The .25-06 and .25-06 Improved

By J.C. Munnell
©Copyright 2010, Precision Shooting Magazine

I have previously expressed my views as to the possible superiority of the various .25 caliber cartridges to those of one caliber less, and have fully expected to be severely taken to task, cursed at, ridiculed, pilloried, threatened with keelhauling, drawing and quartering, (not really necessary if the keelhauling is done correctly), and promised immediate excommunication from the Universal Church of True Believers in All Things Six Millimeter. That last one seemed o.k., but the others caused me at least momentary concern, since several of the stated acts threatened to end my shooting, hunting and writing careers, or at least cause a considerable delay in continuing with them. That such results have not transpired probably – in order of ascending probability: (a) reflects the innate correctness of my views, (b) reflects the vast open-mindedness of the readership, or (c) demonstrates that no one is reading my exceedingly erudite utterings. Nonetheless, here I am, once more testing the patience and understanding of the readers.


The three rifles tested for this article. The one on the left is a Remington M-700 ADL switch-barrel gun, with the .25-06 Improved barrel in place. Center gun is a Ruger M-77 Mk II VT. This rifle is now chambered for the Improved version of the .25-06. Right rifle is the author's ancient Hollow Bolt Ruger M-77 V, chambered for the standard .25-06.

In explaining my fondness for the various members of the .25 caliber cartridge family, I usually list my belief that many of them may very well be the ultimate "crossover" rounds – that is, depending largely upon the configuration of the individual rifle, a .257 Roberts, or a .25-06, for example, can either be a superb rifle for hunting deer/antelope, etc, or else one of the best rifles for varmint/predator shooting, especially at long range. Yes, I know that the .243 Winchester and 6mm Remington are often cited as filling this category and, have been used to slay countless such larger game animals, but I personally do not regard the bullet weights available in 6mm as reliably suitable for such applications, especially if what is usually described as a "raking shot" is the only one presented. Likewise, although there are thin-jacketed bullets available in larger bore sizes, for many reasons I don't regard .26, .27, .30 or 8mm cartridges as being ideal – or even practical—varmint rounds. Only the .25 caliber bullets are readily available and are eminently suitable for both such uses.


The two cases in the middle are our subjects – the .25-06 and .25-06 Ackley Improved. The pair on the left are the 6mm/06 and 6mm/06 Improved. On the right are the 6.5/06 and 6.5/06 Improved.

Of the various .25 caliber cartridges which have been manufactured (or even thought up) over the years, I have tried many, including the .250 Savage, .250 Savage Ackley Improved, .257 Roberts, .257 Roberts Improved, .25 WSSM, .25/.284, .25-06, .25-06 Improved, .25 B.C. (.25 x 6.5 Rem. Mag.), .257 Weatherby Mag. and .25 ICL Mag. The latter two burn entirely too much powder – and therefore barrels – to be truly useful as varmint rounds, and are not particularly efficient even with the slowest-burning powders available today, and of the former, the .250 Savage and the improved version really do not offer enough velocity to reach "way out there". The .257 Roberts, standard and improved, permit the construction of neat light-weight rifles, superbly quick to the shoulder and a joy to use in the deer woods, but, again, are a bit lacking as truly long-range cartridges. The .25 WSSM is simply a dismal wannabe with almost useless brass. This leaves the .25/.284, .25-06, the .25-06 Ackley Improved and the .25 B.C. I have already written on the .25/.284 (TAR, Feb. 2002), as well as the .25 B.C. (TAR, Feb. 2001). I like both very much, but in my opinion, the best of the bunch whenever long shots may be presented are the pair of .25-06s.


A whole flock of .25s. From left: .25 Krag, .257 Roberts, .257 Roberts Ackley Improved, .25 WSSM, .25/.284, .25-06, .25-06 Improved, .25 BC, .257 Weatherby Magnum, .25 ICL Magnum.

