Straight-blowback carbine in .30 Carbine?

[briansmithwins]

Still, it's probably also woth looking at delayed blowback (H&K/CETME roller, Kiraly-Cristóbal/FAMAS lever, etc.) o

In theory delayed blowback is simpler/cheaper than gas piston operation. In practice it seems the required precision of manufacturing and materials required make them just as complex/expensive as gas piston operation.

Recoil operation opens up a jumbo sized can of worms. The list of personal arms (not machine guns) using a recoiling barrel is very short. One of the major problems is if anything touches the barrel you're likely to introduce a stoppage. Providing a shroud over the barrel is a big weight penalty.

BSW

 

[kBob]

Didn't the Ruger 9mm and .40 carbines use a delayed system much like the current R51 Reminton and its 20th century predicessors?

How about the system used in the Pedersen .30-06 rifle of the 1930s? If IIRC the barrel on that was fixed.

I seem to recall some pistols in the 1980s that used a ring in the chamber the case expanded into to add resistance to a lighter recoiling mas system. While it would likely ruin brass ( although I did reload some .380 ACP from such a system ...once... and it was a pain) it might make a working system..... though the steel cased .30 carbine out there might have issues with such a system.

Roller locked sounds doable and no more complex than all those flying levers in the cristobal.

Of course the best solution might be to go out and buy an M-1 carbine and just dream about the rest.

-kBob

 

[barnbwt]

"Didn't the Ruger 9mm and .40 carbines use a delayed system much like the current R51 Reminton and its 20th century predicessors?"
If there were any other Pedersen Action designs besides the Model 51, I haven't heard of them. The Pedersen Rifle was really a true delayed blowback, using abutted toggle links to get the desired mechanical disadvantage. The pistol is more like a blowback initiated recoil action.

TCB

 

[Bexar]

Something I've come to gather from this is it must not take much of a locking lug style bolt to contain a cartridge in a chamber. If a 12+/- pound dead weight can safely handle a 30-06 class cartridge then it stands to reason not much steel or even aluminum in a locking lug is needed. Is my logic correct?

 

[barnbwt]

No. Thousands of pounds are applied to the bolt face, but for an incredibly short time. Such a short time that it can't move a heavy enough object a great enough distance to rupture the case. But if you want to hold the bolt in position rigidly so you have as much time as you need for pressures to fall, it's gotta carry all that load. The R51/Pedersen action has a brief period of movement, which allows pressures to fall enough that when it finally locks to prevent case tearing, much less strength is needed (hence an aluminum lug seems to work)

TCB

 

[Bexar]

No. Thousands of pounds are applied to the bolt face, but for an incredibly short time. Such a short time that it can't move a heavy enough object a great enough distance to rupture the case. But if you want to hold the bolt in position rigidly so you have as much time as you need for pressures to fall, it's gotta carry all that load. The R51/Pedersen action has a brief period of movement, which allows pressures to fall enough that when it finally locks to prevent case tearing, much less strength is needed (hence an aluminum lug seems to work)

TCB

Thanks barnbwt.

 

[briansmithwins]

Didn't the Ruger 9mm and .40 carbines use a delayed system much like the current R51 Reminton and its 20th century predicessors?

I believe they were simple blowback. There is a lever thing that interacts with the bolt but I think that's a safety to prevent OOB firing.

BSW

 

[justin22885]

i just found this thread.. interesting, but why do you guys think its so difficult to blowback a 30 carbine?.. blowbacks dont really seem to rely much on chamber pressure as much as the weight of the bullet, weight of the bolt to determine which direction the pressures going and how fast that bolts going to move.. 30 carbine would only need about a 3.2lb bolt

calculations show that if i increase the pressure of 7.62x25 up to 55,000 PSI like id like to id only need a bolt of 2.5lbs.. what id be more concerned with higher pressures is extraction, the amount of friction youre going to have with the case walls sticking to the inside of the bore, higher pressured blowbacks will probably need chamber fluting.. i just dont view .30 carbine as "worth it".. its marginally better than 7.62x25 on a round for round basis, ammo for it is harder to find, brass cant be made from any other sources, it cant fit in any but highly specialized handguns like the AMT auto mag, its straight wall means its going to feed less reliably AND extract less reliably.. id rather have 7.62x25, standard pressure or jacked up to 55k