Rechambering a .308

[sukivel]

How hard is it to rechamber a .308 Win barrel to a .308 Norma mag? I am interested in doing this to an H&R Handi rifle. The first thing I checked was pressure, and the 308Win has a higher pressure, so I don't see any problems? No boltface to deal with...slight modifications to the extractor...I don't see any reason it wouldn't work.

Any thoughts or comments?

Yeah I know it *may* recoil slightly more than what I would like, but...[smilie=2:

[Texas by God]

If H&R/NEF chambered Handi rifles in 7mm or .300 mag;I would do it. If they didn't- There is a reason. The extra width of the belted mag case may amount to a "bigger hammer" effect on the frame even though the pressures are similar.
Best, Thomas

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[Ballistics in Scotland]

If H&R/NEF chambered Handi rifles in 7mm or .300 mag;I would do it. If they didn't- There is a reason. The extra width of the belted mag case may amount to a "bigger hammer" effect on the frame even though the pressures are similar.
Best, Thomas



Yes, that is a thought worth thinking. It would have had big attractions for H&R - not necessarily the Norma, but a large magnum case - if there wasn't some reason against it.

An Ackley Improved round on the .308-sized head would have had a lot going for it, though, and no magazine follower or lips to worry about.

[charles1990]

308 Norma mag is as dead as Hillary's presidential hopes.

A handi rifle in any magnum is a bad idea. It may come apart and it will beat the snot out of you.

If you want a 30 caliber magnum buy a TC Compass or a Ruger American. It won't blow up and should you ever want to sell it you'll get back most of your money.

The price difference is very small as well.

[troyboy]

You need to calculate bolt thrust prior any conversion. I have a 500 mag H&R wich is considered the limit of the action in regards to bolt thrust. Calcute, compare then decide.

[Texas by God]

Bolt thrust. That's why the Contender would handle the high pressure .223 with its small case head but not the 22-250 with it's wider head. The 30-30 but not the .308. The 45-70 but not the .444 Marlin.
Ballistics, you lost me on that last passage.
Thomas

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[MostlyLeverGuns]

Bolt thrust - actual pressure pushing against the bolt/locking mechanism. 3.1416 (pi) x Head Diameter /2(squared) X Pressure(PSI). Example 30-30 Head Diameter .420 Pressure-38,000 psi
3.1416 x( .420 /2) x (.420/2) x 38,000 = 3.1416 x .210 X .210 x 38,000 = 3.1416 x .0441 x 38,000 = 3.1416 x 1,675.8 = 5,264 pounds pushing against the boltface. There are other factors like brass friction, chamber roughness, brass hardness and stretch but this is the basic. Area of circle= pi (3.1416) x radius squared

[john.k]

As you can see,thrust is not great,about 2 1/2 tons.A small gr 5 bolt can easily support a similar weight with a margin of strength.I doubt that you can buy factory ammo in 308 NM,so you can simply reload to the pressure level you think best.I have rechambered a great many guns to 308NM on a production basis.Norma used to sell a gunsmiths kit to do the P14/M17 without removing the barrel,for the sum of $29.95.IMHO,308 NM and 7x61 S&H are two of the very best magnums.I would think a big increase on 308 performance at a much lower pressure level.With equal backthrust.

[MostlyLeverGuns]

308 Norma Magnum - Head Diameter .512 - Pressure 60,000 psi Do the Math - bolt thrust = 12,353 quite a bit more than a 30-30

[sukivel]

308 Norma Magnum - Head Diameter .512 - Pressure 60,000 psi Do the Math - bolt thrust = 12,353 quite a bit more than a 30-30

What’s the math on 308 win, which would be the donor gun?


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[Ballistics in Scotland]

I thought someone made and then rather needlessly deleted a query about my last sentence. It may have been for the mention of a .208-sized case head, which I have now corrected to .308-sized. For the rest, rechambering to an Improved case shape can in some rifles produce problems with how the rounds stack and feed in the magazine, but that doesn't apply when you don't have a magazine.

I can tell you the bolt thrust on my .40-82 Winchester 1886, with assertive but moderate smokeless loads. It exerts no thrust whatever, since the primers are extruded to the limit of its considerable but not excessive headspace, and the case doesn't move back to push them in again or mushroom them. The case body is held to the chamber by gas pressure, and the case head is held to the body by the strength of the brass. The modern brass case had pretty much the size and work-hardening of a quarter-inch brass rod. Similarly Ackley found that a .30-30 Improved could be fired with his Winchester 94 locking lug removed.

