222 Rem to 257 Rob conversion?

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222 Rem to 257 Rob conversion?

Post by yowie » 19 Aug 2017, 2:12 pm

I have a old but fairly tidy 222rem that i rarely use, just wondering if it is possible to get it re chambered to 257 Roberts? or is the action too small?

If this is possible what does re chambering and a new barrel cost roughly?
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Re: 222 Rem to 257 Rob conversion?

Post by duncan61 » 19 Aug 2017, 2:40 pm

Cases are different sizes.The 257 Roberts is based of the 7x57 mauser which is the same as .243 .308 and a heap of others..222 is way smaller.If you are going to have to change the bolt might as well get a new rifle.Cost about $50-100 to get it reamed to .223 and maybe recrowned
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Re: 222 Rem to 257 Rob conversion?

Post by bladeracer » 19 Aug 2017, 2:48 pm

yowie wrote:I have a old but fairly tidy 222rem that i rarely use, just wondering if it is possible to get it re chambered to 257 Roberts? or is the action too small?

If this is possible what does re chambering and a new barrel cost roughly?


It would depend on the actual model of rifle as to whether the action is large enough.
The .257 Roberts is a much bigger case head so the bolt and extractor would also need work. Is the magazine long enough to take cartridges longer than the .222 Rem?

The new .22 Nosler uses the same .223 case head and is a bit more potent than the .223. An 8"-twist barrel would let you use the heavy bullets as well which would be a significant step up from the .222.
Or maybe 300BLK which would probably be a straight barrel swap.
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Re: 222 Rem to 257 Rob conversion?

Post by duncan61 » 19 Aug 2017, 3:22 pm

How long has the .22 Nosler been around .I like it
.22 winchester .22hornet .222 .243 7mm rem mag cbc 12g
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Re: 222 Rem to 257 Rob conversion?

Post by duncan61 » 19 Aug 2017, 3:25 pm

Just remembered we have a .222 Rem Mag that probably does the same thing
.22 winchester .22hornet .222 .243 7mm rem mag cbc 12g
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Re: 222 Rem to 257 Rob conversion?

Post by yoshie » 19 Aug 2017, 5:05 pm

What about a 6x222 or 6.5x222 or maybe 6TCU, 6.5 TCU?
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Re: 222 Rem to 257 Rob conversion?

Post by Redwood » 23 Aug 2017, 11:56 am

duncan61 wrote:How long has the .22 Nosler been around .I like it


It's quite new.

Was January or February this year I think.
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Re: 222 Rem to 257 Rob conversion?

Post by yowie » 04 Nov 2020, 9:29 am

bladeracer wrote:
yowie wrote:I have a old but fairly tidy 222rem that i rarely use, just wondering if it is possible to get it re chambered to 257 Roberts? or is the action too small?

If this is possible what does re chambering and a new barrel cost roughly?


It would depend on the actual model of rifle as to whether the action is large enough.
The .257 Roberts is a much bigger case head so the bolt and extractor would also need work. Is the magazine long enough to take cartridges longer than the .222 Rem?

The new .22 Nosler uses the same .223 case head and is a bit more potent than the .223. An 8"-twist barrel would let you use the heavy bullets as well which would be a significant step up from the .222.
Or maybe 300BLK which would probably be a straight barrel swap.



its an old CMC mountaineer and It has the same length magazine and action as my Howa 308, just has an insert in the mag to shorten it that can easily be removed.
The barrel is fairly well shot out so if the bolt face can be modified it should work. Might just be easier to turn it into a 223 Ackley or the nosler and just buy a roberts.
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Re: 222 Rem to 257 Rob conversion?

Post by SCJ429 » 06 Nov 2020, 6:50 am

yowie wrote:I have a old but fairly tidy 222rem that i rarely use, just wondering if it is possible to get it re chambered to 257 Roberts? or is the action too small?

If this is possible what does re chambering and a new barrel cost roughly?

A decent barrel like Maddco is about $660 and another $250 to chamber and fit. You would need to open up the bolt face.

You would be better to consider a 6x45, a 223 necked up to 243, which would have ballistics similar to the Roberts. It will fit your action and magizene without modification and is an accurate and efficient case. No need to modify your bolt face.
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Re: 222 Rem to 257 Rob conversion?

Post by yowie » 05 Dec 2020, 12:51 pm

So i just bought a Zastava M70 in 6.5 Sweed, Barrel is shot out but action is still good. Time to start buying all the bits for a custom build and get Zerch to put it all together.
Not sure what i will turn the 222 into yet but a 223 Ackley is on the cards.
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Re: 222 Rem to 257 Rob conversion?

Post by marksman » 06 Dec 2020, 8:33 am

the 257 ammo and reloading data can be pretty anemic because of older firearms chambered for it but in more modern rifles a 140 grain bullet can be loaded to run at 2700-2800 fps showing no pressure, l like the round but reckon an ackley would be better lMO
more powder, more speed :lol: good luck with it

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Re: 222 Rem to 257 Rob conversion?

Post by Strikey » 06 Dec 2020, 8:42 am

Marksman, where are you finding 140grn 25 cal projectiles?????
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Re: 222 Rem to 257 Rob conversion?

Post by marksman » 06 Dec 2020, 8:16 pm

Strikey wrote:Marksman, where are you finding 140grn 25 cal projectiles?????


ooooops :oops:
:lol: :lol: l made a mistake and was thinking 6.5 cal as l'm working on one at the moment :lol: :lol:
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Re: 222 Rem to 257 Rob conversion?

Post by phill55phill » 25 Jun 2021, 5:28 pm

Depends what action it is bjuilt on if it is a mod 70 or m98 no problems quiet a few manufactures built 222 on long actions in past years
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Re: 222 Rem to 257 Rob conversion?

Post by straightshooter » 26 Jun 2021, 8:20 am

marksman wrote:the 257 ammo and reloading data can be pretty anemic because of older firearms chambered for it but in more modern rifles a 140 grain bullet can be loaded to run at 2700-2800 fps showing no pressure, l like the round but reckon an ackley would be better lMO
more powder, more speed :lol: good luck with it

At that rate your 257 Roberts AI would almost be the equal of a 25/06!
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