1377 makeover

[D14Jeff]

those AIM scopes are very popular with the mosin rifle fans , i was gonna get one till i got a killer deal on a simmons 2-6x32 . it should do very well for you .

http://aimsportsinc.com/products/3-long-eye-relief

[Tater]

Looks great Kris. I love the grips.

[maraudinglizard]

~originalThanks guys, managed to get a little shooin' in with old faithful. Went right to the 50 yard mark, no more up close and personal target practice, let's see what this pistol really has under the hood. So here are the results. With the advice from Longhunter on holding methods, I managed to tighten up the groups.  Middle target group is the first round with 20 shots, the lower left group is the second round with 10 shots.  I was using JSB exact heavy diabolo 10.34gr pellet at 10 pumps.

[longhunter]

Guess I am good for something,  after all  . Nice shooting.

[Tater]

That's great shooting at 50 yards with a 1377.

[maraudinglizard]

Good evening, Old Faithful had a small set back over the weekend. I had experienced some power loss with the new piston. First noticed it when I was pumping the pistol, that got real easy all of sudden and the usual creaking sound had stopped, then when I was shooting down range I was mowing the grass instead of hitting the target. To make things short, I found that the piston cup was not flaring out enough to engage the pump tube. Keep in mind that this is a 32 year old pistol and there is going to be some wear and the tube may be just a little bigger. I checked the cup and there was no damage that would have caused any air loss.  So my solution to this problem was to shim the inside of the piston cup. I used a Dasani water bottle, cut a strip from the textured area and made one loop inside the cup with just a very tiny overlap to keep it even. The strip sits just below the cup edge and will stay there without any adhesive. The texture in the plastic strip made the cup flare out to make contact but not to much were I could not install it in the tube, it allowed the air to fill the cup like it was designed to but give it support as well. Here are the chrony results before and after. Everything is back to full speed again. 

First installed
  Crosman hp 7.9gr          609 fps   @ 10 pumps                 
  JSB exact heavy 10.34   550 fps               

Before the shim
  Crosman hp 7.9gr          576 fps   @ 10 pumps
  JSB exact heavy 10.34   520 fps               

After the shim
  Crosman hp 7.9gr          615 fps   @ 10 pumps                 
  JSB exact heavy 10.34   560 fps           

[avator]

Good job Kris. I had a similar situation with an old pumper. As a quick fix i stuffed dental floss in the same area you put the plastic... I had the same good results. Eventually replaced the cup seal.

[maraudinglizard]

Thanks Avator, since this a new piston cup this kind of failure should not be happening. After a few emails and phone calls with Davio, we both came to the conclusion that I may have on a rare occasion a slightly larger diameter pump tube and possibly some of the newer pump tubes may be that way as well. Basically no 2 pump tubes are going to be the same.  These cups are coming from Crosman and are replacing the black and solid white cups that were not holding up very well.  The clear ones are designed to last longer and not break down. Davio thought that was a very ingenious way to fix the cup. With that solution, Davio can help his customers fix their piston cups if they have that happen to their pistols. So hopefully in the next day or so I can get back to business with Old Faithful. 

[beerhippy]

Kris, if  you continue to have trouble with the cup you might try a different style piston.

http://www.mountainaircustomairguns.com/New_accessories_page.htm
Roy uses a double o-ring design with wipers and the o-rings are replaceable. Plus you can adjust the length with the o-rings removed for a more precise fit.   I wish I would have gone that route.

[Hoosier Daddy]

I know this is an older thread but wanted to say thank you Kris for posting a link to it.
I just read the entire thread and what a great job you've done!
Judging from the timeline you posted on getting  Old Faithful, I think you and I are the same vintage... I just took a 30 year hiatus from airguns.
Lot of good info here for the this noob with a new PC77 to play with. The Spring swap is something I hadn't read before.
Hope my results are even close to yours. CONGRATS!

[maraudinglizard]

You're welcome. Glad that the link has helped answer some questions for you. Search 1377 and you will find that there is a great amount of information on them. Welcome to the GTA.

[Airwoods]

Thank you fellas. Here is another update.  The fps at 10 pumps is running about 570fps to 590fps with a 7.9gr. pellet, at 15 pumps it's running about 610fps to 630fps. So the power has returned to this pistol.  The picture below pretty much explains the accuracy. The smaller pic is the 5yd target and this was the first 5 shots for sighting in, the larger pic is the 10yd with ten shots in this group. This pistol shoots all kinds of pellets it's not pellet picky at all. I started at 5yds then moved to 10yds later, both were in the quarter size target zone. I will move out to 15yds and 20yds this weekend.

Very Nice.

[maraudinglizard]

Thank you fellas. Here is another update.  The fps at 10 pumps is running about 570fps to 590fps with a 7.9gr. pellet, at 15 pumps it's running about 610fps to 630fps. So the power has returned to this pistol.  The picture below pretty much explains the accuracy. The smaller pic is the 5yd target and this was the first 5 shots for sighting in, the larger pic is the 10yd with ten shots in this group. This pistol shoots all kinds of pellets it's not pellet picky at all. I started at 5yds then moved to 10yds later, both were in the quarter size target zone. I will move out to 15yds and 20yds this weekend.

Very Nice.

Yep, Old faithful is still going strong. I will be back to showing it some love over the holidays, the yard work is done for now, time to spend time with the air gun children.