Most sources state the .25-06 was "invented" by A.O. Neidner (or Niedner, depending upon the source) (Editor: See Michael Petrov's article on Adolph Niedner in the March '98 PS. On page 82 is a photo of Adolph's shop in Dowagiae, Michigan, with the sign on the building clearly saying "Niedner.") around 1920. Personally, I question the year. The parent .30-06 case had been around for 14 years before that date, and we know that at least Charles Newton was experimenting with a .26 caliber cartridge version at least by 1912 or so (The .256 Newton). I suspect others were doing likewise. Richard F. Simmons, in his 1947 book Wildcat Cartridges, lists a Niedner .25 Hi Power Special, a Griffin and Howe .25 High Power Special, and a Whelen .25 High Power as all being practically the same round. Although he gives no dates of introduction for any of the three, we can see that some pretty well-known experimenters were quite likely involved long before 1920. In any event, the cartridge was already quite long in the tooth when Remington "legitimized" it in 1969. Incidentally, the .25-06 is, in fact, simply the .30-06 necked down to .25 caliber, with no other changes.


"Hollow Bolt" Ruger Model 77 Varmint in .25-06. Like all M-77V rifles the author has owned, it shoots very well.

Several years ago, while lurking in the aisles of a local gun show, I took advantage of the opportunity to purchase what collectors of Ruger Model 77 rifles would call a "hollow bolt" M-77V chambered for the .25-06. Being intimately (No, not in that sense!) familiar with Ruger collecting, two uncharacteristically brilliant thoughts occurred simultaneously to my somewhat addled mind. One was to buy the gun, since it is a relatively scarce variant, and two "leave the darn thing alone!" Don't re-chamber, re-barrel or re-stock it and for God's sake (as well as my own) don't blow it up. Both of these thoughts I have complied with, and have also shot it a fair number of times.

One of my pet theories concerning the original Model 77 rifle (and one that seems to be getting some play recently) is that the varmint-configuration rifles used much better barrels than did the hunting-weight models. We do know that for the first few years, Sturm Ruger and Company used Douglas barrels on the No. 1 rifles, and perhaps did so into the period of time in which the M-77s were introduced (1968). My theory is that Douglas barrels continued to be used on the varmint rifles for several years after their use was discontinued for the standard-weight rifles. I have never had a M-77V that did not shoot well, whereas accuracy with the lighter M-77s has always been an "iffy" proposition at best. (Note that this does not apply to the more recent M-77 Mk II or Hawkeye variants.) This .25-06 M-77V is no exception to this theory.

Since this rifle was quite obviously never going to be carried in the deer woods, up mountains after sheep or across the plains of south-eastern Montana for pronghorn, the first order of business was to mount a suitable varmint scope. At the time I acquired this gun, nobody wanted "them ole' barrel rider scopes that used external mounts", and since the barrel was already drilled and tapped for external barrel-riding windage and elevation mounts, I scrounged one of those "antiquated" Unertl 2" Ultra Varmint scopes in either 15 or 16 power and the mounts to go with it. This scope was used for all my testing with this gun. Subsequently, I put that wonderfully clear glass on another rifle, and mounted a "much more modern" Weaver T-16 on the Ruger. Federal brass was used throughout, as were CCI BR-2 primers and Bonanza (now Forster) dies.

Forming the Ackley Improved cases can, of course, be done in any of three ways. First, factory loads can simply be fired, and out will come perfectly-formed Ackley cases. Second, new brass can be loaded and fired in the new chamber. P.O.Ackley, himself cautioned against using too light of a fire-forming load with this round, stating that incomplete reformation would likely occur. It's wise to pick a load from a reputable reloading manual for the standard .25-06 that is almost the maximum listed, and use this. Third, a charge of 10-15 grains of a fast-burning powder – like Bullseye – can be loaded, followed by a case full of Cream-of-Wheat and topped off with a wax wad. Lightly grease every second case, aim the rifle upward outside, and fire away. Again, a nearly perfectly formed case will result. I prefer this method, feeling it places less strain on the case (and avoids having to part with $ for "shoot-em-up" bullets or loaded ammo).

