Help AR not cycling properly

[XtremehuntR]

I am new to the site. The answer may be in here but I could not find this topic.
Just finished a build with a 300AAC complete upper, C3 lower, Timney drop in trigger and Daniel defense lower parts kit, magpul moe stock and mil spec buffer. Same lower set up as my last 5.56 with a luther walther custom barrel that is a tack driver by the way. I have shot standard Remington 300 blackout factory ammo and reloads including 110 and 125 nosler BT and 130 gr Barnes TSX bullets with H110 in many load configurations.

The gun appears to be cycling completely. It ejects properly and chambers the next round but does not set the hammer. So basically I have to use the charging handle and eject an unused round and chamber the next while setting the hammer. It shoots very well to my surprise (moa). But basically I have a single shot rifle. I put the lower on one of my 5.56 and works fine, so I know there is nothing wrong with it.

I am baffled because hammers generally set by the time the bolt has gone 1/3 of the way back. So how can it completely eject and not set the hammer?

Someone told me it could be cycling to fast and I need to slow down the bolt, may be use a heavier buffer.

I'm sure someone out there knows what I'm talking about.

[certifiable]

You are correct, this subject has been covered exhaustively numerous times.
In order to help diagnose the problem, specifics on your build are needed.
Barrel length
Gas system length
Gas port diameter
Carrier used
Buffer & spring used
Gun run wet or dry
Etc, etc

Possible problems
Gas block not properly aligned
Gas port too small
Too heavy a buffer or spring
Gas key loose

[talonxracer]

Will the bolt hold open on the last shot?

['Borg]

Do a function test on the trigger to see if it's the disconect.
Had one last week do the trick of single feed, holding back bolt, but when I put more ammo in it went crazy.
Changed out to a different BCG and all is well, seems the lower had the trigger/hammer holes about .010 lower than other brands.
This was with a two stage trigger.

[talonxracer]

Swap around the BCG's from one of your 5.56's and give it a go.

[-k-]

I think it's cycling just fine. Load one round in the magazine and check the bolt locking back.

Some light triggers are quite easy to accidentally bump fire. But it happens so fast the hammer follows the carrier forward before the bolt can lock and cannot fire the round. Try consciously pulling the trigger all the way to the rear and holding it there through the shot and recoil.

[XtremehuntR]

Thanks -k- you are correct. It is cycling fine. The bolt locks back when I load 1 round. The hammer is riding back on the bolt so I have a fresh round in the chamber but will not fire.

[Overton-AR]

It's not a function issue at all. Its a trigger issue. Pull
out the Timney and put in a mill spec trigger and check
it again. I bet it works just fine.

Now.....DO NOT take this as a "slam" on Timney. They
make excellent triggers. The facts are.....triggers can
and do malfunction. We all want to think that NO WAY,
I bought the best stuff so it would never mess up. Sorry,
that just isn't reality.

I recently (just 2 weeks ago) had a Wilson TTU trigger
malfunction. I returned it and they replaced it. Both
Timney and Wilson triggers are excellent....but things
happen.

IF this fixes your problem....call Timney and get a return
authorization and they will take care of you.

[-k-]

Gun weight, shooting position, how the gun is held, and caliber/recoil will all play a role with unintended bump firing. Single stage with short pull designs are much more likely to have problems than the two stage trigger design with it's long first stage.

I suspect some of the very light triggers are only tested on 20"+ bull barrel .223 AR's. Larger calibers and lighter carbines seem to bring it out more. There might not be a mechanical problem with your trigger.

[jwb47]

before I tore anything apart I would check and make sure the hammer spring is installed correctly . just the voice of past experience.