6mm-06, .25-06, or .25-05 Ackley Improved

R

RiverRider

New member
EDIT: Uhhh...I meant .25-06 Ackley Improved, not .25-05!

I've been kicking around this idea of rebarreling a rifle I have for a couple of weeks. It's presently a .30-06.

I've been frothing over the idea of a 6mm-06. I don't have a rifle yet between .224" and .284", and I don't think I need a .30-06 at all.

I've had one heck of a time finding reloading data on the 6mm-06. Folks advise me to just use 6mm-284 or .240 Weatherby data, which is fine. But, WHY no data specific to 6mm-06?

I took a look at a wildcat known as the .243 Catbird. A hotdog, to be sure! It's an improved, blown out, and necked down .270 in 6mm caliber, and is reputed to have some pretty impressive ballistics, but I wouldn't expect it to be that far beyond the 6mm-06. What got my attention, though, was a claim that the .243 Catbird's barrel-life expectancy was about 1500 rounds, with good accuracy.

That thought made my mental brakes flat lock up.

Does the 6mm-06 eat barrels nearly that badly? I know it's an overbore cartridge, but...really?!?

So, I began to think maybe just a good ol' .25-06 would be the ticket. I've long held this caliber in very high regard, and can't really cite any its shortcomings, other than it's no .340 Weatherby.

But I'm the type of person that just has to have something a little different, at least if it makes any sense at all. So, I am asking the question, is the .25-06 Ackley Improved enough of an improvement over the original .25-06 to be worth the extra hassle of handloading for a wildcat? And, what's the barrel-life expectancy for the Improved cartridge, and the Remington offering?

All answers appreciated...thanks!

-RR-
 
I would suspect that accurate barrel life would be less then 1000 rounds.

Have you considered 6.5 x 06? I used it for a thousand yard benchrest. With 155gr sierras it seemed to buck the wind better then most of the various 30 cal magnums.
 
NVCDL, thanks for the reply.

Yes, I have thought about the 6.5-06, and I have nothing against it either, in fact I think it's a fantastic caliber, but I already have a .280 Remington I want to keep, so I am looking for something more along the lines of "light big game" to "super varmint" in utility. The 6.5-06 really kind of overlaps with my .280, I think. That's why I am thinking .25 or .24 caliber.

Someday when I win the lottery, I will have a rifle or two in all the greatest calibers. But until I get lucky, I need to kinda spread my resources.
 
Maybe there's no data on the 6mm-'06 because nobody has bothered with it? You could become a trail-blazer? :)

Roughly, a .243 case gets around max at about 40 grains of medium/slow powder; the '06 case at around 54 grains. Mas o menos. That's roughly a 30% increase in capacity. We know what a .243 can do with bullets in the range of 55 to 85 grains. Thinking about it, the larger case pushing hot gas through the 6mm hole means a smidgin longer burn-time and thus more throat erosion. I think. Maybe. Might make for a higher combustion temperature (Instead? As well as?).

Kinda like car-racing: Ya wanna run out front, it costs more money. More faster, more $.

Only from reading, 1,500 rounds and then throat erosion is not all that uncommon for the Super Blazers. There have been some comments here about 1,000 to 1,500 round replacements...

Oh, well. I recall a short article about somebody managing to get a .50MG case down to .22. I think the final comment was something on the order of, "Exciting, but not practical."

Besides, everybody needs at least ONE .30-'06.

