build my sub 16 lb 338 Allen Mag which will be up and running for next season.
Next year, my two rifle pair will be the light weight 7mm AM and the sub 16 lb 338 AM for anything out to 1500 yards, nearly identical to what you are thinking of doing.
Ballistically, the 7mm AM is just flat out obnoxious as far as how little the wind effects it. I had a 1000 yard BR shooter up in the shop the other day looking at my hunting rifles and I had all of my support "crap" there with them including my hard copies of my drop and drift charts.
He was quietly reading the charts and then after a few minutes he loudly stated "B___ S___!!!""
I walked over and asked what the problem was and he said the was no way I was only getting 35" of wind drift at 1000 yards in a 10 mph cross wind.
Ya see he uses a 30-378 Wby loaded with a 200 gr Accubond to 3300 fps and he said his drift was somthing like 60" at that range with a 10 mph crosswind and I agreed with him that sounded about right!!
He said they are the same bullet weight at the same velocity so why the big difference so I headed over to the loading bench and grabbed a 200 gr Accubond and a 200 gr 7mm ULDRBBT and put them in his hand and said that is the only difference and the reason for the very low wind drift.
He still was not completely convinced so we started playing with the ballistic programs. I plugged in all of his data for his 200 gr Accubond load in his 30-378 and came up with 59" of drift at 1000 yards.
Plugging in the numbers for a 338 Edge with the 300 gr SMK we came up with around 47" of drift.
For the 200 gr ULD RBBT loaded to 3300 fps we came up with 35" of drift.
What really got hit attention though was bullet energy. The 7mm AM and 338 Edge are both nearly identical at 1000 yards with right at 2200 ft/lbs of energy. The mighty 30-378 Wby with the 200 gr Accubond has dipped to right at 1400 ft/lbs of energy, still plenty for big game hunting but nothing in the class if the 7mm AM and 338 Edge which are again, nearly identical.
He really got upset when he found out his 30-378 Wby was burning 20 grains more powder then the other two rounds and was getting ballistically beaten up as well!!!
Now I am not saying that this is because of the design of the 7mm AM or the 338 Egde, its because we designed these rounds to be used with high BC bullets at good upper end velocities. It is true that any 7mm chambering from the 7mm STW to the 7mm RUM will get you vastly superior performance using the 200 gr ULD RBBT as apposed to the conventional bullet weights and designs.
Same is true for the 338 calibers. If you put a 300 gr SMK in any chambering from a 338 Wby up to the 338-378 or 338 Kahn you will get dramatically higher performance then with conventional weight bullets.
Some bullets perform on game better then others at long range so that is a consideration as well to keep in mind but again, its more a matter of what bullet you use then what chambering you have behind it.
If the rifle is built well and you load good ammo, you will get great results at long range if you are up to the task.
I have not had alot of experience with the ABS barrels but the few I have chambered have shot extremely well. Personally I guess I am a traditionalist at heart and use all steel barrels.
Case prep for the 7mm AM is relatively simply, neck down, fireform either with live fire or corn meal method, trim to length and shoot. I design my Allen Magnums as big game rounds so no neck turning is required unless you want to take a very slight shave off just to even things up. I personally do not turn any of my necks!!
By the way, the guy with the 30-378 ordered a 7mm AM that day!!!
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
You can't go wrong with the 7mmAM in either the light or heavy configuration...My 7mmAM the Kirby is building will probably end up around 14lbs....I carried my 13.5lb 243AI around quite a bit this year. It wasn't that bad. I did slow down a little, but still when I needed to be steady at long range, it was rock solid. I have a 7mm STW Sendero that is pretty good, but the Allen Mag will launch the heavy, high BC bullets close to 300 fps faster. I think you will be happy with the 7mm AM. Good luck on your choice...