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Same with the Ross, which is a Mannlicher clone..

It works the other way around as well.. the camming action is used on the closing stroke to force the case into battery.. and is why rotary actions (particularly those designed by Uncle Gene AR10, 15 & 18 - and clones!) have to have the "forward assist" feature.. Schmidt Rubin actions have the same problem I understand!

Proper camming breeches like on Gods Own Rifle suffer less from this and do not suffer to the same extent from out of battery stoppages..

You also have primary extraction grief in blowback designs where you have a long case. This is why the Pedersen and Swartzlose had oiled cases and the G3 had a fluted chamber. Stuck cases ended up ripping the base off and the mother and father of jams...!
 
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It works the other way around as well.. the camming action is used on the closing stroke to force the case into battery.. and is why rotary actions (particularly those designed by Uncle Gene - and clones!) have to have the "forward assist" feature.. Schmidt Rubin actions have the same problem I understand!
Nope... Massively powerful primary extraction that works in both directions...

 
Whaddayoumean "Nope"?

My point was that primary extraction works both ways.. both on extraction and loading, which (I think) you agree with..?

What I don't agree with you in your fillum is your statement that semi autos do not need primary ejection.. they absolutely do.. (hence my remarks on oiled cases and fluted chambers).. The Garand you were caressing has primary extraction in the camming surface of the action bar acting on the rotating bolt head. If you don't have primary extraction on an automatic, you end up pulling the extractor through the rim or ripping the base off the case...

What I don't like about rotating actions like the AR is that the maximum pressure is needed at the end (and start) of the stroke to get the bolt into battery. This results in the bolt sticking just before it closes (hence the need for forward assist) or it sticks as you try to open it. Lever type bolts like the FAL, BREN or the EM2 have the maximum pressure before the bolt closes which are far less prone to sticking. The bolt carrier on these designs also have a bit of free run on opening so that there is a bit of momentum available when you reach the point of maximum resistance..
 
The oiled cases / fluted chambers thing is a peculiarity of delayed blowbacks, or badly-timed gas or recoil ops that unlock too soon when the pressure's still too high and the neck is gripping the chamber.

I demonstrated quite clearly that the M1 does not have any effective primary extraction. AR15's, AR18's etc don't either, hence the abortion external camming system on the L98A1 Cadet GP and on some straight-pull AR's.

Here's an AR15 bolt. note that the lugs are cut square at the ends. There's no camming action possible.



Here's what it locks into. Note that the shoulders are cut square, with no camming surfaces:



Everything is absolutely perpendicular - there are no camming surfaces, so there cannot be any mechanical primary extraction.

Also the FAL does not have any either. Turn the gas on one off and put some crappy surplus in it and you'll see it for yourself (done it. Luckily only one person was watching).

"you end up pulling the extractor through the rim or ripping the base off the case.. "


You can equally end up pulling the extractor through the rim on a bolt-action with proper primary extraction and a well-stuck case. I've seen it done.

Also, you cannot rip (i.e. by means of the extractor) the base off of a good case - you can blow the back end of it off in a delayed-blowback. The case wall is many times stronger than the rim, so all the extractor can do is pull through the rim. There is no way the rim can survive but the case wall not, unless it's a crappy case (e.g. FL sized too many times), at which point you can even do it with a bolt-action (again, seen it done).

"The bolt carrier on these designs also have a bit of free run on opening so that there is a bit of momentum available when you reach the point of maximum resistance.. "

The free run gives the carrier / op rod enough momentum to let the pressure drop and simply give the case rim a good whack. That is all the primary extraction there is.
 
Here's how you get primary extraction on a Stoner-type system:

1529498635548.png

A lever and a block. On the outside. Cos there's nothing inside to give it :)
 
Also the FAL does not have any either. Turn the gas on one off and put some crappy surplus in it and you'll see it for yourself (done it. Luckily only one person was watching).
I can confirm that!:(
Being a cheap skate who wanted to collect the cases without having to search in long grass, wasn't such a good idea.
 
The FAL could be argued to have a little bit of primary extraction, in that the bolt and extractor tilt relative to the cartridge base as the bolt is lift up out of its locking slot by the carrier. Perhaps in most cases this is sufficient to break the residual adhesion of the case? I have to say, given that a FAL can fling a case about 30ft, I don't recall one ever having a problem extracting!
 
The free run gives the carrier / op rod enough momentum to let the pressure drop and simply give the case rim a good whack. That is all the primary extraction there is.
Given that the muzzle velocity with M2 ammo is around 2700 fps or a bit more than 32,000 inches per second plus the gas port is around one and a half inches from the muzzle that means that not even one 20th of a millisecond after passing the port the bullet has left the barrel and the gas pressure drops dramatically. Just how far does the op rod move in that time? Gnats whisker?
 
Given that the muzzle velocity with M2 ammo is around 2700 fps or a bit more than 32,000 inches per second plus the gas port is around one and a half inches from the muzzle that means that not even one 20th of a millisecond after passing the port the bullet has left the barrel and the gas pressure drops dramatically. Just how far does the op rod move in that time? Gnats whisker?
Most rifles tap the pressure off nearer the breech earlier and at higher pressure. The M1 gas system is a complete pussycat cos of the late, low-pressure takeoff.
 
