Hello again, I'm sure most of you have visited a german site specialized in high speed photography:
http://www.kurzzeit.com/index_e.htm
They have very good pictures and slow motion films with a front view of a 45 ACP 1911 (actually a SPS, spanish clone of the STI / SVI, fitted with a 16 lbs. recoil spring and a heavy barrel) at the moment of firing, and also a side close view of a compensated Tanfoglio 38 Super.
You can download these films and study them frame by frame, the speed is 1000 frames per second and 2000 FPS. Werner Mehl, the owner of this company, has kindly sent me another film with a side view of the 1911 cycle. Attached is this high speed film of the SPS 45, the speed is 1000 frames per second. He reckons this speed is still not enough to get full a understanding, and promises will have some tapes at 10,000 FPS next year, with new equipment he is developing.
There is so much to learn from a film like this if you really have a good understanding of the mechanism and the time to dissect it bit by bit.
I’ve sutdied the films frame by frame and they correlate pretty well with the theory:
Hammer fall time is not insignificant in relation to the other events, even with a competition hammer and tuned up pistol like this. It is about four or five times barrel time, and about 2 times slide/barrel locked time.
After the hammer hits the primer the bullet exits the case (theoretically the moment of highest pressure) and sends a burst of air, dust and smoke (unburned powder and accumulated debris?) in front of the bullet, out of the barrel.
The slide and barrel recoil a little bit before bullet exit and remain locked. This is not seen very well in this side view, but it is readily seen in on the tape wmsps01 - front view. The pistol moves very little in the hand, obviously little recoil is felt.
The slide and barrel keep on recoiling linearly together a very small distance after the bullet exit and muzzle blast, at this point the hand still feels very little recoil. About this point the slide reaches its maximun speed, and decelerates very little during its rearward travel.
At the point of unlocking the hand feels just a fraction of the recoil and torque, the barrel lower lugs are hitting the frame.
The spent case is ejected before the end of the rearward travel, but it is still dancing around the ejection window at the moment of maximum rear travel (this depend on the ejector lenght).
The slide is not stoped by the recoil spring, but it literally hits the frame at the end of its rearward race. This is the point at which most of the recoil is felt, and the gun torques upwards and also pushes back on the hand.
The slide remains still for a moment at the end of the rearward stroke, and slowly acelerates forward.
The slide picks up a round and feeds it in the ramp. The round changes its angle while feeding into the chamber and engaging the extractor. This "accommodation" movement of the round (more important than its weight) could easily mean some loss of energy and forward aceleration of the slide if the ramp is not well polished and contoured and extractor well adjusted.
The link cams the barrel up, and the upper lugs engage the slide (actually it is like a small impact). The hand feels this forward push and the muzzle comes down a bit.
I'm not too sure, but I've been looking closely at the video, and sequence is like this:
The hammer time is about 4-5 miliseconds.
Barrel time is about 1 milisecond.
Slide and barrel velocity at the moment the bullet exits is only about 5 fps and still accelerating backwards. Slide and barrel are locked together and recoil only a very small distance at this point.
Maximum slide and barrel velocity is at about .6" of recoil travel (they have just unlocked now) and is about 17.7 fps in this gun, firing a 45 ACP major factor ball ammo, with heavy barrel and 16 lbs. spring. The slide begins to decelerate constantly from this point on. Remember we guesstimated 20 fps?
About ten miliseconds after hitting the primer the slide velocity still travels at about 15.9 fps, and is almost at the end of its rearward travel.
About 13-14 miliseconds after ignition the slide stops, hitting the frame.
Average velocity for its rearward travel is about 13.7 fps.
Very little slide movement for about 3-4 miliseconds after this point, then slowly the slide starts forward.
At about 42 miliseconds after ignition the slide hits the round in the magazine.
At 50 miliseconds after ignition the slide is starts to push the round into the chamber.
At 69 miliseconds slide and barrel lock forward completely.
At 72 miliseconds end of forward cycle.
Average velocity of forward slide travel is only 3.2 fps!! (we guesstimated 3.33 fps)
The total cycle time in this gun, not counting hammer time, is 72 miliseconds. If you had sear trouble you'll be shooting at a rate of 830 rpm.
Most probably cycle time would be faster and slide velocity higher in a normal 1911 with a lighter barrel. Also this is a competition gun with a tighly fitted barrel, most probably a normal 1911 would be even closer to our previous estimate.
All these number correlate very well with mathematical model, the dominating principle here is equilibrium of momentum.
Notice that we don’t confirm exactly the initial 0.11" recoil of barrel and slide at the moment of bullet exit (but we can see some small movement), and we can also get a pretty estimation for slide/barrel velocity.
Of course this is just a theoretical exercise to see if we can identify and measure somehow (at least arriving at a ballpark value) the basics that govern 1911 dynamics, things are much more complicated in the real world.
We got pretty close with just basic physics, don’t you think?
As a side note, in a previous discussion on this forum somebody mentioned Kuhnhaussen's explanation of the initial part of the 1911 cycle. I have not read his books, but from the quotes mentioned here apparently he thinks that the slide and barrel are somehow in a static position while the bullet is moving in the barrel, and that they only start moving backwards when the bullet exits due to “residual pressure”. This is impossible, as equilibrium of momentum dictates that the slide/barrel must be moving backwards (albeit at a much slower velocity due to their larger mass) while the bullet is moving forward.
