Monday, February 17, 2014

The KL-3B Fast Deer -- Part 3 Final?

With the ID of the compression tube cleaned up, I decided to lose the leather piston seal and go synthetic. 

Just unscrews from the head of the piston via a M5 phillips head bolt.

I've used these seals before.  Get them from Crosman (part #B18-04-1A) for about $1.10 each.    Cheap and they work.

Had to make a simple adapter from aluminum rod.  It's exactly like the one I made for the Benjamin Sterling.

Through drilled to clear the M5 bolt.

Countersunk for the flat head.


Cut the taper to interface with the 60 degree (included) angle on the new seal--

--and parted off.

Scrounged up a stainless flat head M5 bolt.

Installed.  Not shown--chucked the entire piston in the lathe and dusted a couple thousandths off the edge of the seal to get a better fit to the compression tube.

Test fit.

Here's the other end of the compression tube.  I thought that the transfer port was on the large side at 0.156" diameter.  Going to sleeve it down to 0.125". 

Found a 5C collet.

Finally, an excuse to use my horizontal/vertical collet holder.

To make this easy, I set this up on the mill and used a 5/32" (that's about 0.156") drill bit to line up the drill chuck with the hole.

Then changed to a #8 drill bit and opened up the hole to 0.199".   

And tapped the hole M6 x 1mm.  Now, it's a simple matter to make different sized transfer ports.


Had a piece of M6 threaded aluminum.  Through drilled it to  0.125"


Cut it to length and slit the end for a screwdriver blade.  Here its been installed with a low strength loctite.   It's really just a hollow setscrew.  Like I said, simple.

Went through the mainspring box and found what looks like a good candidate. (The bottom spring)

Installed the sliding compression tube.

Then the piston.

Followed by the anti-bear trap  mechanism.

Then the spring. 

Used the mainspring compressor to press in the end cap.  A drift lines up the holes and acts as a slave pin.

Installed the cross pin--don't forget the trigger blade.

The piston rod safety.

Dug out the misc. spring box...

and found a lighter trigger spring.

Reinstalled the cocking lever,

and hit the parts bins again to find some sights.

This'll clamp to the dovetail.

This is not at all what I was hoping to see down range.  And these are the GOOD targets.

RWS Hobbys, Noricas, H&N--even the 5.6mm Eley Wasp pellets all failed to produce a single credible group.  A quick re-crown also didn't make a whit of difference.  Pulled the open sights and installed a scope.  No dice.  This gun simply won't group.

The only good news I've salvaged is the velocity after the compression tube hone is remarkably consistent:  398, 402, 402, 397, 404, 399, 402 with .22 cal Hobby pellets.  Low powered, but consistent. My almost identical power plant BAM B3-1 puts the same Hobby pellets out in the mid 550's.  So what gives?  Well, the bore on this Fast Deer is on the large size and does little to engrave the rifling onto the pellet.  My gut feeling is the pellet is so loose in the oversize bore, it's half way down the barrel before the piston has a chance to build full compression.   I'm pretty comfortable saying that the only fix to both the accuracy and velocity issues is a new barrel.  Sorry, but I'm calling it quits and shelving this one for the time being.  Too much effort, not enough reward. 

Here's what's on deck:  My Marauder has developed a slow leak.  About 500 psi over the course of a month.  That's up next.  Followed--hopefully--by a .25 cal Webley (Hatsan) Patriot that needs some love.