Wednesday, April 27, 2011

An Aperture for the IZH Diopter Part 1

Needed an aperture for the sight purchased at Findlay. Blog reader Duskwight correctly ID'd it as an Izhmesh biathlon rifle sight.

The silver adjustment knobs are plated steel. The diopter has some heft to it--surprising to me for a biathlon sight. I would have expected it to be lighter.

The hole size for the aperture has a (non-standard?) M9 x 1.0mm thread. Is there a standard? I think some of the Chinese rifles use M8 x 1.0mm.

Here's an aperture from a different target sight. It's essentially the piece I need to make.

Pretty straightforward. But this one has an M9.5 x 1mm thread and fits sights like Anschutz, Feinwerkbau, Walther, etc. so it doesn't fit this IZH sight.

Found a 1" diameter 6061 aluminum rod and cut about 2" off the end.

Faced both ends.

Cut a couple shoulders.

Taking one end down to my threading diameter of approximately 8.95mm.

Added a few steps to make the transition more aesthetic.

The first step from what will be the M9 thread is 12.5mm in diameter. I took some care to get the face flat as this will bottom against the block in the diopter.

Chamfered some of the corners.

Only had a hex die in the M9 x 1.0mm thread, so I used the milling vise as a holder. Was able to cut the thread to full depth by rotating the headstock manually. The carriage wasn't locked so the entire carriage advanced into the workpiece as the thread was cut. Worked perfectly.

Made a relief cut at the base of the thread. It's darn near impossible to cut full depth threads right to the end, so this allows that 12.5mm shoulder to index and seat flat and tight to the sight.

Just a couple more views.

It's good practice to cut threads on a solid rod if possible. Bore it out after the threads are cut or there's risk of collapsing the tube while threading.

The aperture will be used with a rubber eye shade. Usually, the eye shade snaps over the front lip of the aperture for attachment. Works just fine, but I had left some extra material--mostly so the 3-jaw had something to grip while cutting the thread. Decided to leave the extra material on the rim and cut a groove for the flange on the eye shade to fit into.

Getting there.

Used a boring bar to cut a relief.

Done except for the through hole.

I flipped the piece again and drilled out the threaded end. I think I used a 13/64" bit. Wanted to leave just a thin wall of aluminum to drill the sighting hole through. The problem was, I didn't leave it thin enough. No pic of the problem, but I attempted through drilling the hole with a 1mm bit. Of course, the microscopic drill bit snapped off flush in the hole... I had a few choice words when that happened.

More later.

Haenel 303-Super Picture Addendum and Chrony Numbers

The sun came out today so I thought I'd take advantage and snap a couple better pics of the new
barrel weight.

The 3/4" OD tubing was the largest size that would still blend into the front sight band. Didn't want to have to channel the weight for the front sight as this was supposed to be simple.

Here's the 4mm set screws.

Still needs an accessory rail and a hand stop.

Ran the gun over the chrony and it's putting out RWS .177 cal Hobby pellets at an average of 659 fps over a 30 shot string.

The next project will be an aperture for the IZH diopter I found at the Findlay, OH, Toys that Shoot show. Hopefully, just some basic lathe work.

Should have something up in a couple days.

Sunday, April 24, 2011

Haenel 303-Super Reassembly and Muzzle Weight

All set to reassemble the 303 until I noticed the breech seal was dead flat. Might have even been rebated slightly. I don't think that's a particularly good thing for a breech seal. Could have just shimmed it out, but for the time it would have taken me to make a shim, I opted for a new seal instead.

Dug it out, guessed at the correct thickness...

and found a scrap piece of a dead leather sling.

A couple punches on a block of wood,

and we're in business. Hit the seal with some pure silicone oil then started to put the gun back together.

Skipping the boring stuff. Painted the mainspring with a coat of moly.

Even skipped the spring compressor since I knew how little pre-load was involved. Used a deep socket and just leaned into the workbench. The plate and cross-bolt went together easily.

This gun doesn't require the barrel be attached to the compression tube before the mainspring is installed. Moly'ed the daylights out of the pivot joint and barrel latch. Excess will be wiped off.

