Semi Auto less 'powerful' then O/U, S/S, etc?

[Shuck.]

*Yes I know powerful is the wrong wording and sorry if this has already been covered..

 

 

Do cartridges fired from an autoloader, throw shot at lower velocities then when fired from say, an Over Under?

 

It does take quite a bit of effort to cock the bolt manually and I can't see how this wouldn't have an adverse effect on wad velocity when the gases are chambering the next round, as by the time the wad has left the barrel, the gases will still be exiting and a lot will be wasted through the reciever?

 

I ask as (with Escort semi) I noticed when shooting a certain high bird, that there seemed to be a few seconds delay before the clay broke then if I would've used my Pump.

 

It could be a number of reasons such as the escort being faster to cycle the next round therefore less perceived time tracking the clay after the shot, therefore a possible psychological anomaly or somethin but it just made me wonder

 

Has anyone else noticed this or is it an obvious thing?? I confess when I started shooting with semi's I never gave any thought to loss of (*power), as it's not something that arises when people argue over which action type is better. (Would have thought velocity is the most important thing to look for??)

 

Definitely not cartridges as I always use the same every time.

 

Cheers in advance.

I hope its just me as I don't want to start leaving the Escort in the cabinet for fear of over-leading birds from now on

[Imperfection]

Never noticed any difference to be honest.I suppose it could depend on how each gun is choked.

[Shuck.]

I only use full choke in both of the guns but every choke is different I s'pose..

[mudpatten]

If I understand your question correctly,at the moment of firing,when it all disappears up the barrel, the breech of an auto is locked. It is`nt just the resistance on the bolt spring that keeps the breech closed. I`m not familiar with the Escort, but if you take it apart and compare what you see with the exploded diagrams in the manual, you should be able to find what locks it up.

 

So the answer to your question is no. At least not in measurable terms.

[Blunderbuss]

Should be no appreciable difference in velocity. In theory, you might lose a few fps in a gas operated semi, due to the tiny amount of gas being tapped off, but in practise this is negligible and less than other factors such as shot to shot velocity differences due to powder/shot weight variations during manufacture or barrel length.

 

You can become aware of the relatively slow cycling of the action with some semis, which can make them seem "slow" but slow to cycle, is different from lower muzzle velocity - the wad and shot are long gone by the time the breech unlocks, opens and you become aware of it cycling rearwards.

 

Lock time is another issue which can make a gun feel "slower", this is the mechanical delay between trigger release and primer ignition which can vary a lot between models.

Edited August 10, 2009 by Blunderbuss

[Harnser]

There is no difference in velociity . The self loader cannot start to work untill the shot and most of the pressure has left the barrel . These guns have a timing system that will not allow the breech bolt to unlock untill the preasure in the barrel has reduced significantly . Just imagine the bolt coming back with the same velocity of the shot leaving the gun . You wouldnt want that to happen . believe me .

Harnser .

[MC]

Never noticed any difference to be honest.I suppose it could depend on how each gun is choked.

 

 

I only use full choke in both of the guns but every choke is different I s'pose..

 

 

Chokes are also irrelevant, they make no measurable different to range, velocity, or striking energy. The will just give you differing patterns.

[Imperfection]

Chokes are also irrelevant, they make no measurable different to range, velocity, or striking energy. The will just give you differing patterns.

 

Good point.

[neil smith]

In my experiance of shooting shotguns over a chrono the amount of choke used makes only a slight difference to muzzle velocity, with the Remington 1100/1187's I noticed about a 25fps to 40fps increase when a full choke was fitted in place of an improved cylinder when using the same ammo.

 

Those figures were similar with the Browning Gold also, both of them gas guns, I have yet to test the SX3 but I expect similar results.

 

Interestingly the Benelli M2 also gives an increase in MV when full choke is used so its not just a gas operated action trait.

 

The amount is so small its not really something you notice or feel very much or enough to cause you any trouble hitting things.

 

N

[Admiral Von Tirpitz]

I shoot a Escort Semi Auto, usually with full choke and also my other guns and would have to say no difference noticed at all, I think because everything happens so fast there is no real loss of pressure or power, if there is then surely it must be so small, no one would notice.

 

Definately a tighter pattern when full choked, not sure if the shot is anymore powerful at 40 yards or not. Doubtful.

[Shuck.]

I didn't have any idea at all about the bolt being on a timed release system as this makes a lot more sense to what I am experiencing, but it also seems that more then a negligible amount of gas is exiting the receiver after the wad has cleared the barrel.

For instance when I'm firing at dusk I see some pretty big flames exit out the side of the gun, following the empty shell.

