Monday, November 19, 2012

Carbon Fiber Shroud for the S&W 78G Part 2 Final

Nick and I are on a S&W roll lately.   Regular readers will recall that I recently cut a new barrel for my 78G gun to replace the poorly rifled original.   Alas, it's far too short for this shroud project.  Well,  I still have a non-functional Daisy 790 waiting in the wings for repair, so the barrel doesn't have to go to waste.

Back to the S&W 78G shroud candidate.  This was a "Toys that Shoot" Findlay, Ohio airgun show find from a couple years ago.

Basically just gonna make yet another--but extended--replacement barrel.  Lacking a piece of 16" long barrel scrap, a new Crosman 2260 rifle barrel will be sacrificed.

Since it runs completely through the shroud, it needs to be about this long.

Precisely cut with a hacksaw.

Tapered the muzzle end.

Started to thread the end 7/16"-20.  Later, I'll extend the threading and do final fitting from this end for length.

Turned the breech end down to 0.382".  Did this in inch-and-a-half sections, so I was always working near the chuck to minimize deflection.  Likely could've done this on the larger lathe in a couple minutes, but, hey, it was 30 degrees out in the garage.

Cut the leade.

Spotted for the transfer port hole.

Drilled 0.125".

After some test fitting to finish the leade and ensure the bolt closed properly, I extended the muzzle thread for the shroud.

Cut it to length.


This threads into the inside of the front aluminum shroud cap.

Right around fifteen inches of barrel.  Almost double the original barrel length.


Can't see it here, but there's a thin o-ring over the barrel between the gun and shroud.  No metal to metal contact.

Shroud OD was selected so as to not interfere with the iron sights.

At least it LOOKS like a suppressed S&W.   The carbon fiber shroud is light enough to shoot offhand effortlessly.  I find the marginal weight increase to be helpful for stability.  The velocity has increased a bit more than 100 feet per second.  It's now up from 420 fps to over 530 fps with RWS .22 Hobby pellets due to the additional barrel length.  Accuracy is marginally better than before--but still substantially better than what the stock S&W barrel could produce.  Given that the sight radius is unchanged, I didn't expect any significant improvement in accuracy--at least not at 10 meters.  It'll be interesting to get it outside and shoot at 25+ yards where the added velocity should flatten the trajectory.

Continuing the S&W kick, my next project will be (Finally!) getting that Daisy 790 parts gun up and running.  It's been sitting for two and a half years.