Anschutz 380 - specs and disassembly

[HectorMedina]

Thanks Hector, brass shims should be here later today.

Looking at your earlier cutaway diagrams again, I ran the chamber picture through Topaz Gigapixel AI (via Lightroom) to improve the photo's clarity. In the photo, the compression chamber's TP diameter is same or just slightly larger than the bore diameter, i.e., 4.6mm or so. The breech seal TP hole also appears to match the compression chamber TP. This photo looks pretty much spot on with how my gun is configured.

I removed the breech seal w/ hook tool, and re-inspected the black "top cap" of the compression chamber. The black top cap is metal, not plastic as originally reported (sorr for confusion). The top cap is actually a solid milled piece, whose floor is the actual TP wall. The top cap drops down inside the chamber and is soldered/welded directly to the inside of the chamber wall. I can see this inner lip of the top cap from inside the chamber. On the cutaway (directly below the end of the barrel breech), I can see a gray/black round solder/weld joint holding the top cap to the chamber, and just to the right of that is what appears to be a metal ring of some sort, maybe for added support.

In theory, if there was some way to remove that top cap without damaging/destroying the chamber, I could take that top cap to a machine shop and have a new one made with a smaller TP hole size, then have it re-soldered/welded/whatever. Guessing the chamber would need to be heated by a torch or equivalent to work lose the solder/weld joint. Not sure if that "ring" I see in the cutaway near the solder joint would make this task harder or impossible.

Inspecting the chamber TP hole itself, if someone modified this TP they did a clean job because the TP looks perfectly smooth and centered, even under a microscope with high magnification. I researched the TP sizes for some other guns I could find in the forums, believe the largest I saw was around 4mm. So this large 4.65mm hole is a real head scratcher.

In another pic below, a Gamo Match Diabolo is dropped perfectly into the chamber TP hole. The pellet skirt measures 4.66mm, in pretty much exact agreement with yesterday's measurement.

You make me wonder if what you have is a VERY early production model and thereby more closely corresponding the sectioned gun.
I think it is hard to measure things in pictures, but clearly, you have more experience there.

All models change over their life-cycle; some more, some less. The TP COULD have changed and, if so, then there should be two (or more) types of compression chambers.

In any case, let's see how the shim idea works.

Keep well and shoot straight!






HM

[jimk1963]

Thanks Hector. Gun S/N is 09077.  Read somewhere that an estimated 15,000 were made, but I don't know where the serial numbers started. Mine has the plastic cheek piece, which I thought came later on.

Practical problem with shims - my drill index goes from 5/32" to 11/64"  (4.97mm to 4.36mm). I'll probably have to use the smaller bit and see if I can ream it out a little at a time. Tricky with 0.4mm thick brass shims, they're pretty flimsy.

[jimk1963]

Prepped two brass shims, with center holes 4.0mm and 4.2mm. No difference between the two, overall velocity average still right at 400 fps (10 shot average), 2.9fpe, spread of 376-408 fps.

I notice that about 1 out of every 8-10 shots is markedly lower velocity than all the others. If I throw out the 376fps reading, the spread drops from 32fps to about 17fps. This was happening prior to the shims, so nothing new.

With gun apart, degreased using acetone and applied Ultimox 226 this time. Whatever is wrong with the gun, it's not the lube... have tried moly, krytox, super lube, and ultimox, all with pretty much exactly the same result.

Have exhausted all avenues I can think of at this point, except for piston ring replacement. New piston ring is still "in transit" somewhere in US, no estimated delivery date available from USPS.

[jimk1963]

Success!!!!

WCG parts arrived today, pretty much every part is different geometry than the ARH parts I was using. Breakdown below, along with some photos. Summary:

- WCG springs are both significantly longer and have more tension
- WCG inner spring is longer than its outer spring, ARH is opposite
- WCG piston buffer is a full 2mm shorter than ARH - essentially the ARH piston buffer was short-stroking the system by 2mm
- WCG piston buffer BARELY clears the top of the piston - appears to be super accurately fabricated, less than 1mm clearance all around the rim of the piston, impressive
- WCG breech seal is over 1mm taller than the ARH, with a much bigger transfer port hole as well (5.5mm!)

The piston rings are very similar, with the WCG being a little thinner than the OEM piston ring (I bought the gun used so can't be sure if this is the original piston ring or from someone else).