To cut to the chase, the improvement in velocity was pretty much what I expected – 100 or so fps. Any improvement in accuracy (there was some) may have been as much due to the barrel continuing to smooth out as anything else, but the added case life, in itself, was worth the effort of re-chambering. Although I had not fired the 40 R-P cases too often in the original chamber to wear them excessively, still after a total of 17 reloads each, no cases were lost to excessive neck stretching or neck splits. Shoulders only had to be bumped one time, and this was easily accomplished with a C & H/4-D full-length die. At the end of all my testing, I still had 39 perfectly useable cases. (We won't dwell on the fortieth case. Suffice it to say that some dimbulb may have loaded it a tad too hot.) Other than the shoulder-bumping exercise, cases were all resized using a bushing-type die and a .281" bushing. I should also mention that this barrel with either chamber would permit me to seat bullets approximately .10" further out than for my original Ruger. Again, primers used were CCI BR-2, but this time brass was R-P. Groups were my usual four shots at 100 yards, from sandbags, and ambient temperature was between 75 and 95 F for all testing.

Again, with the new chamber, I started with the 85-grain Fowler bullet, this time using powders between H-380 and the various 4831s. With the new chamber, I could increase charges of the same powders and lots as tried before re-chambering anywhere from one to three grains, with most powders tolerating an increase of one to one and a half grains. Of 60 groups fired, only eight went over one inch, and those just barely. (Quite possibly, these were due to "operator error".) Contrarily, 13 groups were at or under 1/2 inch. The most consistent load was 58.5 grains of H-4350 for consistent sub-1/2" groups. Also very good were 62.5 and 63.0 of AA-MRP, 58.5/IMR 4831, and 60.0 grains of IMR 4350. Velocity with all five of these loads was between 3713 and 3839 fps. One surprise surfaced when shooting this bullet. Even though the maximum overall length I could use was 3.277", the best accuracy was obtained .055" shorter – quite a jump actually.

The 85-grain Nosler Ballistic Tip shot much better than it had with the previous chamber (again, probably due to the barrel being more broken-in), and was a bit faster than the Fowler, but it still was not quite as consistent as was the Fowler. For those of you who don't want to go to the trouble and expense of ordering match bullets, the Nosler would be an excellent choice for vaporizing varmints at long range.

Just to get an idea of the velocity increase that could be expected from the improved chamber with heavier bullets, I fired some groups with two different Remington CoreLokt bullets of the pointed variety. I did not particularly expect great accuracy, but what I did get certainly would suffice to slay an antelope 300 yards or so distant. With the 100-grain bullet, 3560 fps was achieved with a charge of 62.0 grains of H-4831, and with the 120, 3317 was produced by the same powder, but with a charge of 60.5 grains. Now go back and re-read the Caution about using your head before you even think of duplicating any of these loads in your gun.

I must now offer a mea culpa to the readership. If any of you go back and read my previous TAR article "Beyond the .25-06", you will note that velocities mentioned therein are 100 fps or so higher than contained herein. Between then and now I discovered that my screen spacing for my Oehler M-35 was short two inches. This allowed velocity readings to be anywhere up to 100 fps too high. For the sake of attempting to be more correct, I arbitrarily reduced my velocity results for the earlier rifle by 100 fps. These lower numbers are the ones mentioned in this article. I suppose even the great ones screw up now and then – but I wouldn't know about that!


Remington 700 ADL switch-barrel rifle, with .25-06 Improved Spencer barrel and Bushnell Elite 4200 4-16x scope.

A couple of years ago, I purchased a very good-shooting Spencer .25 cal. barrel, had Carl Chiocca chamber it to .25 WSSM, fit it to my Remington Model 700 ADL switch-barrel gun, and proceeded to wring it out. Determining that this particular round was about the nearest thing to a useless cartridge ever invented – its performance was no better than a decent .257 Roberts Ackley Improved and the brass is all but unreloadable – but being unwilling (and too blessed cheap!) to let a perfectly good barrel go to waste (even as a .25 WSSM, it was very accurate), I decided it was about time to re-visit the .25-06 Improved. First, Carl dug out our community chamber reamer from one or the other of his various Footlockers of Forgotten Tools. (Rumor has it that he rents a 250,000 square foot warehouse for all of his Footlockers.) Next, he spoke to his lathe in soothingly sweet tones usually reserved for telling Dottie that it's a gun show weekend, and he gave his cutting fluid container a gentle kiss. Speaking in undecipherable incantations, burning lots of incense (used anti-seize compound?), and working only in the early pre-dawn of a moonless night, he proceeded to whack off the offending .25 WSSM chamber, re-thread the barrel and cut a brand shiny new .25-06 Ackley chamber into the Spencer barrel. Finally, being convinced that I was too ten-thumbed (perhaps with more than a modicum of cause) to do so myself, he screwed the barrel into my Remington receiver and returned it to me after firmly declaring that absolutely the barrel could not be rechambered again. Although he cautioned me to irretrievably lose any thoughts to the contrary, that's the same thing he told me last time. (Being even more senior than me – one of a rapidly vanishing breed--, he apparently forgot that last detail.)

