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Discussion Starter · #1 ·
I've had my sear for a few years and have experienced occasional light strikes in multiple calibers.

At first I changed out the hammer spring to a rifle caliber one but the problem continued. I then tried the HK parts burst hammer spring with no change in the amount of light strikes. I also tried an extra strength spring but it made the gun only cycle in semi-auto. In full auto or burst mode it would fail to feed every time after ejecting the empty case.

I read about re-timed hammers and thought maybe that could be the problem but everything is about SEF, not burst packs. I'm not sure if my hammer is timed properly but the ROF in my mp5k clone is ridiculous (ly awesome).

Anyone have any advice? Should I just throw the extra strength spring back in and fire a few thousand rounds in semi-auto to break it in and hope it will eventually cycle in full-auto, and that it hopefully reduces light strikes?

Firearm Gun Trigger Assault rifle Rifle
 

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I don't own an auto sear so this is just from information I've gained reading here. An auto sear will change the position your hammer sits when it's cocked. So, instead of being 20° from horizontal it's 30° (don't try to measure, I made up the numbers). So when it does fire you don't get a full stroke and that's what causes light primer strikes. A retimed hammer has a different notch cut into it so that it sits in the correct position when using a sear. I would think this is a problem for both SEF and burst packs. A picture of the cocked trigger pack might help someone who knows what they're looking at identify that problem.
 

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You can tell if your hammer is retimed by how low it sits in the pack when locked in it's lowest position. Page two of this thread has a pic that will show you the difference between standard and retimed hammers. I've broken several retimed hammers through wear and tear (thousands and thousands of rounds), and from now on I'll buy only those hammers made by Mike Otte of Michaels Machines. Mike is on this board and has a thread somewhere with a video of him beating the sh!t out of a hammer with a big ass hammer in a vice...and he worked up a sweat before it broke.

http://www.hkpro.com/forum/hk-nfa-talk/129925-retimmed-hammer-2.html

If you've tried springs with no luck, get a new hammer...they're about $100 but you need a spare. Good luck!
 

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Light strikes with S&H sear in a 4-position burst pack

If you run an S&H or Fleming sear you need a re-timed hammer regardless of the type of trigger pack. The location of the auto sear (or in HK-speak the auto "catch") does not change between SEF, Navy, and burst designs.
 

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Having been down this road in the past, I believe most of your issue is particular to the .223 host. The light-strike may be caused by the bolt not fully seating. When releasing the bolt normally (cleared firearm), does the bolt always seat fully?
Now I'm surprised that the rifle caliber won't fully cycle with the heavy spring as I have not had that issue. I would try to focus on whether the bolt moves "freely" in the receiver.
With regards to timed hammers, there is no question that the MM hammer improves performance in a SEF pack. To obtain his hammer in your burst pack will require you to send it to him. That is on the top of my list for the new year.
I have many hosts and my light-strike experience only occurred, years later, with .223 hosts, and clones at that.
 

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Also consider replacing your recoil spring, which when worn will slow bolt carrier velocity forwards and result in a non seated carrier and bolt head. Once the hammer drops, its energy is lost seating the bolt carrier against the head, rollers, and trunnion, and not enough power remains to strike the primer with sufficient force. Ditto what the other guys said on hammer timing for burst packs (marked 'XX' on HK parts), and know that there are only 2 types of hammer springs: .308 and everything else (yes, the .223 caliber guns use the same hammer spring as subguns...).

Also might help to know what you're running this sear in, as your picture shows some kind of clone that may have other issues that are contributing to the problem.
 

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Discussion Starter · #7 ·
Thanks for the info guys. I have the following clones:

Coharie CA94SD
Coharie CA94K
Brethren Arms BA33


I experience light strikes with all of them fairly equally. As far as .223, the day I first got the BA33 I shot about 800 rounds of Wolf steel cased and gold as well as some M855 through it and had maybe a dozen light strikes.

I haven't replaced recoil springs but I have shot a lot of rounds through the 9mm hosts, so I will give that a try. I'll also post a picture of my pack later tonight.
 

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You can tell if your hammer is retimed by how low it sits in the pack when locked in it's lowest position. Page two of this thread has a pic that will show you the difference between standard and retimed hammers. I've broken several retimed hammers through wear and tear (thousands and thousands of rounds), and from now on I'll buy only those hammers made by Mike Otte of Michaels Machines. Mike is on this board and has a thread somewhere with a video of him beating the sh!t out of a hammer with a big ass hammer in a vice...and he worked up a sweat before it broke.

http://www.hkpro.com/forum/hk-nfa-talk/129925-retimmed-hammer-2.html

If you've tried springs with no luck, get a new hammer...they're about $100 but you need a spare. Good luck!
^^^ This.
 

