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How much power is lost by S/A Marlins .22lr

Discussion in 'Rifle Country' started by ivanthehunter, Jan 18, 2009.

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  1. ivanthehunter

    ivanthehunter Member

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    Power loss of 22lr ammo when cycling the action of a marlin when compared to that of a bolt action.

    I have heard reports that claim a 1/4 loss of power but that seems crazy.
    I don't have a chronograph to measure the muzzle velocity of my semi auto and even compare that to the velocity stated on the ammo box.

    Can any one shed any info on this.

    Thanks Lads
     
  2. John828

    John828 Member

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    Less power loss than you get when you shoot Remington bulk pack. Ever notice how some rounds are quieter than others? The minute discrepancies in powder charge makes big differences on the chrony.

    It never occurred to me that a semi-auto cycling would siphon off some of a load's power and velocity, but if it does, it would be a very, very small amount.
     
  3. ArmedBear

    ArmedBear Member

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    Good question.

    I wish I knew the answer. I have to get a chronograph and compare. In fact, that might be the first thing I do, when I finally get one someday.:)

    However, I don't believe we're looking at all that much, definitely not 1/4 of the velocity or anything.
     
  4. ArmedBear

    ArmedBear Member

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    You have to consider that a .22 does not have a bolt lock. It's just a bolt on a spring.

    An AR-15 remains locked shut until the bullet passes the gas port and the gas pulse has traveled back down the gas tube. Therefore, there's no pressure loss at all until the bullet is near the muzzle.

    With a .22 blowback design, you can start to get some pressure loss sooner. I believe it happens as soon as the pressure drops below the point where the case is held against the chamber walls (obturation), but I could be mistaken.

    A .22 blowback is such a completely hokey design that it's a wonder it works at all, to say nothing of having really good reliability (at least in the better-designed guns, like Ruger .22 pistols).
     
  5. CajunBass

    CajunBass Member

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    None. The bullet has cleared the barrel by the time the breachblock starts to move backwards under recoil.
     
  6. Picher

    Picher Member

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    The amount of energy and velocity loss is so little that it's insignificant. I haven't noticed that bolt action or semi-auto bullets both strike with about the same drop at 100 yards when both are sighted in at 50 yards.

    Remember two things:

    1. The maximum velocity of a .22LR is reached in the first 16 inches of barrel.

    2. The cartridge case does not move until pressure reduces to the point that the case doesn't bulge when it exits the chamber. If it exited when there was full pressure, it would bulge and perhaps burst.

    Picher
     
  7. rangerruck

    rangerruck Member

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    none is correct; lets do a little mental expirement here. take a round, and shove it down, in the end of your muzzle, not more than say 1/4 of an inch. Leave it there. go and chamber a live round, and pull the trigger. What would happen? because of the intrusion in the end of the bbl, all the bolt stuff will explode backward into your facial area. Why? because the bullet has not yet cleared the end of the bbl, and is now acting as a stuck round, causing way too much backward gas pressure/expansion.
    now then, try the same thing, with a clear bbl, and chamber and fire a live round. bolt just cycles. Why? becuase the bolt does not start to unlock and move rearward, until the bullet is at the end, leaving the muzzle.

    So semi's are designed to work, to unlock the bolt, as the bullet leaves the muzzle, otherwise, the gas pressure would be far too great, if the bullet were still traveling down the bbl, and the bolt started to unlock, the rearward pressure would be damaging to the rifle and the shooter.
     
  8. Mike U.

    Mike U. Member

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    Ya probably wanna start this little exercise in stupidity with the cleared barrel first.

    Also, please videotape it. It'd make one a slam dunk for a Darwin Award. :D
     
  9. wayne in boca

    wayne in boca Member

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    I'm not sure that it's possible to videotape a mental experiment.If it is,I'm going into the porn industry.:)
     
  10. Mike U.

    Mike U. Member

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    Ahhh, what fun would it be as a mental exercise? Your right, it wouldn't be possible to videotape a mental experiment, plus it wouldn't make for a very good video. Drat...
     
