Ferritic Nitrocarburizing for Airgun Parts

Sidetracked by FNC?  Yes.  Yes I was.  

An opportunity came up to have some of my airgun projects professionally finished.  Extra space was available in a batch of parts last week.  The parts were to be Ferritic Nitrocarburized--a hardening and blackening process that chemically alters the metal surface with additional nitrogen and carbon.  FNC is also known as Melonite or Tenifer.  The finish is similar to a case hardening.  It's done in a molten salt bath at approximately 1000 degrees F that hardens the surface and makes it both highly wear and corrosion resistant.  

H&M Metal Processing in Akron ran the job.  Their website has a good description of the process.

I sent a couple barrel sleeves for break barrels and my multi-shot breech.  The previous cold blue jobs I had applied look good, but will wear through in spots after enough handling and require rework.  

But first, I had to undo all the time spent bluing and take the parts back down to bare steel. There was a bit of hesitation.  I didn’t exactly know what to expect from the FNC treatment.  Would the finish be uniform?  Aren’t the parts already good enough?  Steeled up my courage and minutes later, the parts were back in the white.  

And then they were in a box and out the door. 

A day later, the driver showed up and the parts were done.   Oily, but done. 

The parts are dark black— like a black oxide finish.  But now they’re black and around 64+ Rockwell on the C scale.  It’s unlikely the finish on the barrel sleeves will ever wear again.  The treatment sounds ideal for a break barrel air rifle. 

 

I’m thrilled with this process. Aside from a fresh abrasive blast to remove the cold blue, I did zero prep work.  This was a very last minute opportunity.

If/when this comes up again, the barrel sleeve on the Weihrauch 35E will be next in line.

Back to the QB78 re-seal real soon.

Volvo’s QB78 Deluxe CO2 Tanker Rifle Part 2

After too much internet hunting for this air rifle's exact model name, it turns out Volvo simply mixed and matched a bunch of parts from Archer Airguns.  So there you go.

Anyway, the CO2 was coming out as fast as it was going in, so I did some tear down.  We've covered the repair of the almost identical models in detail cataloged under AR2078A, Crosman 160, Crosman 180, QB77, QB78, TF79.  Find those blog posts using the index on the right of the page.                           —————————〉

Note the thinned bolt probe for more gas flow.  This is courtesy Rich From Mich.

The second barrel set screw looks like it was added by Rich.  

I don't know the origin of this riser plate.  I'm not seeing it on the current Beeman version of the rifle.  Thinking Rich machined this for Volvo so a 9oz paintball tank would clear the barrel.

The ice maker tubing transfer port trick.

Reference photos to help with reassembly.  

Finally, the valve.  And I don't have a valve wrench for this one.

Scrap of .750" DOM tubing.

JUST fits into the gas tube.

I made a quick valve tool.  The long cuts on the sides of the valve are one of the tricks used to help increase gas volume--and velocity.

Valve body o-ring looked like it was starting to go.

Don't think this is an original valve stem.  Looks like it was custom made from PTFE or acetal.

Some valve body o-rings.

A shot of Crosman pelgun oil for the seal.

On to the trigger.  Light pull, but there was something dragging in the initial movement.  Felt like it was clicking.

I'll do some polishing on sear faces later. The dovetailed trigger blade is amazing--why bother with the additional machining steps?

Small metal chip in the trigger.  Clicking gone.

This is the old trigger from my (also old) QB77.  Just gonna swap it in and see if it's a fit.

Fits!  

Replace with a hex head.

The o-rings on the barrel shank are torn up as they always are.  Front end of the breech usually has some sharp and snaggy edges that shave the o-rings twice--every time it's assembled and then disassembled.  

The offset drop block for the tank.  This offset is necessary for a paintball tank to clear the underside of the barrel.

That o-ring has seen better days.

Cracked in several places.

This is a normal o-ring failure in a CO2 gun.

Replaced with some viton o-rings.

One of the two M4 screws holding the drop block to the gas tube.   

The original fasteners seem to be made of some pretty soft steel.  I'm swapping these out for better fasteners as I go.

Here's another M4 fastener that anchors the stock to the drop block.  These also got swapped.

Except there was only ONE replacement in black oxide in my fastener collection.  The right side gets stainless steel for now.    Kind of a non-genetic caused heterochromia?   Sorry, it's getting late.

Some CO2 options below:

AirSource 88/90 gram CO2 cartridges work with an adapter.

This thing turns two 12g cartridges into an AirSource.  If that actually makes any sense.

Got it all back together and gassed it up.  Now, I'd like to give it a few days to make sure it holds before I start fiddling.