Did not want to derail the M1 timing thread - but do have questions regarding re-barreling the carbine and converting it to round like the 300 Blackout which head spaces on the shoulder...my theory being that the Blackout case design has more potential for accuracy, and a bit higher pressures which might enable the carbine to launch 110gr bullets closer to 2400fps? Is the operating system capable of functioning at higher pressures?
M1 Carbine Re-chamber
- Thread starter JEC
- Start date
JEC, want better accuracy from a rifle that was never designed to deliver more than 4-6 inches at 100 yards and you need to do more than just rechamber it.
You need to take a look at why the system is not accurate in the first place. I am working on a M1 Carbine at present that has a 22in match grade heavy Shilen take off barrel installed. Compared to most M1 Carbines it is a tack driver. Can more be achieved from it??? Likely. Is the little bit more worth the effort? Not likely. Also, what will the cost be??? Prohibitive at best IMHO.
I'm only doing what I am because I had the parts on hand and the tools to do the job. If I had to pay to have it done and I really wanted a 300 Black Out, I would look at converting a Mini 30 or getting an AR system rifle that was built to handle it. The overall length of the 300BO is to long for the mag IMHO of the 30 M1 Carbine.
You need to take a look at why the system is not accurate in the first place. I am working on a M1 Carbine at present that has a 22in match grade heavy Shilen take off barrel installed. Compared to most M1 Carbines it is a tack driver. Can more be achieved from it??? Likely. Is the little bit more worth the effort? Not likely. Also, what will the cost be??? Prohibitive at best IMHO.
I'm only doing what I am because I had the parts on hand and the tools to do the job. If I had to pay to have it done and I really wanted a 300 Black Out, I would look at converting a Mini 30 or getting an AR system rifle that was built to handle it. The overall length of the 300BO is to long for the mag IMHO of the 30 M1 Carbine.
I am somewhat familiar with bolt action accuracy enhancing features but novice regarding the carbine. I suspect that generous bolt to action tolerances, action flex, etc. limit accuracy potential ...but beyond that improvement should be possible with some action bedding and attention to minimizing barrel movement at the barrel band. I expect I will eventually replace the barrel, and that would be the time to consider another chamber.
Travis Bickle
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Would love to have seen one in 7.62x25mm Tokarev.
Never even looked into the basics of feasibility aside from the obvious "30 cal connection".
I'd imagine feeding would be an issue to overcome and magazine would have to be custom modified.
That cartridge would be zipping out of a 18-20" barrel like greased lightning.
Plus the cost savings for ammo would be incredible compared to .30 carbine.
Never even looked into the basics of feasibility aside from the obvious "30 cal connection".
I'd imagine feeding would be an issue to overcome and magazine would have to be custom modified.
That cartridge would be zipping out of a 18-20" barrel like greased lightning.
Plus the cost savings for ammo would be incredible compared to .30 carbine.
I can tell you from personal experience, you gain nothing by bedding an M1 Carbine receiver. You also gain nothing by bedding the barrel. The real big question is how do you extend the mags and open up the receiver to feed the new round?
I made one up in 7.62x25 and it worked well. However it required opening up the bolt face and very carefully reshaping the extractor with judicious grinding. The Chinese converted quite a few of them if rumor is true. I did manage to look at one in Lever Arms that came in with a batch of worn and beaten M1 Carbines a few years back that were supposedly out of China. That gave me an idea of what needed to be done.
The 7.62 x 25 round is typically loaded to much lower pressures and other expedients are needed to get the rifle to chamber and eject reliably. Another issue is the cartridge OAL is shorter than the 30 Carb round. If you are going to attempt this particular conversion you will find the mags hold and feed pretty well. You will also find that the feed ramp on the receiver will need to be honed and slightly reshaped. This is not a straight forward action to be converted. It was pretty much specifically designed for its intended purpose/cartridge.
Anything is possible thought within reason and the capabilities of the receiver/bolt/gas system/op rod etc. Be sure you have the patience/time/tools etc to take on such a project.
I made one up in 7.62x25 and it worked well. However it required opening up the bolt face and very carefully reshaping the extractor with judicious grinding. The Chinese converted quite a few of them if rumor is true. I did manage to look at one in Lever Arms that came in with a batch of worn and beaten M1 Carbines a few years back that were supposedly out of China. That gave me an idea of what needed to be done.
The 7.62 x 25 round is typically loaded to much lower pressures and other expedients are needed to get the rifle to chamber and eject reliably. Another issue is the cartridge OAL is shorter than the 30 Carb round. If you are going to attempt this particular conversion you will find the mags hold and feed pretty well. You will also find that the feed ramp on the receiver will need to be honed and slightly reshaped. This is not a straight forward action to be converted. It was pretty much specifically designed for its intended purpose/cartridge.
Anything is possible thought within reason and the capabilities of the receiver/bolt/gas system/op rod etc. Be sure you have the patience/time/tools etc to take on such a project.
Greenhorse six
CGN Ultra frequent flyer
Ruger makes a Mini 14 in .300BLK , but only with a 16" IIRC .
