Anschutz 380 - specs and disassembly

[jimk1963]

Anschutz Model 380 Disassembly:
1)   Remove rear plastic end-cap 103 – see Anschutz photo #1 in disassembly instructions (see Hector's external link)
2)   Remove the plastic collar 93 covering the breech – see Anschutz photo #2 in disassembly instructions
3)   Remove Philips screw 95 from underside of receiver
4)   At rear of cocking lever, make note of position of eccentric bolt 80. The bolt has a tiny dot that points towards a sprialgraph of lines. When re-assembling gun later, the dot should point at the same line as before disassembly
5)   Remove e-clip (retaining collar) 82 from eccentric bolt 80, then slide/punch eccentric bolt out of its slot
6)   Pull cocking lever 75 back as far as it will go, then remove cocking rod 76
7)   Slide inner barrel/trigger assembly rearward, separating it from the outer receiver 92
8.   Loosen the tiny 2mm hex screw 13, then remove trigger block mounting screw 14 from front of the trigger assembly
9)   With cocking lever 75 still pulled back, remove screw 12 and abutment 11 from the RIGHT-hand side of the receiver. Note: cocking lever 75 is pulled back so this screw 12 can be accessed
10)   Close the cocking lever, by sliding a thin screwdriver into the trigger assembly to disconnect pawl 38 from the cocking lever ratchet wheel 83. While pressing on the pawl, the lever should easily move forward. See Anschutz phto #4 in disassembly instructions. Sounds harder than it is - just drop a thin screwdriver down into the trigger assy, right next to the base of the trigger, and gently push down and forward (towards the muzzle) until you feel a little spring-loaded "pawl" down in there. Once you feel it, gently pressing on it will separate the pawl from the cocking lever ratchet, so the cocking lever will move freely. We want the cocking lever closed because we're going to put the receiver into a vise next. The cocking lever mechanism sits at the very rear of the receiver - when the cocking lever is closed, the rear of the receiver becomes "flat-ish" and creates a good surface for the rear vise jaw to press against
11)   Clamp device in a strong vise; Anschutz estimates ~ 55lbs of spring force
12)   Remove screw 12 and abutment 11 from left-hand side of receiver, near the rear. At this point, the trigger and spring are only held in place by the vise
13)   Slowly back out the vise, making sure to hold onto the trigger assy to keep it straight as it slides out
14)   The trigger assy remains as a solid block, while the two mainsprings (inner and outer), the piston, and the compression chamber will all separate into individual pieces

Easier than FWB 300 disassembly from what I've read/watched, no major "tricks' to learn here. Now if anything were to ever go wrong with the trigger assembly... that might be a chore to work on, as that thing reminds me of a Swiss watch. Lots of little pins/e-clips/springs/ and poor visibility into the inner workings.

[HectorMedina]

Thanks Hector,

Questions about the springs:
1) In your photos, you show a broken inner spring lying beside the outer spring. Photos can be deceiving, but appears your inner spring is also shorter than the outer spring? (even when I account for the small broken part)
2) Did you purchase new springs for your 380? If so, do you recall from where - JM, Waffencenter, other?
3) JM 380 springs will be here Friday, also ordering springs from Waffencenter (still working on bank transfer details)

Re: piston inner guide, mine is metal like yours.

Last question: do you know how to remove/replace the breech seal? My compression chamber has this black plastic "cap" at the breech end, and I notice in your picture this "cap" appears to be metal (is that right? Maybe another difference between model years). I'm unclear if that "cap" must be removed, prior to removing the breech seal - or if the breech seal just pulls straight out, passing through the "cap". Since this is a critical area of the system, I don't want to just pry off that black plastic cap without good understanding, as it could create a leak path if I gouge it.

James;

I thought I was clear in my posts that these pictures are NOT mine.

When I did mine, MANY years ago there weren't many digital cameras around and I was not in the habit of documenting as much as I am today.

I got three sets of springs from JM, checking them today, yes the smaller spring is also shorter.

Conical seals have a "lip" against which they should rest, otherwise they would pop out spontaneously.

In the sectioned drawing I do not see any ""collar" holding the conical seal, but it is an aspect of sectioned guns that some parts get lost.

What you describe as a black ring could well be a "collar" of some sort.

Again, if your gun passes the blow tests do not even consider changing the seals.

Apologies for the misunderstanding.







