Offset moderator for .25 Huben Pistol

[subscriber]

Yesterday, a fellow forum member contacted me via PM, asking if I could design a muffler for his .25 Huben pistol. Specifically, 1.5" OD x 5" long. It needed to have an offset bore, so the stock sights would not be obscured.

I whipped up the design below in about 8 hours; then made some improvements to include a printed 1/2-20 thread version, and a version that would accept a 5/8" - 11 / 1/2 - 20 thread insert.

As I did this design for free I retain the right to share it as I see fit. Anyway, I notice some guys asking about offset moderators for the Huben pistol. So here is a potential candidate that anyone could 3D print for themself.

No one has printed this design yet; let alone tested it. I have no control over your material choice or print quality. So, should you print one for your own use, you assume responsibility for your own safety. If I was selling the design or parts, I would have test results indicating acceptable performance, strength, durability and grouping ability.  I am in a sense posting this design before it has been proven; partly because I just posted it on AGN, where the Huben pistol bug seems to have bitten hard.

The design sports a "can in a can" approach, to have a longer path that "looks conventional" to the projectile. This is to reduce the time the projectile spends travelling through asymmetrical turbulence.

The design has 4 mm thick walls around the primary blast chamber. That chamber communicates with a forward offset expansion space via 16 x 2 mm diameter vent holes. The rear of the primary blast chamber is cored out with slots around the barrel stud thread, These slots are to reduce pressure wave bounce in the primary blast chamber. Ahead of the primary blast chamber the wall thickness is thinned down considerably because the bulk pressure is lower there; and to keep the unit mass close to 100 grams.

The forward-most expansion chamber vents downward into its own offset space, via a single large triangular opening. The triangular shape is so that the unit can be FDM 3D printed, while standing on its front end; threaded end up. That is the only position in which this part can be FDM printed.

I will need to attach the STLs in their own zip files due to the low number of bits allowed on GTA per attachment.

[subscriber]

Same design as above, but for thread insert.

STL inside attached ZIP file

[subscriber]

I forgot to add that you will need to use shim washers to clock the offset OD out of the line of sight.  0.025" and thinner shim washers.  Or, if you print the muffler version that accepts the thread insert, that can be rotated slightly to clock the offset to any position when installed.

[Mr.P]

That looks beautiful - pretty big service you are providing there subscriber

I’d love to get one of these airguns.  Some day!

[Back_Roads]

 I recently started reading the Huben post on AGN, I got to where everyone wants them quiet now, need to finish catching up, I do not want any added length, but for indoor shooting it would be nice.

[subscriber]

Forgot to mention that the threads are deliberately tight for maximum strength; intended for chasing with a tap.  If you want a low intervention experience, set your print slicer X and Y axis to 101 %, but leave the X axis at 100 %.

In any event, printing only the threaded section first is a good idea so save time, until you have confidence in the thread fit.

[Back_Roads]

 I have no printer, but would do a test fit etc...

[subscriber]

I had a request for more muffler configurations for the Huben pistol.  A 1.5: OD x 8.5" long offset version; and an oval muffler with more sight plane offset; 6.5" long and 1.5" at the widest point.

See images of the trio of Huben pistol mufflers below.

The STLs for the latter are too large to attach to GTA, even when zipped.  However, they can be found here:

Oval:
https://www.airgunnation.com/attachments/oval-offset-huben-pistol-25-ldc-1-5-x-6-5-inch-half-20-thread-zip.387945/

1.5 OD x 8.5" long: 
https://www.airgunnation.com/attachments/stl-for-offset-huben-25-ldc-1-5-x-8-5-inch-half-20-thread-zip.387492/

Rotate part in slicer to ensure that you print with threads facing up.

[Back_Roads]

 Down loaded will see if I can get a print.

[subscriber]

It would be great to get some feedback, James

Obviously these mufflers can be used on other platforms than a Huben pistol.

[subscriber]

I just noticed a typo in the quoted text below:  Leave the Z-axis alone and adjust the X and Y axiis, if you want the adjust the thread fit.

Forgot to mention that the threads are deliberately tight for maximum strength; intended for chasing with a tap.  If you want a low intervention experience, set your print slicer X and Y axis to 101 %, but leave the X axis at 100 %.

In any event, printing only the threaded section first is a good idea so save time, until you have confidence in the thread fit.

[miksatx]

5" in PETG and 1 in ABS on the plates printing at this time. really nice looking ldcs Peter.

[miksatx]

Vyper crashed and died. So no ABS one drats.

[subscriber]

Thanks Mike and MrP for your positive words.

Bummer about the print failure.  Thanks for giving it a go, Mike.

[miksatx]

Thanks Mike and MrP for your positive words.

Bummer about the print failure.  Thanks for giving it a go, Mike.

Shopping for a new printer. Parting out the viper. For 199 bucks it printed lots of ldc lol.

[miksatx]

my last surviving Crosman project. .22 shooting 14.3 16ftlbs.

[subscriber]

Mike,

That looks like the 1.5 x 5" offset Huben muffler?

It was designed "strong" for 80 FPE, so it might not be as effective as some of my lighter but longer designs.  What are your impressions?

Thanks

[miksatx]

Mike,

That looks like the 1.5 x 5" offset Huben muffler?

It was designed "strong" for 80 FPE, so it might not be as effective as some of my lighter but longer designs.  What are your impressions?

Thanks

It is the Huben muffler  not bad on my 16ftlbs without it shouts 120.5dBA with the huben 118.3dBA. I can definitely tell the difference lol.
I do have a new airgun a AEA Element ultra light .30cal it’s generated 73 FPE. I’ve got a Donnyfl Sumo for it.  3lb 4oz scoped.  Sent it back to the shop so they could install a 300 cc tube adaptor.

[subscriber]

Thanks, Mike

That looks like a monster.

[miksatx]

Thanks, Mike

That looks like a monster.

Any chance I could get you to do the offset Huben in.30 cal?