This little sport of ours can drive you mad at times. It's a full time occupation too.
I've spent more time with this gun than all the others by far.
Initially, I couldn't group this gun with pellets or slugs at 30 yards. They wouldn't even hit the target. The gun grouped without the LDC.
This gun is a little different than modern day rifles. The LDC is a slip on, held in by two grub screws in the iron sight. I tried several projectiles without success.
Talked to an airgun friend, and he recommended a brass shim. Found a place that sold .002" thick stock - 6" x 6" sheet for $3.
Tightening up the clearance, but did not fix the problem. This made me think of all kinds of ways to align the barrel to the LDC. Reminded me of this clip:
I then called an LDC maker, as my thoughts were going wild. He said to drill out the first 1" of the LDC.
Thought I could shoot this gun without the LDC. Wrong. It was like shooting a rimfire. dB with LDC at muzzle: 102.5dB; without: 118.5dB. Medium power (green): 40FPE, high power (red): 55FPE
Dimensions of the LDC before drilling:
Enter hole (flush to crown): .293
Exit hole: .273
Need: 7.5mm or M for the next size up -> .2953
Finding an M drill bit is harder than you think. Found a 4.3" locally.
Drilled out the first 1", then painted with white nail polish.
I could see clipping. Called back LDC maker. He said use needle files.
Tried the recommendation. Painted again. Still clipping, but in another area. Tried again, and no luck. Saw now clipping in the paint 3rd time around. This meant the clipping was occurring deeper in the LDC.
After three attempts, I couldn't handle it any longer. Needed a 6.3" drill bit to complete a passthrough. After several calls I found one locally.
Drilled through both ends for a .2953 enter and exit hole. Many projectiles still did not shoot well, even at 10M. Eventually I'll refinish the LDC.
Found that the first version of JSB .25 monsters work well.
Still experimenting with slugs. This gun goes from 200BAR to 100BAR in 10 shots. So basically this 55FPE gun is good for five shots.
I am going to try Monster redesigned against the initial version above, but this gun did not like slugs at all. Gun is now grouping sub MOA @ 30 yards with pellets.
Some guns do not want to shoot slugs. All the other slugs had a shotgun pattern: Typical were 3", 5 shot groups at 10M:
1. ZAN 25.5gr.
2. ZAN 28gr. (Tightest @ 1/2", 5 shot group at 10M!)
3. ZAN 30.5gr.
4. ZAN 33gr.
5. H&N .218 25gr.
6. H&N .218 27gr.
7. H&N .218 30gr.
8. NSA 24.8gr.
Slugged this barrel. That was fun from the breech, and with such a short loading gate. .2183 groove diameter. What do know, AVS carries .2183 slugs.
Promising @ 30 yards. Need a couple more groups to verify:
https://www.pyramydair.com/product/seneca-22-cal-28-5-grains-domed-125ct?p=1468
Just to let you know someone is following.
In my case, it was a Sumatra bought used in about 2007-2008. No idea when it was actually made. Old enough to be the skinny tube version, (380cc’s ?) metric muzzle threads, and in 5mm.
Well..at least it was threaded, even if it was a metric thread.
Paid a machinist to make a muzzle adapter. Basically a 1 ½ length of tubing, internally threaded to fit the metric threads and (not threaded) 16mm outside diameter. Would use a grub screw LDC.
Idea was to get the adapter on tight...align the grub screw LDC….then slow cure (gray/steel) Devcon the LDC to the adapter when aligned. Was just going to bond the LDC to the adapter “forever”.
Ended up going with a shorter fatter (for the internal volume of the LDC) rather than a longer skinnier LDC. Basically had to rebuild/strengthen a RWS “brake”. Easier to get the baffle holes aligned over a shorter length, maybe give up a little sound reduction for the volume for being short.
Three evenly spaced LDC grub screws worked out best. Thinking not evenly spaced would still work, but be more “twitchy” to adjust. If yours does grub screw to the front sight….maybe add a grub screw at 6 o’clock?
It’s not much slcak, so not much movement, but enough, to eventually vary screw tension to get the LDC into visual/range rod alignment.
Range rods or just a visual check for alignment.
Range rod (at least for 5mm) had to be made. It’s just a long length of dead straight steel rod, but has to fit evenly and tightly into the bore and hang out the muzzle by about 8”. Three Teflon tape bushings can get the rod tight and bore centered, the hanging out part is how you judge center to the LDC baffles.
Visual: Action open, small tuff of white cotton, light from the side on the cotton, and look straight down the LDC and bore. Range rods seemed more accurate, but the visual was just as predictive.
No commercial slugs (then or now) in 5mm….only heavy pellet was the EunJin (varied over the years, call it 22.7-23.2gr.)….had to be a little less than max tune to keep it to 23gr/1000fps/ 50 foot pounds.
You’d think that would never last….but it has to this day.
5 shots @ 20 yards with redesigns. First time shooting them out of this gun:
https://www.pyramydair.com/product/jsb-redesigned-monster-pellets-22-200-ct?p=1420
