Derrick's IZH 61 Tune Part Uno

Alternative working title: Armchair tuners please be kind.

Been shooting the IZH 61 for about 2 weeks now. I've been shooting it exclusively at 10-meter rifle targets and thinking about what I like and dislike about it's firing characteristics. It's pretty mellow as is, but I thought I'd see if I could make the shot cycle less twangy. And, just for fun, (and so you could see how badly I screw this up) and partly to get a baseline, I shot the rifle across the chronograph. Over 20 shots, the velocity ranged from a low of 498 to a high of 513 feet per second with RWS Hobby pellets. Good enough for paper punching.

Now all the bad news up front: It's always a safe bet that there will be velocity loss with a "lube tune". Anyone who tells you they just moly greased a bone-dry gun and got another 100+ fps should be treated with great suspicion and a wary eye. At this point, I wondered how much speed I'm willing to sacrifice to lose the spring vibration. Considered, too, that the Hobby is a lightweight pellet--so, it's already on the high end of the velocity range to begin with. Also looked at the spring through the cocking slot and noticed that it's at full compression when cocked--so there's really no room to shim the spring. Oh, man. This is gonna look bad if we just look at the velocity numbers later.

Here we go.

Removed the telescopic stock.

I removed the HW front sight (just unscrews from the barrel) and the Beeman Sport Aperture sight I'd installed here. Not necessary, I just didn't want to damage them inadvertently. Took out the 3 stock screws and set the stock safely aside.

Unscrewed both trigger/sear pins.

Took a good look at how the trigger and sear assembly fit together. Took a few pics at different angles in case I needed reference on reassembly. IZH manual refers to this as "sear 2". The trigger and "sear 2" are held by the rear pin. (IZH manual calls them "threaded pivots"--nice!)



The IZH manual calls this "sear 1". It's held by the front "threaded pivot".

Removed the circlip from the cocking lever pivot...

And pulled out the base of the cocking lever. I slid a pin punch into the pivot hole after I pulled the cocking lever out as a safety precaution.

Fished the "rocker"--the hinged part of the cocking lever that fits into the piston body--out at the front hole in the cocking slot.

Bracing the end cap against the work bench, I pulled the pin punch out and rotated the cap about 25 degrees. This removed a locking tab from a notch in the compression tube. Carefully let the spring ease out. The spring is only under about 30 lbs of preload. I didn't think a spring compressor was warranted. Do wear eye protection.

Piston and it's synthetic seal.

Used a diamond hone to remove any and all burrs.

Buffed the entire piston body.

More to come...

A Prototype Adjustable Aperture Disk, Part 3

Almost done.

I used some Oxpho blue to colour the parts. I got a poor result for some reason. Hey, it's a prototype...I'll figure that out later.

That's a 1/16" ball on top of the tiny spring inside one half.

Screwed together.

Mounted on the sight. Tightened up the disk is on the wrong side.

Also I didn't make the boss long enough and the body fouled against the sight body.

So I made a short spacer to time the threads and place the disc on the right side.

Tiny hole.

Large hole. 8 different holes selectable by rotating the disk.

You can see I put a coarser knurl on the disk.

A Prototype Adjustable Aperture Disk, Part 2

On I go...

Finding the edge.

Spot drilling the pivot hole.

Counterboring one of the two screw holes with a twist drill, which is less than ideal. I wish I had a #2 counterbore...

Getting there.

Drilling the pivot hole in the other half of the body.

Drilling screw holes.

Tapping #2-56.

Boring out a recess with a 1/2" end mill.

Enlarging with a boring head. Boring doesn't work well on the Taig mill but I've already figured out how to do it easily on the lathe...just need to make a faceplate fixture. Like I said, this one's a prototype.

Test assembly.

Blurry shot of winding a spring from a, well, spring. I didn't have any .01" dia wire handy.

A Prototype Adjustable Aperture Disk, Part 1

When he saw my replacement aperture disk for the Beeman Williams Sport Aperture sight, Derrick told I should have made an adjustable aperture disk. Because he lives to make my life hard.

Turning down some steel.

Drilling a 1/16" diameter hole.

Putting an exceedingly fine knurl on the OD. This was a mistake, in hindsight. Later on I found that I needed to re-knurl the disk so that I could get some traction on it while selecting the aperture. That's why it's a prototype...

Drilling the first of many holes with the chuck mounted to the rotary table.

8 holes around the center.

Now the 8 different apertures.

The last one.

Parting off the disk.

I drilled deep enough that I was able to make two discs, just in case. Note the revisions already appearing on the drawing. That's why it's a prototype...

Turning one half of the aperture housing.

Drilling the hole.

Threaded 7/32"-40. The shoulder isn't as long as it should be...That's why it's a prototype...

Boring the face of the other half.

The aperture housing parts, parted.

A Mid April Ramble.

It's been a while since I last posted a ramble. Basically I don't have much to say and I prefer to just post about projects. But here's a few things I want to mention:

First off, the blog is over a year old with over 200 posts! That's far more than I thought I'd do when I started it. Much of the credit is due to Derrick writing all of his excellent posts. Just a reminder that I have most of the posts indexed here. I'm working on an index by airgun model but it's taking a while.

Now a brief commercial:
Do you need some ball bearings?

Tiny ones?

Large ones?

How about 10 each of the following 12 sizes, 1/16", 3/32", 1/8", 5/32", 3/16", 7/32",1mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm. Grade 25 Chrome Steel. 120 ball bearings total, lovingly and infuriatingly packed into tiny baggies and labelled. $25.00 postpaid by First Class mail anywhere in the U.S.A.
I have no idea why I thought this would be a good product, given how much time it took to package them. Oh well. Just email me if you want a set.

My airgun collecting has slowed to a standstill of late. I haven't been finding any to buy that meet my criteria: cheap and broken. If you have a beater or project gun sitting around, why don't you sell it to me? Or better yet just give it to me. Yeah, that'll work...

I'm really interested in getting the following airguns:
Anything by Weirauch
Anything by Haenel
Crosman 105/106, 99, 109/110, 622, 1100, Mark I or II, 600, etc.
IZH 61 (Derrick inspired me) especially with the steel breech. IZH 512 or 513 in .22
Any Hammerli CO2 airguns.
Sharp or Taiyo Juki airguns.
Yewha or other non-PCP Korean airguns.
Any Benjamin or Sheridan pistols.

I'm not holding my breath, but I had to put it out there. Did I mention how cheap I am?

We could still use some advertisers, sponsors, what have you. While we're doing this for the love of airguns, it is still a somewhat expensive hobby and writing all this stuff is time consuming. How much would a book containing all of our posts be worth to you? That little? I shouldn't have asked.

In any case, glad to have you guys reading all of our tinkering! More projects to come...