  11. rcmodel

    rcmodel Member in memoriam

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    Give the man a cigar for being the first with the correct answer!

    rc
     
  12. rangerruck

    rangerruck Member

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    cigars, and toilet paper for all my friends!!!! Go to youtube, and look for a slow motion fire , of a ar and a ak rifle, you will see it happen. bolt does not start to open up, until the round clears the tube...
     
  13. ArmedBear

    ArmedBear Member

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    The Marlin 60, Ruger 10/22, and other .22 semiautos do NOT unlock the bolt, because the bolt DOESN'T lock. See my post above.:)

    rangerruck -- I'm sorry, but this is utterly irrelevant to the question.

    These are gas-operated, locking-bolt action designs, bearing essentially no relation, functionally, to the actions in question. See my post above. They also incorporate a delay, since it takes a finite amount of time for the pressure pulse to travel from the port, back down the gas tube. Neither a bolt loc, nor a gas tube, exists in the rifle designs we're discussing.

    The OP asked about blowback rimfires with relatively long barrels. I do not know when the bolt begins to move rearward. I do believe that obturation by the brass is the only de facto form of "locking" in a simple blowback design.

    I would guess that it may start to move back before the bullet has left the barrel, once the pressure has dropped below X. I just don't know what X is, and when X occurs.:)

    Anyone know about the engineering of a blowback rimfire?
     
  14. Shear_stress

    Shear_stress Member

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    That's because in an AK or AR the action is locked until combustion gases reach the gas port and start to bear on the piston or bolt carrier, respectively--and both the piston or bolt carrier start moving backward as soon as this happens. Just like in a 1911 pistol, the piston or bolt carrier allow a small degree of backward motion *before* they cam open the bolt. If you look at an AK bolt carrier, you'll see a little gap between the back of the bolt lug and the bolt carrier. This is what allows the bolt carrier to move directly backward for an 1/8" or so before it turns the bolt. This gives the bullet enough time to escape the muzzle.

    This is absolutely not the case in a blowback .22lr. As ArmedBear has pointed out, the blowback action is *not* locked. If the bolt (or the entire rifle for the brief period of case obturation) didn't start moving in a blowback, neither would the bullet. There's no getting around Newton here.
     
  15. ArmedBear

    ArmedBear Member

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    Small addendum: X being the pressure required to "inflate" the brass and keep it stuck in the chamber.
     
  16. Shear_stress

    Shear_stress Member

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    The thing to remember in a blowback is that the bolt is much heavier than the bullet and will move backward a lot slower than the bullet travels forward. In many blowback actions, there may be even be a point where a small portion of the rear of the case is actually outside the chamber before chamber pressure has dropped to zero. This is one of several reasons why blowback actions are limited to relatively low pressure cartridges.

    In fact the Remington Model 51 .380 pistol used an action that *required* the case to recoil out of the chamber a small distance before locking.
     
  17. rcmodel

    rcmodel Member in memoriam

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    You get a cigar too!

    rc
     
  18. czarjl

    czarjl Member

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    I think that could be tested if you were able to “lock” a bolt on semi-auto rifle in the forward position and fire it, measuring the bullets exit velocity. Then with the same rifle let it cycle when fired and measure the bullets velocity again. Assuming the rounds are exactly the same and no other differences in powder, primer, bullet weight and case weight (most plausible way to do this is fire many rounds and average there readings). A difference in velocity would mean a loss of power.
    The other thing to do is to film the action and muzzle at the same time with a high speed camera to see if the bolt is moving back in relation to the bullet exiting the muzzle.

    My prediction would be that there is a very slight loss of power due to the cycling of the action. The loss of some of the energy to moving the bolt back at the same time the bullet is moving forward (the bullet does not have the solid “push off” of a fixed bolt).
    I believe that the bolt starts moving back before the bullet exits the muzzle (if it didn’t the pressure from the powder would be gone). In a theoretical scenario the bolt starts moving back at the same time the bullet starts moving forward (if we ignore things like friction and the case expanding) . The bolt is heavier than the bullet and will therefore move much slower (F=m*a, Newton’s Second law)

    Now I just need to convince my wife that I need to buy a good chronograph and to spend the weekend at the range testing this.
     