Once again, I began with the 85-grain Fowler bullet. This time around, I eliminated H-380 powder from consideration, but added H-1000. I immediately became very glad I had done so. My most consistent load proved to be 68.0 grains of this latter powder for average groups of 5/16", and velocity of 3715 fps. (This was with the correct screen spacings.) Although this is a fairly mild load, it is just about all of this powder the case will hold. With most other powders, slightly over 3800 fps could be achieved. Other very accurate loads with this bullet were 63.5 grains of H-4831 (3732 fps and maximum pressure), 61.0 grains of Accurate MR-3100 (the original stuff – 3792 fps, and, again, near max), 59.5/H-4350 (3778) and 58.5/IMR 4350 (3762fps). With this barrel, I could safely increase powder charges one to one and a half grains above those which had been safe in the Ruger .25-06 Improved, even though both chambers were cut with the same reamer.

Some no-longer-made Starke Red Prairie 85-grain bullets also gave sterling accuracy, with the best load being a near max load of 64.0- grains of Hodgdon's 4831 for 3740 fps and 1/4 and 1/2 inch groups on a consistent basis. The Nosler Ballistic Tip simply did not perform well in this gun, with very few groups under one inch and none less than 5/8".

With this gun, I decided to re-visit a couple of 75-grain projectiles – the 75-grain Hornady V-max and the 75-grain Sierra H.P. With both, 3900 fps was easily reached, and both gave accuracy nearly on a par with the Fowler and Starke bullets. With the V-Max, 65.0 of H-4831 (3803 fps), 61.0/H-4350 (3816) and 60.0/IMR 4350 (3799) all gave regular one half inch groups. (Note the velocity "sweet spot" demonstrated here, which is not present with the next bullet.) With the Sierra bullet, great loads were 63.5/AA-MRP (3809 fps), 64.0/AA-3100 (3912 fps!) and 63.0/IMR 4831 (3886 fps).

As good as the accuracy was with the two 75-grain bullets, the computer, in the form of a couple of ballistic programs, shows a decisive edge in favor of the heavier projectiles. Again, however, if you prefer to avoid the hassle of obtaining custom bullets, either 75-grain bullet would be a fine choice.

To be as consistent as possible, I again used R-P brass, and CCI BR-2 primers with this chamber. Barrel length is 251/5", and rifling twist is 1-in-10", as it was in both previous rifles. The same dies were used in both Ackley-chambered rifles. Ambient temperatures for these latest tests were between 70 and 80 degrees F. Over-all cartridge length varied from 3.108" (the Sierra 75) and 3.232" (the 85 Nosler). Like those fired in the first Ackley chamber, cases seemed to last forever; only one shoulder bump was required in 14 loadings, and trimming was done only after the initial forming.

Although there are absolutely no flies, warts or pimples associated with the original 90-100 year old .25-06, I feel the Ackley version is better. With today's slower and more carefully formulated powders, the case cannot be considered "overbore" (whatever in blazes that means!). It is entirely predictable and well-behaved. Brass life is great and accuracy – at least in my guns – is superb. Eastern ground hogs, at least out to 633 yards have regretted my preference for this round!

As an aside, Ackley omitted this round from his earlier book, and admitted in his later two-volume set that he had to "pay the piper" for having done so. It seems that even "way back then" we precision shooters knew a good thing when we saw it!