:), Art
 
I think Art is on the right trail here.
As I see it, the main problem is that all these cartridges are based on the old 30/06 necked down (270 Win. & 6mm/06) and in addition blown out (25/06 Improved & 243 Catbird??).
Now some people would hold that the original 30/06 is "over bore" to begin with: It holds more powder than is optimal for ideal ignition and the increase in velocity achieved over shorter cases is not proportional to the amount of powder burned.
Being that the original 30 caliber bullet is slightly over bore in this case (not a bad thing in and of itself), the problem gets worse and worse as you neck down to smaller and smaller bullets and in addition blow out the taper for even more capacity. Since the ignition is not ideal to begin with, at some point it gets pretty bad and you begin to eat up barrels pretty bad. It is entirely possible that at some point you begin to loose top fight accuracy because of this after what seems to be absurdly few rounds.
But what do we mean by top flight accuracy? I remember, but cannot reference off the top of my head, reading that one of the bullet manufacturers figured out about how long they could expect a top flight barrel to last for the purposes of accuracy testing of bullet lots. They tested and recorded accuracy data on a couple of well known barrel brands in factory testing of 308 bullets fired in the 308 Win cartridge, a round much praised as being well balanced and definity not "Over Bore". They concluded that accuracy began to be measurably affected after about 4,000 rounds in all the brands. They were getting something like 3/8" five round groups at 100 yds before 4,000 rounds out of their machine rest heavy barrel test rifles and after that things began to open out a bit. Thats accuracy that most of us can only deam about in our more practical rifles, but I would take that as top flight accuracy and about all you can expect with the most efficient of cartridges.
So perhaps 1500 rounds is not too high a price to pay if you must have something that is really hot. And the rifle will still no doubt be quit good and usable long after this peak performance has come and gone. If it gets to be too bad, then you just have to rebarrel the thing, so don't invest in fancy engraved barrels, just good plain ones.
 
Thanks for the responses so far, guys.

I am aware of the shortened barrel life of overbore cartridges. What I would like to know now is whether or not there is a significant difference in barrel life between the 6mm-06, .25-06, and .25-06 Improved. I do not know what the overbore/barrel-life curve looks like. In other words, is there a specific point where things get ridiculous, or is shortened barrel-life necessarily proportional to the bore diamteter:case capacity ratio? Or, put another way, taking the '06 case as an example, would barrel life be proportional in some way to the bullet diameter selected, or is there a point where things simply go to hell in a big hurry in terms of bullet diameter (as the diameter is decreased)?

I'm still not convinced I have effectively communicated that question. Oh well. I think you guys can figure out what I am trying to ask.

AND...is the .25-06 Improved's performance superior enough to the original .25-06's performance to justify the extra trouble involved in handloading for it?
 
Operating on the basis that I wan't full of garbage in my previous post: I'd guess that the 6mm-'06 would "burn out" faster than the other two. The showroom-stock .25-'06 barrel should last the longest. Obviously, that puts the "improved" critter in the middle...:)

The AI versions of most cartridges seemed to have gotten some 100 to 200 ft/sec better performance than stock. Given the general improvements in powders, Ackley levels of performance (then) can be attained in stock cartridges now. The improved versions would still do better, of course, but the question is whether that relatively small gain is worth the rest of the hassle or shortened barrel life.

Following Herodotus' commentary about the '06 case starting out as a bit of overbore, I'd say it's not the one to base an improved and necked down package upon. Unless you just gotta have a Super Blazer, and never mind the barrel life and cost factor.

Hope all this helps; lotsa guesswork.

Art
 
You bet I have, Dangus. And one day I'll have one, but this is a rebarreling project on an existing .30-06. I'm considering 6mm-06 because it's an '06 case (easy conversion), it's different, it's a hot dog, and I don't have anything between .224 and .284 in a rifle.

I never thought it would be so difficult to make a choice, but I think I have found myself stuck between my affinity for simple practicality and my other affinity for unique and exotic things. Me and myself are having one hell of an debate over this.

;)
 
Hey RiverRider, First off, I completely agree with Art's last post. It reflects my thoughts as well

I've also looked at Jarrett's Catbird, the 6mm-06, as well as a whole bunch of other 6mms and 25cal Wildcats. I was enjoying Wildcatting at that time for the same reason you mentioned - to have something a bit different.

Don't let barrel life be the determing factor, because that is just part of the cost of having that "something different". (You can not enjoy a 427cu.in. big block, run Regular gas or expect to get 100,000 miles on it!) Plus, your actual "Minute of Critter" barrel life might be 3-6 times that amount. Lots of factors involved, with the primary one just being the same old, "don't shoot while the barrel is hot".

