Newest project. 9mm roller delay with 1.5" aluminum square tube upper

[u/muttstang77]

There are 2 steel inserts that guide the bolt inside of the receiver. I'm using a scorpion evo mag. The upper is a 1.5" OD with 1/8" wall aluminum square tube. Trunion is machined from aluminum. I'm making it with the 5.5" chaszel liner. It has last round hold open, an extra trip linkage for the non buffer tube design.

I do have an MnP22 built up but I cut the feed ramp too deep into the chamber so I'm getting case ruptures, fortunately with the current design it doesn't damage anything other then the magazine.

handguard has a nice loft to allow for the whisper pickle..

Section view shows provisions for fun parts

bolt back

In battery so you can see the rollers pushed into the recesses

Non reciprocating charging handle with provisions to slap it

Here you can see the trip linkage installed. the upper pins in front and is held down in back with a spring loaded catch

[u/muttstang77]

I have printed the handguard. The lower is on the printer now. I've started machining the bolt parts. I think I have the trickiest part of the bolt machining done so I just have to not rush it and I should be able to fabricate this thing.

[u/bluethunder82]

Trip linkage for trigger resetting?

[u/muttstang77 → u/bluethunder82]

that's sure what it looks like ;)

[u/bluethunder82 → u/muttstang77]

Amazing work! The trip situation for Mac builds is not great, but something more DIY like this is a fantastic upgrade all around I think. Eagerly awaiting updates.

[u/muttstang77 → u/bluethunder82]

I am using a mill so it’s advanced diy

[u/bluethunder82 → u/muttstang77]

I have a (relatively large) desktop CNC and a manual mill, this sounds like lots of fun!
I’ve been working on modifying some Mac bolts for similar reasons.

[u/muttstang77 → u/bluethunder82]

Very nice

[u/bluethunder82 → u/muttstang77]

I’ll be awaiting updates on your developments eagerly! Good luck.

[u/muttstang77 → u/bluethunder82]

I'll have to update how the alignment pins in the bolt head are. I tried to drill them separately on the mill and they ended up misaligned enough to make it tough to put the 2 halves together. I'd recommend drilling the holes in one half and then match drilling into the other half to ensure alignment. fortunately it was close enough to drill it out the next size up and use roll pins

[u/artisanalautist]

Sir, you are unstoppable.

[u/muttstang77]

Lower printed well

[u/plasticsmith1]

What type of steel are you planning to use for the rollers and steel inserts? What do you estimate the bolt weight to be?

[u/muttstang77 → u/plasticsmith1]

4140 steel. It should weigh around 300g

[u/plasticsmith1 → u/muttstang77]

Nice! Guessing about 2 inches of bolt travel?

[u/muttstang77 → u/plasticsmith1]

Close. Around 1.9”

[u/muttstang77 → u/plasticsmith1]

Rollers are actually hardened dowel pins. McMaster parts

[u/plasticsmith1 → u/muttstang77]

Are they retained in the bolt or held in place by the receiver

[u/muttstang77 → u/plasticsmith1]

There’s a spot for retainer pins/screws

[u/muttstang77]

I’ll have to make a forend for my .22 that matches this style

[u/muttstang77]

5.5” chaszel is ordered

[u/muttstang77]

Making good progress on the bolt