M*CARBO Brotherhood

First Round Fires

I put one round in the chamber and fired. It ejected the spent round and loaded the second round. I pulled the trigger but it didn’t fire. It just clicked! I used another mag and same thing happened it only fires the first round.
The weapon ran flawlessly before upgrading all of the internal MCARBO parts. I went step by step with the videos, and by the way they are awesome.
What could I have done wrong?

2 Likes

That’s a weird one. I don’t have an answer, but I’m in for anyone else with info. The hammer is obviously hitting the firing pin with enough force to fire rounds, but only the first one? Strange, indeed…

What do the primer marks (if any) look like on the rounds that didn’t fire after the first round? How to they compare to the marks on the rounds that did fire?

Any difference in “click”/hammer drop sound or feel after the first round is fired like maybe the hammer fully cocks back only when manually cycling the first round into the chamber?

1 Like

There was only one round that had any markings and it was lite. The trigger felt the same and it did click. I’m new to this game and was completely blown away. I took the video seriously and stopped it at every point.

1 Like

Please pull the round that was in the chamber when you got click instead of pew. Was it the spent casing that went pew originally? Is it an unfired round? If unfired, is the primer dented or untouched?

2 Likes

Did you collect all the fired cases? Since you said more than one first round fired, there has to be more than one case with a visible primer strike. Or, were you only referencing the rounds that didn’t fire? If so, what did the fired cases’ primer strikes look like?

Pull the bolt and use a punch or something to fully depress the firing pin forward from the back of the bolt. See if it feels “crunchy” or anything. It sounds like it could be a dirty firing pin channel or possibly a broken firing pin and/or return spring.

2 Likes

Is the hammer resetting in the correct position to fall with enough force to strike the primer on the follow-up shot?

4 Likes

Good point. I asked about that, too. Seems like the hammer may only be fully resetting when manually cycled.

2 Likes

@Bj2k my first thought is you may have reversed the hammer spring when you reassembled your S2K?

4 Likes

@Bj2k I provably should have elaborated more…

If the hammer spring is reversed then the first round will fire the bolt group would cycle, loading the next round, but the hammer would not return to the cocked position to fire.

3 Likes

Why would the hammer cock when manually cycled, but not when firing? The hammer doesn’t know what caused the bolt to ride over it. Honest question…

1 Like

What ammunition are you using? Some of the cheaper steel-cased ammunition, especially the Russian brands require a good, hard primer strike for them to go off.

Gene Beaird,
Pearland, Texas

3 Likes

@Wedge I don’t know that it would…would fire the first time but not return to battery when the bolt cycled.

Might no be the issue after all!

Good catch brother!

1 Like

It’s been busy on my side today. I will check into the questions that ya’ll have ask tomorrow.

2 Likes

From his description it sounds like it’s returning to battery fine. It fires the first round and feeds the next one properly, but it just won’t fire when the hammer is dropped again.

1 Like

im leaning toward firing pin, but are they any drags on the unfired cases? did you replace the trigger guard, and are you going to full lock position? in the locked position, mine has about .0005 movement when the lock is fully engaged,cold bore. that goes by by after the first round. (heat expansion) if its tight to start with it could cause drag on the casing, slowing the bolt.
but thats a reach not knowing what you replaced.

1 Like

@GOBLIN if was firing pin or ammo then first round shouldn’t fire…sounds like it does, but only first round.

Fact that it ejects round tells us it is cycling.

Does trigger return to battery after first shot??

But hammer not falling on second round?

Hmmm…hold my beer while I puzzle this one out!

2 Likes

had a ithica that did the same, but it was a light strike issue, worn firing pin. it was sorta a guess with each pull of the trigger… cracked or broken firing pin spring,cracked or broken recoil spring, extractor not fully seating (bolt not going full battery) if we knew what was replaced be easier to trouble shoot…

3 Likes

So, I’m just stuck until I get answers to the questions I asked. When he talks about finding one round with marks - was it the fired casing that was marked? Where did he find it? Was it the first second round, the second round, the third, etc. Can we establish the pattern? Does cycling the charging handle reliably result in a first round fire condition. If rounds are autoloading per design I’ll be ready to join the braintrust of spring fitment engineers.

@FoldedCarbine also brings up a good point regarding hardness variance between primers which could be at play here.

Finally, what is the OP doing to establish first round that does fire? E.g., does it fire after cycled with the charging handle or only when mag is removed and reinserted or does he have to make an offering to JMB to get it to fire.

Fair warning … If we establish that it is cycling rounds but failing - my next step is the dredded function check. It seems that something is disrupting sear/hammer function and I suspect that an examination of what is required to produce a predictable “fire” result.

4 Likes

Have yall established the trigger is re-setting? Just thinking out loud.

2 Likes

I put one round in the chamber and fired. It ejected the spent round and loaded the second round. I pulled the trigger but it didn’t fire. It just clicked! I used another mag and same thing happened it only fires the first round.

2 Likes