Anschutz LG 380 rebuild issues

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jimk1963

jimk1963

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Jun 19, 2022
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California
Hi All, have an LG380 S/N# 9077, black plastic cheekpiece. Gun was rebuilt in 2012 by Randy Bimrose. After a few years sitting, pulled out the gun, it was shooting around 500fps with 8.2g RWS Meisterkugelns, same as when Randy returned it. Significantly lower than expected.

WIth a ton of help from Hector Medina over at GTA, was able to disassemble the gun and fix some obvious issues. However, since that first disassembly, the gun now shoots only about 400-420fps with the MK pellets. Gun has gone through a nearly complete rebuild, only thing missing is a new piston ring which is on the way. Tried many other pellets w/ various skirt diameters, anything around 8g shoots in the low 400's. I'll list out the steps taken to date, looking for any advice, thanks.

Reference: https://www.gatewaytoairguns.org/GTA/index.php?topic=200482.0 (tons of pictures and info)

1) Initial Disassembly
- Found a smashed pellet at the bottom of the compression chamber, and a little bit of oil (silicon oil maybe, dunno) in the breech/piston buffer areas. Cleaned all that up

2) Subsequent rebuilds
- Degreased piston (piston ring attached), compression chamber, both springs (this gun has an inner and outer spring), rear spring bushing
- Replaced piston buffer (Maccari)
- Replaced breech seal (Maccari)
- Replaced springs (Maccari)
- Re-lubed gun with Moly (first time), then Krytox on subsequent rebuilds (after degreasing to get rid of Moly), and finally Ultimox 226 (after another degreasing)

Hector has a 380, he estimated the transfer port to be 4.25-4.35mm using drill bits poked into the chamber. On my gun, the TP is 4.65mm, which of course is why pellets can easily fall backwards into the compression chamber if one isn't very diligent when smushing the pellet into the breech. Hector flagged this as a potential issue, so I ordered some round brass shims (16mm dia, 0.4mm thick) and carefully milled a couple, with center holes 4.0 and 4.2mm. Sandwiched each shim, one at a time, behind the breech seal, to create a reduced transfer port diameter. I know... there's a whole science behind TP's, this isn't optimal, etc. The goal was only to find out if reducing that TP hole made any velocity difference whatsoever. It didn't .

Piston ring from WCG cleared customs over the weekend and is now in the USPS system, with a TBD arrival date (USPS really sucks at handling DHL inbound packages). All I know is the package left NJ last night...

I'm skeptical that the piston ring is the culprit, these rings should be good for several hundred thousand shots. But it is the last piece I can change out, other than the chamber and piston which is like finding water on Mars.

Does anyone have experience with TP's this large? Looking very closely at the compression chamber, the TP looks original to me, i.e., does not appear to have been bored out by anyone. Further, enhancing an old 380 cutaway photo (see below), looks to me like the bore, breech seal TP hole, and compression chamber TP hole are all very close to the same diameter, same as my gun. All 5 breech seals purchased from Maccari have center holes ranging from 4.65-4.80mm, again in agreement with this photo. Seems weird to me to have a TP the size of some pellets - asking for trouble.

LG 380 Compression Chamber Close-up Edited.jpg
 
Have never worked on that gun, but my understanding is that they were intended to run dry for minimum velocity variation. It is possible high viscosity grease on the piston OD and cylinder ID could generate enough drag to affect velocity. I would wipe everything down leaving an invisible film to prevent rust, then very lightly lube the springs with grease. Velocity might improve. Try target talk to see if anyone there knows what the original factory lubrication consisted of.

The 500 fps you were getting is actually fine for 10 meter shooting. Just need to cut clean holes in the target. Not sure what the original velocity spec was. Again check on target talk. My FWB 300s has always been a little over 600 fps.

One odd thing I see in the photo is the way the cylinder cap is attached and sealed. It looks to be a one-time snap with o-ring seal. If that o-ring is leaking I suppose that could be a problem. No way to get it apart that I can see. And would have to find a way to pressurize the cylinder to test for leakage. If it can’t be disassembled, a TIG weld repair might be possible.
 
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Thanks Michigander for the inputs. I read elsewhere that perhaps only 15,000 380’s were ever made so there aren’t many “artisans” out there who know the gun. Google is a ghost town, endless dead ends.