Then again I have no expertise whatsoever regarding gas operated semi's, Harnser and Blunderbuss you clearly have spent time researching the subject.

I just find it amazing that it would only account for a mere few FPS.. I understand where you are both coming from about the slow bolt cycle action but that wasn't what brought me to think there was a power shortage.

 

Thanks for the in depth replies you have most likely made complete sense just I cannot see it while I'm looking at the Escort

[Shuck.]

In my experiance of shooting shotguns over a chrono the amount of choke used makes only a slight difference to muzzle velocity, with the Remington 1100/1187's I noticed about a 25fps to 40fps increase when a full choke was fitted in place of an improved cylinder when using the same ammo.

 

Those figures were similar with the Browning Gold also, both of them gas guns, I have yet to test the SX3 but I expect similar results.

 

Interestingly the Benelli M2 also gives an increase in MV when full choke is used so its not just a gas operated action trait.

 

I never thought about that but I suppose it makes perfect sense, blockage of barrel = higher pressure = higher velocity. Can understand it won't make a smidge of a difference in practice though!

[Harnser]

Shuck .

The very nature of the gas operated shotgun is such that a certain amount of flame may be seen coming from the open breech in the dark . This flame if any should be negligble . It could depend on what powder is being used in the cartridge ,a slower burning powder will proberbly show a bit more flame .

 

Once the shot and the wads have left the barrel and the pressure has dropped dramatically in the barrel the last of the gas from the fired cartridge will start to bleed back through the gas holes onto the gas piston . The piston is now able to move backwards and to start to the cycle the breech bolt to the open postion ,on its way back the bolt will take a cartridge out of the magazine tube and draw it back into the action . once the breech bolt has been pushed back by the gas pressure to the end of its stop it will be pushed fore ward by the action spring and the fresh cartridge will be chambered into the gun ready to shoot again . Remember , this whole cycle has taken place in a fraction of a second .

Harnser .

[Shuck.]

Once the shot and the wads have left the barrel and the pressure has dropped dramatically in the barrel the last of the gas from the fired cartridge will start to bleed back through the gas holes onto the gas piston .

 

Ah so you're saying that no gas is wasted as the barrel is fully pressurized and just the excess gas is forced through the gas ports on reserve to operate the piston? I'm catching on now

I guess it would be burning powder that is just leaving with the empty cart.. I thought it was gas

 

If that's the case and the barrel is fully pressurized and all the excess gas is collected into the recoil chamber then would that make it more accurate then a non-autoloader as there would be an initial direct push and no left-over gas pouring out of the barrel so not disturbing the wad's flight?

 

Cheers for that I never thought of the exact mechanics of the gas release

Edited August 10, 2009 by Shuck.

[Blunderbuss]

Once the shot and the wads have left the barrel and the pressure has dropped dramatically in the barrel the last of the gas from the fired cartridge will start to bleed back through the gas holes onto the gas piston

Sorry, this is incorrect. The gas starts to bleed through the gas port as soon as the wad passes it, but whilst it and the shot are still in the barrel. Why would the gas vent down such a tiny hole if there was a big 12 bore hole (the muzzle) it could take instead? There is only enough pressure to allow it to enter the gas port is the short time between the wad passing the port and leaving the muzzle. However in the time taken for the gas to push the piston back against the transfer bars, cam and rotate the locking breech block, the shot and wad have left the muzzle which means the pressure has dropped to a safe enough level to allow the breech to open.

[Harnser]

Nothing starts to happen untill the shot and wads have left the barrel . No gas is wasted in the gun , the full amount of gas has been used to propell the shot and the wads . Its just a tiny amount of gas that is bled back through the piston to operate the gun . The small amount of gas used would have left the barrel via the muzzel on an ordinary gun behind the shot and the wads instead it is routed via the gas piston on a self loader .

Harnser .

[Blunderbuss]

Harnser, you are partially right. I agree that the amount of gas used is tiny. I agree that the breech does not unlock nor case eject etc until well after the wad and shot have left the muzzle.

 

However.........

 

SOMETHING does happen before the shot leaves the barrel. Think about it, there is simply no way enough gas would vent through the tiny gas holes to push the piston back, unlock the breech and push the bolt back against the powerful recoil spring - if it could take a much easier route, through the open muzzle. For the gas to vent through the gas holes with sufficient pressure to do the work required the whole barrel must be pressurised, i.e. pressure acting in all directions - against the wad, the breech, the barrel walls and the piston (via the gas port). The piston simply would not move otherwise.

 

It the job of the gun designer, to get the delicate balancing act right, where the gas bleed and initial piston movement happens whilst the charge is still in the barrel, but the the breech does not open until after it has left.

