1377 to 1322 upgrade, my results. Need stronger hammer spring?

1377 to 1322 upgrade, my results. Need stronger hammer spring?

Joined: January 9th, 2008, 5:55 am

October 8th, 2011, 2:24 am #1


Today I upgraded my 1377 with Crosman steel breech to a 1322. I still haven't decided which barrel I am going to keep as I have a 14.65" one from a 2250, a Mellon Air 12" one (*very* nice! Will order more!) or what I currently have on there which is a 24" Crosman barrel.
I ordered from Mellon air the Adjustable FT piston, FT valve, bolt and 2289 barrel band. Installed them all today.
Before I installed the FT piston and valve I did some baselining:

.177 pellets are CP 7.9's
.22 pellets are CP 14.3's

Stock 1377, 10 pumps: 506 fps 4.49 fpe
15 pumps: 555 fps 5.40 fpe
20 pumps: 573 fps 5.76 fpe
( I also tried a CP Heavy 10.5 with 20 pumps and got 497 = 5.76 fpe )

.22 testing using the stock valve/piston
I then put on the 10 inch, 14.6 and 24" barrels and tested with the stock valve/piston.

10 inch:
10 pumps: 444 fps 6.26 fpe
15 pumps: 468 fps 6.92 fpe
20 pumps: 508 fps 8.19 fpe (only tried this once, not 5-6 times like the others)

14.6 inch:
10 pumps: 466 fps 6.89 fpe
15 pumps: 490 fps 7.62 fpe
20 pumps: 508 fps 8.19 fpe (only tried this once, not 5-6 times like the others)

24 inch:
10 pumps: 513 fps 8.35 fpe
15 pumps: 549 fps 9.57 fpe
20 pumps: 566 fps 10.17 fpe (only tried this once, not 5-6 times like the others)

This was all very tiring, and as of yet I had no idea how much harder pumping would be with the FT piston in

I installed the FT piston and valve and tested ONLY with the 24" barrel:

8 pumps: 526 fps 8.78 fpe
9 pumps: 544 fps 9.399 fpe (note all 6 shots I took were 554.x fps!)
10 pumps: 552 fps 9.67 fpe
11 pumps: 562 fps 10.03 fpe -- NOT dumping all it's air.

Since it wasn't dumping all at 11 pumps I wasn't going to go any further, but wanted to try at least one shot with 20 pumps and got 2 shots with the air:
1st shot 483 fps 7.40 fpe
2nd shot 550 fps 9.60 fpe
7.4 + 9.6 is 17 fpe! I want to be able to dump all that in a single shot!

..so to reach this goal I guess I need a stronger hammer spring? Should I just go and order a 2200 magnum spring?
I may hit Ace Hardware tomorrow and see if there is something that I can use there in the meantime.

Suggestions?

[ Note I'm posting this same text to multiple AG forums ]
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Joined: March 19th, 2011, 2:50 am

October 8th, 2011, 2:34 am #2

instead of the heavier hammer spring, you could also try a power adjuster (mellonair makes one for 1377s) and/or a lighter valve spring.

I've tried a heavier springs in mine, but I much prefer the lighter valve spring with an AC Customs wire stock that has a built in power adjuster. I have mine set to dump 15 pumps.
With the heavier hammer spring, it felt like I was putting extra stress on a lot more parts.
Another plus with using a power adjuster, it makes swapping springs much quicker since all you have to do is unscrew the power adjuster to remove the spring.
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Joined: February 25th, 2011, 10:27 pm

October 8th, 2011, 2:45 am #3

Today I upgraded my 1377 with Crosman steel breech to a 1322. I still haven't decided which barrel I am going to keep as I have a 14.65" one from a 2250, a Mellon Air 12" one (*very* nice! Will order more!) or what I currently have on there which is a 24" Crosman barrel.
I ordered from Mellon air the Adjustable FT piston, FT valve, bolt and 2289 barrel band. Installed them all today.
Before I installed the FT piston and valve I did some baselining:

.177 pellets are CP 7.9's
.22 pellets are CP 14.3's

Stock 1377, 10 pumps: 506 fps 4.49 fpe
15 pumps: 555 fps 5.40 fpe
20 pumps: 573 fps 5.76 fpe
( I also tried a CP Heavy 10.5 with 20 pumps and got 497 = 5.76 fpe )

.22 testing using the stock valve/piston
I then put on the 10 inch, 14.6 and 24" barrels and tested with the stock valve/piston.

