Donation

All Springer/NP/PCP Air Gun Discussion General > Big Bore AirGun Gate

Subscriber designed 3D printed offset reflex moderator

(1/5) > >>

mackeral5:
Several months back Subscriber and I were engaged in several moderator design discussions and eventually the topic of my little .357 blaster came up.  it is a gun I really enjoy shooting, but could not shoot frequently due to being so loud. 

81gr pellets running 750-800fps out of a 12" barrel is loud, and with a very fast opening/closing valve the muzzle blast is an extremely sharp "CRACK". 

The problem with this gun is there isn't much space between the barrel and tank for a large moderator.  All I had was a 1.25" OD moderator that was originally for a .22, which I bored to .357.  While it helped, the gun was still LOUD.  Previously Subscriber had mentioned offset moderators and in this instance, the timing was right, I was in the mood to try something new so why not.  Let's try one out. 

A lot of back and forth with Subscriber and another board member (who graciously contributed the printing expertise/capability) took place over the course of several weeks.  Lots of test printing, etc.  This gun presented an additional challenge of having a slip-on (glued on) 1/2-20 adapter that created a bulge at the end of the muzzle, which was significantly larger in OD than the barrel itself.  This meant the reflex portion would have to slip over the bulge, but then have a way of being secured to the smaller diameter of the barrel. 

This gun was designed to be modular and has many different possible configurations.  Here is a pic from early in its life, one of many configurations.  This one shows the limited space for a moderator. 



This pic shows the 1/2-20 muzzle adapter and its OD being greater than that of the barrel. 



Later I added a breech riser which helped a bit, and allowed me to run larger OD tanks. 

Here is the gun as it sits today.  12" barrel with Subscriber's offset reflex moderator.  As configured, it is tuned for 20-25 shots of 81gr pellets with a 750-800-750fps bell curve.  Regulating it will yield a tighter string, but for such a short range gun I found regulation to be an unnecessary level of complexity, while it also limited the gun's energy potential.  Unregulated I can lean on the hammer spring and get a much shorter string, but above 800fps.   With the 16" barrel it maxes out just under 200fpe.  While I do not often use the gun this way, it is neat to dial it up every once in a while.

 

Believe it or not the moderator is not affecting the scope's field of view.  When on low power, you barely see a slight blur at the bottom.  I can shoot this as often as a I want with no worries of disturbing neighbors.  Earlier today I was smacking my 70 yard gong and squirrels were cluelessly running around the area, largely unaffected by my discharging 100fpe in their direction.

A few more pics.

Rear showing threaded hole to allow the muzzle bulge to pass through.



The split nut with tapered threads designed by Subscriber and the member contributing 3d print services/expertise.   This is a very trick piece, printed from a flexible print material.  A very slick solution to the problem created by the bulge at the end of the barrel. 

 

And the muzzle end.



I was very skeptical of a 3d printed moderator on my .357 blaster.  After a few hundred rounds of early testing, regulated at 1800psi and tuned in the 100fpe range I became confident in the design.  That is when I reconfigured the gun as unregulated, which when using the 16" barrel and leaning on the hammer spring can produce just under 200fpe.  To date the 3d printed guts epoxied inside an aluminum tube have shown no signs of movement.

All in all this was a very satisfying experience.  3 GTA members who had never met nor heard each other's voices, living across the US, collaborated to design  and manufacture a one-off solution for a very specific application.  The design proved to yield a very effective end product that was very easy to assemble.  a piece of 2" aluminum tubing and epoxy is all that was required after having the 3d printed pieces made.  I made a few mistakes in the assembly process, but thanks largely to Subscriber's design efforts the design was very tolerant of and I was able to recover from those mistakes.   



Hopefully my fellow collaborators will see this and chime in with additional details around their areas of expertise.

tennx:
⭐️⭐️⭐️⭐️⭐️…..I gave it 5 stars Incase they don’t show up here….u and your collaborators got mad skilz….kudos and good luck

naptemp:
Can you share the STL files?

3crows:
That is a cool rifle and an interesting muzzle device for sure!

I am more interested in what barrel that is and how does it attach to the breach/receiver?????

Nice work :).

subscriber:

--- Quote from: naptemp on July 22, 2023, 09:10:17 PM ---Can you share the STL files?

--- End quote ---

John, I am not sure what the STLs for a completely custom design would do for you?  If you just want to see what is inside, perhaps the section images below would help?

The hollow box sections front and rear are assembly alignment features, that are removed after the epoxy between tube ID and inserts, and between the front and middle inserts has set.

The concept features a "can in a can" design, with a large eccentric wrap-around forward blast chamber, ahead of the large reflex blast chamber.

Navigation

[0] Message Index

[#] Next page