[Shuck.]

For the gas to vent through the gas holes with sufficient pressure to do the work required the whole barrel must be pressurised, i.e. pressure acting in all directions - against the wad, the breech, the barrel walls and the piston (via the gas port). The piston simply would not move otherwise.

 

This gets me wondering again that a pretty sufficient volume of gas must be diverted from the initial line of travel (the barrel) and since the gas diverts into the gas ports as soon as the wad passes them, then surely there's a dramatic loss of pressure before the wad leaves the barrel, therefore hampering its full potential of the charge?

 

Even as the piston is not travelling until the wad leaves the barrel, the pressure must still be decreasing in the barrel to get enough kinetic mass to start to move the piston.

[neil smith]

It the job of the gun designer, to get the delicate balancing act right, where the gas bleed and initial piston movement happens whilst the charge is still in the barrel, but the the breech does not open until after it has left.

 

Blunderbuss is correct, semi auto's guns like the Remington 1187 have a device that surounds the gas chamber, its a spring loaded strip of steel that puts pressure onto two small ball bearings, (pressure relief valves in effect) they allow the excess pressure from over powerfull shells to be vented off because its not needed, but on lower power shells they remain closed ensuring enough pressure acts on the piston rings to cycle the action.

 

As he says its a delicate balancing act & many different ideas have been tried, I prefer the Benelli inertia system that does not rely on gas pressure at all & uses stored inertia forces within a spring in the bolt body in order to cycle, its a very reliable & much cleaner design.

 

N

[Shuck.]

Has anyone out there got a spare Escort they don't want so we can weld the piston closed and possibly blow up for the sake of science?

 

....Anyone?

[Shuck.]

Blunderbuss is correct, semi auto's guns like the Remington 1187 have a device that surounds the gas chamber, its a spring loaded strip of steel that puts pressure onto two small ball bearings, (pressure relief valves in effect) they allow the excess pressure from over powerfull shells to be vented off because its not needed, but on lower power shells they remain closed ensuring enough pressure acts on the piston rings to cycle the action.

 

As he says its a delicate balancing act & many different ideas have been tried, I prefer the Benelli inertia system that does not rely on gas pressure at all & uses stored inertia forces within a spring in the bolt body in order to cycle, its a very reliable & much cleaner design.

 

N

 

Your Benelli cycles a bolt without using gas pressure How does it work?

[Blunderbuss]

This gets me wondering again that a pretty sufficient volume of gas must be diverted from the initial line of travel (the barrel) and since the gas diverts into the gas ports as soon as the wad passes them, then surely there's a dramatic loss of pressure before the wad leaves the barrel, therefore hampering its full potential of the charge?

 

Even as the piston is not travelling until the wad leaves the barrel, the pressure must still be decreasing in the barrel to get enough kinetic mass to start to move the piston.

No, the amount of gas bled is tiny and so is the pressure loss - almost insignificant. It is acting against a very small area (the diameter of the piston head) and only has to move a relatively small breech block, a few inches, relatively slowly (compared to propelling an ounce or more of shot at 1200-1300 fps).

[Shuck.]

they allow the excess pressure from over powerfull shells to be vented off because its not needed, but on lower power shells they remain closed ensuring enough pressure acts on the piston rings to cycle the action.

That makes sense, but with the Escort the gas ports are constantly open, therefore maximum load cartridges in this case the 3" Mag would be adequately pressure regulated, whereas the 28g or maybe heavier would be losing the same percentage of gas, but as none of it would be excess as the gun is proofed for much, much heavier loads, then you would only lose performance.. That's the only way I can see it

[Harnser]

Once the cartridge has been fired and the shot and the wads have travelled beyond the gas holes in the barrell you will then have the same pressure on the gas piston via the gas holes as you have in the barrel . The piston is unable to move because the breech bolt is locked tight . Once the shot and wads have left the barrel the timing allows the breech bolt to unlock . Ther is enough pressure in the barrel at this stage to operate the piston .

Harnser ,

[Shuck.]

No, the amount of gas bled is tiny and so is the pressure loss - almost insignificant. It is acting against a very small area (the diameter of the piston head) and only has to move a relatively small breech block, a few inches, relatively slowly (compared to propelling an ounce or more of shot at 1200-1300 fps).

 

I see that the initial pressure needed to get the piston moving is minimal, however once the piston has moved about an inch backwards, then the whole forend is exposed to the gas upon exiting the air pocket around the piston 'o' ring so there is room for alot more pressure on its journey the remaining 3 or so inches as the bolt is being cocked.

Granted the wad will have left the barrel by now, but the pressure has still been diverted from its main course pushing the wad out. Don't you agree?