10 inch:
10 pumps: 444 fps 6.26 fpe
15 pumps: 468 fps 6.92 fpe
20 pumps: 508 fps 8.19 fpe (only tried this once, not 5-6 times like the others)

14.6 inch:
10 pumps: 466 fps 6.89 fpe
15 pumps: 490 fps 7.62 fpe
20 pumps: 508 fps 8.19 fpe (only tried this once, not 5-6 times like the others)

24 inch:
10 pumps: 513 fps 8.35 fpe
15 pumps: 549 fps 9.57 fpe
20 pumps: 566 fps 10.17 fpe (only tried this once, not 5-6 times like the others)

This was all very tiring, and as of yet I had no idea how much harder pumping would be with the FT piston in

I installed the FT piston and valve and tested ONLY with the 24" barrel:

8 pumps: 526 fps 8.78 fpe
9 pumps: 544 fps 9.399 fpe (note all 6 shots I took were 554.x fps!)
10 pumps: 552 fps 9.67 fpe
11 pumps: 562 fps 10.03 fpe -- NOT dumping all it's air.

Since it wasn't dumping all at 11 pumps I wasn't going to go any further, but wanted to try at least one shot with 20 pumps and got 2 shots with the air:
1st shot 483 fps 7.40 fpe
2nd shot 550 fps 9.60 fpe
7.4 + 9.6 is 17 fpe! I want to be able to dump all that in a single shot!

..so to reach this goal I guess I need a stronger hammer spring? Should I just go and order a 2200 magnum spring?
I may hit Ace Hardware tomorrow and see if there is something that I can use there in the meantime.

Suggestions?

[ Note I'm posting this same text to multiple AG forums ]
did you try this? MellonAirs Power Adjuster?

http://www.mellonair.com/index.php?p=1_8_Power-Ajusters

You can increase spring tension with it.

Note: If you are using a steel breech, you may need to add a tiny washer under under rear breech screw, use a shorter screw, or file down the screw. Reason being that the top screw may pinch the spring...
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Joined: January 9th, 2008, 5:55 am

October 8th, 2011, 3:10 am #4

Several people have suggested the MellonAir power adjuster (http://www.mellonair.com/index.php?p=1_8_Power-Ajusters ) rather than just replacing the spring-- that sounds like a good idea to me as well so I'm going to order one of those right now
If I could get 15 fpe on 15 pumps as others report I'd be satisfied (at least for now, you know how these things go )
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Joined: April 28th, 2010, 12:23 am

October 8th, 2011, 3:15 am #5

basically have it as a true pumper dumper. dont have it shut after the hammer hits the valve .. its duration , not a matter of spring strength
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Joined: January 9th, 2008, 5:55 am

October 8th, 2011, 3:27 am #6

How would I do that?
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Joined: December 3rd, 2008, 11:42 pm

October 8th, 2011, 6:26 pm #7

Today I upgraded my 1377 with Crosman steel breech to a 1322. I still haven't decided which barrel I am going to keep as I have a 14.65" one from a 2250, a Mellon Air 12" one (*very* nice! Will order more!) or what I currently have on there which is a 24" Crosman barrel.
I ordered from Mellon air the Adjustable FT piston, FT valve, bolt and 2289 barrel band. Installed them all today.
Before I installed the FT piston and valve I did some baselining:

.177 pellets are CP 7.9's
.22 pellets are CP 14.3's

Stock 1377, 10 pumps: 506 fps 4.49 fpe
15 pumps: 555 fps 5.40 fpe
20 pumps: 573 fps 5.76 fpe
( I also tried a CP Heavy 10.5 with 20 pumps and got 497 = 5.76 fpe )

.22 testing using the stock valve/piston
I then put on the 10 inch, 14.6 and 24" barrels and tested with the stock valve/piston.

