Hey everybody. I own a DD M4V5 in 300 Blackout. The gun functions great with supersonic ammo, but won't cycle with the subsonic stuff. I called DD, they shipped the gun back and adjusted the gas block, but when I got it back it still won't work. I have tried a few different types of 220 grain ammo so I don't think that is the problem. I'm using an Osprey 9 on the front. I also noticed the buffer is an "H" so maybe I need a lighter one or a lighter spring? Any thoughts?
Thanks,
Aaron

Apologies before hand, I don't have an answer to your question but would like to ask how the rifle sounds with the supersonic rounds. I have heard .223 supersonic suppresses, but not .300.

The 300 supersonic is probably a little bit quieter than the .556. I've never fired the supersonic rounds suppressed because my suppressor is not rated for it. The 300 subsonic with the suppressor is pretty quiet, not .22 with a sparrow, but pretty quiet.

How wet are you running the BCG ?? The H buffer should be fine in a full length rifle. Try loading just 1 round in the mag and see if the bolt will lock back on empty...

This message has been edited. Last edited by: CandyMan.45,

Try using a carbine buffer.

A lot of our customers start with H and go heavier and can't figure out why the same problem keeps occurring (because they are used to solving things the 5.56 way).

300 subs are delivering a lot less energy back into the system--a carbine weight buffer is your quickest and likely cheapest fix.

What buffer do the ISRs come with, i wonder. anyone know?

H Buffer

Ok, thanks for the feedback. I had read on some other sites that the carbine buffer could solve the problem but wanted some expert opinions.

As an aside, the .300 Blk is supposed to switch back and forth between supersonic and subsonic seamlessly and that does not seem to be the case. Still a great gun and a great round though.

Id send it back again. You pay a premium from a company like DD to ensure you get a working rifle and impeccable service after. Id find out what ammo they used to test it and try it for yourself.

Im trying to send it back again. Their customer service was great the first time, really responsive and helpful. They replaced the BCG, put upgraded safety selector and cover and even sent me a free mag. But since i got the rifle back they have stopped being helpful.

Oh and to answer CandyMan.45, i usually run it so wet that it leaks all over my carrying case.

quote:

Originally posted by aesposita:
Hey everybody. I own a DD M4V5 in 300 Blackout. The gun functions great with supersonic ammo, but won't cycle with the subsonic stuff. I called DD, they shipped the gun back and adjusted the gas block, but when I got it back it still won't work. I have tried a few different types of 220 grain ammo so I don't think that is the problem. I'm using an Osprey 9 on the front. I also noticed the buffer is an "H" so maybe I need a lighter one or a lighter spring? Any thoughts?
Thanks,
Aaron

I don't see where DD offers a V5 in .300 B/O.

Is this rifle a custom build from them or did you put a .300 barrel in it yourself?

Did you send your suppressor back with your rifle?

It's a couple years old, I think they are up to V7 now. I bought it brand new from a dealer.
I didn't send the suppressor to them, the specifically told me not to, and that would make me kinda nervous anyway.

quote:

Originally posted by aesposita:
Im trying to send it back again. Their customer service was great the first time, really responsive and helpful. They replaced the BCG, put upgraded safety selector and cover and even sent me a free mag. But since i got the rifle back they have stopped being helpful.

Oh and to answer CandyMan.45, i usually run it so wet that it leaks all over my carrying case.

Did they even hint as to why they replaced those things?
Does it fail to cycle every round of subsonic or a couple times a mag?

They said the BCG might be worn so they just replaced it in case. They also said that the gas block gets loose over time and that I wouldn't notice it with the supersonic rounds but would with the subsonic. Not sure why they replaced the rest of the controls.
It fails to cycle every single subsonic round. It has never successfully ejected a spent case and loaded a new one. Most of the time it ejects the spent brass but doesn't pick up the next round and closes on an empty chamber. Occasionally it can't even eject the old one and it jams.

Im really surprised it came back and you cant cycle a single round. Starting to think they jsut threw some parts at it and didnt test fire.

It was a little confusing because they said they test fired it, but I don't think they have a suppressor. They also said they don't recommend firing it subsonic without a suppressor because it won't generate enough backpressure. Im starting to suspect they didn't test fire it too either.

I ordered a 3 oz buffer so hopefully that solves the problem.

quote:

Originally posted by aesposita:
It was a little confusing because they said they test fired it, but I don't think they have a suppressor. They also said they don't recommend firing it subsonic without a suppressor because it won't generate enough backpressure. Im starting to suspect they didn't test fire it too either.

I ordered a 3 oz buffer so hopefully that solves the problem.

So is your problem with Subs with or without the suppressor... or both ?? So companies do tune their stuff to run subs w/ a can only. And I think DD has more then enough suppressors at their disposal.

Both. It won't function with or without the can.

How many rounds of supersonic have you fired through it?


A buddy of mine built an 8.5 inch suppressed 300 BLK and it was a jammomatic until he had a few hundred rounds of super through. Now it is reliable with subs and the can.

I have about 1500 supersonic rounds through it. Although I have only put 100 though it since they replaced the bcg.