HM

[jimk1963]

Thanks Hector, my apologies for the misunderstanding re: pics.

So the inner spring is shorter than outer spring… good to know.

Re: breech seal, the plastic outer ring must be the “lip” holding in the breech seal, as you noted. I won’t mess with it for now, seems to be fine.

[jimk1963]

Received new springs from JM today. The inner spring is similar in length/turns to the old spring, but the outer spring is a full inch+ longer. I’m hoping this means that the old outer spring had taken a set and “shrunk”, reducing its power. Does that happen with these springs?

[jimk1963]

Maddening. New springs went in with more force than originals, cocking stroke noticeably stiffer, yet velocity did not move at all. Still around 407 fps (3.0 fpe) with 8.2g Meisterkugelns.

Has to mean there is a leak path somewhere in the compression chamber. Breech seal looks fine, but am not 100% sure if it is - and don't know how to remove it.

Ordered new piston ring from Waffencenter, who knows when that will arrive. I'm utterly baffled.

[HectorMedina]

Maddening. New springs went in with more force than originals, cocking stroke noticeably stiffer, yet velocity did not move at all. Still around 407 fps (3.0 fpe) with 8.2g Meisterkugelns.

Has to mean there is a leak path somewhere in the compression chamber. Breech seal looks fine, but am not 100% sure if it is - and don't know how to remove it.

Ordered new piston ring from Waffencenter, who knows when that will arrive. I'm utterly baffled.

If there is a leak, it is not in the seals.
Blow tests are useful because at the low pressure that human lungs can provide, leaks are MORE apparent than at high pressures where the sound barrier acts as a leak-stopper in most pin-hole cases.

Questions that should have been asked before, but I overlooked them, I apologize for that:

Have you cleaned your barrel?

If you have, have you slugged the barrel with the pellet you are using?

Loose pellets can not only fall back into the compression chamber, but they will also yield lower energies.
There is a reason why H&N makes match pellets from 4.49 to 4.53, you would be amazed at how much the head size contributes to proper energy yield.

Just as an example: a short stroke D54 I am preparing yields 15.5 ft-lbs with the 9.56 Baracuda Hunter Extreme (4.52 head size), then it yields 13.5 ft-lbs with the H&N BFT (4.50 hed size), same weight of pellet, same alloy, same manufacturer.
I THINK the example is applicable because both guns (the 380 and the 54 in question) have short strokes and are extremely optimized to the "objective" pellet.

If you push a MK's through the bore and feel no, or very little resistance, then we have problem. If there is not enough "starting" pressure/force for the pellet to act as the "liberator" of the shot cycle, we have a problem. Slug the barrel with different pellets and note the difference in starting forces and friction drags along the barrel.

HTH






HM

[jimk1963]

Thanks much Hector, I haven’t cleaned the barrel - will do. Re: the Meisterkugelns, I have noticed they are not the tightest fitting pellet. Will try slugging the barrel with them, and others , thanks for the great suggestion. I guess with this fixed side lever I’ll need to disassemble the gun to push the pellet through from the breech end.

[HectorMedina]

IDEALLY, yes, all rods should be run from the breech end with no spring load.

In the real world that is not always possible. In a well made barrel (like the Anschütz') you should have no problem pushing a pellet from the breech using a Swab-it:

https://www.swab-its.com/products/17cal-177cal-4-5mm-air-rifle-gun-cleaning-bore-whips-by-swab-its?variant=2561680323

The choke may be a bit of an effort, but this is my benchmark for a really good barrel. The constriction will be there, but the barrel will be finely enough made that a flexible "rod" is enough to push the pellet through.

Keep well and shoot straight!





HM

[chuckinohio]

   If you do pop your breech seal out, be advised that there may or may not be shims present under the seal.
  These shims are present on some rifles to adjust the height of the breech seal in its bore, which in turn adjusts the lock up of the rifle as the compression cylinder goes into battery. Basically it adjusts the squish of the seal to the breech end of barrel, which is determined by how much effort it takes to fully close the cooking arm until it latches.

  There's a measurement for that squish factor, but I do not remember where I read it or saw it mentioned.
  Hector may have input on that, and I would bet money on his guess over most others. Diana 54 experience should translate over to the 380 concerning the lock up effort on the side lever.

  Edit-
  The information is at the very end of the English language portion of the manual. Cocking lever pre stress is the technical term. 3mm is the number.