10 inch:
10 pumps: 444 fps 6.26 fpe
15 pumps: 468 fps 6.92 fpe
20 pumps: 508 fps 8.19 fpe (only tried this once, not 5-6 times like the others)

14.6 inch:
10 pumps: 466 fps 6.89 fpe
15 pumps: 490 fps 7.62 fpe
20 pumps: 508 fps 8.19 fpe (only tried this once, not 5-6 times like the others)

24 inch:
10 pumps: 513 fps 8.35 fpe
15 pumps: 549 fps 9.57 fpe
20 pumps: 566 fps 10.17 fpe (only tried this once, not 5-6 times like the others)

This was all very tiring, and as of yet I had no idea how much harder pumping would be with the FT piston in

I installed the FT piston and valve and tested ONLY with the 24" barrel:

8 pumps: 526 fps 8.78 fpe
9 pumps: 544 fps 9.399 fpe (note all 6 shots I took were 554.x fps!)
10 pumps: 552 fps 9.67 fpe
11 pumps: 562 fps 10.03 fpe -- NOT dumping all it's air.

Since it wasn't dumping all at 11 pumps I wasn't going to go any further, but wanted to try at least one shot with 20 pumps and got 2 shots with the air:
1st shot 483 fps 7.40 fpe
2nd shot 550 fps 9.60 fpe
7.4 + 9.6 is 17 fpe! I want to be able to dump all that in a single shot!

..so to reach this goal I guess I need a stronger hammer spring? Should I just go and order a 2200 magnum spring?
I may hit Ace Hardware tomorrow and see if there is something that I can use there in the meantime.

Suggestions?

[ Note I'm posting this same text to multiple AG forums ]
On 15 pumps with the mods below I was able to get

1377 15 pumps - 750fps
1322 15 pumps - 650fps

Flat top
lighter valve spring
heavier hammer spring
24" barrel
trigger mods
Didn't want to mess with the port

I had fantasies of getting 1000fps, somebody may be able to do it. I stopped and am happy with were they are. Acuracy is great and shot placement counts for alot.
Cleaning and oiling the barrel can get you abit more fps.
Have fun


Last edited by ehbob on October 8th, 2011, 6:35 pm, edited 1 time in total.
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Joined: April 28th, 2010, 12:23 am

October 8th, 2011, 10:59 pm #8

How would I do that?
maybe a different valve all together, or wayyy bigger port..
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Joined: September 26th, 2003, 2:20 am

October 9th, 2011, 12:21 am #9

How would I do that?
There needs to be some sort of balance between the striker spring and the valve return spring. If there isn't, you can damage the gun. The cocking pin will strike the front of the slot, and the pin will bend. The slot will get ginked and the striker won't slide as it should. The striker could smack the valve face if the valve stem is short, or if the valve stem is too long to go entirely into the valve, it will get bent.
In order to go further, the transfer port needs to be made a bit larger, up from the 1/8" port to 3/16" or 1/4". 3/16" would probably be best. Use 3/16 ID clear poly tubing, like you find in a refrigerator or aquarium. Open up the port on the valve to the same size, and the prot in the barrel as well.
As to barrels, it long been thought that the optimum length for this sort of thing is about 18".

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Joined: September 6th, 2006, 3:27 am

October 9th, 2011, 6:42 am #10

And , A stronger hammer spring should be added.
For .177 to .22 I use 1/4" poly tube for the port seal, for .22 to .25 I use 5/16". for anything larger then .25 cal, use 3/8 tubing...though that last bit of info has little to do with a 13xx build.
I found the optimum barrel length for a .22 cal 13xx in pistol configuration is 12" for power,looks and handling.
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