Slowing the ROF on the Max-31K

[strobro32]

This post is for those who may want to slow down the rate of fire on Lage Max-31K, that is made for the M11/380 SMG.

The ROF of my custom Gen1 steel Max-31K at 600 RPM.

The ROF of my Gen2 aluminum Max-31K is around 700-780 RPM depending on ammo.

I played around with some tungsten a.k.a "W" weights I found at Hobby Lobby (used for pine wood derby cars) to slow the ROF.

Here is the current Max-31K bolt.

Here is the selection of W weights. I used all 5 big weights. Collectively it added 2.45 oz to the bolt.
https://www.hobbylobby.com/Crafts-H...g/Pine-Cars/Cylinder-Tungsten-Weights/p/26239

Here is the W in the bolt.

It reduced the ROF from 731 to 589.

In either bolt configuration, the bolt never made contact with the buffer. I think the weights made shooting less bouncy.

 

[LotsaTiques]

I don't have one of those guns but man, they fit perfectly. Hobby Lobby no less. Who'd a thunk it!.....Good job!

David

 

[Dropsith]

Very cool. That's a surprising difference that those few weights make on the fire rate. I was thinking through a similar idea the other night to slow down an M10/45 bolt where you could mill a pocket in the bolt (would probably need to anneal, I've never worked on these bolts so not sure about hardness), weld in a small steel "rebar" then pour lead in the pocket to harden in place.

Maybe I'll try these weights instead before going through all that extra work. Small blocks of W on Amazon are not cheap, but derby car weights are. Great idea, thanks for sharing!

 

[Battering ram NIB]

Can I buy it back now? Very smart. I’m sure much more enjoyable too!!

 

[strobro32]

Can I buy it back now? Very smart. I’m sure much more enjoyable too!!

Sure.

 

[rybread]

Awesome, video? Good work!!

 

[Battering ram NIB]

Any concern the extra weight will damage your gun? There’s gotta be a reason Lage chose the rpm vs bolt size vs spring .

 

[nklf]

Do you plan to epoxy or solder the weights in place?

 

[strobro32]

Any concern the extra weight will damage your gun? There’s gotta be a reason Lage chose the rpm vs bolt size vs spring .

I don't think the added weight to the K bolt would hurt the gun. The Gen2 K bolt is very close in weight to the Gen2 31A bolt. 31A complete bolt assembly is 552 grams, and the 31K is 511 grams and 31K + W is 583 grams. The main difference between the systems is barrel length. I think the only problem could be how hard the bolt hits the sear, but since Richard relocated the sear notch further back on the bolt and the fact the bolt does not have the speed/force to hit the sear hard. Weight would make the bolt recoil less and have less force to hit the sear.

Richard removed weight from the K bolt over the 31A bolt because of the shorter barrel and the change in resistance between steel and aluminum uppers. Richard has a manufacture perspective. Parts commonality is a factor.

Of coarse, I could be wrong.

Do you plan to epoxy or solder the weights in place?

I have no plans to epoxy the weights into the well. I like that they are easily removable. I did tape the weights together for a snug fit to avoid movement in the bolt.

I had fun testing but there is a need for other experiments. It's up for sale again.
http://www.uzitalk.com/forums/showthread.php?94519-WTS-Max-31K-upper&p=840611#post840611

 

[m11stuff@hotmail.com]

You will get wear marks on the inside top of the upper. The weights will bounce around a little when firing. I did a similar experiment with the MAX-10/31.

When we design the bolt for each gun, we test it with a wide variety of ammo. You never know what ammo a customer is going to use. Weaker ammo can be problematic, so we make sure the gun will work with it also. So, yes, there is room to tune it for a specific brand/spec of ammo.

 

[Galil#1]

So for a M10/9 with your MAX 10/31 and 10/31k... other then your VBSs, what other "simple" methods/items can be used to tune up or down ROF, i.e. recoil springs perhaps etc.? Thinking plug n play by simple, not re-engineering to jack up your fine designs. Thank you kindly.

 

[Gaujo]

From Russia with love
https://www.amazon.com/Ruisita-Tung...ywords=tungsten+weights&qid=1629036651&sr=8-8

 

[Galil#1]

The Spy Who... never mind ha ha!

 

[Gaujo]

How did you mill the pocket Stobro?

 

[strobro32]

The pocket is OEM Lage.

 

[gt3499a]

From Russia with love
https://www.amazon.com/Ruisita-Tung...ywords=tungsten+weights&qid=1629036651&sr=8-8

I tried the amazonians kit. Dropped my rof from 609 to 571. Still choppy to me. I like the cfw-a in there better but it's an expensive way compared to this

 

[strobro32]

What brand of ammo was used? I did not find a brand that ran at 600 RPM.

 

[gt3499a]

118gr cast, coated hand loads, 5.3 GR WSF. It's not weak. Might be pushing the bolt back further than wwb

Usually faster with a can, but I was trying to eliminate variables