Saturday, August 29, 2009

Crosman 600 Grips Part 1

Yep, typecast as a grip guy. I already see it coming. Look, it's like this, I bought another Crosman 600 and the right grip panel was badly cracked. I needed to come up with something. So, just a simple set of replacement grips this time. Pretty much a copy of the originals, but in wood. Oh, and just a bit more secure on the gun so they don't wiggle around--and it would also be nice if they look somewhat presentable. That's pretty much the only criteria.

Had a 1/2" thick cherry board. Just traced the old grips. Left some extra on the top.

Chopped them out with the scroll saw.

Sanded the top edge flat on both sides. The flat edge will be the reference point to fit the grips to the frame.

Only 120 grit, but it's enough. The top flat edge goes against the grip frame and buts against the gas/valve tube. Marked the holes with a transfer punch and drilled through for the grip screws. Pics??? Uhhhh, dog ate them?

Inletting is minimal. After getting the mounting bolt holes drilled, there's a small pin at the bottom rear of the grip. Pressing the grip against the frame will indent the wood at the location to drill. Drilled the grip with a bit the size of the pin--1/8" I believe. The pivoting safety lever on the left side was easy enough. Eyeballed and pencil marked the limits of travel.

Then, a sharp router bit, and I was done with the safety lever notch in under 2 minutes. I took some wood out from a couple other spots at casting marks just to ensure the grip sits flush. Pressing the wood against the grip frame left imprints to use as guides.

The next hurdle was the lack of threads in the frame for the grip bolts. On the plastic factory grips, the right bolt goes through the entire frame and threads into a nut in the left grip. Crosman used a #6-32 bolt and it never comes close to touching the sides of the hole in the frame. It's a sloppy fit at best and contributes substantially to the play in the grips. It was a feature I didn't want to copy. I thought about just tapping the frame and threading bolts directly in. Not a bad idea at all, but I decided to try a threaded bushing first.

Chucked a piece of scrap drill rod into the lathe and faced both ends.

Center drilled then through drilled with a #36 drill bit.

Tapped the bushing #6-32 then turned it down to fit the hole in the grip frame. I tapered one end slightly so it was a snug press fit. I had to drill and tap first before turning the OD down, otherwise the thin tube would have collapsed when tapped.

Cut it to length and pressed it in. The grip screws can now thread into a zero play bushing. If I ever need to reinstall factory grips, the bushing can be either pressed out or two #6-32 bolts can be used instead of the bolt/nut arrangement.

Counterbored both grips for the #6-32 bolt heads.

And bolted on for the first test fit.

There's some nice grips in there somewhere.

Got my #2 pencil ready. Just marked the edges where the wood overhangs the frame.

Then sand that off...

This was faster to sand the bottom edges.

As well as removing copious amounts of wood from the sides.

Right-side test fit. The scribble marks are areas to be thinned. I made the right side first--no real reason. The right side just had less happening so it was easier.

The original left grip on a Crosman 600 has a pronounced thumb rest that I really want to duplicate.

A lot of wood has to be removed up top to create that thumb rest.

Taking over half the grip thickness off areas on the left panel.

Slowly getting there. The ridge for the thumb rest is at the full 1/2" thickness.

Forming up the rest using a small drum.

Still playing with the lines. Sometimes it works, sometimes it doesn't--like here. Too angular on the edge of the thumb rest. All the other lines are curves, so the sharp transition line doesn't work aesthetically. I'll either put a more gradual transition into it or just make it into a continuous curve starting at the heel.
Sanded so much off, I lost the counterbore. Drilled another.

Test fit. Still getting there. Grip feels too chunky in the hand. Lines are still not quite right.

The 600 grip frame is thick. The grips will need to be much thinner for comfort. Here's a great view of the thumb rest. Way too sharp of a transition. Still need to do a lot of sanding.

More to come.

Wednesday, August 26, 2009

Tweaking the IZH513M Rear Sight, Part 2

On I go...

You can see there's a bit of a deformity in the elevation bracket, as well as ample play.

It wiggles side to side with a huge gap.

This shows how the left side is not parallel to the right. I tweaked it by bending it gently.

The pivot holes have a nasty burr...that got filed off.

I made some thin delrin washers to try and eliminate any play.


Parting off each washer...

The washers in place.

Then I found that I needed another washer between the knurled head of the but and the outside of the bracket.

In place. This thickness was hard to get right, as the screw has to securely lock the sight to the dovetail and allow the elevation bracket to move.

Just right, the spring can push the sight up but there's a small amount of drag.

Reassembled, you can see there's a lot less twist. And I'll probably end up putting a scope on it after all of that!

Tuesday, August 25, 2009

Tweaking the IZH513M Rear Sight, Part 1

I know, I'm a bit sight obsessed...

The sight on the 513M was a bit twisted off perpendicular.

The sight is fairly simple.

It mounts on a dovetail milled into the breech.

The main reason it's twisted is the elevation screw bears on one side of the sight and there is enough play in the pivot that it twists upwards on the other side...

The elevation screw underside.

One screw is both the pivot and the mounting screw for the sight base.

Screw, knurled nut, spring and elevation screw. Notice the dimple that locates the spring.

The base slides off.

The leaf sight is mounted as a unit to the elevation bracket. Notice the little dimples and the screw that bears against them? You can adjust side to side for gross windage, and there are two rows so you can alter the presentation of the leaf sight...

Angled back...notice the burr on the end of that screw...

Or perpendicular...

The sight unit.

Fairly simple again, just a screw, stamped sight and spring in a tube.

Machined from solid round stock...
More to come...