HK Removable Sear Trips by Armament USA

[navgunner]

Before reading my comments below, please know that I have no affiliation with Armament USA.

I recently had Armament USA complete a sear trip modification service to one of my carriers and I'm impressed (I immediately sent them another two carriers for this same service). I received great service and the job was completed quickly (about a two week turnaround). This is a wonderful option for registered transferable sear/pack owners and post samples for licensed dealers. Of course, All NFA Rules Apply.

LINK -- "trip service" | Armament USA

 

[Chisel]

I bought their RCM MP5 carriers with removable trip. They work great in my SP5 and MP5SD SP5 conversion.

 

[navgunner]

It is worth mentioning that RCM makes fantastic products!

 

[StenAtopia]

It is worth mentioning that RCM makes fantastic products!

Gods truth. Hk purists will burn me for saying this but RCM stuff is super darn close. Shhhhhhhhhhhhh….

 

[Nome Nomad]

Armament did two carriers for me. Excellent work and fast turn around!

 

[LawBob]

What’s the purpose I don’t understand

 

[slimshady]

Some of the MP5 clone imports do not use the HK shelf mount for the grip, they use the front pushpin like the FA model does. To prevent conversion to FA by swapping in a minimally modified factory FA lower they weld in a bar at the rear of the receiver that requires the carrier be machined to clear it. That missing area is where the sear trip surface is on a FA model.

Prior to the 86 MG ban a popular method of HK conversion was to use a registered sear or trigger pack which is allowed to be put on any gun since the registered item is the MG. Since a bolt with a sear trip surface on it won't enter the receiver on these newer imports you can't just install one on them without converting it to the HK pattern. An expensive proposition.

So a solution was devised. Machine a carrier and a new piece to restore the carrier to HK spec by bolting it in through the bottom of the receiver once the carrier is in place. You have to remove it to pull the bolt assy out but it solves the problem cheaply.

 

[cockednlocked45]

Now days you can buy a super safety. It does the same thing. I have $1500 in a k model that does the same bang, bang, bang. If I owned a an "hk" shooter, as an investment, I'd probably sell now.

 

[hawkin]

I just sent off a sp5 and mke carrier for the mod. Can’t wait to get my ap5 sd up and running.

 

[Beowulf]

Now days you can buy a super safety. It does the same thing. I have $1500 in a k model that does the same bang, bang, bang. If I owned a an "hk" shooter, as an investment, I'd probably sell now.

What lower do you use for your super safety? I’m thinking of throwing one in my Omega OM9 or maybe picking up one of the new AP5SDs and doing the barrel swap

 

[A&S Conversions]

The conversion needs a specialty grip housing that uses AR fire controls instead of HK style fire controls. That way a whole new fire control mechanism for the roller locked guns wouldn’t be required. There is an additional tripping frame that must be added to the bolt carrier to activate the forced reset mechanism.

I wonder about the AR fire control. The original Colt 9mm subguns used a bolt that was not ramped like the rifle caliber carrier. Because of the 90 degree cocking surface of the Colt 9mm bolt, this put high stress on the hammer pin. The hammer pin would have a tendency to break in the center, as there is a detent in the middle of the pin hole. The factory profile of the AR fire control pins have a reduced diameter in the middle of the pin. Sometimes when the hammer pin broke in the middle, the pieces would not only stay in place, but the gun could continue to fire. The broken pin halves would be at an angle. This would cause the hammer pin hole to become oblong. This would be a huge concern to the owner of one of only 100 factory Colt SMG lowers. So Colt eventually machined a ramp in the cocking surface of the 9mm bolt and changed the fire control pin material to stainless steel as it had more give than the brittle hardened steel standard fire control pins.

The HK style arched hammer, doesn’t need the ramp on the cocking surface of the bolt carrier. But the AR fire control does. Are those who are using AR fire control using a ramped cocking surface on their HK style carriers? I don’t know. It was enough of an issue that those with a rifle style hammer would get their Colt style 9mm bolt cocking surface ramped.

Scott

 

[Galil#1]

So? This is for fake/non-factory made MG/SMGs ?

 

[A&S Conversions]

So? This is for fake/non-factory made MG/SMGs ?

I don’t understand the question you’re asking.

Scott

 

[Galil#1]

Is this for like the "sear ready" type firearms? Sorry for my confusion.

 

[A&S Conversions]

Yes, The original poster was extolling a service he got on a couple of roller delayed carriers that were modified for use with a registered sear in a modified pack or registered trigger frame conversion, to allow such machine gun conversion devices to function in some of the recently imported semi auto guns. The term “sear ready” normally refers to a semi auto gun that is in a configuration that would allow the use of a registered sear in a pack or trigger frame to be dropped into the host gun without further parts modifications and to function as a machine gun.

The member “slimshady” went on to explain why the modification of the carrier was required for use with a registered HK conversion device because of the sear block welded into the back of the imported roller delayed semi auto guns.