Here is the best link I've seen to an article that explains a way to increase barrel life. Moly Coating has been praised and denounced ever since it became popular. This is a long article, but be sure to notice the amount of bullets through the "hot" 6.5mm the Norma folks were using as a benchmark. http://www.precisionshooting.com/aug98.html


But, there are a few "concerns" you need to be aware of. First off is the reduction of powders available to be useful in the 6mm-06 case. It is close enough to the 240Wby in volume as to allow you to research what powders work well with it. Then if you go to the slightly longer 270Win case(less to neck down), blow it out, push the shoulder forward and increase the shoulder angle, then you really cut the list of powders available that will work with it. There are some available, and I can get you to them, but it would take me awhile to locate their sources. Primarily MilSurp stuff or Pulled MilSurp is what you will need. Special Pressure Detection devices would be recommended as well and they can run $1000 plus a Laptop. (Not absolutely necessary, but would help.)

In order to see the advantage, you need to get a 28" barrel as a minimum and a 30" barrel gets you into the area where you will be able to get those real HIGH Velocities. Also requires special twist rates that apply real well to a small segment of bullet weights, so chopping off the chamber and another 3" or so of the barrel, then reusing the barrel stub "might" or might not be a waste of time.

Bullets will be limited to a very few that can withstand the rotational stress as well as the Impact Stress at those increased speeds. The BarnesX is about the best candidate I can think of for these velocities. As you are probably aware, some barrels like them and some don't. But, any of the Super Premiums "might" work. Just depends on the accuracy level you can get from them. I've had some "Lots" of Nosler Partitions seem to be as acurate as Match bullets. So, you "might" be fortunate enough to get them to work for you.

Once you decide on the bullet, you can get the rifle specifically throated for it. Then if the rifle doesn't like that particular bullet, you "might" be lucky and have another brand shoot well in it anyhow. Along these same lines, you have to decide if you want lots of Freebore (helps get blistering speed) or a good fit with the bullet of choice (helps with accuracy until the throat burns).

Of course, you will want a SAAMI "Minimum" chamber and a tight neck. That means you will want to preselect your cases based on their average diameter across the Case Head and get 500 of them. Some brands just differ in this dimension and you do want as good a fit as possible (don't you?). Then you will need to decide if you want the neck area of the chamber cut for a "tight neck" which helps with the accuracy as well. If that is an option you want, then invest in the very best "Neck Turning" tools you can find.

Finding a Gun Smith to do what you want, the way you want it, can be a bit of an experience in itself. Some are real Prima Donnas, but there are some that will do their best to give you exactly what you are looking for. If you find the "correct one", he will help you find the correct balance of all these details to meet your needs. Start looking for the Gun Smith 1-2 years ahead of really committing yourself to the project. Then look a this work and see how his customers like dealing with him.


Or, you could do none of the above. Then if the rifle doesn't perform up to your velocity or accuracy expectations, you at least know the things that "might" have gotten you to where you wanted to be, "IF" you had done them.


Actually, the "biggest" cost of a Wildcat is your "time investment". It might take 1-3 years to get the rifle to the point you want it. Just part of the program. The "time investment" is the main reason I no longer mess with the Wildcats.

Good hunting and clean 1-shot kills, Hot Core
 
Hot Core, I am not even considering the .243 Catbird, or anything exotic...all I am planning to do is have the rifle rebarrelled to 6mm-06. I doubt that necking down .25-06 cases to 6mm is going to turn into some impossible two-year project, and I doubt that bullet selection is going to become impossible just because I may get 200 or 300 fps more than the .244 Remington. And I am positive that somewhere between IMR4350 and Reloader25, there are readily available powders that will do just what I want.

All I am unsure of is whether I am willing to accept the shortened barrel-life of such an overbore cartridge. If it is going to be similar to .25-06, fine. But if it is significantly shorter than .25-06, then "NO" I am not willing to accept it, and I would simply go with .25-06.
 
Hey RiverRider, I wasn't trying to start an argument with you. Just trying to share a bit of Real World "Experience" when dealing with Wildcats.

