View Full Version : re-chambering a .308 barrel

February 9, 2011, 04:38 AM
say you have a barrel with a .308 chamber on it... now say you would like a .30-06... could you have the chamber lopped off and a 06 reamed into the .308 barrel and be ok? now would that be cost effective?

February 9, 2011, 08:01 AM
If the chamber is too short [308 has a short receiver] a 30-06 won't feed properly !!

February 9, 2011, 10:10 AM
I think he meant that if the action is too short the magazine won't hold and feed the longer cartridges and the bolt may not open far enough for single feeding to be easy or for ejection to work properly. But as to the barrel itself, it depends on the contour of the original barrel. Most barrels are thicker over the chamber area. If you cut off too much you may not have enough of the wider portion of the metal left for a longer chamber. On the other hand, if you have a barrel that is cylindrical for a certain length or is just longer than necessary at the chamber OD, as some barrels are, you may no issue with this. You don't need thick metal over the neck.

As it turns out, despite the greater taper of the .30-06, you only have to cut off 1.06" of an in-spec, maximum tolerance .308 chamber to get enough metal to be sure a tight .30-06 reamer will clean it up. If the chamber is more average in dimensions, an inch will do it. If it is tight, 0.8 inches will do it. So, give or take, if your contour allows you to lose an inch without getting too thin at the shoulder of the cartridge and if your action is long enough to work with the longer cartridge, then this can be done.

Whether or not it is worth it, is another matter. You need a gunsmith that normally does the work of setting back and rechambering barrels. I've always done that for myself, and don't know what current prices are, but expect it to cost as much as installing a lower grade new replacement barrel. This could be worth it to recycle a custom barrel but not a for a cheap one.

February 9, 2011, 10:50 AM
Ok, so I have to ask this. Why couldn't you just run a 30.06 reamer in the barrel without cutting it off (given there is enough thickness left after the chamber to be safe)? Since you can resize 30.06 cases down to 308s, the 308 chamber should be smaller than a 30.06 chamber all the way from the boltface, correct? Would this not work for some reason? I am not trying to hijack the thread, just give another option if it would work.

February 9, 2011, 10:58 AM
The .308 is shorter but has less taper to the sides, so it is wider at the junction of the case sides and shoulder. If you just run the .30-06 reamer in, you'll be left with a small step where the .308 shoulder's wide spot was. It will actually chamber and fire .30-06 just fine, but your sizing die will really work the heck out of that step and just below it, and that can lead to cases separating just below the shoulder on subsequent firings.

February 9, 2011, 11:49 AM
In regards to cost effectiveness, I have to ask, why are you doing it? The 30-06 is barely more potent than the 308, and if you really want just the ability to put heavier bullets on a 308, get a longer throat reamed and hand load what you need. Alternatively, if your rifle can handle the pressures, get a 300 WSM or RSAUM done, for some true performance upgrades without needed to cut the barrel (the chambers are wider than 308 at all points afaik).

February 9, 2011, 07:37 PM
the reason i ask is i see lots of varmint take off .308 barrels from remington 700's. i have a 700 in .30-06 that i want to re-barrel to a varmint weight and was wandering if it would work and if it would be cost effective to do so. remington barrels are top notch so i don't see anything really gained by buying a top end match barrel if you could re-chamber for less.

February 9, 2011, 09:17 PM
If you want to do that, just keep it as a 308 barrel on a long action. That combo will work just fine. You can even seat your long bullets shallower and they will still fit in that long-action magazine.

February 13, 2011, 02:05 AM
I have a 700 Remington long action that I replaced the factory 270 barrel with a 308 heavy Sendro barrel. It works great, this is basally what the army m-24 has been for years.

The heart your problem is barrel quality and action trueness. If you want your 700 to shoot like a target rifle you are going to need to spend a little money on the whole package.

Instead of trying to rechamber a Remington factory sporting weight barrel spend the money and get a good quality custom barrel. Douglas, Hart, there are a dozen good ones.

Then have the action trued and the barrel installed. Then have the action glass beaded into the stock (pillared as well). After all of this you will have the rifle that you really want. It wont be cheap but it will be worth it.