Bearhunter ... thanks for sharing your experience. I am tinkering with the idea of using a 223 for the parent case, along the same lines as used to create the Blackout...but at first blush, it is doubtfull that sufficient shoulder could be established. If it could, running a reamer in the existing chamber to take out some taper might provide enough girth to create a shoulder. Just dreaming.
You know what would be a cool project? An M1 carbine in 8mm kurz. Rounds are roughly the same length and would probably work in the original mag as well. Rounds probably cost approx. the same as 300 blk
edit: did a bit of research and the 30 carbine has a max chamber pressure of around 39000 psi (according to wikipedia) and the 8mm kurz has a max chamber pressure of 49000 psi (also wikipedia) so it is a viable project although if the info above about GI carbines being proofed to 50000 psi is correct, youd be pushing the design to its limits if you don't tinker around a bit
pressure figures were rounded for simplicity
edit: did a bit of research and the 30 carbine has a max chamber pressure of around 39000 psi (according to wikipedia) and the 8mm kurz has a max chamber pressure of 49000 psi (also wikipedia) so it is a viable project although if the info above about GI carbines being proofed to 50000 psi is correct, youd be pushing the design to its limits if you don't tinker around a bit
pressure figures were rounded for simplicity
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Back in the day some M1 Carbines were converted to several different cartridges as mentioned in a previous post. In all honesty it isn't really a system that should be modified unless you are doing the work yourself. Two of the most popular conversions were to a 17 cal wildcat which involved shortening the case and necking it down. The other wildcat was just the standard case necked down to 22 cal. Be very careful with any of these conversions the pressures that they are capable of generating are much higher than the action/bolt/gas piston are capable of handling.
I did build a 223/30Carbine but didn't drill out the gas vent. I used it as a bolt action and it was very good on Coyotes/Ravens/Racoons and ground squirrels with 40-55 grain bullets. I used a take off Remington barrel with a 1-14 twist rate which also helped to keep the pressure down.
The 30 M1 Carbine action was purpose built for a specific cartridge. I have seen them converted to 44 Special and 357 Mag as well. I have even seen a few converted to 351 Winchester but that was a stretch as well. All of those Carbines gave a lot of trouble feeding as well as with parts breakage. I haven't seen one working in a long time.
To long for the mags and receiver.
I continue to tinker with the idea of a modified 300 Blackout ... and think it has potential .. It involves shortening the BLK neck by .070 and setting the shoulder back by about the same (0.030 would be enough). The modified reamer could be run into the existing 30 carbine chamber. It would likely be necessary to open the Carbine boltface by up to 0.020. The end result SHOULD be a cartridge with a bit more boiler room capacity, that headspaces on the shoulder rather than the case mouth. Same COAL as the Carbine, close enough to the same diameter that feeding from the mag should not be an issue. In spite of some differences in rim thickness and angle it looks like it should still eject without further modification.
Of course, some care needs to be taken to insure pressure remains within the capability of the carbine.
Of course, some care needs to be taken to insure pressure remains within the capability of the carbine.
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You my friend are tinkering with a lot of trouble and expense. That action is limited by its length and its lack of strength. The problem with a case you are dreaming of developing is that it's potential far exceeds the capabilities of the receiver/bolt/gas system and if you have the same tendencies most have, you will eventually test those limits.
You are thinking of running a .300 reamer into the carbine barrel, and altering the boltface to suit?
Can't see that the cartridge change would contribute to increased accuracy. If gas port pressure were higher, the action would hammer badly.
Can't see that the cartridge change would contribute to increased accuracy. If gas port pressure were higher, the action would hammer badly.
Good advice ...and I'll take it. I made up a "modified" case using a .223 parent and it looked good, but nothing can compensate for the pressure limits inherent in the action. I am new to the Carbine after years of shooting bolt builds and have fallen for the charm of that little bugger. Sounds like the best physical modification is to put up a lighter gong at 100m to get a better "ring" ...and then accept that a 4" group is really not all that bad
If you're planning on doing this, you're on the right track. I searched online and have found some load data for the 300AAC that is limited to 40000 psi. with a 110 gr bullet. As long as you keep to that pressure you'll be fine. You will get more gas volume going to the piston due to the increased powder capacity, but this can be limited by carefully modding the gas block by adding an adjusting screw that bisects the gas passage. I did this on my 22/30 M1 carbine conversion years ago, and it worked fine. You could set it up to use the factory 300 AAC case length, but the neck is a bit short and you have to seat the bullet quite deep to make the overall length of 1.680"
This conversion is not insurmountable, but needs careful execution. The extractor mod has to be done carefully so that the extractor retains its strength. Your 5 round mag will also hold one round less.
M1 carbines can be made accurate. If the receiver fits the recoil lug properly, and the barrel "hangs" with about a 1/8"-3/16" gap above the barrel channel before adding the upper handguard and sliding on the front band, it should print well with good quality ammunition. I replicate ball ammo with SB cases trimmed to 1.285" and 14.5gr of H110 or 15gr of W296 and topped with Hornady or Sierra 110gr FMJ or Soft points seated to a max overall length of 1.680".
This conversion won't add a whole lot more usefulness to the carbine, and realistically, the 22/30 conversion makes more sense, but should be fun nonetheless.
Hope this helps.
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