Pivot bolt snugged up.

Lock bolt installed.

Trigger unit goes up then forward into the tube.

Like so.

Installed the end cap (I ran out of enthusiasm to make a steel cap) started the cross pin, installed the safety lever and drove the cross pin home. It's not a tight fit. It just keeps the trigger group in location.

Had to deepen the spring seat about 1/16" to accommodate the more substantial steel "button" made in the last post.

Button with a bit of moly. The cocking lever sits on top of this button and slides across the face as the rifle is cocked. The spring loaded button pushes the cocking lever upward against the compression tube. Installed all the stock bolts and trigger guard and test fired the gun. Vibration is now virtually non-existent, though the gun still has some recoil. No surprise--it's at least four pounds lighter than a typical 10-meter rifle. Trigger is now in the realm of useable. Feels pretty much like a Rekord at this point. I'm not really interested in making this an eleven pound target beast, but the gun does need some additional muzzle stability.

Ordered a piece of 3/4" OD steel tubing from Speedy Metals. It's a DOM tube--Drawn Over Mandrel--the tolerances are typically tighter and the seam is essentially removed during manufacture.

It's not quite the slip fit over the barrel that I'd hoped for. It has an ID of 0.560" but the barrel measures between 0.555" to 0.562". Gotta open the bore up a tad. I don't have a boring bar 4" long so...

Chopped about 8" of tubing into three random length pieces.

Faced all the ends on the Taig.

Then bored all the pieces out. The longest piece was bored out just beyond half it's OAL, then flipped around in the jaws and finished. The amount of overhang shown here didn't work well.

The steady rest took care of the flex from the tube. Now, the flex from the boring bar was another matter--but it worked.

Two of the three pieces bored to size. Testing involved trying to slide them over the muzzle. Tricky.

The medium length piece was voted most likely to be tapered.

The compound was used on the crosslide to cut the taper. I didn't measure anything--just set an angle that looked good.

Lot of light passes at this stage will cut the final finishing time tremendously.

The three pieces lined up. About seven-and-a-half inches here after-all-the-facing.

Chucked each piece and sanded. Yes, the lathe bed was protected with extra aluminum foil from my hat.

A fine sanding pad followed by 500 grit emery paper worked well.

Need some set screws to attach the weight to the barrel. Luckily, I had just enough M4's--all the gun's fasteners are metric, so I try to stay consistent. A #30 drill bit is pretty close to the tapping size I need.

Centered up a vee block and spotted the pieces with a center drill.

Followed by the #30.

The long piece gets two set screws, so to put them in the same line, I drilled and tapped one hole before drilling the second.

I left the tap still threaded into the first hole sticking up.

By sighting from the side, I rotated the tube until the tap appeared parallel to the drill bit. It's not the perfect solution, but it works well enough for projects like this.

Still trying out the Van's Instant Gun Blue. So far, the "after-rusting" that plagues most of the cold blues hasn't happened. Van's is supremely easy to blend and doesn't wipe right off on an oiled rag the next day. It's possible to really buff the work with steel wool and the bluing stays put. So far, I think it's a winner.

Looks like a close color match. Really trying to make the weight unobtrusive. Want it to look like an original part from the factory.

The, uh, front sight.

Lots-o-options. Like no weights.

Or one weight...

Two weights--option A.

Two weights--option B

Three weights. Heady stuff!

The three combined add just over a quarter pound of additional weight to the muzzle.

Final: Well, sleeving the transfer port took care of the piston hammering into the end of the compression tube. As I was shooting the gun this evening, it was so nice, it was almost easy to forget just how bad it actually was from the factory. It's now very, very close to what I envisioned this old gun to be when I first saw it.

I didn't have time to set up the chrony, so next time it's out, I'll probably throw some velocity numbers in here.

I'm calling it quits on the Haenel for now. I'll probably come back to it in a couple weeks. Entertaining the idea of inletting an accessory rail into the forend. Yeah, the rail is already sitting here, but I want to do some work on the new TF79 from Guy first.

More soon.