The cylinder cap, if you’re referring to the compression chamber photos, is welded or soldered directly to the chamber. The cap has a lip that drops down into the chamber. If you’re able to decipher the cutaway diagram, you can see this configuration. There is no o-ring. The only seals are the breech seal (inverse conical shape to conform to the conical shaped bore breech), and the piston ring which is the only thing sealing up the chamber. The piston buffer at the front is actually smaller than the chamber diameter, does nothing for generating compression.
 
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Success - gun now shooting 590 fps with 8.2g, 650 fps with 7 grain.

Details posted on GTA, bottom line soluton was a complete swap-out of ARH parts with WCG parts. Completely different geometries. If anyone owns a 380 and needs parts, recommend to go with WCG for this particular gun (breech seal, piston buffer, piston ring, springs). Have ARH parts in all my other guns, all working perfectly. Just not the right stuff for this old Annie.

Anschutz 380 - specs and disassembly - Airguns & Guns Forum

Anschutz 380 - specs and disassembly, Air guns, Airgun Forum
www.gatewaytoairguns.org
 
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Do you know if Randy Bimrose is still in business? Or alive? I've got a 380 that he tuned up for me back in the late 90's (I think) - maybe early 2000's. I used it for offhand practice in my yard. Great air rifle for that. Anyway, I pulled it out recently and it is non-functional. Doesn't create a charge when cocking. I'll look at your GTA page but never have worked on airguns before. Not sure where to start with this one. Thanks!
 
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Afraid I don’t know if he’s still around, lost touch with him after 2010 or so. With some straightforward effort, you can repair it yourself. I had never taken any air rifle apart (nor firearm either) and was able to fix mine. I did my best to fully document the procedure and specify exactly where to order the parts (Waffencenter Gotha). The only “tool” you’ll need that you likely don’t have is a spring compressor. The springs in this gun are not strong, all you need is a bar clamp. I bought this one off Amazon:

Groz 48-inch T-Bar Woodworking Clamp | Heavy Duty | Malleable Iron Head (39101)​


Put a wood block on either end (I added a round felt pad to the barrel-tip end to keep it from scratching), wrap some bubble wrap around the bar to protect the action, and you are good to go.

If you read through the procedure and are still stuck, let me know. I’ll do my best to walk you through it. I’m in the San Diego area FYI.
 
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Yah, I have a phone number for him and have left several messages but no reply. I'm a fairly experienced gunsmith, mostly from working on my own gear but also friends' gear and have had nothing but good feedback over the years, so I'm not too worried about giving it a try, especially with people who are experienced in it and like yourself have documented it thoroughly. From what I have read I'm hoping it's just springs. It's such a great rifle that I hate the idea of making it a wall hanger or worse yet, junking it.

Thanks for getting back to me. I'm thinking my first step will be to disassemble and examine and maybe get an idea of what parts I will need. Though I'm thinking It might be good to order the spring set just because whatever else it needs, it will probably need those. It hasn't been shot in near 15 years.

Mike
 
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Mazzman said:
Yah, I have a phone number for him and have left several messages but no reply. I'm a fairly experienced gunsmith, mostly from working on my own gear but also friends' gear and have had nothing but good feedback over the years, so I'm not too worried about giving it a try, especially with people who are experienced in it and like yourself have documented it thoroughly. From what I have read I'm hoping it's just springs. It's such a great rifle that I hate the idea of making it a wall hanger or worse yet, junking it.

Thanks for getting back to me. I'm thinking my first step will be to disassemble and examine and maybe get an idea of what parts I will need. Though I'm thinking It might be good to order the spring set just because whatever else it needs, it will probably need those. It hasn't been shot in near 15 years.

Mike
Click to expand...
Sounds good Mike. I recommend to purchase the two springs now, as WCG takes a while to ship them out, will be several weeks to a month before they arrive. Because of that, I also recommend purchasing a new piston buffer and breech seal from them. These may be just fine on your existing gun, but since WCG charges shipping for the springs, and it takes a while, best to spend another 10-15 euro to have those parts on hand too. Lastly, FYI I tried using Macxari’s 380 springs and piston buffer/breech seal, they did not work at all as you will see in my posting. The geometries are completely different than the WCG parts, which worked perfectly. If you haven’t purchased from WCG, they require a wire transfer (or they did anyway), I used Western Union and it took me a little research to get it right. Best of luck, please reach out any time if you run into any issues.
 
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