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

[Shuck.]

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

 

I understand what you're saying, but the gas ports are only half way down the barrel, so if by the time the wad passes the gas ports and there's the same pressure on the gas piston then only 1/2 of the pressure is following the wad to the end of the barrel, as opposed to the full amount in any non-autoloader.

 

Edit: I'm not trying to be awkward and arguing for the sake of it, I genuinely don't understand how the gas is reused in full in the time it takes for the wad to leave the barrel IF the ports are half way down it.

Edited August 10, 2009 by Shuck.

[neil smith]

Shuck

 

The gas ports are permenantly open, they are holes drilled into the barrel after all, later designs allow for gas pressure regulation by means of a spring & rubber seal inside the gas piston body, the gas regulation & bleed off is what makes your semi auto get filthy inside the forend.

 

By not using gas at all the Benelli system means the gun does not get dirty around the magazine tube or inside the forend, there are no ports drilled into the barrel, the system relies on the rearward inertia forces generated by the gun during recoil, the energy is used to compress a strong spring inside the bolt body which unlocks the rotary bolt head & sends the bolt rearward, the return spring is located within the buttstock as with many other semi-auto designs & works in the same way to complete the reloading of a new cartridge.

 

N

[Harnser]

All gun powders are propellents and not explosives . This means that once a cartridge has been fired the pressure in the barrel starts to build up and because the powders are realitively slow burning (compared to explosives ) the powder will burn and increase the pressure in the barrel all the way up untill it is vented to the air . Thats why we use slower burning powder for heavy loads and faster burning powder for lighter loads . Basicly the pressure in the barrel increases all the way up untill the bullet leaves the barrell . There is more pressure in the barrel just before the projectile leaves the barrel than when the projectile has just started its journey .

Harnser .

[Blunderbuss]

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 .

Correct

 

The piston is unable to move because the breech bolt is locked tight

Incorrect

 

The piston does begin to move, as soon as the wad passes the port. After some travel it begins to operate a cam mechanism to unlock the breech, usually by rotating locking lugs of some sort on the forward part of the breech block. But crucially, this unlocking does not happen until after the shot has left.

 

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

How can this be? How can there be insufficient pressure to move the piston whilst the shot is in the barrel but forward of the gas ports, but then enough once it has left the barrel completely and all pressure is dissipated to atmosphere? Also, if this was the case why arent the gas ports near the muzzle? On most guns they are bured under the forend, about half way (or thereabouts) down the barrel, which means the full pressure is operating against the piston for the whole of the second half of the shots travel down the barrel. Why would the piston not move for the whole of this period, but suddenly decide to do so once all the pressure has gone?

 

Interesting discussion BTW

[Shuck.]

All gun powders are propellents and not explosives . This means that once a cartridge has been fired the pressure in the barrel starts to build up and because the powders are realitively slow burning (compared to explosives ) the powder will burn and increase the pressure in the barrel all the way up untill it is vented to the air . Thats why we use slower burning powder for heavy loads and faster burning powder for lighter loads . Basicly the pressure in the barrel increases all the way up untill the bullet leaves the barrell . There is more pressure in the barrel just before the projectile leaves the barrel than when the projectile has just started its journey .

Harnser .

 

Ahh

I knew there was a weak link somewhere! It all makes perfect sense now. Of course, the pressure slowly builds up thats how its possible to cycle different loads with no cycle issues

 

Thanks for that I thought I was going mad

[Shuck.]

How can there be insufficient pressure to move the piston whilst the shot is in the barrel but forward of the gas ports, but then enough once it has left the barrel completely and all pressure is dissipated to atmosphere? Also, if this was the case why arent the gas ports near the muzzle? On most guns they are bured under the forend, about half way (or thereabouts) down the barrel, which means the full pressure is operating against the piston for the whole of the second half of the shots travel down the barrel. Why would the piston not move for the whole of this period, but suddenly decide to do so once all the pressure has gone?

 

My point exactly.. I guess that's why we're here discussing simple physics and the designers are probably working on Quantum Mechanics

I thought I had it at first, then I lost it, then again then again.. maybe I should just give up Maybe ask Hatsan why they over complicate things?

