m4-2000/10.5" barrel rifle setup questions

[rrpederson]

hello everybody, i recently purchased an aac m4-2000 to go onto my lmt 10.5" upper and rock river lower. i have done a bit of searching and decided to make my own thread so that i can get more specific answers to my questions. i would really appreciate if anyone chime's in to help me out. if there is any additional info that u need to answer the questions, please feel free to post it. thank you in advance. now onto the questions.

my first question is, i want to change the setup and parts combination of my rifle to work better and more reliably while using the suppressor, and also without the suppressor. after my first shooting session, i noticed the following issues.

issues

1. intermittent failure to hold breach open on an empty magazine.

2. excessive gas blowback into the shooter's eyes.

now onto the other questions to increase reliability.

1. do i have to reduce or increase the size of the gas port of the barrel? and why.

2. do i need to find a matching gas block, if i reduce or increase the size of the gas port? and why.

3.do i need to change the buffer weight? if so, reduce or increase weight? and why.

4. do i need to reduce or increase the buffer spring tension? and why.

5. do i need to change bolt carriers? if so, to what and why.

6. are there any other parts that i should buy to increase reliability suppressed and not suppressed? and why.

i know it seems like alot of stuff, but i am confident that u guys out there really know your stuff. thanks again for any help.

richie

[JSGlock34]

You might want to look into the PRI gasbuster charging handle to help alleviate the excessive gas blowback issue. As for the magazine lockback, I'm curious to hear the recommendations of those more experienced than I am, but I imagine they'll want to know what buffer you currently run and what ammunition you are using.

[rrpederson]

just took a look at that part u mentioned. probably gonna have one sent from larue within a few weeks. anyone know how well it works?

[Iraqgunz]

I have a BCM 11.5" and I am switching to an H2 buffer because I had some failures to lock back. I am fairly certain this will solve the issue. I am using a standard auto BCG and a gas buster charging handle. I am also using an AAC M4-2000 suppressor.

As a caveat I do not shoot crap ammo either.

[eodinert]

It fails to lock back with, or without the suppressor?

What kind of ammunition were you shooting?

Do you have any of your fired brass? Examination can help diagnose...

[rrpederson]

It fails to lock back with, or without the suppressor?

What kind of ammunition were you shooting?

Do you have any of your fired brass? Examination can help diagnose...

sorry, i didnt think to mention that stuff.

failed to lockback a couple times with the suppressor attached.
i was using hornady 55gr practice ammo.
i didnt keep any of the brass. i probably will next time.

[m4fun]

I would go with a heavier buffer. This sounds like classic bolt bounce. The suppressor forces so much more gas right back at you pushing the BCG back faster/less dwell time and it is coming back so much faster it misses that bolt open. Get some buffers of greater weight than you have(e.g. if you just have a CAR buffer, get an H, H2, H3) and work your way up to reliability.

Could be a weak buffer spring too, if it is a new rifle, doubtful, but if it is a 1972 SP1 carbine, you might want to pick up a Wolff spring.

You could pick up a little more mass if you have a semi-carrier and switch to a FA carrier, but that isnt much.

I would really stay away from modifying the gas port - it will only get bigger, especially on a shorty. There are adjustable gas blocks and gas tubes, you adjust the gas coming back like some piston uppers or a FAL, but you dont see them too many of them, at least I dont, and I think there is a reason for that.

I too use the PRI Gasbuster - Awesome CH, especially with the big latch. It blocks some of the gas, but there is still a lot coming back. I even applied silicone to it and still a lot of blow back. Its a suppressor...they all do that.

[rrpederson]

thanks a lot for the help. looks like just a buffer and the charging handle are the biggest things right?