  19. CajunBass

    CajunBass Member

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    Not only is the bolt on a 22 semi action heavier than the bullet, there is a recoil spring that has to be overcome in the process of driving the bolt back. Between the weight of the bolt, and that spring, the much lighter bullet is long gone before the bolt moves. The pressure has nothing to do with it. It's blowback, not gas operated. Once the bolt has reached the end of it's rearward travel, that same recoil spring now pushes the bolt forward where it picks up the next round in the magazine and pushes it into the chamber as the bolt returns to batter.

    Hi-Points, which are also blowback operation, work the same way. That's why they have such massive slides and strong recoil springs.
     
  20. Funderb

    Funderb Member

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    the reason it works is because the bolt is simply much heavier than the round leaving the barrel. The bolt starts moving fairly quickly, but the round leaves the barrel before the shell clears the chamber.
     
  21. ArmedBear

    ArmedBear Member

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    There's nothing about the weight of the bolt or the tension of the spring that would keep the bolt from moving before the bullet is gone. Since the whole mechanism is lubed, there's only a little static friction to overcome, which means that the bolt would start moving essentially as soon as the bullet does. Every action has an equal and opposite reaction.

    Yes it does. It keeps the brass stuck in the chamber while the pressure is high enough. It's also the reason that reloading procedures require cleaning the case lube off the brass before using the rounds: lubed cases slide back and put excess pressure on the bolt face or the frame of a revolver, while clean cases expand into the chamber and stick in place during peak pressure (obturation).

    Funderb has it.

    However, that doesn't answer the original question. The shell may not be clear of the chamber, but there still may be pressure lost, if only because the moving shell enlarges the volume in which the powder expands. In reality, there's also some leakage, I think.

    How much, and exactly when and where during the bullet's travel down the barrel determines the velocity lost due to the action.

    And this is what we still haven't found out.:)
     
  22. Ratshooter

    Ratshooter Member

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    No one ever mentions it but the hammer also holds the bolt in the closed position.

    Try this, take a Ruger 22 auto that has been fired and has the hammer at rest against the bolt. Pull the bolt back. Did you feel how much initial resistance there was? Now do the same thing with the hammer cocked. There is a difference isn't there.

    The hammer pressure is part of the design and has a bearing on how heavy the bolt spring needs to be. Thats why I am not a fan of lighter hammer springs in semi-auto 22s.

    And yes the bullet is long gone before the action opens.
     
  23. rcmodel

    rcmodel Member in memoriam

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    Someone with a semi-auto .22 and a chrono needs to measure it.

    You can easily hold the bolt closed on a .22RF with your bare hand on the bolt handle.

    Hey wait! Thats it! Yea!
    Thats the ticket!

    Anytime you need more power, just hold the bolt closed!

    Just don't expect to see any differance, cause there won't be any.

    rc
     
  24. Funderb

    Funderb Member

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    I wish i had some device for measuring the pressure gradients, if I could invent it.....


    but there would logically HAVE to be some loss of energy in a semi-automatic that runs on straight blowback. Think about it, the amount of energy that is used to run the bolt in a semi has to come from somewhere. It might not be very much compared to the energy delivered to the bullet, but it just as well exists.

    Unless you want to say that that energy is just turned into the slightly higher recoil of the bolt action.

    I methinks there would be energy loss, and there is.
     
  25. rangerruck

    rangerruck Member

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    I still say, that there is too much resistance to overcome, and that the bullet is at the muzzle, or gone from the tube, before the bolt moves back. Lets look at what it has to overcome first, before it starts moving back.
    Case expansion, then case retraction, weight of bolt assy., operating rod friction, op rod spring, gravity of bolt, and friction of bolt, sliding on bottom and side rails, hammer, or sear setup. All this has to be overcome, before it starts moving backwards, and I am sure this is not all, I'm just not that smart.
     
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