This past July 4th my friend Victor got access to a collection of guns. My friend Kythe and I tagged along to check them out and shoot them of course. I was more interested in filming some machine guns in slow motion so we selected a few guns to shoot and film. We decided to focus on slo-mo WWII machine guns and a Luger pistol. I figured filming the toggle action on the Luger in slow motion would be fun.

Slow Motion @ TFB:

• DIY Schlieren Imaging of Bullets In Slow Motion
• Muzzle Dip? Strange Unexplained Physics In Non-Firearm Pistol Recoil
• Shockwave Shadows by Smarter Everyday – Supersonic Vs. Subsonic Bullets

Slo-Mo WWII Guns

The guns we set aside to film in slow motion were:

1. Luger P08
2. MP40
3. Sten SMG
4. Grease Gun
5. Thompson SMG

It is not often we get a chance to shoot guns from WWII, especially the ones that are full auto. This was a grail of sorts for some of us. Here is the video of all the slo-mo WWII guns

Luger P08

The Luger P08 surprised me with how hard it was to control the muzzle climb. When the Luger fires, the barrel slides back a bit and then the toggle link hits the ramped part of the frame. This causes recoil and muzzle climb. I think it is exacerbated by the toggle link moving upwards. The barrel and bolt close while the pistol is at its muzzle climb apogee.

MP40

To start off the slo-mo WWII machine guns, my friend Kythe shot the MP40.

There is a bit of barrel whip and you can see the recoil impulse when the bolt travels rearward. The forward recoil, when the open bolt closes right before the gun fires, is more pronounced than the rearward recoil.

Sten MKII

The markings on the magwell look a bit odd. We assume it is a MKII but the II looks like a box.

According to Victor, the Sten was having issues like double feeding.

Since I brought the Chronos 1.4, we used it to see the malfunction in this slo-mo WWII Sten. You saw in the video earlier that Sten is having problems ejecting. Victor thinks the extractor and spring need to be replaced. As you saw in the video, the brass was extracted but failed to eject properly. If the ejector was the problem, then it would malfunction all the time. The brass is released but fails to be kicked out of the ejection port. It performs a couple summersaults and the bolt closes on the brass. One thing I was not expecting was how much the barrel whips on the slo-mo WWII Sten.

In another video clip, shot on my iPhone in slow motion, I noticed a backdraft-like event in the ejection port of the slo-mo WWII Sten. Unfortunately, I did not notice this until afterward and it seemed to be a rare event since we did not see the Sten do this again when we filmed it with the Chronos 1.4.

M3 Grease Gun

I remember a friend of mine recommending the M3 Grease Gun when I shot machine guns for my bachelor’s party. I questioned his judgment but that was from ignorance. We shot it and I immediately understood the allure. The rate of fire is a wonderful cadence that you get to enjoy the machine gun. Now my friend Kythe got to enjoy his first Grease Gun mag dump. His face reflects how any gun lover feels when shooting a Grease Gun for the first time. Sheer elation.

There is very little muzzle climb or recoil in the grease gun but there is a bit of muzzle dip from the heavy bolt slamming forwards.

Thompson SMG

There were multiple Thompson SMGs so I decided to focus on the one with the finned barrel and compensator. In the slo-mo WWII video, you can see how much recoil there is from the slamming of the bolt at its most rearward travel. We prefer the M3 Grease Gun over the Thompson. The M3 is lighter and easier to control in full auto.

I brought my Schlieren rig along and decided to film the Thompson compensator. You can see how much gas and shockwaves escape before the bullet flies out of the muzzle.

I moved the barrel higher up so we could better see the bullets flying out. Now you can see gas rings/mushroom clouds come out of the muzzle before the bullet.

Due to my Schlieren setup, the light casts a shadow on the mirror and we see double.

After we finished, Victor wanted to shoot twin Thompsons with night vision. He was hoping the muzzle flash would illuminate his face. Sadly, there is not much muzzle flash from the Thompsons.

Final Thoughts

A huge thanks to Victor’s friend for granting us access to these guns. This is one of the best Independence Days we have ever had. Filming slo-mo WWII guns is a blast and we got to see things we do not normally get to see. The Chronos 1.4 really helped diagnose the issue with the Sten MKII. I hope we get to go back and check out their other guns in slow motion.