Would their be any benefit in putting the gas ports nearer the chamber? If there was any loss of pressure that would certainly cure it.

[Blunderbuss]

All gun powders are propellents and not explosives .

 

I'm in my comfort zone now Gunpowder (i.e. blackpowder) as well as "smokeless" propellants ARE very much explosives. They are however LOW explosives, which deflagrate (burn very quickly), not high explosives which detonate (a much more violent and energetic reaction than deflagration). I think this is what you mean?

 

This means that once a cartridge has been fired the pressure in the barrel starts to build up and because the powders are realitively slow burning (compared to explosives ) the powder will burn and increase the pressure in the barrel all the way up untill it is vented to the air .

Usually, but not always. There are progressive, regressive and constant rate propellants, and the choice of propellant and barrel length need to be optimised to achieve what you describe.

[Shuck.]

Usually, but not always. There are progressive, regressive and constant rate propellants, and the choice of propellant and barrel length need to be optimised to achieve what you describe.

 

Yep and slow burning powders wont generate force if there's no pressure, which had me stumped at how the piston can actually cycle at all once the wad has left the gun

[Imperfection]

Basicly the pressure in the barrel increases all the way up untill the bullet leaves the barrell .

Harnser .

 

and why longer barrelled guns have more recoil.

 

 

Like i said earlier-i havent noticed a difference between my semi & O/U though on how long it takes the shot to reach its target.I would imagine the amount of gas forced into the two vents is negligable.

[Blunderbuss]

Would their be any benefit in putting the gas ports nearer the chamber? If there was any loss of pressure that would certainly cure it.

Ah, but this would knacker the timing. You would need a huge breech block and recoil spring to prevent the breech opening too early, i.e. before the shot had left the muzzle. This would be very bad for your health!

[Blunderbuss]

which had me stumped at how the piston can actually cycle at all once the wad has left the gun

It can't!

[Shuck.]

Out of curiosity, what Semi have you got Imperfection?

 

Anyway what made me bring up this subject in the first place is that I feel I actually did experience a speed decrease albeit slightly as the bird was quite a distance, and any shorter distance then that I would have failed to notice it.

 

I suppose that's what it all boils down to in the end. These firearms are manufactured to such a degree that performance only varies once a certain distance has been reached, maybe the Escort indeed does lose quite some velocity but the actual practical implications are indeed only seen after reasonably practical ranges have been exceeded therefore the debate is academic.

 

The topic isn't a complete waste of time as its something to discuss I suppose

Edited August 10, 2009 by Shuck.

[Catamong]

*

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.

 

My goodness, that must have been a VERY high bird, if there was a "few seconds delay" before it broke.

 

The simple fact is, there is no percetible difference in muzzle velocity between a pump, semi auto, side by side, over & under using the same ammo, and that's a fact..............it must all be in the mind..??

 

Cat.

[Shuck.]

My goodness, that must have been a VERY high bird, if there was a "few seconds delay" before it broke.

 

The simple fact is, there is no percetible difference in muzzle velocity between a pump, semi auto, side by side, over & under using the same ammo, and that's a fact..............it must all be in the mind..??

 

Cat.

 

It was indeed a high bird Maybe it was all in my head, isn't that the joy of clay shooting?

 

P.S. Just to clarify; if the shot did not take under a second and a half to reach the bird, I would have no idea at all whether shot was in fact faster or slower to reach the target from another gun.

As I said before could have been any number of factors, wind being one at that altitude even if there is was none felt at the ground level.

Edited August 10, 2009 by Shuck.

[Andy H]

Not quite an auto shotgun but the ak 47 works on the same principal , Have a look at this slow motion animation

http://www.video4viet.com/watchvideo.html?...%20Ak47%20Works

or this

http://www.video4viet.com/watchvideo.html?...Automatic+Rifle

[Blunderbuss]

Not quite an auto shotgun but the ak 47 works on the same principal , Have a look at this slow motion animation

http://www.video4viet.com/watchvideo.html?...%20Ak47%20Works

or this

http://www.video4viet.com/watchvideo.html?...Automatic+Rifle

Excellent animation which quite clearly shows the piston moving BEFORE the bullet leaves the barrel.