Sorry there is no cheap way to get a super accurate rifle. (though buying a savage is an idea)

February 13, 2011, 11:08 AM

Is the Sendero .308 barrel a custom barrel made with the Obermeyer 5-R rifling profile (http://www.kriegerbarrels.com/5_R_Rifling-c1246-wp6676.htm) (5 lands and grooves; sloped land edges)? That's what's on the M-24; its not a Remington-produced barrel. I've been astonished to read of the life of the M-24 barrels, some still shooting half moa at close to 20,000 rounds.

James K
February 13, 2011, 02:37 PM
Unclenick is correct on just rechambering. I have seen a rifle which was rechambered from .308 to .30-'06 just by running the '06 reamer into the chamber. It worked fine and the owner didn't reload (at that time .30 GI was $3.00 a hundred) so the "step" in the case didn't bother him at all.


F. Guffey
February 13, 2011, 03:05 PM
and every 308 W chamber I have seen or know of still has some of the 308 W chamber that the 30/08 reamer did not clean up, I suggest the 30 /06 Ackley Improved or the 30 Gibbs, the shoulder of the 308 W is .011 thousand larger in diameter than the 30/06 when measured from the head of the case to the shoulder.

The shoulder (ring) will allow the shooter/reloader to use the ring imprint on the case to track skid, as in case stretch and skid marks, everyone insist their cases stretch, so I assume the case skids as it stretches. I have never seen the marks but if the case stretches the skid marks must be there.

F. Guffey

F. Guffey
February 13, 2011, 03:39 PM
Funnier still is "The firing pin drives the case forward"

F. Guffey

February 14, 2011, 01:12 AM
I have considered the 30-06 Ackley Improved. I planned on having the everything trued and squared up. to be honest a sporter weight can be just accurate as a varmint barrel if it had the same stuff done to it. if the barrel vibrates the same every time thats the name of the game to make a accurate rifle. the barrel could vibrate a foot in theory if it does it the same every time it will punch tiny holes. its just easier to do with a heavier barrel. does anybody have any info on the 06 ackley or knows where to get it? if I go the ackley route I see me getting some reloading stuff because I have never seen anything for any ackley loading like brass.

February 14, 2011, 01:51 AM

The 30-06 AI is a very old wildcat that has dies reamers and gauges readily available. Brass will probably have to be fireformed from standard 06 brass and then reloaded for your regular shooting or hunting rounds. Ballistically you'll be right there with 300 H&H mag or touch less. Debatable wether or not its worth it over standard 06

James K
February 14, 2011, 01:46 PM
Depending in part on the rifle, getting the AI round to feed may require modifying the feed rails in the receiver due to the different shape of the case shoulder.


February 14, 2011, 05:51 PM
I don't believe the .30-06 was one of the rounds that benefited as much as some others from Ackley's treatment. Folks used to complain it just made them use more powder to get to the same velocity as .30-06 or maybe 50 fps more. But that was back nearer P.O. Ackley's day, and now there are newer powders to choose from, so it may do a little better. I haven't looked at it for awhile.

What the A.I. should do is get you around the step issue and the case life of the A.I.'s is always pretty good. One of the features Ackley built into his design concept is that they be safe to fire the commercial parent cartridges in to get a formed case, even at full pressure, so you don't need special forming dies. You just buy the reloading dies and use them on the ejected cases of the parent rounds.

February 14, 2011, 06:59 PM
Lets go back to the OPs question. He is wanting to put a .308 chambered barrel (because they are very available I'm guessing) onto a receiver that is currently a 30-06. I go back to my point. I think the best alternative is to leave it as a long-actioned .308. You wouldn't gain much at all by attempting to rechamber the barrel. Just screw in the barrel, set the headspace, and shoot it.

February 15, 2011, 06:49 AM
I would like to stay with the 06 because I hunt elk and heavier bullets are needed.