[jimk1963]

Thanks Charles, manual does show a shim in the parts diagram, sitting right behind the breech seal. I don’t see the “3mm cocking lever pre-stress” anywhere in the manual? I’m referring to the manual link provided by Hector.

Still not sure how to “pop out” this seal… just pry it out using a small jewelers flat-head? This is how I’ve seen others removing FWB 300 seals. Or I could hook the center hole, but am concerned with damaging the spacer behind the seal. No experience with the Diana 54 (someday!).

The cocking lever has an eccentric bolt #80, which goes in a specific way - there’s a dot on the bolt that points to a spiral graph etched on the cocking lever. Manual says to remember where this dot points and return the bolt to the same position on reassembly, which I did. I wonder if rotating that bolt changes the lock-up effort??

[chuckinohio]

  Page 16, bottom right corner. Tells you how to check and set pre stress on the side lever.

  If you are set on changing out the breech seal, then I would work it out with a dental probe. Paying particular attention to not gouging or scratching the bore of the seal recess of course. There may be more than one shim under the seal, so eyes open on that aspect.

[jimk1963]

  Page 16, bottom right corner. Tells you how to check and set pre stress on the side lever.

  If you are set on changing out the breech seal, then I would work it out with a dental probe. Paying particular attention to not gouging or scratching the bore of the seal recess of course. There may be more than one shim under the seal, so eyes open on that aspect.

Thanks, was fumbling around in the disassembly section. Breech pressure seems pretty spot on, also saw the eccentric bolt explanation on the next page. It does increase the pre-stress as I suspected.

After slugging and cleaning the barrel, and adjusting the eccentric bolt for more pressure, velocity has not moved. Examined the breech seal under a microscope, I can see where the seal meets the compression chamber wall (exit port). Appears there is no spacer. Won’t know for sure until I wiggle it out.

[jimk1963]

Removed seal, using a hook tool, stabbed into the side wall of the seal. Pulled straight out, no "lip" or anything holding it in, and did not require a lot of force (I've read that other breech seals can be very tough to pull out). The new seals I have came from Lewis Reinhold via JM, and don't appear to require a spacer behind them.

I checked the pre-stress using the manual's instructions, the interference begins roughly 1/8" (3+mm) from level-lock, which seems to be per spec. I've also been advised to leave the gun closed in the uncocked position for 24-48 hours to help the seal form around the breech. Not sure how much that matters but will give it a try. First few shots, velocity was up but only marginally, around 420-430 fps. The fact it changed at all likely indicates some leakage around this seal area.

Since there was no spacer behind the seal, I also can't be 100% sure if a spacer is needed or not. I'm judging things based pretty much on the cocking lever pre-stress just prior to latching. With the old seal, I tried rotating the eccentric bolt #80 to more aggressive and less aggressive positions, and I did observe minor velocity changes (10-15 fps or so), nothing close to how the gun should be shooting but indicative of some sensitivity to the seal pressure I guess.

Lastly, on my compression chamber, the top is a single piece of hard black plastic as shown in the photo, encompassing the entire top of the chamber. On other photos (Hector, et al) I've noticed this top section may be metal. Perhaps indicates a change in production at some point, or the pics I've seen are faking me out.

[chuckinohio]

 My compression tube looks identical to yours.

[HectorMedina]

Jim;

Glad you are dealing with this ONE STEP at a time.
It is immensely useful to the community. THANKS!

My compression chamber looks like yours.

I am sure there were several production changes along the history of the rifle. Sectioned models are usually made with pre-production or very early production models and almost always are used as training aids.
We need to remember that in Germany adding or removing METAL from a gun by an unlicensed gunsmith carries a hefty legal penalty. So if some parts are made of plastic, that makes maintenance easier for the user.
Therefore factories made sure that factory reps travelled with the sectioned models all around the country showing gunsmiths how to deal with their guns.

An old rep I know from past IWA's, told me that in a year, he would drive over 200,000 kms to cover all his "visits"; in one year, he had his engine completely overhauled TWICE. Of course this was many years ago, before re-unification.
For Germany, that would be like an American driving a million miles a year.

How history has changed.

Thanks again, and keep us posted!






HM

[jimk1963]

Thanks Hector, interesting history note re: the plastic outer section. This has been quite the learning experience overall.

