Need help - 1701P frame and steel breech install

[WyoMan]

A decade ago James Perotti built a 1322 that would do 16 fpe on 18 pumps (with the oem barrel). His valve pressure was over 3200 psi and he could dump it all using the stock hammer spring and hammer.

I can't get anywhere near those numbers.  But I have built 10 or so of these and only one would retain air. The problem was an intermittent snag of the hammer by the top tube slot.

A lighter valve spring will help - as will some pre-load on the hammer spring...but...I can't help but think that something is dragging on the hammer.

Try shooting a 10 shot string over the chrony at about 6 or 7 pumps for each shot and see if your velocities are consistent....

[FLplinker]

A decade ago James Perotti built a 1322 that would do 16 fpe on 18 pumps (with the oem barrel). His valve pressure was over 3200 psi and he could dump it all using the stock hammer spring and hammer.

I can't get anywhere near those numbers.  But I have built 10 or so of these and only one would retain air. The problem was an intermittent snag of the hammer by the top tube slot.

A lighter valve spring will help - as will some pre-load on the hammer spring...but...I can't help but think that something is dragging on the hammer.

Try shooting a 10 shot string over the chrony at about 6 or 7 pumps for each shot and see if your velocities are consistent....

Thanks for the input. I'll post my readings now that I know what's going on and see if there are more suggestions.

[FLplinker]

Bone stock, 15 yr old, only shot about 5 times 1377. I did 5 shots with 1, 3, 5, 7, 8, 9, & 10 pumps. Then did 3 shots with 12 pumps and 1 with 15 pumps.
  1 - 147, 174, 168, 181, 155
  3 - 329, 332, 332, 340, 327
  5 - 409, 417, 409, 410, 409
  7 - 455, 470, 458, 464, 469
  8 - 483, 481, 493, 482, 477
  9 - 498, 488, 481, 498, 509
10 - 512, 505, 508, 514, 516
12 - 524, 525, 535
15 - 563

Then I installed items listed in earlier post (mainly longer barrel, longer bolt probe, power adjuster, hammer for 1701P grip assembly, and larger transfer port).
  1 - 205, 205, 214, 202, 219
  3 - 367, 368, 363, 370, 370
  5 - 438, 438, 444, 442, 456
  7 - 488, 496, 503, 498, 494  (Was so excited about improvements forgot to do the 8 pump string!)
  9 - 528, 539, 544, 557, 543
10 - 556, 571, 558, 563, 569
12 - 598, 583, 585
15 - 609

Put aluminum flat top valve and brass piston in as last mod (for now)

  1 - 220, 225, 235, 245, 227
  3 - 407, 402, 420, 416, 410
  5 - 512, 517, 515, 505, 525
  7 - 579, 578, 580, 588, 612
  8 - 635, 621, 586*, 610, 624
  9 - 587, 513

*I wondered why there was such a dip in the readings on 8 pumps. So after the second shot (621) I opened the bolt, closed it, pull trigger. Repeat and there was a good pop. Repeated again and there was a lesser pop. Repeated a third time and it was only the hammer hitting sound. So 586 was a cleared valve with 8 pumps.  Shots 4 & 5 were with no valve clearing. Just open bolt, pump 8 times, put pellet in, close bolt and fire. Since I am brand new to this modding, I didn't know what the details of using the power adjuster were and didn't do anything with it. I new by examining it and where it went that it either increased or decreased the pressure on the hammer, but didn't know why to adjust it.

After the 513 on 9 pumps, I opened the bolt put a pellet in, closed the bolt and fired over the chrony. It was 618 without any pumps. Did the same again and got 469 on the 3 shot. Then I quit out of lack of knowledge on what was going on and frustration that the numbers showed what they did.

What is the best way to set the power adjuster? Run it all the way in for maximum spring pressure, or adjust it to reach just enough pressure to get a full dump? Is there more modding to be done to insure a complete valve dump on one trigger pull?

[1377x]

I got 662fps using Berman Kodiak 21 grain pellets. The .22 barrel was 14.5" and the hammer spring was .062 stainless wire. IIRC it took30 pumps, the actual mods and numbers are or should be  around here in a thread I started.. the base gun is a phase 2 1377.  The old hammer assembly was molded the the extra heavy spring. I didn't secure  the assembly properly and it eventually fell apart. 20fpe was a milestone achievement never accomplished with the newer bolt charging 13xx.

