wilkup
Well-Known Member
.532" meaning something like a 270-300PRC!? Cuz that would be quite a deadly screamer, especially with the newish interest in heavier projectiles for this caliber and the 6.8mm coming out with such strong hype.
270 AI equals 280AI?
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The case capacity is different, obviously. I love my 280 Ai, personal choice reigns supreme.
Yes. I hope they do it longer than .375 H&H's case length.
Kodiak Special
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I prefer the 270, great terminal ballistics.
wilkup
Well-Known Member
Wouldn't they basically be the same if both were AI…?
TRexF16
Well-Known Member
For a .270 Win vs a .270 Win AI, expect that case capacity will increase just under 4%, and velocity (with all other factors held the same) will increase maybe 1% or a tad less.
The .280 AI picks up a lot more over the basic .280 mostly because the basic .280 is a 60K PSI round and the AI version is a 65K round (SAAMI specs). Since the .270 Win is already a 65K PSI round there is very little room to grow by only blowing out the shoulder. Longer barrels and longer magazines permitting longer-than-standard COALs are going to contribute a lot more than the AI chambering.
Nosler's load data is useful to illustrate this since they list the water capacity of all their cases at the spec'ed OAL. Referencing the 150 grain data, the .280 AI has only 3.6% more water capacity than the .280 Rem, but Nosler's top loads with the same powders are increased by as much as (in the case of R-22) 12.8%, taking advantage of the 5K PSI extra pressure. Whereas at the same pressures, we'd expect no more than 1% more velocity, the extra pressure from all that extra powder lets them achieve 5.5% more velocity (with R-22), all else being pretty equal (both test rifles with 26" barrels and 3.330" COAL).
That won't be the case with the .270 AI. Another way to look at it is that the .270 AI will give just a little less velocity that the .280 AI with the same bullet weight, for two reasons - the reduction in cross-sectional area of the smaller diameter bullet, and the slight decrease in case capacity due to the .280AI's shoulder being a little further forward than the .270AI's. [Geekery alert] IF all you did was neck down the .280AI to .270, and kept the shoulder location, velocity loss at the same pressures would be about one quarter of the percentage reduction in cross-sectional area. The area is reduced just under 5%, so velocity would be reduced in the neighborhood of 1.2%, if everything else were held constant.
Still though, a fantastic cartridge, both the basic and AI versions. I have a 1:8 barrel being put on my 270 WSM right now, and might follow up with one of my .270 Wins later own. Doubt I'll AI it due to the factors above, but who knows. Anxious to hear how your project turns out.
Cheers,
Rex
Did you read the link I provided in #11?
TRexF16
Well-Known Member
Yes Sir. I did and found it interesting. Before I discuss it, what part of what I wrote above do you disagree with? And what part of the link you shared refutes it? The references are factual and the contentions are just physics and well established relationships. I'm not trying to be a smart *ss, what part is incorrect? I'm happy to learn.
I still contend that regarding the impressive velocities your friend got in the link, the answer to the OP's question of how much higher would they be with an .270AI versus a standard .270Win is "about 1%, if pressure and all other factors are equal." Why is this wrong?
In your link I saw some big numbers. But that is not to accuse the writer (nor you) of being way over pressure - too many other variables.
The important things I noted about your friend's rifle are a 26" barrel, and COALs of 3.484 to 3.496, providing both increased powder capacity and increased combustion room.
I have Berger first edition but there is no 170 grain data in it for the .270Win, nor did I see it on their website, but maybe I missed it and someone else knows it. What is Berger's published maximum charge and velocity for their 170gr in the .270 Win with RL-26? And what are the COAL, twist, and barrel length they used?
One of the respondents quoted Berger as listing 2899 FPS as the top speed with RL-26 and the 170gr in the .270 Win, and your friend's target of about 2970FPS doesn't sound at all unreasonable if the Berger data were derived in a shorter barrel and at SAAMI COAL. I've bee unable to locate the reference for that Berger data though.
Cheers,
Rex
I have a 6.5x55 AI that just works, if I want to shoot far and really accurately, that's what I take. (I know this is about 270 vs. 280, I threw that in for perspective and I like AI) I've used standard 280 for a long time very effectively on anything that walked. I traded a guy a 338 rifle for an older late '70's Remington 700 in 270 win. This particular action is perfectly timed and minimum bolt play so I was excited about re-barreling it to 280. One of my good friends whom I trust implicitly when it comes to effective rounds for an application told me to go shoot it in 270 and see how it shoots. If it shoots then leave it alone because a 270 will do everything a 280 will do. I asked myself if an AI would be of any real benefit and I came back to my personal belief that the quest for the highest velocity possible is moot in most applications. A standard 270 will send a round at about 3000 FPS, more or less depending on bullet weight. Do I need anything more than that? I don't, I'm not shooting elk at 900 yards. Last year I shot a Whitetail at 404 using Hornady precision Hunter 145ELDX. I hit him in the neck just like I wanted and he dropped right there. This rifle is not a half minute gun but it does shoot the factory Hornady ELDX under an inch all day and for an effective hunting round it works just fine. I'm not knocking the AI variants at all but it's a little overkill for most ranges that folks hunt. If I had an extra 10 grand lying around and wanted to build a rifle for mountain hunting that was super light and effective at long range then the 280AI or 270AI would be right at the top of my list. I say just pick one and be happy with it. The Berger .277 170 and the 7mm 170 are so close that in the real world, flip a coin. By the way, the 10 grand would include a Tangent Theta scope.