[Shuck.]

Not quite an auto shotgun but the ak 47 works on the same principal , Have a look at this slow motion animation

 

Thanks for that, it's filled in the final blank for me.. the pressure while the wad is still in the barrel is already moving the piston and the piston is already traveling so fast that when the wad has left and the pressure has dissipated, the piston has enough kinetic energy to move it into place. Cheers

[Harnser]

I'm in my comfort zone now Gunpowder (i.e. blackpowder) as well as "smokeless" propellants ARE very much explosives. They are however LOW explosives, which deflagrate (burn very quickly), not high explosives which detonate (a much more violent and energetic reaction than deflagration). I think this is what you mean?

 

 

Usually, but not always. There are progressive, regressive and constant rate propellants, and the choice of propellant and barrel length need to be optimised to achieve what you describe.

Gun powders are not classed as explosives ,but are classed as propellants . Yes of course you can make gunpower explode under the right conditions ,as you can coal dust ,flour and candy floss .

Harnser .

[Blunderbuss]

Thanks for that, it's filled in the final blank for me.. the pressure while the wad is still in the barrel is already moving the piston and the piston is already traveling so fast that when the wad has left and the pressure has dissipated, the piston has enough kinetic energy to move it into place. Cheers

Absolutely bang on

[Imperfection]

Out of curiosity, what Semi have you got Imperfection?

 

Anyway what made me bring up this subject in the first place is that I feel I actually did experience a speed decrease albeit slightly as the bird was quite a distance, and any shorter distance then that I would have failed to notice it.

 

I suppose that's what it all boils down to in the end. These firearms are manufactured to such a degree that performance only varies once a certain distance has been reached, maybe the Escort indeed does lose quite some velocity but the actual practical implications are indeed only seen after reasonably practical ranges have been exceeded therefore the debate is academic.

 

The topic isn't a complete waste of time as its something to discuss I suppose

 

I have an Escort too and havent noticed any sort of speed difference when compared to my O/U.It could be the lack of recoil which might fools you into thinking the shot is travelling slower?

[Harnser]

Absolutely bang on

Yes the timing of the gun has taken over and not allowed the breech to open untill the pressure has dropped . Iam off up the pub .

Harnser .

[Shuck.]

Yes of course you can make gunpower explode under the right conditions ,as you can coal dust ,flour and candy floss .

Harnser .

 

If only.. every time you fired it smelled of burnt caramel and cost a lot less..

Edited August 10, 2009 by Shuck.

[Blunderbuss]

Gun powders are not classed as explosives ,but are classed as propellants . Yes of course you can make gunpower explode under the right conditions ,as you can coal dust ,flour and candy floss .

Harnser .

I think you're referring to the UK legal situation, i.e. the fact that you don't need an explosives licence for smokeless propellants (although you do for black powder)? That is a point of UK law, but by the chemical and almost any other definition propellant powders ARE very definitely explosives, except they are deflagrating LOW explosives rather than detonating HIGH explosives. Trust me on this, it's my job and has been for the last 30 years.

Edited August 10, 2009 by Blunderbuss

[mr salt]

hi

i fire all the styles of guns you talked about,o/u s/s auto.

At the range i would take on a pigeon ,i would say no.

I do notice a difference in speed from cartridges sometimes ,

i shoot gamebore clear pigeon and do ok,

but when i use my friends RC 32s i have to give less lead.(both plas wad)

sorry about spelling iam ill at moment.

I would say all the guns you talk about will shoot differently.

so if you want to get good with a semi ,only shoot a semi.(same for each style).

semi autos do differ from the other styles ,but i love to shoot them.

but if i pick up a o/u it takes a few shots to get my eye in.

cheers scott

[Shuck.]

Yea your right Scott its best to just use one gun and shoot it.. and shoot it good

Every different action be it SxS O/U etc have completely different styles and as such are all used differently..

All users have their pro's n cons. Just shoot what you prefer to shoot with

 

Nowt wrong with having a go on the pump every now and then mind