FWIW: CMMG 9mm Rotary Delayed Blowback Buffer Weight Comparison

I love how with those converted mags, it looks like you somehow accidentally shoved 9mm into a standard AR and it just kept working

Was there a change in felt recoil or the recoil impulse?

did you have that extra weight inside bolt carrier? Mine came without it (whole rifle) and in standard configuration accuracy and consistency of ejection were very poor. It got better when I put that extra weight in.

Then chopped that barrel to 12", put on 15" inch hand guard and suppressor just for looks.

I think it would be a good idea to get the weights CMMG produces for their RDB guns and give those a try. They were designed specifically for their system, so they ought to do the trick a little more precisely.

Give a follow up if you test more.

I have an idea why the ejection pattern is inconsistent. I think its because of the different position of the buffer weights in the buffer. Let me try to explain. In my opinion the bolt system og the Banshee works like the Famas or G3. The pressure of the gases in the barrel are forcing the casing back against the bolt face, do to the angled surface of the locking lugs the bolt moves backwards and rotates, this rotating movement is transmitted to the cam pin and the cam pin is translating this movement to the bolt carrier and because the bolt carrier is resting against the buffer the buffer is forced to move to. In my opinion bolt carrier and buffer are accelerated by the Banshee like the bolt carrier of G3 and Famas.
Now the movable buffer weights come into play. In case #1 the weights are located towards the fort, they are moved as soon as the bolt carrier is moving and their inertia is added to the total weight of the accelerated mass. But in case #2 the weights are located in the rear. As soon as the bolt carrier is moving, the inertia of the buffer weights is keeping them in place. Therefore their mass in not count into the mass of the accelerated mass. Effectively you are firing a weapon with a bolt only kept shut by its masses inertia but the mass in slightly changing with each shot, because of the differing position of the buffer weights.
The first solution that came to my mind was to fix the puffer weights in place, but this will be dangerous, because this prevents them from doing their work, preventing dangerous bolt bounce. Blow back operations are very prone to this phenomenon.
A better solution would be to install a weak spring, nearly strong enough to overcome the friction in their own travel. This can cause a more consisted ejection pattern, because the weights would be in the same position at each shot.

To test this theory one only have to hold the barrel to the ground after each shot and shake is slightly, to move the buffer weights in their forward position.

The last time I asked a question it went on a bit so hear goes again – does the extra barrell lengths velocity give you any real distance increase that is noticeably better?

I can't wait until you tune this enough to be competition reliable.

I wonder how the tuning would be unique from gun to gun.

A 9mm AR looks so incredibly fun. The last firearm I ever shot was in November 2018 with a 16" barrel SIG MPX. Very gentle shooting and every hole poked was enjoyable.

That's really throwing them forward

The ejection pattern was interesting – It looked like two forward, one back. Not sure what causes that.

9mm AR's are fun, if sometimes wonky. I don't know of one that hasn't required some tuning. Mine sure did. AR-10 buffer spring, hydraulic buffer and SS hammer and trigger pins. I really need to chop the barrel and Form 1 it as an SBR. 16" is too long for 9x19mm.

Unusual to see a long barrelled 9 mm

Why you didnt do the "Grip Clamp C" Style?

If and when I come into money, Karl's, Ian's and your videos on the matter will be my bible for upgrade and maintenance of a WWDS2020.

Use to practice on the SA80A1 with a 22LR conversion kit on a 25m range, it was also a great way to teach marksmanship principles.

gncdfs