I lubed only the following, using Ultimox (everything was degreased using Simple Green in an ultrasonic bath, followed by paint thinner by hand):
- Piston Ring (roughly a 2mm drop, spread around the perimeter)
- Inner spring ends (similar amount)
- Outer spring ends (similar amount)

Installation notes:
- WCG piston buffer took tremendous force to install, unlike the ARH buffer. I have no idea how I'll ever replace it, will literally have to dremel it out because there is zero lip to work with to pry it out
- WCG breech seal also took tremendous effort to install, even worse than the piston buffer. Same story, that thing will never come out without destroying it.
- WCG piston ring actually went on easier than OEM, a lot easier. Interesting. Under a microscope they look pretty much identical.

First 10-shot group, using RWS Meisterkugeln 8.2g wadcutters:
- Velocity (avg) = 590 fps
- Energy (avg) = 6.33 fpe
- Min speed = 581 fps
- Max speed = 602 fps
- Spread = 21.6 fps
- Std Dev = 6.6 fps

This is much more in line with expectation for this gun. In the past I had found owners who were getting right around 600 fps w/ 8 grain. With 7 grain I expect this will hit 650 fps or so.

Huge THANK YOU to Hector and Chuck, who stuck with me through this anguish.

Conclusion: the right parts make all the difference, and in this case WCG definitely had the right stuff. Couldn't be more pleased.

[jimk1963]

Remaining pics:

[chuckinohio]

  OUTSTANDING!!!!

  I was rooting for you man, and it looks as if your perseverance has paid dividends.

  I clammed up for a bit because you were solidly in Hectors zone talking about transfer port adjustments. My input was exhausted somewhere back around piston ring replacement!

  590 is right in the butter zone, and you may gain a smidgen as the new set up beds in.

  Happy day today, I am as pleased as punch to hear that you got it up and running in spec..Congratulations on a successful work through, and thanks for the direct comparison of the ARH and WCG spares. That is EXCELLENT info for the Anschutz 380 archive.

  Now go enjoy the finely crafted fruits of German engineering!!!

[jimk1963]

Woohoo! Thanks so much again Chuck for all the advice. Can't tell you how happy I am after struggling with this for weeks.

As an unbelievable bonus, I pulled out my A380 parts box (DeWalt parts organizer thingy) and mounted the original Anschutz front/rear diopters; front has a clear annular ring insert which I love. Those sights have not been on that gun in 10 years, almost to the day.

Never saved any marks on the gun for re-mounting these, I just slapped them on and adjusted the rear back and forth until it felt good.

Below is the very first 10m benchrest shot I took, with an RWS Meisterkugeln 8.2g. VERY FIRST SHOT!!! I have never in my life had this happen when re-mounting sights of any kind (scope, diopter, open, peep...). I literally almost started crying I was so happy.

The gun is firing just beautifully, no recoil at all, butter smooth, trigger is dialed in, man I am just in heaven. And the pellets are hitting hard, like my FWB 300's. There is a massive difference between 400fps and 600fps - a THWACK vs. a "pop". Feels like a gun again!!!

Took a few 5-shot groups with other pellets too, posted below.

[HectorMedina]

GREAT!

Perseverance has paid off.

Congrats on a job well done.

Now, don't be a stranger and keep us posted.

;-)







HM

PS.- I am glad I was wrong.  LOL!

[jimk1963]

Thanks Hector! Without your help I never would have been able to get this far.

One interesting takeaway is the size of the transfer port on this gun. At 4.65mm (and breech seal TP at 5.5mm), requires care with pellet seating, at risk of the pellet falling backwards into the compression chamber. Like the smushed pellet I found on initial disassembly.

Another takeaway is that the spring tension should be pretty strong, as the stroke is on the short end and the piston diameter isn’t large either. The original springs, amd the new ARH springs, were both very easy to handle with my homemade gun vise - too easy as it turned out. Was immediately noticeable how much more force was required to compress the WCG springs. I believe this was the #1 factor in fixing the issue.

Last takeaway was the breech seal and piston seal. I think the less-thick ARH version could possibly work but needs about 1mm of shim behind it. The red ARH plastic is also quite a bit softer than the WCG green material. Getting those green WCG parts to seat was a real chore.

I’m less sure about the ARH piston seal. It juts out well beyond the end of the piston and shortens an already short stroke. It would probably work ok but I would expect a drop in velocity.

Ironically, the piston ring was probably A-OK as is. Live and learn!

[HectorMedina]

I am glad you are happy!

Just not to leave any stone unturned, I would test the ARH springs with the WCG bumper.

IMHE, match guns need precious little "force" to generate energy.

And, yes 2 mm's stroke difference in ANY piston airgun will mean 1 to 2 ft-lbs difference in output.

Keep well and shoot straight!





HM