You seem to think I'm all wrong. Thats fine, I don't mind disagreeing with polite folks at all.

Good luck with the project, Hot Core
 
Hot Core...I did think you got a bit too heavy with the super-detailed advice. It's not my wish to snub you or denegrate you in any way. I just think that you do not realize what my objective is, which is to do a sensible rebarrel of a nice rifle in a caliber that is not common, yet keep it simple. One day I may well want to do the ultra-precision-competitive-benchrest-super-hotrod-30-inch-barreled wildcat, and if I ever do, I will spare no expense, and I would also likely follow the guidelines you described. But in this case all I want is a simple necked down '06 rifle to shoot at paper occasionally and at varmints often (hopefully).

I can't say you are all wrong about anything you have said, and I have to admit that those are the things I would have to do if I wanted to do this thing to the Nth degree, but all I want is a fairly unique varmint/sporter on a Sako action.

Sorry I went off on ya, and thanks for sharing your ideas.
 
No Problem

Hey RiverRider, Not a problem at all.

When I was into Wildcatting, I'd get to "thinking" about a project and it would always seem to get started like a small snowball at the top of an ant hill. Then before I knew it, the snowball was getting bigger and rolling down the side of a mountain, gaining size as it went.

So, if you have the ability to hold those weaknesses "that I had" in check, then you should be able to create a fun project rifle.

Also agree that if you stick with the 30-06 "length, taper and shoulder angle" case for the project, then the powder availability is much better than going with the longer, full blown-out 270Win case.

One other thing I did neglect to mention is that sometimes those "high angle" shoulders on the AI cases can create feed problems. Just tend to catch or hang slightly as they enter the chamber. One additional step of applying a small radius on the edge of the chamber goes a long way to alleviate this problem.


We all sometimes get a bit "wound up". I know I do anytime I have to deal with Democrats! So, as I said before, I don't mind having a disagreement with polite folks at all.

Good luck on the project with whichever caliber you select, Hot Core
 
Still a somewhat popular wildcat.

A friend of mine in Sacramento uses a 6mm-06, standard '06 shoulder, for the 1000 yard tactical matches, and competed against my 6.5-06. His 6mm-06 was built on a Win Model 70 action, and McMillan stock. Between relays, he and I were comparing notes, and it turned out we both use the same powder, H-4831SC. He used .25-06 brass, necked down, while I use 7x64 Brenneke brass, also necked down. If he ever gets around to selling it, he'd better give me a call!!!
 
River Rider

I have a couple 25-06 Ackleys and am well pleased with them. They have given me from 100-300 FPS increase. Accuracy didn't change once a load was found. Basiclly, I'm getting 257 Weatherby preformance with 10 grains less powder.

As to throat erosion, people that I have talked to that are smarter than I am (doesn't take much) that have burned out a lot of barrels ( Walt Berger is one of them) seem to think that erosion can be kept to a minimum if you keep your barrel heat down i.e. take your time between shots and/or keep your rapid fire shots to 2 or 3 at most.

I had an old 25-06 M700 that I had rechambered to AI and I use that for fire-forming so my HS-Precision will last that much longer.
 
I have been playing around with a neat .25 wildcat. It uses a .243 or .308 case and has a 40 degree Ackley shoulder.Initial accuracy testing is encouraging if the weather ever warms up enough to shoot I will chronograph it.I think the .308 case is better suited to the quarter bore than the 30-06 I hope to get near 25-06 velosity with 100 gr. bullets.What ever you decide on I wish you the best of luck and always remeber when you aproach maximum load the angels sing.
 
I don't have a clue.I purchased the barrel and dies used on the net.It was threaded for a rem 700 action and I was able to rethread and headspace it for a Sako L579 action.The dies were made by shortening .257 roberts improved dies.Since a .25 X .308 is a 25 souper I was going to call it a 25 souper-duper.I really doesn't matter as long as someone a deer camp asks me what calibre my gun is so I can mess with their head.If it is a .257 Durham jet then so be it.
 
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