Have followed with some interest talk about .308 Ackley Improved. There is little to no data concerning this round except for those [of us] who are actively shooting this round, or who are seriously looking for this 'new round'. In his books Ackley did NOT show an improved chambering for this round; I know, because I have both of his books in my shooting library; nowhere is that shown. This may well be because the .308 Win. round was a relatively late developing round [starting in WWII], its parent case being the 300Savage a much older round. That said, the .308Win. round is a very much appreciably undervalued underdeveloped round, in its own right. The availability of technology edge ...primers, brass, heads, and propellants simply was not around at the time the round was stood up. Consequently all the "wars" about it or a 6.5Creed, 6mmARC, 6.8 Grendel...etc., are wars fought with old terms over old technologies, and the ones waging them are basically trying to compare apples to oranges. Conclusions drawn from comparisons will inevitably be incorrect.
The .308Win.-A/I round is the logical end state expression of what the .308Win. round is capable of and is a more than credible 1000 yard+ ELR round. Some one posting that the Ackley Improved was a waste of time or money? I do not know if he is basing that judgment on empirical knowledge or some vague personal animus grounded in an uninformed opinion? Bruce Artus shooting in Pueblo Colorado holds a record for Extended Long Range shooting with the .308Ackley Improved for gong shooting at 3,120 yards set with an AI round capped with a 220grn. Sierra MatchKing. Artus also has the longest witnessed single shot live animal kill set at 2,632 yards, same round.
For the record, I shoot a .308Win.Ackley Improved rifle, built on a MacMillan A-4 stock, Savage 112 Precision Single Shot Target short action married to a 30" Bartlein 5R heavy Palma barrel with a full progressively ported brake timed to the riflings. The rifle was shot in and then broken down and the action, receiver, and the barrel was molten salt nitride treated. The scope is the SWFA-S/S 12X 42 fixed power scope [I prefer scopes with as few to no moving parts as possible for repeated accuracy]. The SS performs every bit as good [image clear bright crisp and contrasty rain snow, low light fog, or shine] as the currently high priced spreads. The object here is to shoot and not brag about the money you spent on the diamond settings in your wedding ring. If you are seriously contemplating going the .308Win. A/I you will NOT get there in a standard 24" barrel, and 20" barrels are simply laughable; you are going to have to build your rifle. I drive a 200grn. Berger Hybrid; when the barrel was married to the receiver I had it throated for this round; the chamber was cut to "the" smallest dimensions 2.0067" with a "GO" of 1.6664", gages supplied by Pacific Tool and Die. Consequently in "the forming stages" for brass all my necks are shaved to .0135"; normal casing thickness of .308Win. Lapua is .0155. ALL brass in annealed after every firing; you want a soft neck that releases cleanly and evenly that will make a good efficient gas tight seal with the 40deg. shoulder. Additionally before seating ALL necks are graphited with laboratoy grade graphite [ ease of seating, die-electric electrolysis protection] Along the way, you are going to have to develop your own dies; mine came from John Whittington, for decapping and sizing only. I use Wilson Co-Ax dies for seating exclusively. The straightness in run-out is very critical; no other seating die currently available comes even remotely close to the Wilson Co-Ax. You are going to have to decide on brass; not all brass is created equal. I shoot exclusively .308 Lapua Palma brass. If you are going to go this route, go there. Case weights for Lapua are extremely consistent. Standard .308 brass with standard large rifle primer pockets will not stand up to stresses; the primer cups are stretchy. The .308 Lapua Palma has a small rifle primer pocket and is ~ly half as large as the standard pocket. This translates into far more brass in the head which makes for a greater tighter grip on the primer; currently I am on the 6th iteration of brass and the primers are very nearly as tight to seat as they were first from the factory; you want tight primers. Additionally a photomicrograph of primer burn of a standard large rifle primer shows a burn that resembles a badly decorated Christmas tree; a micrograph of a magnum small rifle primer shows an almost "columnar" burn straight up through the core of propellant. To get the power and the even burn and pressure build up you need that character of burn.
As far as propellants, this is where the rub comes in. Standard ball propellants BLC-2, Win. 748, Acc.2460 are good but they simply will not give you the power down the bore to get velocities up, they're good for M14, M40, M110...etc., but that don't get it here!!!!. None of the large cut sticks work well at all, not developing in a slow burn that gives you the velocity you want without really developing dangerously high chamber and case pressures. What is wanted is a double based super short cut stick propellant specifically designed fo medium capacity cases that will achieve maximum total burn-out in 75% of barrel length not to exceed 87.5% of barrel length. Currently, I use Alliant Re17; Alliant is a Swiss based company and their propellant is very high quality and reasonmably priced. I drive a 200grn. Berger hybrid for an E/MV[Exit Muzzle Velocity] of 2740fps. [Ohler three gate chronograph with four separate runs and an average of 2740fps with a MAD of 3fps; I could drive it higher, but to what point?
The point to long range and extended long range is not how fast the bullet leaves the muzzle; the point is where down range does the bullet go into a transition event and how far?? down range and how large is its subsonic floor ofsub-sonic transition stability. That is the question that the rifleman has to answer; how fast is fast enough?
This Ackley Improved round is still supersonic at 1400 yards--1135fps; at 1760 yards it is stable subsonic at 972fps and does not go through its floor until about 2200 yards at 870fps. From 1400 yards to 2200 yards [~ly 800 yards] this bullet is stable. Not a 7mm Rem.Mag, a 6.5 Cred or 6mmARC even begins to approach this. The floor of sub-sonic stability for realistically accurate ballistic firing solutions for a .30 caliber round is 870fps. This is so because short fat stubby bullets are inherently more stable than long thin bullets; this is not a matter of opinion but fact. The Aussies routinely shoot 2000 yards [with accuracy in the wind] with a straight .308Win. chambering. I do NOT shoot at less than 500 yards with this rifle; that is its starting zero. That would be a waste of "time and money". Ignore comments about "waste of time and money"; the context in which they are made is unknown and generally the people making them do not know what they do not know. In a future posting I will send pics of brass and the weapon; I am happy to answer any questions.
