KAC SR-15 FTF w/ SD-3G

[Charlie Don't Surf]

I had an extra SD3G trigger lying around so I put in my SR15 mod 0. During the last stage of the half and half drill I experienced 2 ftf with light primer hits. The rounds fired fine later. The ammo is American Eagle 55gr 5.56mm.

My diagnosis is that I’m firing too fast for KAC’s finely tuned gas system and the hammer is following the bolt. I have never had a malfunction in this rifle before. So the original KAC trigger is going back in for now.

Am I correct here, or is something else going on?


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[TomMcC]

I doubt seriously you could out run the bolt during firing and if you're actually getting hammer follow then there is something wrong with the disconnector.

[ssc]

How many rounds have you fired with the SD3G? The one big issue I have had with FTF, all came back to my SD3G. I have a post here about the issue. I checked everything and replaced the extractor and spring. I checked headspace and ejector. I changed ammo and tried different BCG's. I tried switching uppers with different lowers. I thought I had fixed the problem after the new extractor. However the issue arose again.(Only with the lower with the SD3G.) The only common denominator was the SD3G. I changed the hammer spring to a new one.

Since I changed the hammer spring I have not had any FTF in the last 2,000 rounds. (Both reloads and factory ammo and with different uppers.)Keep in mind that the only FTF happened with that particular lower with the SD3G trigger. Perhaps, it was a coincidence, I don't know. That particular lower with the SD3G is only used in gun game situations and I do run some drills with it. It is not my SHTF/HD gun. However, if it suffers one more FTF, I will be replacing the trigger.

YMMV, Cheers, Steve

[Rogue556]

Out of curiosity, did you swap the hammer spring out with another of the same weight, or was it a heavier spring?

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[Charlie Don't Surf]

Out of curiosity, did you swap the hammer spring out with another of the same weight, or was it a heavier spring?

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It was the lighter geissele spring.

I've had between 100-200 with the SD3G, only problems were when I've tried to shoot fast.

[ssc]

Out of curiosity, did you swap the hammer spring out with another of the same weight, or was it a heavier spring?

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I called GA and asked if the SSA hammer spring was the same as the SD3G hammer spring. They said it was and that is the spring I used. They affirmed that it would work with the SD3G. I keep a few new SSA hammer springs in my parts bin.

Cheers, Steve

[Wake27]

Is it installed correctly? I had a super tricon that would have light primer strikes every now and then, but it was so rare I thought it was just a hard primer. Turns out I made the rookie move of installing the legs wrong.


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[MegademiC]

It was the lighter geissele spring.

I've had between 100-200 with the SD3G, only problems were when I've tried to shoot fast.

Whats your fastest splits with that same (type) trigger in a different gun?

[georgeib]

If you're getting light strikes, my money is on the hammer spring being installed backwards.

[Charlie Don't Surf]

Is it installed correctly? I had a super tricon that would have light primer strikes every now and then, but it was so rare I thought it was just a hard primer. Turns out I made the rookie move of installing the legs wrong.


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I thought I did. I’ve put in over a dozen triggers. Since I’ve already put the KAC trigger back in, there is no way of knowing for sure if it was correct or not.


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