F. Guffey
February 15, 2011, 09:49 AM
Shades of differences: The neck on the 30/06 is shorter than the neck of the Ackley Improved version meaning when a 30/06 chamber is reamed to to the Ackley Improved chamber not all of the old chamber is removed. In the perfect world the Ackley chamber is cut as a new chamber, in the other world the chamber is cut with an existing 30/06 chamber, some drawings list the difference in length between the two case necks as being .030 thousands, the Ackley being the longest.

.030 thousands and it's significances, The old saying that has been handed down since the Internet is not true "Ackley designed the Ackley Improved chamber to head space factory ammo". That part is true but when a 30/06 chamber is reamed to the Ackley Version the shoulder/neck juncture is not removed and if the chamber had XXX amount of head space before reaming factory ammo when fired will still have xxx head space.

Back to the perfect world, the short neck of factory ammo is sized (head spaces) when chambered in the Ackley chamber, when fired the rest of the shoulder and case body is (blown out and forward to form the rest of the shoulder, keeping up with two thoughts at one time, part of the shoulder is formed when the case is chambered) formed, and when blown out the case gets shorter, it does not stretch and the firing pin does not drive the case forward (on my rifles).

F. Guffey

Then the question becomes "Why would I waste your time with details"? 'Shades of difference' the availability of dies and reamers', Ackley neck length is .419, the length of the neck on the 30/06 is .389 + or - a few, point? one die can not size cases for both chambers. For the reamer to remove all of the 30/06 chamber the barrel should be set back, then the 30 Gibbs becomes an attractive choice, the Gibbs reamer removes all of the chamber, but when the Gibbs reamer is used, check the length of the chamber, My Gibbs chamber retains the length of the 30/06, there is an up side, the neck of the Gibbs is .217 + or-, in my opinion the neck needs all the help it can get, if 30/06 cases are used to form the Gibbs cases forget the length advantage, after forming and firing the Gibbs will be .040 thousands shorter than the parent case, because the case does not stretch nor does the firing pin drive the case forward, nor is the shoulder driven forward .202 thousands, part of the shoulder becomes part of the case body and part of the neck becomes part of the shoulder, all of this forming shortens the case when the case body is blown out when formed.

And I still think it is funny, the case, powder, bullet and primer accelerates to a speed equal to the speed of the firing pin to escape the strike, only on my rifles, my primers are crushed before the rest of the components know the primer was crushed.


F. Guffey

February 15, 2011, 01:01 PM
Lets go back to the OPs question. He is wanting to put a .308 chambered barrel (because they are very available I'm guessing) onto a receiver that is currently a 30-06. . .

It's the other way around. The OP has the .308 and wants .30-06. That's why all the action length and reaming considerations and alternate chambering suggestions.

F. Guffey
February 15, 2011, 04:54 PM
Unclenick, and the part about lobbing off the chamber of the barrel,, there will not be enough metal left to cut a new chamber nor enough metal left to cut the threads for the shank.

F. Guffey

February 15, 2011, 08:26 PM
It's the other way around. The OP has the .308 and wants .30-06. That's why all the action length and reaming considerations and alternate chambering suggestions.

Dooh. That's what I get for not paying good attention in class.

February 15, 2011, 09:05 PM
ok to relieve all confusion... I have a remington 700 chambered in 30-06. I am interested in buying a take off .308 barrel from and sps varmint or police model and re-chambering it to 30-06 or 30-06 AI or maybe .30 gibbs.

February 15, 2011, 10:03 PM
ok to relieve all confusion... I have a remington 700 chambered in 30-06. I am interested in buying a take off .308 barrel from and sps varmint or police model and re-chambering it to 30-06 or 30-06 AI or maybe .30 gibbs

It turns out I was paying attention after all. Why not keep the new barrel .308? The ballistic advantage of a 30-06 really only comes into play if you want to launch bullets greater than about 200grn. Certainly, the cost of rechambering would be much higher than just finding a 30-06 barrel in the first place.

February 15, 2011, 11:35 PM
aftermarket barrels run $300+ without the chamber cut. I can't see how
re-reaming a new chamber would be any more than cutting a new one into a new barrel. I think even with the new barrel you still would want to square everything up even the barrel. if everything ends up costing the same I would get a new barrel but I don't see that being the case

February 17, 2011, 11:10 PM

I have a 26" barrel long action 308. There really is nothing that a 30/06 can do that this 308 can't. If you get a chance to chronograph loads from a 308 and load from a 30/06 you will fine very very little difference. The difference often goes towards the 308.

