and if anyone thinks this is a stupid question let me expand:
blowback automatics fell out of favour in generally as did low velocity rounds, which is why I think the telescoping bolt fell out of favour. It was incidental.
The trend towards light rotating bolts and high gas pressure/DI kind of killed them, it was too hard to telescope a rotating bolt and the short travel ment there wouldn't be much point
>it was too hard to telescope a rotating bolt
Not really. It's the same machining, just done farther back in the carrier. >the short travel ment there wouldn't be much point
An AR-15 rifle with a telescoped bolt set back at the rear half of the carrier could eliminate the buffer tube altogether, allowing a folding design. Unfortunately you can't really shorten the receiver much as that's limited by the length needed for the magazine, trigger, and grip, though I suppose you could put the magazine on the side ala fg-42, allowing the fire control group to be underneath the magazine, but now you're getting way beyond the original telescoped bolt question.
But that's exactly where I'm going with this. Telescoping bolt is easy, and the space saved behind the action becomes more relevant when you're feeding a longer round.
Both minor, but the major point is that it let's you strip a round on the rearward stroke really neatly, so you can get better feeding at a high rate of fire or from weird mags
>the space saved behind the action becomes more relevant when you're feeding a longer round
That's incorrect, which should have been obvious upon the most superficial of inspections, wherein you would notice that the telescoped bolt designs proliferated around the extremely short 9mm cartridge where, according to your hypothesis, there would be the least advantage. This was one of the points
>it was too hard to telescope a rotating bolt
Not really. It's the same machining, just done farther back in the carrier. >the short travel ment there wouldn't be much point
An AR-15 rifle with a telescoped bolt set back at the rear half of the carrier could eliminate the buffer tube altogether, allowing a folding design. Unfortunately you can't really shorten the receiver much as that's limited by the length needed for the magazine, trigger, and grip, though I suppose you could put the magazine on the side ala fg-42, allowing the fire control group to be underneath the magazine, but now you're getting way beyond the original telescoped bolt question.
was making - the length of the receiver is limited by the length of the magazine + trigger + grip. Designs like the Czech and Uzi subguns benefitted because they also telescoped the grip and magazine, meaning the receiver was now only limited by the length of the trigger + gripazine, making it possible to usefully shorten the receiver with a telescoping bolt - but the gripazine is only practical with very small cartridge, the opposite of your hypothesis. For a rifle cartridge that is too long to function as a grip, your options are to run it on the top (ala fn-p90, hk g11, or Bren) or out the side like the fg-42, at which point the telescoping bolt is the least of your design changes.
The bolt has to travel backwards at least as far as the bullet case is long, I think telescoping bolts are used in 9mm because of the association with the fixed firing pin of simple blow back.
The gripazine shortens the receiver but that's neither here nor there I'm just saying that even in a linear rotating bolt design a telescoping bolt is preferred.
>The bolt has to travel backwards at least as far as the bullet case is long,
wow that's an amazing insight sherlock. if that were the limiting factor then it might be important, but if you closely inspect a rifle using a non-telescoped bolt, say an AR-15, you will probably notice that the receiver is *much* longer than the length of a cartridge. In fact, you will probably discover that the length of the receiver is the length of the barrel threads plus the length of the magwell plus the length of the trigger plus the length of the pistol grip mounting area; of these only the length of the magwell is closely related to the length of the cartridge itself.
And now bufferless ARs are gaining popularity because they can be folded like AKs and have a very low overall length. Most of these have clumsy forward springs but I think we're at the point now where the telescoping bolt may make a comeback
I don't see a reason to put a telescoping bolt in an AR. It wouldn't solve the problem of spring location, which is moot anyway since there already needs to be a piston or gas tube above the bore. The only problem it solves is bolt mass, which is a non-issue on the AR since it's no problem to make the low required mass of the bolt fit within the upper receiver, as every bufferless AR has been doing already.
Guessing here, but blowbacks need mass anywhere on the bolt to slow it down, locked breech guns need don't need mass, they just need a bolt strong enough to not blow apart
>they just need a bolt strong enough to not blow apart
And, depending on the operating mechanism, a bolt long enough to manage the torque that causes carrier tilt.
they didnt? the term changed but go look any piston gun. ak, g3/m5, sig etc
part of the boltcarriers/piston/op rod mass is infront of the chamber.
its a more refined and complicated design than something like an uzi bolt but the concepts still the same. mass is moved over the barrel instead of behind it.
and if anyone thinks this is a stupid question let me expand:
blowback automatics fell out of favour in generally as did low velocity rounds, which is why I think the telescoping bolt fell out of favour. It was incidental.