The FAL could be argued to have a little bit of primary extraction, in that the bolt and extractor tilt relative to the cartridge base as the bolt is lift up out of its locking slot by the carrier. Perhaps in most cases this is sufficient to break the residual adhesion of the case? I have to say, given that a FAL can fling a case about 30ft, I don't recall one ever having a problem extracting!
The extractor is on the upper half of the bolt, and the rear of the bolt tips upwards, tending to cause it to more or less stay put since it'll be pivoting more or less about a point on the top of the bolt face. I've not got one handy to check exactly, but I should do later in the year :)



Edit to add - bet it's not even touching the rim while the back of the breech block pivots up anyway :)
 
The extractor is on the upper half of the bolt, and the rear of the bolt tips upwards, tending to cause it to more or less stay put since it'll be pivoting more or less about a point on the top of the bolt face. I've not got one handy to check exactly, but I should do later in the year :)



Edit to add - bet it's not even touching the rim while the back of the breech block pivots up anyway :)

OK, here's another one:

(this the problem when you get people thinking!)

Perhaps the FAL gets primary extraction from the initial velocity and inertia of the carrier/bolt group?

I.e. the energy transferred from piston rod to bolt carrier might be at peak delivery (because the rod is at full acceleration in its tube), but the carrier assembly initially only moves very slowly (because of inertia, and because it is working to cam up and lift a bolt that itself is at full recoil against its locking face).

Thus you have high energy and low rearward speed for the period when extraction is starting, which effectively duplicates the same condition as a bolt rotating against a cam face or similar.


Stoaty, you are going to have to get yourself a high speed X-Ray camera to prove/disprove this :D
 
OK, here's another one:

(this the problem when you get people thinking!)

Perhaps the FAL gets primary extraction from the initial velocity and inertia of the carrier/bolt group?

I.e. the energy transferred from piston rod to bolt carrier might be at peak delivery (because the rod is at full acceleration in its tube), but the carrier assembly initially only moves very slowly (because of inertia, and because it is working to cam up and lift a bolt that itself is at full recoil against its locking face).

Thus you have high energy and low rearward speed for the period when extraction is starting, which effectively duplicates the same condition as a bolt rotating against a cam face or similar.


Stoaty, you are going to have to get yourself a high speed X-Ray camera to prove/disprove this :D
What you've just described there is "dynamic" primary extraction, i.e. the carrier twats the bolt after unlocking it. Which is how the overwhelming majority of self-loaders do it :)
 
(...) You also have primary extraction grief in blowback designs where you have a long case. This is why the Pedersen and Swartzlose had oiled cases and the G3 had a fluted chamber. Stuck cases ended up ripping the base off and the mother and father of jams...!
The Pederson, Swartzlose HMG, and G3 were blow-back. The case pushes the bolt back under gas pressure and the extractor does nothing to "extract" the case unless the round was a dud.

The reason the cases needed to be either lubricated or the chamber fluted was because the case was moving continuously from the moment the round was fired rather than being pulled out after the bullet has left the muzzle and the pressure dropped. This meant that the case must be prevented from sticking at any point in the cycle at all costs as otherwise the base would fail under pressure.

Thus the idea of "primary extraction" doesn't really apply to a blow-back firearm at all. Instead, you are trying to apply what I will call, to coin a phrase, "primary slow down the case from being blow out of the breech". Some cheap blow-back .22 cal hunting rifles had no extractor at all.

To me, "primary extraction" applies to bolt action or gas or recoil operated firearms where the mechanism has some sort of extra mechanical advantage applied in the first bit of the extraction cycle to give it a bit of "leverage", often through the use of some sort of cam. This eases stuck cases out gradually instead of simply hammering them out and in the case of manually operated rifles reduced the strength required from the operator.
 
The Pederson, Swartzlose HMG, and G3 were blow-back. The case pushes the bolt back under gas pressure and the extractor does nothing to "extract" the case unless the round was a dud.

The reason the cases needed to be either lubricated or the chamber fluted was because the case was moving continuously from the moment the round was fired rather than being pulled out after the bullet has left the muzzle and the pressure dropped. This meant that the case must be prevented from sticking at any point in the cycle at all costs as otherwise the base would fail under pressure.

Thus the idea of "primary extraction" doesn't really apply to a blow-back firearm at all. Instead, you are trying to apply what I will call, to coin a phrase, "primary slow down the case from being blow out of the breech". Some cheap blow-back .22 cal hunting rifles had no extractor at all.

To me, "primary extraction" applies to bolt action or gas or recoil operated firearms where the mechanism has some sort of extra mechanical advantage applied in the first bit of the extraction cycle to give it a bit of "leverage", often through the use of some sort of cam. This eases stuck cases out gradually instead of simply hammering them out and in the case of manually operated rifles reduced the strength required from the operator.
Quite. There is no extraction as-such on a blowback - the extractor is entirely passive and only serves to give the case a point to pivot around on ejection (and as you say, plenty of cheap blowbacks don't even bother with this - there's some cheap .22 short pocket pistols that didn't bother with one), or to manually eject a live round or a misfire.

Every time someone says "and the extractor rips the head off the case" in the context of a (delayed) blowback, Baby Jesus sporterises a rare Lee-Enfield :D
 
Well that's me put in me place then....!

In my defence, the bit about the primary extraction in FAL/BREN/EM2 was what was told to me by Dan Raschen back in the day... and I don't think I was suggesting the blow backs needed primary extraction.. my point was that if you don't have it, it leads to other issues...

My main point however remains that in (some!) rotary bolt guns, the point of maximum resistance is at the end of the closing cycle, whereas this occurs earlier in rocking bolt designs... I was always led to believe this assisted in more reliable chambering and lack of the need for "forward assist"..

Obviously opinions vary...!
 
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