TESTED: CMMG Radial Delayed Blowback

Was that additional little bump perhaps the hammer resetting off the disconnector?

Wow amazing work 👌🏻

The movement you couldn't explain, could that be the sensor picking up the trigger reset?

Love this. Testing claims scientifically.

I be interested to see the recoil difference between the lightweight plastic stock (the cheap hollow one some many companies use), a wood stock, a laminate stock (like Boyds), and something high end like a Manners or some other rigid fiberglass or carbon fiber stock.

Maybe use something like a .308 Ruger American or .308 Tikka.

On the software side you may want to look into a program called "Igor". It is designed specifically to help research scientists fit math curves to mountains of numerical data! I have used it for years to analyze XPS (X-ray photoelectron spectroscopy) data which are similar in format to the data files you are collecting. You import the data as a text file and use Igor to not only normalize data and automatically select data range, but also to identify and fit peaks to the data. It makes it possible to do data analysis on huge amounts of data very quickly!

I have a Banshee in 45 ACP with the 5” barrel. It’s a very accurate gun with my hand loads. I am pushing 230 grain XTPs to around 1000 fps. I am running a Rugged Obsidian 45 suppressor on it and finally have it running reliably. I had to add the largest CMMG tuning weight to the bolt along with a 5.3 oz 308 carbine buffer. Recoil is so smooth now and with the suppressor it is so quiet. It would be nice to see the effect of suppressors on firearm recoil using your new test rig.

I believe ferfrans has a component in it's bolt assembly that will tame the recoil but will reduce the fire rate.

its the bolt going back into battery

I have a Aero Precision EPC9 with a JP Enterprises BCG, Can I just swap the BCG for a RDB-BCG?

Adjustable gas block both standard and bleed off style.👍🏼

As far testing I think you mentioned most of what would be interesting to see.

I’d be really interested in how a rough phosphate BCG compares to a really slick JP BCG or Chromed Microbest BCG

You should do this test on stribog Gen 1 and Gen 3

I was excited, I thought you were trying out a new tooling insert on your PM lathe…. CMM(G) 😉

Great video! Love the data!

Nice work! As a physicist, I totally geeked out from yout test rig.

Love these kind of videos that compare claims of these companies with legit data that people can use when making a purchase. In this case is the extra worth it for radial delay. The next interaction could be straight blow back vs radial delay vs roller delay like mp5. Another great experiment could be how the data looks for gasses in the action on these different operating systems. See how these systems effect gasses shooters experience while running suppressed.

Thanks for this video. I have a CMMG RDB gun in 9mm so this is like I have validation for choosing the platform. I have no regrets, and now I have data to validate.

Hell yeah. May look into automotive data logging in order to maybe get some ideas into collating that sensor data into something aside from excel. I dunno if it will help but it may. Thanks Gavin. You’re badass and I wish it were the old days and the commies were still hidden so you could operate freely as you wish with your content. Like a normal American. Smh. Anyways thanks again.

Do you think the 2nd peek in the bolt/buffer all the way back is the radial blow back is the bolt backing into the bolt carrier group?

Do differences in shoulder soft tissue compression and rebound enter into your thinking and analysis? Thanks for all your efforts,what fun

Thanks for the detailed test!

My wife Shot a bunch of PCCs and chose the CMMG Guardian model in 45 ACP. She said it had the least kick out of several. With a couple of Kriss conversion Glock mags and one 13 rounder in the gun, her truck gun would be a big surprise to anyone with nefarious intentions toward her. Eight inch barrel shoots one inch groups at fifty yards all day long. Also, the most expensive gun I've ever bought.

Surefire OBC vs standard bolt
Carbine buffer and spring vs rifle buffer and spring

Awesome video.

Looks like under RDB the bolt opened later (with delay) but closed faster than direct blow back?

I've shot a CMMG Guard for years now in USPSA so I understand the system pretty well.

My biggest complaints is that CMMG could have licensed this design to other 3rd parties and have their RDB become the de facto standard in AR style PCCs. Instead they are going to lose market share to JP Enterprise and Angstadt Arms who has developed a roller delayed locking bolt for AR style uppers.

Also CMMG has terrible fit and finish issues. I've never had a gun with more issues and back and forth with a manufacturer for any of my other guns. As they update the design in the very least they should QPQ Black Nitride their RDB bolts for the price you pay because the system runs filthy.

I'm thinking the late spike is the sled rebounding or dumping energy back into the pressure sensor and butstock. Think of striking an anvil with even a light hammer. U can feel the wave of energy on/in the mass of the anvil, even though its probably 200plus × the weight of the hammer. The sled would have to be incredibly heavy/dense to not be detected by such a precious sensor.

Bro, you must have made a fortune with MSN because you always have the best toys!

Never knew Gavin worked at MS. That's cool.

I have a Banshee. Recoil is light. Gun shoots very flat. Almost no muzzle rise. Don't have a blowback AR-9 to compare with, but I'm delighted with my Banshee.

Absolutely awesome video. I love it!

what if that first blue hump isn't the bolt unlocking, but the actual impulse from the cartridge passing through all of the parts into the brace, into the sensor?
The reason the blowback one has no such impulse is because it's not locked, so the backward recoil impulse isn't imparted to the receiver at all until the bolt bottoms out because there's nothing resisting it but spring tension, and that's really just to return the bolt, not resist it.
But any delaying or locking system allows some of that impulse to pass through the entire gun, just like a bolt action. It just so happens that unlike a 308, a 9mm has very little (felt) impulse from the cartridge. It's the blow back bolt that has much more impact. Obviously the force from the cartridge is actually nigh equal to the bolt, it's just that it's felt differently based on differing velocities vs masses and whatnot. I don't fully understand the magic of this myself, but suffice to say that this is what allows a 9mm delayed blowback pistol to feel more comfortable than a straight blowback pistol, and an AK feel snappier than an AR (both lock but have differently weighted reciprocating masses and the mass is distributed differently in line with the shoulder, also the bullet and powder masses are different so to be fair it's not just the action)… but also sometimes semi autos kick LESS than bolt guns, and that has to do with spreading the force out over time. But that depends heavily on cartridge too.

PS- hrm. maybe they're the same thing. After all, the impulse is what's unlocking the bolt, not gasses. So the recoil impulse is being imparted differentially on the ramped surfaces which rotate the bolt, which is transferred via the cam pin into linear motion, not of the bolt but the carrier, which allows for the bolt to "stay locked" long enough to allow a better burn and accuracy. During that period of the forces being trasnferred via 2 sets of inclaned planes, first into radial motion (the rampled lugs), then back into linear via the cam pin in the track. That period allows some of that energy to go into the receiver and brace or stock… like during a gas gun's initial impulse, or a bolt gun. So maybe it IS the action… AND the cartridge impulse, which is why it's a complicated little double hump.

Ur getting more recoil from your bolt, and buffer slamming into the buffer tube's end than actual recoil from the rifle.