The trend towards light rotating bolts and high gas pressure/DI kind of killed them, it was too hard to telescope a rotating bolt and the short travel ment there wouldn't be much point
>it was too hard to telescope a rotating bolt
Not really. It's the same machining, just done farther back in the carrier.
>the short travel ment there wouldn't be much point
An AR-15 rifle with a telescoped bolt set back at the rear half of the carrier could eliminate the buffer tube altogether, allowing a folding design. Unfortunately you can't really shorten the receiver much as that's limited by the length needed for the magazine, trigger, and grip, though I suppose you could put the magazine on the side ala fg-42, allowing the fire control group to be underneath the magazine, but now you're getting way beyond the original telescoped bolt question.
But that's exactly where I'm going with this. Telescoping bolt is easy, and the space saved behind the action becomes more relevant when you're feeding a longer round.
Both minor, but the major point is that it let's you strip a round on the rearward stroke really neatly, so you can get better feeding at a high rate of fire or from weird mags
>the space saved behind the action becomes more relevant when you're feeding a longer round
That's incorrect, which should have been obvious upon the most superficial of inspections, wherein you would notice that the telescoped bolt designs proliferated around the extremely short 9mm cartridge where, according to your hypothesis, there would be the least advantage. This was one of the points
was making - the length of the receiver is limited by the length of the magazine + trigger + grip. Designs like the Czech and Uzi subguns benefitted because they also telescoped the grip and magazine, meaning the receiver was now only limited by the length of the trigger + gripazine, making it possible to usefully shorten the receiver with a telescoping bolt - but the gripazine is only practical with very small cartridge, the opposite of your hypothesis. For a rifle cartridge that is too long to function as a grip, your options are to run it on the top (ala fn-p90, hk g11, or Bren) or out the side like the fg-42, at which point the telescoping bolt is the least of your design changes.
The bolt has to travel backwards at least as far as the bullet case is long, I think telescoping bolts are used in 9mm because of the association with the fixed firing pin of simple blow back.
The gripazine shortens the receiver but that's neither here nor there I'm just saying that even in a linear rotating bolt design a telescoping bolt is preferred.
>The bolt has to travel backwards at least as far as the bullet case is long,
wow that's an amazing insight sherlock. if that were the limiting factor then it might be important, but if you closely inspect a rifle using a non-telescoped bolt, say an AR-15, you will probably notice that the receiver is *much* longer than the length of a cartridge. In fact, you will probably discover that the length of the receiver is the length of the barrel threads plus the length of the magwell plus the length of the trigger plus the length of the pistol grip mounting area; of these only the length of the magwell is closely related to the length of the cartridge itself.
And a later walther
While I wouldn't call it a succession the MAC10 is notable for being bizarrely small
And now bufferless ARs are gaining popularity because they can be folded like AKs and have a very low overall length. Most of these have clumsy forward springs but I think we're at the point now where the telescoping bolt may make a comeback
I don't see a reason to put a telescoping bolt in an AR. It wouldn't solve the problem of spring location, which is moot anyway since there already needs to be a piston or gas tube above the bore. The only problem it solves is bolt mass, which is a non-issue on the AR since it's no problem to make the low required mass of the bolt fit within the upper receiver, as every bufferless AR has been doing already.
Guessing here, but blowbacks need mass anywhere on the bolt to slow it down, locked breech guns need don't need mass, they just need a bolt strong enough to not blow apart
Well you're right in they bolts are more very light and thus inherently compact, but it's more the length of travel especially with rifle rounds.
Yea it's only two inches saved, but I see the real advantage here being the mechanical potential of a forward bolt
>they just need a bolt strong enough to not blow apart
And, depending on the operating mechanism, a bolt long enough to manage the torque that causes carrier tilt.
You tell me
Cut a long story short I think we could get a bufferless AR and use a telescoping bolt to accelerate feeding.
You'd get a mp7 in 5.56, which I think is what the world needs.
Whatever length you saved would go to barrel length
The mass of the bolt would make the gun unwieldy if you are trying for a straight blowback 5.56. No one really wants a 20lbs AR
they didnt? the term changed but go look any piston gun. ak, g3/m5, sig etc
part of the boltcarriers/piston/op rod mass is infront of the chamber.
its a more refined and complicated design than something like an uzi bolt but the concepts still the same. mass is moved over the barrel instead of behind it.
There's something about the stamped steel look that I just love