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Evening everyone, for awhile now I've been prototyping a safety block that will allow owners to use the safety function in a semi auto MG42 grip that has a Franklin arms binary trigger installed. I'm posting this to gather any feedback, ideas or tips and am happy to hear any critiques that you may have. As it is now the safety block functions as I've already stated, is made of PETG plastics and has a built in "seat" for a spring that keeps it off the trigger mechanism.

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Looks pretty much like the one I have from BRP?
It is similar but different placement/size of the ridge that blocks the trigger, the angle beneath the hole in the front is at a very steep degree to allow movement of the trigger, it also doesn't have the oval that the BRP one seems to have and instead has a shallow wider diameter to allow the placement of the spring seen in the middle and right grip. The spring is there to make sure the trigger block remains on the opposite wall out of the way of the trigger which I've heard the BRP safety sometimes wobbles over into the way of the trigger when firing.

I just posted a video that better explains and illustrates the function:
 

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Discussion Starter #5
Looks great, and very clever. Are you confident the plastic will hold up?
Appreciate it, short of a severe hammer swing it shouldn't be a problem, 3D prints are very strong when printed perpendicular to the force applied, its kind of hard to explain. I don't know about longevity, though PETG should still hold the same strength for at least 3 years
 

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That safety functions nill for actual safety in using a binary. We advise against using one(binary) in a semi MG42 and using one in our guns voids any warranty. Reasons that most people overlook or flat don’t understand because 99% of people don’t understand how the Mg42 actually works. It is not wise to use a binary in an MG42. Sure in theory the Mg42 is capable of 1200rpm, as an open bolt. As a semi auto it is quite possible to blow it up in your face..
 

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That safety functions nill for actual safety in using a binary. We advise against using one(binary) in a semi MG42 and using one in our guns voids any warranty. Reasons that most people overlook or flat don’t understand because 99% of people don’t understand how the Mg42 actually works. It is not wise to use a binary in an MG42. Sure in theory the Mg42 is capable of 1200rpm, as an open bolt. As a semi auto it is quite possible to blow it up in your face..
Hmm interesting, is it safe to assume the problems with using a binary trigger are similar to the early reports of bolt bounce (in the original mg42), where it had a tendency to fire out of battery? Or is there another inherent problem with a binary that allows the firearm to malfunction.
 

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Bolt bounce, firing pin peen causing the pin to get jammed in the bolt and the gun runs away, breaking internals due to excessive slam, and several other factors. In our experience with the MG42 semi-auto guns(I built about 50 last year), not a good idea.
 

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Haven’t heard of firing pin peen being a problem with binary triggers, that’s something to be aware of.

And yes I’m aware of your company’s stellar reputation when it comes to MG42’s and copies, my comment was to only better understand not shed doubt
 

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Basically it accelerates the rate of wear on the semi parts leading to runaway guns and or broken components. Along with the OOB possibility with bounce as mentioned.

I wasn't saying you were questioning, just putting it there for the others who venture in here to read our conversation.
 

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I have several SBR ARs with binary triggers . S/W AR-15-22 , several normal lowers in .22LR , 5.56 , 300 B/O , .458 Socom and just registering one with a Fight Lite belt fed upper .
Does the warning above apply to those MG-34 uppers that can be placed on an AR lower ? I don't have one , but it is on my " want to get " list , but only with a binary as I have no FA M-16 type lowers ( also , I don't think you can put one on a full auto , IIRC .)
Thanks , Chris
 

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Basically it accelerates the rate of wear on the semi parts leading to runaway guns and or broken components. Along with the OOB possibility with bounce as mentioned.

I wasn't saying you were questioning, just putting it there for the others who venture in here to read our conversation.
I have to say I don't know I am convinced by your argument? Does it accelerate wear because you are shooting twice as much? I mean each hit on the firing pin it another hit on the firing pin, is it not? However clearly 500 hits is twice as much wear as 1000? Seems all you are doing is shooting more and the more you shoot the more chance for wear and more run-a-ways? What am I missing? What does spacing the individual shots do to reduce this issue?

I could maybe see the bolt bounce issue but its still going to be much slower than the original cycle rate, much... I grant there is more potential for bolt bounce to cause an out of battery given the semi design and the lack of a system to ensure the bolt it closed before the firing pin and strike... but I think you would quick see if this is an issue. The Germans made it through WWII without fixing this issue with the FA design.