I consider my rifles as tools, the right tool for the right job, and.....the right rifle for the right game. I black bear hunt and I whitetail hunt and have what I consider to the appropriate cartridges for the game that I like to hunt. For whitetail hunting I built two Ruger 77 tang safety rifles for my son and and for myself. Thank you FEENIX for the inspiration!!! I was going to build a .280 Ackley Improved, but refused to be help hostage by Nosler to have to purchase their brass!! Right now their brass is $105/50 pieces, and.....not available!! These rifles were built on blueprinted, Ruger 77 tang safety actions, original Ruger contoured 26 in (1-10) Lilja barrels, glass bedded, floated and pillar bedded on the original walnut stocks. With the Nosler ABLRs I am getting 3300fps, getting 2 shot 1/2-3/4 inch groups at 300 yards. Because the barrels have been contoured the group will open up 1-1 1/2 inches on the third shot. Sighted in at 100 yards the round drops about 9 inches at 300 yards. I don't think that I would build a .270 AI with a twist for heavier bullets because I don't have a need to shoot the heavier bullets for whitetail deer hunting. I just built a Ruger 77 only in 30-06 to use as a back up rifle for whitetail hunting. This rifle is of the same configuration only it is 30-06, and.....it too has a 1-10 twist barrel. I feel very confident at shooting game out to 300 yards, however would not hesitate to take a 400-500 yard shot if presented and if the conditions were right. I believe that building a rifle to fit one's needs, in any configuration is something that we all ought to do. Right now I have another Ruger 77 tang safety donor rifle in 30-06 that I just picked up sitting in the safe!! I'm looking to fill in the void for a back up rifle for the 35 Whelen and the 1895 Marlin in 45-70 for black bear hunting. And..............this is for another thread......................................
!!!Good luck with your build.
You cannot go wrong with the .270 Ackley Improved.
Besides performance the round is an awesome looking cartridge!!!
You cannot go wrong with the .270 Ackley Improved.
Besides performance the round is an awesome looking cartridge!!!
wilkup
Well-Known Member
I wanna hear about your next tang safety Model 77 build!I consider my rifles as tools, the right tool for the right job, and.....the right rifle for the right game. I black bear hunt and I whitetail hunt and have what I consider to the appropriate cartridges for the game that I like to hunt. For whitetail hunting I built two Ruger 77 tang safety rifles for my son and and for myself. Thank you FEENIX for the inspiration!!! I was going to build a .280 Ackley Improved, but refused to be help hostage by Nosler to have to purchase their brass!! Right now their brass is $105/50 pieces, and.....not available!! These rifles were built on blueprinted, Ruger 77 tang safety actions, original Ruger contoured 26 in (1-10) Lilja barrels, glass bedded, floated and pillar bedded on the original walnut stocks. With the Nosler ABLRs I am getting 3300fps, getting 2 shot 1/2-3/4 inch groups at 300 yards. Because the barrels have been contoured the group will open up 1-1 1/2 inches on the third shot. Sighted in at 100 yards the round drops about 9 inches at 300 yards. I don't think that I would build a .270 AI with a twist for heavier bullets because I don't have a need to shoot the heavier bullets for whitetail deer hunting. I just built a Ruger 77 only in 30-06 to use as a back up rifle for whitetail hunting. This rifle is of the same configuration only it is 30-06, and.....it too has a 1-10 twist barrel. I feel very confident at shooting game out to 300 yards, however would not hesitate to take a 400-500 yard shot if presented and if the conditions were right. I believe that building a rifle to fit one's needs, in any configuration is something that we all ought to do. Right now I have another Ruger 77 tang safety donor rifle in 30-06 that I just picked up sitting in the safe!! I'm looking to fill in the void for a back up rifle for the 35 Whelen and the 1895 Marlin in 45-70 for black bear hunting. And..............this is for another thread......................................
Good luck with your build.
You cannot go wrong with the .270 Ackley Improved.
Besides performance the round is an awesome looking cartridge!!!
How heavy is that ABLR you're shooting… 150gr? I'll need to be on the lookout for some of those going forward. You have a photo of a loaded round? Sounds like a real performer!
Right now I'm limited to what's available and I've got 150gr Nosler BTs, Berger 140gr EHs and Cutting Edge 120gr MTHs.
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Lots of talk about the 270 and the 270AI verses the 280, etc. And I'm just wondering why there's no talk about hot rodding it all the way with a 270 Gibbs. I have 4 AI's and two Gibbs - a 240 and a 6.5 - and I have no problem with reloading any of them. I've not experienced any of the "too short neck' problems. Just wondering...,
wilkup
Well-Known Member
I've done a few of Rich's wildcats that take the -06 case to the next level and know his 270 Sherman would definitely boost me into another league. The extra time required for the forming process of his and the Gibbs cartridges, along with not being able to fire standard rounds within the same chamber in a pinch is just not as convenient.
I realize true wildcat and hotrod fans will likely scoff at that, but it's just the way it is for me and this rifle this time around.