The member “cockednlocked45” turned the conversation to the possibility of using aftermarket parts to convert the same style of roller delayed host gun for use with the Super Safety system. Then I brought up the issue of the geometric differences of the hammers between the original HK style of hammer and that of the AR style of semi auto hammer and how the hammer cocking surfaces of a AR carrier and HK roller delayed style carriers were different. This difference reminded me of how the original 9mm conversion made by Colt had problems with the 90 degree cocking surface for a standard style of AR hammer, which the HK style of carrier has a 90 degree cocking surface of the carrier.

Since the Super Safety installation in the roller delayed guns is a fairly new, I wondered aloud if this hammer cocking geometry difference could cause problems for the hammer pins of Super Safety installations using a standard AR semi auto hammer in roller delayed guns with unmodified HK style carriers. It is my understanding that the current HK style grip frames that can be used with AR fire control are made from plastic. Would the extreme force of cocking the AR hammer with a 90 degree cocking surface cause the hammer pin holes in the plastic grip frame to deform instead of the hammer pins breaking? This in turn leads me to wonder if the Super Safety users are using semi auto 9mm hammers? The 9mm AR semi auto hammers have a very different geometry than a M16 hammer, or a semi auto standard hammer (the auto sear hook at the top rear of the M16 hammer has been removed for semi auto use, as that hook is only for use to engage the auto sear in a full auto application). I would think that it might take a some rounds of use before any hammer pin/grip housing hammer pin hole problem might show itself.

Sadly, I sold my Fleming sear to cover my expenses for developing the Tenko adapter. Hopefully I can rectify that problem soon. I miss shooting my sear with my host guns. But I am not going to spend thousands of dollars on tax stamps and braces so I can shoot my host guns with a Super Safety.

Scott

ETA, boy did I go down a rabbit warren with this answer.

 

[Galil#1]

^^^^ That's why you are... Scott The Great ^^^^

Lots of awesome information especially for us dummies and such, thank you Sir for your time and full explanation! I can learn something new everyday but still die stupid, as they say Ha Ha!

 

[slimshady]

To further confuse you, sear ready can also refer to the trigger pack itself that the registered sear is going to be installed in. Today full auto trigger packs are available everywhere, they used to be cheap like $75 cheap. Back in the day however HK was not releasing parts to the US market and there was little
surplus available. So an actual full auto trigger pack from the factory was a rarity. If you had one of those all you had to do is notch it properly to fit over the semi-auto mounting shelf and install a bolt with a full auto trip on it. IIRC, DLO made a few from the mg spec pack boxes and registered the boxes themselves instead of the sear.

So the registered Sears had to fit into a standard semi-auto configuration trigger pack. Part of the problem is the cutout in the front is so big it takes out the space where the original sear pin was installed, so the sear has to be mounted on the relocated semi-auto pin. And of course the pin that limits the trigger travel to the semi-position has to be removed. Anyway the relocation of the sear means that if you use a standard full auto hammer the timing is off.

The standard functioning of an HK is the bolt carrier moves that last fraction of an inch to fully closed and trips the sear which releases the hammer. The hammer pops up from it's fully cocked position, if the trigger is not pulled or was pulled in semi-auto the hammer will hit the sear mounted inside the trigger, holding the hammer back in a slightly less cocked position. In full Auto the triggers pulled back far enough that Sear is clear of the hammer and is free to fall all the way forward and smack the firing pin.

With the relocated Autosear, or catch as HK calls it, the hammer timing is off with a factory Hammer and the notch the sear catches on has to be adjusted to correct the timing. Installing a registered Sear in an Ambi or burst pack requires more extensive mods and timing.

Used to you could buy Sear ready packs that were already timed but ATF decided they were machine guns since you could get a slamfire out of them without it installed. And at this late date a sear that wasn't already installed in a pack would be a rarity. But if you decide to swap your registered Sear from an SEF lower into an Ambi or burst lower, you're going to need to get a sear ready pack made for it.

 

[A&S Conversions]

By the way I bought close to 100 G3 complete trigger groups (50 steel mostly with green grips and the rest are Navy style black) about ten years ago for $40 each. The only downside is that the hammers are not pinned to the strut. This was the norm until HK developed the MP5K. The 900 per minute ROF of the K can cause the hammer to “float” on the strut. So HK made the pinned hammer to the strut the standard for all hammers going forward. I have a special project in mind for the trigger packs. I had a bunch of the grip frames clipped tight. I hand fitted the grip frames to many of my host guns for a custom fit.

Scott

 

[JC556N]

Now days you can buy a super safety. It does the same thing. I have $1500 in a k model that does the same bang, bang, bang. If I owned a an "hk" shooter, as an investment, I'd probably sell now.

Yeah I wouldn't.

The court case on the FRT only exempted the Rare Breed trigger, nobody has an ATF approval letter in hand yet not even rare breed, and multiple states have outright banned FRT triggers but not registered MGs. Remember the entire case against rare breed was whether the government treated them fairly, not whether the trigger was legal.

You do as you please, but I have a good 2A attorney whos a big name in the 3D2A sphere and his advice was to stay clear of these triggers unless I wanted to be a test case.

As such, I'll be keeping my factory Mp5A2.

 

[cockednlocked45]

What lower do you use for your super safety? I’m thinking of throwing one in my Omega OM9 or maybe picking up one of the new AP5SDs and doing the barrel swap

3d printed leber v2. Its been flawless!
You can get the files off odyssey website