[WyoMan]

Check your rear breech screw to make sure it's not interfering with the hammer spring...the last shot string looks like inconsistent hammer strikes. Also check your chrony setup. You got 513 fps, 618 and 469 with a single valve charge...that's over 15 fpe.

The PA or RVA is not really necessary for dump valve guns - it's mostly used for tuning pcp, hpa, and co2 guns. Screw it in to where the bolt won't cock and then unscrew 1 turn at a time until the cocking effort is acceptable.

[FLplinker]

Check your rear breech screw to make sure it's not interfering with the hammer spring...the last shot string looks like inconsistent hammer strikes. Also check your chrony setup. You got 513 fps, 618 and 469 with a single valve charge...that's over 15 fpe.

The PA or RVA is not really necessary for dump valve guns - it's mostly used for tuning pcp, hpa, and co2 guns. Screw it in to where the bolt won't cock and then unscrew 1 turn at a time until the cocking effort is acceptable.

Thanks WyoMan! That's what I needed to see. I'll give it a shot. Should of done my homework and I could of saved $35 for a mod that isn't for my pumper.

[WyoMan]

It's not a total loss. The RVA does some good. A little bit of spring pre-load with a spring guide will generally get you a crisper opening of the valve 

[FLplinker]

It's not a total loss. The RVA does some good. A little bit of spring pre-load with a spring guide will generally get you a crisper opening of the valve 

After reading your advice I adjusted it as you suggested. I kept unscrewing the adjuster and pulling the bolt back. The bolt would not latch open and I repeated until the knob came out the back!!! I then thought of your advice about the rear tube screw. Loosened it about 1/8 - 1/4 turn and heard a clunk and sure enough the bolt would lock back now. This was the first time the bolt gave me that problem. So I took the adjuster out and put the stock plug & spring back in. I did notice there is a grey discoloration and slight deformation of the spring guide at the hammer end. The guide is only about 1" long. Do I need to shim the screw, cut it shorter or what to resolve this problem and re-install as a working pre-load?

Also, with the stock spring I was still able to get 2 shots out of it on 5 pumps. I didn't put any pellets through it (sitting in the living room), but based on the sound the 2nd shot would of been less than 150fps but more than spitting it out the end of the barrel. So instead of ordering a heavier spring I'd just like to get the adjuster setup properly.

[bgmcgee]

You can shim or cut the spring either way. The steel breech should have came with a shorter screw. My preference is to cut the screw. It needs to be long enough to mate in the rear plug but not long enough to catch the spring. Most likely just a couple of threads off the end will be enough. Then you can use the rva like Wyoman suggested.

[WyoMan]

^^^ What bgmcgee said 

[quickster47 †]

Only question I have about that rear screw is did you perhaps change the rear sight or do you have a rear sight on this gun?

Carl

[FLplinker]

No rear sight since original will not work with steel breech. Using open optics on breech. (Crosman red dot)

[1377x]

Did you get the solid hammer from mellonair? If so his are slightly oversized, IMO, I had to sand and polish the heck out of then it worked correctly. Arkmaker made me one the same size as the original and it works great.  There is a reason the challenger hammer has flat sides. From what I have read its tube doesn't have relief hole the 22xx tubes do. IMHO the flats on the challenger hammer relieve the air cushion that slows the hammer down. In the 13xx guns the hammer is small enough to not create that cushion but my Mellon hammer did, it had a larger od than the stock hammer. The arky hammer was made to factory specs and has worked perfectly.

[MaxPow3r]

Your flat top valve is holding air!
Take the trigger/sear spring out of the grip frame you replaced and put it in the flat top valve.  It is a little bit lighter spring and should allow you to dump all the air out of the valve.  Worst case is that you may have to cock the gun before pumping.

You can also go with a power adjuster from C. Mellon but I would try the change of valve spring first.

I bought a 1322 with the FT piston and valve work done for me. I can't pump it without cocking the gun first. Can you explain to me why this happens and if I need to try and fix it?

[bgmcgee]

I bought a 1322 with the FT piston and valve work done for me. I can't pump it without cocking the gun first. Can you explain to me why this happens and if I need to try and fix it?

Most likely it has a light spring inside the valve and could have a stronger hammer spring. Without any air pressure in the valve the hammer is keeping the valve open. There is nothing wrong with this setup as you can dump quite a bit more are from the valve resulting in more power as long as you don't mind pumping a bunch.