The reason we can't dispense with bolts and breechblocks, when they are such a nuisance, is that chambers can be wet or oily, and people do reload cases until they get head separations, and the strength of brass becomes none whatever. Rifle design normally allows for the worst, but I do believe H&R, in not going for the magnum case head, knew what they were doing.

[Texas by God]

I thought someone made and then rather needlessly deleted a query about my last sentence. It may have been for the mention of a .208-sized case head, which I have now corrected to .308-sized. For the rest, rechambering to an Improved case shape can in some rifles produce problems with how the rounds stack and feed in the magazine, but that doesn't apply when you don't have a magazine.

I can tell you the bolt thrust on my .40-82 Winchester 1886 Winchester, with assertive but moderate smokeless loads. It exerts no thrust whatever, since the primers are extruded to the limit of its considerable rbut not excessive headspace, and the case doesn't move back to push them in again or mushroom them. The case body is held to the amber by gas pressure, and the case head is held to the body by the strength of the brass. The modern brass case had pretty much the size and work-hardening of a quarter-inch brass rod. Similarly Ackley found that a .3xe 0-30 Improved could be fired with his Winchester 94 locking lug removed.

The reason we can't dispense with bolts and breechblocks, when they are such a nuisance, is that chambers can be wet or oily, and people do reload cases until they get head separations, and the strength of brass becomes none whatever. Rifle design normally allows for the worst, but I do believe H&R, in not going for the magnum case head, knew what they were doing.I didn't reply directly, but yes you had me baffled for a bit with talk of .208 heads and magazines haha. I agree about not rechambering to the belted magnum as well. NEF would have if they could have because they would have sold a bunch.

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[John Taylor]

It does seem strange that a 30-30 with 42,000 psi will back out the primer with head space but a 7MM with around 49,000 will stretch the brass so the primer is flush. Some of the test P O Ackley did proved that the brass on some cartridges would stick to the chamber wall and have no bolt thrust. I would not depend on that as I have seen some head separations that would be dangerous. The bolt thrust on a 308 is around 8,000 pounds. On a 12 gauge it is around 5,000.

[sukivel]

I didn't reply directly, but yes you had me baffled for a bit with talk of .208 heads and magazines haha. I agree about not rechambering to the belted magnum as well. NEF would have if they could have because they would have sold a bunch.

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NEF could have sold alot more of several different calibers if they just offered it. But...they did offer a .444 and .500 s&w...aren’t those heavy recoilers?


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[MostlyLeverGuns]

Recoil is based on bullet weight, powder charge weight, bullet velocity and weight of the firearm, pressure is not directly involved. A lightweight 45-70 with a 300 grain bullet at 2000 recoils far more than a 11 pound 243 with an 85 grain bullet at 3100, though the 243 runs at much higher pressure than the 45-70.

[sukivel]

Recoil is based on bullet weight, powder charge weight, bullet velocity and weight of the firearm, pressure is not directly involved. A lightweight 45-70 with a 300 grain bullet at 2000 recoils far more than a 11 pound 243 with an 85 grain bullet at 3100, though the 243 runs at much higher pressure than the 45-70.

Ah, good point!


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[RPRNY]

308 Norma Mag is 64,000 PSI under CIP. The maximum SAAMI pressure cartridge that the H&R Handi Rifle was chambered in was 65,000 psi (270 Win). SAAMI max pressure for 308 Win is 62,000 psi. No magnum rifle cartridges were ever chambered in the Handi Rifle.

Reaming the 308 Norma Mag chamber is technically feasible but would likely require having a new extractor cut, which may be tricky.

FWIW, in my opinion, it represents a greater risk than it does reward.

[sukivel]

Thanks for all the replies. I did learn a few things. I guess the 308NM will have to be an ‘opportunity knocks’ rifle.

On second note...I find tons of .308 H&R Handi rifles out there...what would be some ideal rechamberings for these?


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[Texas by God]

The only factory round I can think of that would clean up the chamber is the 30-06 (if it will). Whoops-there is the 7.5x55 Swiss but good luck finding a reamer....may I ask what's wrong with the #1 30 caliber cartridge in the world?

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[swheeler]

Thanks for all the replies. I did learn a few things. I guess the 308NM will have to be an ‘opportunity knocks’ rifle.

On second note...I find tons of .308 H&R Handi rifles out there...what would be some ideal rechamberings for these?


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30-06 Ackley Improved or 30 Gibbs come to mind.

[Ballistics in Scotland]

The only factory round I can think of that would clean up the chamber is the 30-06 (if it will). Whoops-there is the 7.5x55 Swiss but good luck finding a reamer....may I ask what's wrong with the #1 30 caliber cartridge in the world?