I have only built one of these using a rewelded receiver, so I am far the an expert. However I would love to understand more and frankly, I think a binary trigger is an obvious awesome thing for this gun.

What do you think about using a MG3 mount? Those guys are spring loaded and lets just say tend to help the gun fire quicker. I have never hear of issues there.
 

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Accelerated wear on the carrier, the rear lip of them is very thin and prone to break if abused. Banging thru shots at speed the bolt/spring have a much higher probability of recoiling slightly off and breaking the rear lip/spring retainer off. BRP sells a repair for this but it involves machining and welding. Accelerated wear on the sear/disconnect surfaces more prone to chipping as they may or may or be fully seated before being banged by the bolt carrier slamming to the rear. The FCG isn’t designed for the forces applied, it works but they are prone to wear, AR15 parts are cheap to replace. Accelerated wear on firing pin as you are more likely to bang thru many more rounds in a session, between cleaning and inspecting, and not catch wear such as a firing pin peening or sticking because it has debris in it from extra shooting etc.
So from a warranty stand point, you see why it voids our warranty. Bolt bodies aren’t exactly cheap, accelerated wear causing premature failure, higher risk of OOB...
 

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Accelerated wear on the carrier, the rear lip of them is very thin and prone to break if abused. Banging thru shots at speed the bolt/spring have a much higher probability of recoiling slightly off and breaking the rear lip/spring retainer off. BRP sells a repair for this but it involves machining and welding. Accelerated wear on the sear/disconnect surfaces more prone to chipping as they may or may or be fully seated before being banged by the bolt carrier slamming to the rear. The FCG isn’t designed for the forces applied, it works but they are prone to wear, AR15 parts are cheap to replace. Accelerated wear on firing pin as you are more likely to bang thru many more rounds in a session, between cleaning and inspecting, and not catch wear such as a firing pin peening or sticking because it has debris in it from extra shooting etc.
So from a warranty stand point, you see why it voids our warranty. Bolt bodies aren’t exactly cheap, accelerated wear causing premature failure, higher risk of OOB...
I have a new made BRP bolt Carrier, so I am not overly concerned there. The sear and disconnector are made by the company that makes the binary triggers so it seems odd to say they are not designed for it? I mean the AR15/M16 trigger group was designed for FA fire so I guess I am just not following what you mean there? I don't see anything that would scare me there.

As far as the firing pin, I do follow a bit there. Its likely to peen the end more quickly but only because you shoot it more. I see where that might cause an issues going to remove it. However I can't see where this would cause issues firing it. However if the firing pin is head treated correctly, just like other firing pins, it should be able to stand up to FA fire levels of firing just like lots of firing pins in MGs.

I don't have one of your guns and I don't know anything of your warranty. Its your warranty and your prerogative. That said, no I don't know I see why it would void your warranty. Frankly, if I was making them to sell, I would be figuring out a way to make this work as it would sure make purchasing one of these guns MUCH more attractive to anyone buying it to shoot it. Anytime a gun it shot more, it wears and eventually breaks. However I don't know that 10K shots spaced at 1 second apart would do significantly less wear than 10K shots all done with a Binary trigger.

Back to the OP, I would be interested in learning more.
 

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Having built more PS and semi-42s than I care to, on some of the last new semi builds, my solution to the destruction of the thin recoil spring retaining walls on the rear of the carrier was just to remove the walls and weld in the repair retainer that is much sturdier. Made my own repair ring just to have them around. Then the gun does not come back for that repair.
The issue of potential bolt bounce is considerably mitigated by the heavier bolt body. I install new recuperator springs, too as added protection against bolt bounce. Relieving the face of the extractor so it is flush with the boltface and relieving the boltface slighty are further experiments that I've done to protect against bounce. The idea is to use the elasticity of the cartridge case as a bit of a cushion when chambering a round and try to reduce or eliminate the direct contact of boltface and breechface. I have no empirical evidence these experiments are effective but they are worth a try.
Over many years, going back before post-May samples, etc I repaired quite a few 42s that suffered detonations before the owners were educated enough to check for ramp damage, use the bolt catches and have their recuperator springs replaced.
In my opinion, using the binary trigger will encourage development of a stronger more reliable semi-42 from failures due to it's use, but only if parts suppliers and builders want to build that customer base. If the current materials and build techniques are not up to the stress of binary trigger firing, make the changes necessary in materials and techniques so they are. Owners will continue to install binarys in their guns anyway. The current semi system is an excellent base from which to make improvements. FWIW
 
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