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Well, since you're experiencing it on all 3 hosts to some degree - it's more than likely something wrong with the timing on your pack, or trip lever, or the sear itself. If the trip is allowing the hammer to release early, it will be falling on a carrier that's not fully seated to the bolt-head, and will rob the power from the firing pin strike.

Timing is crucial, and without know what kind of setup you're running - there's not much else I can suggest.
 

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Discussion Starter · #10 ·
Well, since you're experiencing it on all 3 hosts to some degree - it's more than likely something wrong with the timing on your pack, or trip lever, or the sear itself. If the trip is allowing the hammer to release early, it will be falling on a carrier that's not fully seated to the bolt-head, and will rob the power from the firing pin strike.

Timing is crucial, and without know what kind of setup you're running - there's not much else I can suggest.
Good points. I am not sure how to check for those problems. Here is how my hammer sits:

Gun Firearm Trigger Starting pistol Airsoft gun

Gun Firearm Trigger Starting pistol Airsoft gun

Based on the photos in the other thread it would appear my hammer is not timed properly. Looks like I am going to be sending it off to someone for a fix.
 

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Because the issue is with all three hosts, I would send the pack and hosts to a smith. Is the trip lever worn or out of spec? Is the hammer worn or out of spec? Is the trigger frame itself worn or out of spec? It would seem unusual that all three hosts have a worn out recoil springs. If your car stalled every once in a while, you could ask an internet forum what "might" be wrong with your car. "Replace this, check that" and maybe you find it and maybe you don't. If it is my car, I check a few things and get it to a mechanic. I could send you a surplus trip lever if you wanted to try that. If it was my sear and pack, I would get it to a competent smith that specialized in sear pack conversions with the hosts, and have him figure it out. A semi gun that runs most of the time is a PITA. A machinegun that doesn't run makes me crazy. Good luck with your pack problem.

Scott

ETA After looking at the two photos of your hammer position in your pack ( should have looked at them before posting), I went down and checked a SEF factory full auto pack (I didn't go into the safe to get out my SEF sear pack) and your hammer is much higher (further forward) in the pictures than factory. In the factory pack when the hammer held back on the "catch" (HK term for auto sear) the back of the hammer is a little over a quarter inch from the trigger frame of the one I looked at. When held by the trigger sear it is as far back or maybe further than your hammer being held by the sear. So I would expect that you have a factory full auto hammer rather than a retimed hammer being used with your registered sear. With the change in geometry of using a registered sear, using the semi auto trigger return pin to rotate on, with the factory hammer, the hammer is not held back as far as it would with the factory geometry. So the hammer starts forward closer to the firing pin, which would take less time to hit the firing pin. The trip lever, trip groove in the carrier, for that matter the whole system is designed to work together. If something is changed, it effects the whole system. Being further forward the hammer also has a shorter time to accelerate so the hammer won't have as much inertia and the hammer spring has less tension so it won't put as much energy into the hammer. I would think, a retimed hammer might fix your problem. If not send it to a smith. But I would think a retimed hammer would help a lot.

I don't know if this is because you have a burst pack but there seems to be wear on the side of your hammer like it is rubbing something in the pack. Extra friction always makes for cycling issues.
 

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Good points. I am not sure how to check for those problems. Here is how my hammer sits:

View attachment 78938

View attachment 78946

Based on the photos in the other thread it would appear my hammer is not timed properly. Looks like I am going to be sending it off to someone for a fix.
Can you take a pic of the pack out of the trigger housing and show where the auto sear pin is located?
 

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Discussion Starter · #14 ·
I wanted to post an update to this thread for anyone who might read it in the future. I figured out the main problem was loose tolerances between a German A3 stock and different Clone receivers. This resulted in enough slop for the trigger housing to move around just enough and not be able to properly reset. What I thought were light-strikes were actually just the firing pin normally bumping the primer with inertia. I fixed this problem by gluing a brass shim onto the back of the trigger housing to tighten it up. I made the shim by cutting up an empty 5.56mm case.

I figured out the problem when I tried various A2 fixed stocks and had no malfunctions. I realized the A2 stocks fit much tighter around the trigger housing. I have two full sized trigger housings and can only fit the shimmed one with the A3 stock as the A2's are too tight.

The issue took a little longer to solve because certain military ammo like IMI 5.56mm wouldn't detonate regardless due to a weakened trigger spring.
 
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