Yesterday I looked closely under the microscope at the compression chamber, piston, and piston ring. There is very minor scratching toward the rear of the piston in one spot, I mean very minor as in 0000 steel wool-type faint marks. I considered running some 1200 grit wet/dry over the piston surface, but I can't image such small marks at the rear of the piston would really matter. I polished the compression chamber using only a dry cotton wheel attachment (no polishing paste or lube of any kind), to a mirror finish with no hint of any scratches/blemishes inside. Looks gorgeous. I examined the piston ring very carefully, it was darkened from years of whatever, so I ran it over a 1500 grit wet/dry pad to restore it to its shiny original condition (outer edge, inner edge, and both sides). After all that, I applied a tiny amount of krytox around the piston ring only, and reassembled. I wanted to see if a "dry" compression chamber with only a tiny amount of krytox on the piston ring might work out better. It didn't. Same poor velocity in the low 400's.

WCG items have shipped, including a new piston buffer, breech seal, piston ring, and inner/outer springs. I will compare those to the parts I obtained from JM.

Read/watched a bunch of Paul Watts stuff last night, was intrigued by his frequent comments that compression chambers are often in need of honing to correct for tapering/out-of-round/etc issues. He noted drops of over 100 fps on some guns with poor chamber integrity. This gun did shoot around 510 fps with 8.2g prior to disassembly, so I don't think the chamber is that far off or else the gun never would have shot in the 500's. Still, given everything else I've changed (literally everything except the piston ring), does lead me to wonder if there's something like this afoot.

[chuckinohio]

  I would be very surprised if the problem was due to an out of round compression tube. My bet at this point would be on the compression ring being out of spec.
  The FWB 300 uses a similar compression ring on its piston, and there is a measurement or assembled dimension to check allowing you to ensure that it is in tolerance, and the allowable variance is very small. I have not been able to source a similar dimension for the ring in the 380 allowing me to be able to check my own, or to provide a figure for you to check yours unfortunately.
  I will keep looking, and if I come up with anything the information will be posted in this thread so all this good 380 info can be archived for future reference.

[jimk1963]

Thanks Chuck, a new piston ring is now en route from WCG, should be here in the next week or less.

Re: the ring’s spec, dumb question: if I measure the outer diameter of the ring with the open end closed down, should that diameter be equal to, or just slightly less than, the compression chamber’s diameter? I assume the critical spec is with the ring perfectly closed, otherwise air would leak past the gap.

[chuckinohio]

  As far as I can remember, the critical dimension of the piston ring is the cross sectional thickness, measured from inner to outer bearing surfaces.
  This measurement does directly affect the end gap of the ring when it is installed, which in turn affects how much bypass the ring will allow under compression.

  I do remember a post from the past where one fellow had a piston ring that was .001 or .002 out of spec, and it did affect the MV of the rifle, verified over a chrony. The specific numbers escape me, but the message went into the mental rolodex as an area to check when addressing an unexplained drop in power not rectified by a new breech seal.
  The piston ring bypassing air also becomes an issue when these type of rifles are grossly oversprung in an attempt to gain more FPS for various reasons..

  Once your new piston ring is in hand, I would definitely check the cross section of new VS old. This should give you an immediate indication of whether your currently installed piston ring has worn and is bypassing.
  If you would be so kind sir, please share your measurements and findings with the collective so that we can all benefit from the information.

  Edit-

  Later today, I will record a 10 shot string from my 380 with RWS Hobby and RWS Meisterkugeln pellets to give you a baseline, goal, target velocity to aim for.
  Rifle has approximately 3k pellets through it after a full refresh, including new piston ring.

[HectorMedina]

Ooohh, Chuck, now you've gone and done it!
You MADE me get my 380 out and have a chrono session!  LOL!

Actually, both, her and me needed the exercise.

;-)

Chronoed a dozen pellets, but the really noteworthy would be:

1.- RWS MK's.- 680 ± 2 fps
2.- QYS Olympic.- 653 ± 6 fps
3.- Eley Ventus 4.50.- 577 ± 2 fps
4.- H&N FM 4.49.- 621 ± 3 fps
5.- GTO.- 670 ± 7 fps

And just for the sake of completeness of the thread:

Here is my breech:



My rear sight:


Right side of gun:


Left side:


S/n is 0203XX, so it is not an early model.

I did realize that my breech closing pressure is on the light side, but the gun passes the blow tests easily and the MV's are good, so I will not mess with it.

HTH, keep well and shoot straight!





HM