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Counting semi-legitimised wildcats, I suspect that we have a hundred times more cartridges than we have the slightest need for. "What's with...? may not be the right question to ask.

[sukivel]

The only factory round I can think of that would clean up the chamber is the 30-06 (if it will). Whoops-there is the 7.5x55 Swiss but good luck finding a reamer....may I ask what's wrong with the #1 30 caliber cartridge in the world?

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There’s nothing wrong with it, I just want something different.


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[MT Gianni]

Mike Belm warns against top loads in the Encore with 300 Winchester as it can exceed the max psi of 60K. An Encore is built a lot tougher than a Handi. They still have quite a following, I might sell and buy something else if I was tired of it. Still in 308 you have a perfect truck gun.

[Texas by God]

Nowadays you can trade a Handi for a decent bolt action. In the future you can trade it for a nicer bolt action because the Handis are no more.

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[RPRNY]

If you want something interesting, think rimmed. The single shot break action rifle cries out for a rimmed cartridge. Headspacing on the rim is quite convenient.

Three Wildcats come to mind that might suit: the 30-40 Ackley Improved; the 30-444, another Ackley special, and for way out of the box (but readily available brass) the 308 Epps (a 303 Brit Improved but necked to .308). Not sure the Handi is up to the 30-06 AI.

Highly recommend the 30-40 AI, effectively a rimmed 30-06 in a Handi.

[Hannibal]

The trouble with rimmed cartridges is keeping the **** rims a consistent thickness. A new brand of brass, a new rim thickness. And no way to readily compensate for it, like the 'bottleneck' boys have.

But, if you aren't particularly concerned with accuracy, rimmed cartridges are fun to shoot and cool to eyeball.

[MostlyLeverGuns]

A 30-06 Improved ( Ackley, Gibbs) is probably the best rechamber, working pressure is about the same. The .455 shoulder of the .308 won't 'clean up' without an improved version of most standard cartridges. There are some wildcats on the 8x57 but you do need something that will clean up the chamber. The 30-40/303 British case head (.456) is too small to work in the 308 (.470). A 444 wildcat would work, as the case was/is based on a rimmed '06.

[sukivel]

If you want something interesting, think rimmed. The single shot break action rifle cries out for a rimmed cartridge. Headspacing on the rim is quite convenient.

Three Wildcats come to mind that might suit: the 30-40 Ackley Improved; the 30-444, another Ackley special, and for way out of the box (but readily available brass) the 308 Epps (a 303 Brit Improved but necked to .308). Not sure the Handi is up to the 30-06 AI.

Highly recommend the 30-40 AI, effectively a rimmed 30-06 in a Handi.

Those are interesting. There is a Handi in 30-06...that would be a good contender for AI. Yeah the .30-40AI looks cool.


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[Texas by God]

308 Ackley improved

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[sukivel]

Now I’m looking stupid...not a bad idea.

Maybe the op could have come up with a simple idea like that. [emoji15]


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[Texas by God]

I remembered what our Scot friend stated in post #3 after we all ran a few laps. Fun, though.

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[ulav8r]

Mike Belm warns against top loads in the Encore with 300 Winchester as it can exceed the max psi of 60K. An Encore is built a lot tougher than a Handi. They still have quite a following, I might sell and buy something else if I was tired of it. Still in 308 you have a perfect truck gun.

Somewhat questionable, top loads implies handloads maybe. Handloads can be whatever pressure the loader wants, or is stupid enough to cram into a case. This needs to be remembered by all handloaders, the pressure obtained is determined by the components/quantities used. Whether or not a wildcat provides the desired performance at the pressure desired is up to the loader. If the pressure is too high to get the velocity you want, go to a bigger case.

[Ballistics in Scotland]

I remembered what our Scot friend stated in post #3 after we all ran a few laps. Fun, though.

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It took me a while to realise that that was me, suggesting that a possible alternative to a magnum rechambering in this rifle would be rechambering a .308 to .308 Improved. Well so it would, although I thought for a moment of being so cynical as to suggest that leaving it the way it was would be practically as good. The Improved offers very little in exchange for a special reamer and dies, and much head-shaking and sucking of teeth if you ever want to sell it.

You can indeed load a cartridge any way you want - or don't want. But that is liable to end up as how much cartridge and chamber you care to build around the performance usable and useful (if different) in the H&R. As is very often the case, this does seem to come down to "something different".

[Texas by God]

Very true. Something different can be realized with reloading. For a mild example: I've always wanted a .35 Rem bolt action. My CB loads in my .358 Win Rem 700 are the same ballistically. I can get .38/.357 level also. I can get close to .35 Whelen loading the other direction.

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