Just some light hearted Labor Day fun.
The Poll question is: What happens when you remove the extractor, load one round in the mag and fire it?
Do you know what really happens? Have you tried it?
Post up your experience or best guesses.
I thought it would be worth knowing and tried this today. Will post up results sometime later.
Technical details:
IMI M193 and WOLF 55 ammo
Faxon 18" rifle gas upper
A5H2 buffer and spring
Deleted
Interesting. I’m not sure what would happen and have never tried but my guess would be extraction will happen most of the time, and you may even get ejection every few rounds. I’m guessing this because of a thread years ago that seemed to have evidence that the empty brass contributed to bolt speed. So maybe it will make its own way out of the chamber when the extractor is removed.
Numero 3
Another interesting follow on question;
Is the result the same for all barrel and gas system configurations?
Clint, results are going to be dependant on residual pressure in the bore after the bolt unlocks and how much stiction there is between case & chamber
The results for this particular test was option 3, brass and steel left behind.
I didn’t attempt to see how sticky the case was or if it would rattle loose with the muzzle up.
I then swapped the BCG for the normal one and was easily able to snap it into battery and a normal firm pull on the charging handle sent the case flying.
This 18" rifle gas configuration has one of the highest delays relative to bullet exit.
That in combination with the heavy buffer should mean that this setup unlocks relatively later with a very low chamber pressure.
This seems to be supported by the fact that the case remained in the chamber.
Other configurations that unlock sooner may pop the brass out under residual blowback action.
Anyone ever try this on a 16-18" barrel with carbine length gas system? Not sure why you’d do it, except for this thread.
That would be a good test. The 16" CAR has the earliest unlocking of any common configuration.
The cycle starts before the bullet exit by a good deal, which IMO is generally bad for the operation.
In this context “cycle start” means when gas first reaches the BCG.
So the “bullet exit to cycle start time” is simply the gas delay (time it takes gas to travel down the gas tube) minus the dwell time (time it takes for the bullet to travel from the gas port to the muzzle).
If someone with a 16" CAR could try it, the results would be interesting.
Nevermind
Lookie here
Wow, that is a very real way to show what is just keyboard commando theory to some. I am going to try this with the LMT e carrier vs standard carrier.
If T=0 is primer ignition, then shot ejection (in a 16 barrel) occurs at about 3/4 millisecond.
Bolt carrier motion (in a carbine length gas system) starts at about T= 2.0 milliseconds.
Chamber pressure at bolt unlock is about 250-350 psi
Caveat: assuming a P-T curve similar to M193 Ball.
In big automatic cannon, 20 mm or 30 mm, the gas system only unlocks the bolt, all the rest of the energy necessary to complete the operating cycle comes from blow back from the residual chamber pressure…
The round will fire, and the carrier will cycle, creating a FTE type “double-feed” if another round is loaded. If this is the sole round in the mag, it will fire, the carrier will cycle and lock back, and the round will remain in the chamber. It should be removable simply by pointing the weapon upward/barrel at the sky.
Was this a 16" with carbine gas?
He already posted a picture of what it will do
No, I dont have that configuration handy.
To restate was was mentioned defined previously, when the bullet first passes the gas port and gas starts to flow, it is a race between the bullet getting to the muzzle and gas getting to the piston cavity in the bolt carrier.
Which one wins the race depends on how far each has to go and how fast they’re moving.
The different barrel length and gas system combinations set the “how far” part.
The bullet is going anywhere from 2350-3200 fps depending on barrel length and load, while the gas is estimated to go at 5700 fps.
The way this all shakes out is as follows:
The 10.5" car and 18" rifle have a lot of delay, meaning the bullet exits the muzzle well before the gas hits the carrier.
The 12.5" car and 16" mid have almost no delay, meaning the gas hits the carrier at the same time as the bullet exits.
The 16" car has a lot of negative delay, meaning the gas hits the carrier well before the bullet exits.
The bullet exit event is important because the bore and chamber pressure drop more rapidly afterwards.
I call this phase the “blowdown time”.
Chamber pressure at the time of extraction has an effect on the actual effort required to extract the fired case.
Here is a summary of some further testing i did on this.
Configurations included:
10.5" car
12.5" car
16" mid
18" rifle
A5H2 buffer 5.4 oz as baseline
CAR2S buffer 2.65 oz w/ rifle spring and spacer
Ammo was IMI M193 and wolf WPA 55 steel case.
The M193 never self extracted in any configuration. Cases were NOT stuck and were generally easy to pluck out of the chamber with long forceps.
The Wolf reliably self extracted in the “no delay” configurations and stayed put in the “high delay” configurations.
A reasonable explanation of this is the higher chamber pressure of the no delay configurations helped the steel cases blowback and self extract.
No, the gas velocity in the gas tube is choked, that is the velocity is Mach 1, around 1800 fps at the temperature of the gas in the tube. The gas velocity in the barrel is not choked, and does have a higher velocity. not quite twice the projectile velocity, though. The barrel gas velocity is around 4000 to 4500 fps.
Close but not quite. You can calculate the gas flow if you want, here is a nice paper on how to do it: Gas Flow in Gas Operated Weapons, by Joseph Spurk
Calculations will show that all of them have a delay between shot ejection and gas getting to the piston. However, self ejection of the case it has nothing to do with the bullet and when it exits, it has to do with the chamber pressure at the time of unlocking. This is governed by many factors, of which where the gas port is located relative to the muzzle is but one. The port pressure, size of the gas port, the mass of the bolt/bolt carrier/buffer, leakage, friction and length of the gas system will change when the bolt actually unlocks, as it will change the pressure in the piston cavity and the BCG acceleration will be altered. After shot ejection, when blow-down starts, the gas flow in the gas tube actually reverses. In gas systems with the muzzle closer to the gas port (ie 10.5" CAR and 18" Rifle) total amount of work available is less due to the loss of tube pressure, this makes for slower unlocking (and less bolt velocity). [Actually, it always reversed, it is just in the case of longer barrels and shorter gas tubes, it does not influence the bolt velocity nearly as much.]
The fact that the IMI did not behave the same as the Wolf, shows that the port pressure (and therefore the cycle time) changed and this was the main reason the IMI ammo never popped out.
What you call a “high delay” configuration is actually a slow unlocking system. To-may-to/to-mah-to, I know…