1377 build........" El Cheapo "

[MountainMan126]

I have recently developed a need to upgrade my garden defense tool. I have had a bunch of pc77 take-off parts hanging around doin' nothing and a 16" barrel that was not up to par on arrival. After seeing a post recently on another members 1377 build and the numbers potentially possible with some new ideas on low volume high pressure mods, I got started a few days ago with what I have on hand. 

My goal is to build a very wallet friendly, still pistol shaped replacement for the current rifle.

I will have to buy some of the parts I need, a metal breech is the first that comes to mind. On hand now I have the barrel , .177 cal. , and 16" in length. I just did an at home re-crown on it today, looks decent but once together we shall see what the paper says. This is gonna get painted when done.
 I did a lot of work on the valve, the reference pics and write up I had were great. I made a few changes here and there, but followed a similar idea , lower volume, higher pressure. I chose to cut the stock spring to the desired length, and while not a lot, I did enlarge the inlet port for easier pumping. I also enlarged the exit port inside, but not down from the top so it will still use the factory seal.  Mine is not a flat top since that would require buying/making a piston, Maybe another time. I added an oring to the front of the piston behind the cup to get it a better seal against the valve , and against the wall of the tube. 

I got some dicks sporting coupons in the mail. If they let me combine them I can save 20 off a new 1377. Get it down around the price of a refurb w/shipping.

[bradyman1]

Good luck on the project. Keep us up to date and throw up some pics.

[MountainMan126]

Thanks , I have big hopes for all the valve works pending a sealed pressure test. I am still working out an extended bolt idea and a few others.

[airgunandy]

1377 build-off just started on the Green Crosman forum.

http://www.network54.com/Forum/275684/thread/1323299777/2012+1377+Build-Off+Announcement

[MountainMan126]

I can't see myself in too many more forums, I just don't spend enough time on the computer to keep up with everything. I would be happy to steal this idea and build-off 1377s here. Anyone else up for some friendly competition?

[poomwah]

that would be a neat idea

[1377x]

since you are not flat topping yet!
you can stuff the stock piston add an o-ring under the pump cup and shave a little of the point off the valve face for a better fit in the cup
you will see some gain from those mods!

[MountainMan126]

since you are not flat topping yet!
you can stuff the stock piston add an o-ring under the pump cup and shave a little of the point off the valve face for a better fit in the cup
you will see some gain from those mods!

Thanks , already did it. I went to Dick's today and they will combine coupons. I got the 1377 brand new for a shade over 50 bucks. Chrony testing soon to get a start point and then tearing it down to put my valve in and should have the piston done tomorrow. I am working on a way to make it more rigid, so it will flex less under higher pressure.

[MountainMan126]

OK guys, I know we are all familiar with what these look like, but here is the brand new unaltered start pic.



This is the power adjuster I made, I used the original piece from the back and drilled all the way through, 5/16. Then tapped all the way at 3/8-16 and spent 70 cents for the set screw at the hardware.



I will post more pics and chrony #'s as we go.

Ethan

[1377x]

alrighty then!
sound like you are on the right track!

[MountainMan126]

I saw a post at some point that referenced using metal rods on the outside of the piston to stiffen it for less flex during pumping. I don't know where I saw it, but I haven't been able figure out a good method of attaching them where it will be secure enough to use. So I came up with this and drill a hole 5/32 straight down the middle and threaded this screw all the way through. Some light sanding on the base of the pump cup to clear the head, not much with the o-ring in there to space it out. A dab of adhesive on the top to make up for any lost friction having the pump cup spaced out from where it usually sits and here it is.





Anyone else done this, any documentable results, hunches?
Thanks , Ethan

[poomwah]

hey mountain man, could you post some more pics of the whole gun please

[MountainMan126]

The current pic is accurate, I have been modifying all the take off parts from my last project to use on this one. I want to get the chrony numbers of everything perfectly stock so I can have a start point and see what has an effect and how much. I will post plenty of pics as I go. Should get some more up tomorrow.

[1377x]

I saw a post at some point that referenced using metal rods on the outside of the piston to stiffen it for less flex during pumping. I don't know where I saw it, but I haven't been able figure out a good method of attaching them where it will be secure enough to use. So I came up with this and drill a hole 5/32 straight down the middle and threaded this screw all the way through. Some light sanding on the base of the pump cup to clear the head, not much with the o-ring in there to space it out. A dab of adhesive on the top to make up for any lost friction having the pump cup spaced out from where it usually sits and here it is.





Anyone else done this, any documentable results, hunches?
Thanks , Ethan

it called stuffing the piston
i used a very stiff rod about the size of a metal clothes hanger
cut it down ,a little longer than the slots in the plastic piston, leaving points on the end of the rod pieces
press them in the points lock the rod in place
i did see some gains cant recall right now what they were
ill try to find the post i put the results in

[MountainMan126]

First I will qualify by saying this is not a permanent addition, more an excercise in seeing if I could do it. This is the stock bolt and will only fit the plastic stock breech. I am hoping to get some info on extended vs. flow through in 177 , and will probably order the nicer looking product from Mellon air when I get a metal breech.

But in the spirit of " If you can you must " , here is the at home bolt extension. I used the dremel to make a dip in the center to keep the drill from walking, and the made a hole as deep as I thought I could without breaking the end off. Cut a piece from a broken drill of the same size, and made the first half of the hole larger to accomodate more epoxy. A little sanding and here it is. It is not pretty, but it is good for free.





Thanks for the info 1377x , I knew there had to be a name for it.
Ethan

[4th Yote Recon Bn.]

Hi All:

Let me start off by stating great thread. I had read the same article and the four rods were cut to size and epoxied in place. Mountain Man on your power adjuster how long was your 3/8 set screw and how many turns in to get the adjustments you were trying to get.

Thanks
4Th Yote

[MountainMan126]

Hey 4th yote, The set screw is short maybe twice as long as what is show in the photo. Is cut to a point on the forward facing side to seat on the spring with no additional grinding etc. From what I can see the position in the pic should put little to no tension on the stock spring, and be adjustable inward for more pre-load from there. I used 3/8-16 coarse thread because it was an easy fit to the hole sizing available , and has a better selection of hardware. I can get you better pics from the inside etc. if you want them.

[MountainMan126]

In an effort to remain as scientific as possible I will do all chrony numbers with CPHP ammo and worry about what it likes the best once complete. All numbers taken at 10 pumps. So here are the stock numbers I got right out of the box.

1-488.4
2-491.6
3-484.2
4-499.9
5-497

Average-492.18 FPS
Total deviation-15.7 FPS

[4th Yote Recon Bn.]

Mountain Man:

I would like to see additional pix. Now tell me how much energy you will expect to get by using this power adjuster?? I just saw your refurbed bolt and upgraded piston are there any plans to do a flat topped valve as well??

4Th Yote

[MountainMan126]

I installed the power adj. and it does not seem to have a huge impact on velocity. Numbers are bery similar to stock. I think what this means is that the factory spring does not generate enough force pre-loaded or other wise. This will get the disco spring eventually.



I have made a ton of mods to the valve, will post pics and right up on mods pending successful install and pressure test.