@Johnksg I think a ak recoil spring is similar in diameter as the s2k. Maybe the ak spring is stiffer? Cz uses a shim to tension the spring on the scorpion. That might be the better option.
Depicted below is what seems to be an evolving consensus on an alternative charging handle design. It makes no reference to the material used, but it does depict the supporting circumferential “wings” that ride along the bottom of the bolt tube/receiver to relive some of the stress on the CH shaft and a U-shaped notch for the recoil spring to retain the CH. I also added additional support for the wings. Since this CH design is unidirectional, I also depicted one of many alternative shapes that could be used other than the round shape imposed by the existing design. Perhaps seeing it depicted this way will help us all better refine our thinking. (The “wings” are omitted from the side views because they would block the view otherwise).
For example, now that I have drawn it, I think perhaps the U-notch should extend to the sides of the CH shaft and the recoil spring should be fitted with a firmly attached metal end piece shaped something like the piece at the bottom of the illustration. That might make reassembly a bit “fiddly” but once done the CH would be firmly held in place.
@CatFood AK springs are built around a linked shaft (at least the combloc ones were). Not sure that would work so well.
@JoeFridaySays Brian that is some nice work brother! If you keep this up your gonna have to quit your day job!
Before this thing gets built some one will have to run some prototypes to see how much drag is generated in order to dial in the proper spring tension.
@Johnksg As a trial lawyer, helping folks who really need it is usually enough to get me up in the morning - well, that and the paycheck; which isn’t as good as people think. But there are days like today when opposing counsel is being a completely unreasonable horse’s a$$ that your suggestion sounds like a really great idea.
This version may never get built, but it looks like @CatFood may have his prototype done tomorrow.
@JoeFridaySays will that wing come near the users face though? Some people (myself included) rest their face at the forward end of the receiver.
@Kona That’s a legitimate question. Assuming the CH can be pulled in tightly, I am not envisioning the “wings” extending more than an additional quarter of an inch and certainly not even up to the base of the serial number. Testing might be appropriate but I do not believe much additional real estate would actually be needed to spread the stress - IF most of the slack is removed. John may have a different opinion.
Where do you rest your face? Would wrapping the top of the CH around the bottom of the bolt tube/receiver that small extra amount bring it appreciably closer to your face?
@Kona Just to be clear, my estimate of how long the wings would need to be is a total SWAG. My engineering degree is from the John Deere school of duct tape, baling wire and bubble gum.
Nice Work’ Hell of Idea’ And the Thought Put into It !
@Kona you plan on resting your face under the receiver tube? Suck it up buttercup - I am sure their will be some fitting and trial and error involved.
@JoeFridaySays some of the greatest firearms designers came from that school!
I really don’t think the wings need to be that large to do the job. Just a close fit, and I think that has been covered.
The drag should be minimal - can tune up the spring idea once there is a proof of concept.
@Kona you think we could get Chris to knock out a few prototypes for some simple beta testing?
I would even offer to chip in towards costs?
@Johnksg they have multiple CH already established. The chances of them diverting resources to work on another are pretty slim. Not trying to speak for MCARBO at all, just the observations of a long time customer.
@Kona besides they sell you a lot of them!
Actually I get that…not trying to give away MCARBOs money.
But you know this is kinda cool if it works, and actual part completely designed on a forum!
I am looking forward to what @CatFood comes up with.
@Johnksg MCARBO parts have a lifetime warranty, I technically only ever had to buy one if i wanted to make a claim. I’ve only bought more to support them. Don’t need a handout every time haha
Right now I’m choosing the steel/aluminum for the bolt rod. I’m thinking of testing s7 tool steel, inconel 600/718 as well as 6061 and 7075 aluminum. Not in a rush at the moment as I’m dead busy with work (on break now lol). I’ll be using 1" delrin rod for the handle.
After looking at the RCH I noticed all edges are quite sharp and not that rounded. Especially where the shaft meets the CH. It’s a sharp edge and no chamfer (or what ever it’s called. The spring perch edges are pretty sharp too.
@Kona, yikes that’s close!
@Kona Looks like you better stick to breaking them! And start setting aside money for dentures down the road. Seriously, man. Doesn’t it beat you to death with that cheek weld? I don’t get down on it nearly that far and still feel like I’ve been on a bucking bull after 150 rounds. You the man!
@JoeFridaySays here’s another angle from the range the other day. That wing would slice my throat haha
@Kona I actually think it would be less of a risk to you than the two fingered one you are using which actually does have an edge zipping past your throat. My limitations as an illustrator are influencing your assessment and you are seeing sharp edged wings where their are none. It is too late to draw something, but imagine an oar (the receiver) in an oarlock (the wings). The edges of the wings would be rounded and snug against the bottom sides of the receiver.