A heavy 308 is a sweat shooting rifle, with little felt recoil. The accuracy greatly increase ones confidence in the field.

If you feel that the 308 is not enough gun for your elk hunting needs then you may want to make the jump to a 300 Magnum class or larger. I have a 338 Win Mag for my Elk, Moose, Mastodon needs.

Build a long action long barrel 308 and try it. If you don't like it have it rechambered to 300 Winchester.

February 18, 2011, 02:36 PM
While reading the posts on p 1, it dawned on me-you cant fool mother nature-or mother gunsmith.

AI w/ several more grains of powder to gain 50 fps-not for me. I usually down load for max accuracy anyway.

February 18, 2011, 04:56 PM

Brownells used to send a list with their catalogs to dealers of suggested service prices. Back in the early 90's it was $40 to rechamber. Today it's probably $60-$80, but that's just labor. If Reamer rental is involved you'll have to add that.

You still have the issue of whether or not there is enough metal. If you have something beefy like a Shilen #7 contour barrel to start, you'll be fine because the thick portion goes forward of the receiver 4". But if you start with a light sporter one, like a #3, where the thick portion is only 2.5" long, you may not. That will have to be determined by the gunsmith. But I would think that in most instances there will be enough to go from .308 to .30-06 AI because you don't need to set the shoulder back or re-thread the barrel. If you went to regular .30-06, the added labor is unlikely to make it as worthwhile.

If you load the .30-06 and the .308 to their respective SAAMI maximums (60 kpsi vs 62 kpsi), you get about 100–150 fps more velocity out of the .30-06 from a 26" tube, depending on the bullet weight. Add another 50 fps for the AI format, and you should have a 200 fps advantage over the .308. It's not magnum but it's not nothing, either.

With commercial loads you often don't see that .308 and.30-06 difference because the latter is more likely to be underloaded out of liability concerns for old rifles. The velocities were much closer when both were constrained to using 4895, which the .308 handles more efficiently. But the '06 can actually handle a slower powder better than the .308, and that picks up its potential. You just can't count on using a slower powder in the Garand or other gas guns as readily.

Loading for yourself, you can work up reasonably to maximum performance for your weapon. If you work up based on brass pressure signs, you'll likely discover your gun is happy running .30-06 AI at the same pressure as .308, in which case another 25 fps will be picked up.

February 19, 2011, 05:08 AM
according to noslers website the difference in a 180 grain bullet is more like 300 fps.

February 19, 2011, 08:38 AM
I would like to stay with the 06 because I hunt elk and heavier bullets are needed. If my memory is correct, .308 barrels have a twist that optimizes 150 grain bullets and 30-06 barrels have a twist that is intended to stabilize 180 grain bullets. So (if my fuzzy memory is correct), such a re-chambering would not make sense if the OP wants to re chamber to use heaver bullets.

February 19, 2011, 05:29 PM

Actually the common 10" twist in .30-06 military barrels came from stabilizing the old 220 grain round nose Krag bullet. They just kept it when the .30-03 and later .30-06 were developed. For .308, the army started with a 12" twist n the M14, IIRC, which is just fine for even 180 grain bullets if the air conditions are normal. The military marksmanship units later switched to 11" twists, but most civilian .308's I see these days are using the 10" twist same as the .30-06.


300 fps is pretty optimistic. If I look through my Nosler Reloading Guide No. 6, the maximum velocities they list for their fastest loads with 24" tubes on both are:

Bullet .308 .30-06 Difference

125 gr. 3284 fps 3418 fps 134 fps
150 gr. 3001 fps 3056 fps 56 fps
165 gr. 2910 fps 3002 fps 92 fps
180 gr. 2718 fps 2872 fps 154 fps

There are some new higher speed powders from Alliant and Hodgdon. I don't know yet how these will stack up. Take a look through other load data to get a better idea what's out there. Hodgdon's site is another place you can look.