Anchor'sAweigh/SemperFi
ChiefBull
The .308Win.-A/I round is the logical end state expression of what the .308Win. round is capable of and is a more than credible 1000 yard+ ELR round. Some one posting that the Ackley Improved was a waste of time or money? I do not know if he is basing that judgment on empirical knowledge or some vague personal animus grounded in an uninformed opinion? Bruce Artus shooting in Pueblo Colorado holds a record for Extended Long Range shooting with the .308Ackley Improved for gong shooting at 3,120 yards set with an AI round capped with a 220grn. Sierra MatchKing. Artus also has the longest witnessed single shot live animal kill set at 2,632 yards, same round.
For the record, I shoot a .308Win.Ackley Improved rifle, built on a MacMillan A-4 stock, Savage 112 Precision Single Shot Target short action married to a 30" Bartlein 5R heavy Palma barrel with a full progressively ported brake timed to the riflings. The rifle was shot in and then broken down and the action, receiver, and the barrel was molten salt nitride treated. The scope is the SWFA-S/S 12X 42 fixed power scope [I prefer scopes with as few to no moving parts as possible for repeated accuracy]. The SS performs every bit as good [image clear bright crisp and contrasty rain snow, low light fog, or shine] as the currently high priced spreads. The object here is to shoot and not brag about the money you spent on the diamond settings in your wedding ring. If you are seriously contemplating going the .308Win. A/I you will NOT get there in a standard 24" barrel, and 20" barrels are simply laughable; you are going to have to build your rifle. I drive a 200grn. Berger Hybrid; when the barrel was married to the receiver I had it throated for this round; the chamber was cut to "the" smallest dimensions 2.0067" with a "GO" of 1.6664", gages supplied by Pacific Tool and Die. Consequently in "the forming stages" for brass all my necks are shaved to .0135"; normal casing thickness of .308Win. Lapua is .0155. ALL brass in annealed after every firing; you want a soft neck that releases cleanly and evenly that will make a good efficient gas tight seal with the 40deg. shoulder. Additionally before seating ALL necks are graphited with laboratoy grade graphite [ ease of seating, die-electric electrolysis protection] Along the way, you are going to have to develop your own dies; mine came from John Whittington, for decapping and sizing only. I use Wilson Co-Ax dies for seating exclusively. The straightness in run-out is very critical; no other seating die currently available comes even remotely close to the Wilson Co-Ax. You are going to have to decide on brass; not all brass is created equal. I shoot exclusively .308 Lapua Palma brass. If you are going to go this route, go there. Case weights for Lapua are extremely consistent. Standard .308 brass with standard large rifle primer pockets will not stand up to stresses; the primer cups are stretchy. The .308 Lapua Palma has a small rifle primer pocket and is ~ly half as large as the standard pocket. This translates into far more brass in the head which makes for a greater tighter grip on the primer; currently I am on the 6th iteration of brass and the primers are very nearly as tight to seat as they were first from the factory; you want tight primers. Additionally a photomicrograph of primer burn of a standard large rifle primer shows a burn that resembles a badly decorated Christmas tree; a micrograph of a magnum small rifle primer shows an almost "columnar" burn straight up through the core of propellant. To get the power and the even burn and pressure build up you need that character of burn.
As far as propellants, this is where the rub comes in. Standard ball propellants BLC-2, Win. 748, Acc.2460 are good but they simply will not give you the power down the bore to get velocities up, they're good for M14, M40, M110...etc., but that don't get it here!!!!. None of the large cut sticks work well at all, not developing in a slow burn that gives you the velocity you want without really developing dangerously high chamber and case pressures. What is wanted is a double based super short cut stick propellant specifically designed fo medium capacity cases that will achieve maximum total burn-out in 75% of barrel length not to exceed 87.5% of barrel length. Currently, I use Alliant Re17; Alliant is a Swiss based company and their propellant is very high quality and reasonmably priced. I drive a 200grn. Berger hybrid for an E/MV[Exit Muzzle Velocity] of 2740fps. [Ohler three gate chronograph with four separate runs and an average of 2740fps with a MAD of 3fps; I could drive it higher, but to what point?
The point to long range and extended long range is not how fast the bullet leaves the muzzle; the point is where down range does the bullet go into a transition event and how far?? down range and how large is its subsonic floor ofsub-sonic transition stability. That is the question that the rifleman has to answer; how fast is fast enough?
This Ackley Improved round is still supersonic at 1400 yards--1135fps; at 1760 yards it is stable subsonic at 972fps and does not go through its floor until about 2200 yards at 870fps. From 1400 yards to 2200 yards [~ly 800 yards] this bullet is stable. Not a 7mm Rem.Mag, a 6.5 Cred or 6mmARC even begins to approach this. The floor of sub-sonic stability for realistically accurate ballistic firing solutions for a .30 caliber round is 870fps. This is so because short fat stubby bullets are inherently more stable than long thin bullets; this is not a matter of opinion but fact. The Aussies routinely shoot 2000 yards [with accuracy in the wind] with a straight .308Win. chambering. I do NOT shoot at less than 500 yards with this rifle; that is its starting zero. That would be a waste of "time and money". Ignore comments about "waste of time and money"; the context in which they are made is unknown and generally the people making them do not know what they do not know. In a future posting I will send pics of brass and the weapon; I am happy to answer any questions.
Anchor'sAweigh/SemperFi
ChiefBull
