397 PA Reseal

397 PA Reseal

Joined: November 11th, 2013, 4:46 am

December 3rd, 2017, 5:02 am #1

Greetings,

Here's a couple of pictures of a 397pa I purchased from an archery buddy for fifty bucks. He said he wasn't shooting it but it would hold and shoot, the serial shows a Nov. 2013 manufacture. The rifle looks nearly new. To get this into shooting shape, I started by cleaning out the over spray in the barrel. It wasn't much but probably why he had the stock rear sight cranked to the right. I test fired it and it shot dead on with the rear sight centered. The accuracy proved to be very good with crosman 10.5 grain. I decided to re-condition the valve by using urethane rings and replace the probe o-ring with urethane as well. I disassembled and cleaned the 397. I should have took a couple of photos of the stuff that was in the tube.

The rear sight was removed and a Baker scope mount was added. I have an inexpensive 3x-9x to mount but I plan on getting an upgrade. This is my second 397pa. The other is an '09 that looks beat but is very accurate. I re-sealed that one about 5 years ago with urethane rings, it is still going. I rarely use 8 pumps - usually 6 or for longer shots - 7 max. The older one has a peep and is accurate with most any ammo - so I use mostly crosman hp's or pointed as they are easy to find.







Here's the older 397pa. I'll post some targets when I get out to shoot....EagleWhistle





Last edited by EagleWhistle on December 3rd, 2017, 10:56 pm, edited 1 time in total.
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Joined: November 11th, 2013, 4:46 am

December 3rd, 2017, 11:26 pm #2

There was a slight right to left breeze. Both 397s seemed to be most consistent at 6 pumps with CPHPs. First...the rifles...



The range...it is the second bale from the right. It is hard to see but the targets are on this bale.



Here's the first 5 shots taken with the Williams Peep. I was shooting the 10.5 brown box for this at 6 pumps. I was a little surprised at the consistency since I could just see a speck. I did manage to hit the dot one time, the others seemed to be affected by wind. These and all that follow are from a sitting position, with a right to left wind.



Here's a shoot-n-c from the same rifle/peep - 40 yards. Two are off, one on either side, but it's the shooter. I need more practice.



Here's a target with some sighters but the four in near the center are what I would consider how the newer 397pa will group with the scope at 40 yards.



Another target from the scoped 397...mostly sighters in this one. Maybe I can get some practice in when there is a calm day.



Good shooting....EagleWhistle
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Joined: September 2nd, 2012, 9:45 pm

December 4th, 2017, 12:52 am #3

Greetings,

Here's a couple of pictures of a 397pa I purchased from an archery buddy for fifty bucks. He said he wasn't shooting it but it would hold and shoot, the serial shows a Nov. 2013 manufacture. The rifle looks nearly new. To get this into shooting shape, I started by cleaning out the over spray in the barrel. It wasn't much but probably why he had the stock rear sight cranked to the right. I test fired it and it shot dead on with the rear sight centered. The accuracy proved to be very good with crosman 10.5 grain. I decided to re-condition the valve by using urethane rings and replace the probe o-ring with urethane as well. I disassembled and cleaned the 397. I should have took a couple of photos of the stuff that was in the tube.

The rear sight was removed and a Baker scope mount was added. I have an inexpensive 3x-9x to mount but I plan on getting an upgrade. This is my second 397pa. The other is an '09 that looks beat but is very accurate. I re-sealed that one about 5 years ago with urethane rings, it is still going. I rarely use 8 pumps - usually 6 or for longer shots - 7 max. The older one has a peep and is accurate with most any ammo - so I use mostly crosman hp's or pointed as they are easy to find.







Here's the older 397pa. I'll post some targets when I get out to shoot....EagleWhistle




Good looking gun there.

A lot can be done to the Benji valves to improve velocity.

I think 950 FPS with 8 pumps is possible with a 397.

Ronald
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Joined: November 11th, 2013, 4:46 am

December 4th, 2017, 1:31 am #4


Mr. Ronald,

I haven't thought about valve mods. The limitation on these 397s seems to be the pivot pin on the lever. It is thin - but hardened like a bearing.

What mods would get this to that power level? Would this put significantly more stress on the lever?

EagleWhistle
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Joined: September 2nd, 2012, 9:45 pm

December 4th, 2017, 3:43 am #5

If I had a 397/392 I would:

Flat top the valve and piston.

Bore the valve floor back about .100".

Machine a new valve seat with a 1/8" delrin valve stem.

Open the throat to .240".

Increase the valve TP to .170".

Port the TP opening.

Add a second O-ring by the TP opening.

I used a a Bengi valve in a gun with a Disco tube and got 825 FPS with 10 pumps with 14.3 CPHPs.
That was with a large valve volume with all the above mods except the second O-ring.
A 17 cal should get around 150 FPS more and with a lower valve volume around 1000+ FPS.

It would put more stress on the pivot if you pumped it towards the high end.
You don't have to pump it that high, it would be more efficient so less pumps required.

All my pump arm pivots are about 3/16" and I don't have any problems.

Ronald


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Joined: November 11th, 2013, 4:46 am

December 6th, 2017, 3:56 am #6

Ronald,

That would be nice if I could pull these mods off. My skill level and available tools are the limitations. I was thinking maybe stuffing the valve would get more pressure. These are good performers as is though.

Your suggestions sound a lot like a steroid conversion. I did own a Mac1 modified 392. It was a beast at 14 pumps with 18.1 JSBs. Should have kept that one but it was sold to fund a discovery/pump. Should have kept it as the build was high quality.

EagleWhistle
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Joined: September 2nd, 2012, 9:45 pm

December 6th, 2017, 2:31 pm #7

The steroid mod focuses mainly on beefing up the pump arm along with some valve mods.
There is a lot of performance to be had in the valve along with a FT piston and valve.

A steroid pump arm and a FT setup and other valve mods should yield around 950+ FPS with 14 pumps.
That is using 14.3 CPHPs.

I got 960 FPS with 15 pumps, same valve, 7" x .750" stroke with a reinforced 140 pump arm.

My MK based gun gets 791 FPS with an 18" choked LW barrel on 15 pumps.
It only has a 4" x .750" stroke, about 55% of a 392.
Longer is not better as the tube starts to flex as length increases.

Some steroid numbers:
http://www.network54.com/Forum/275684/m ... C+my+data-

CPs 14.3 grn:
4 pumps 565, 569, 563
6 pumps 658, 658, 660
8 pumps 728, 732, 731
10 pumps 762, 778, 772
12 pumps 814, 819, 814
14 pumps 840, 841, 840

Ronald
Last edited by GunNut10 on December 6th, 2017, 6:29 pm, edited 1 time in total.
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Joined: April 12th, 2002, 5:26 am

December 14th, 2017, 2:19 am #8

Good looking gun there.

A lot can be done to the Benji valves to improve velocity.

I think 950 FPS with 8 pumps is possible with a 397.

Ronald
in the cone of the valve, so you either make a new valve front end, or turn the old one down, solder on an addition and re-machine. Far easier is to fit an adjustable pump rod, or unscrew the valve front a half turn, to cut the head space.

Using an AS model rear half(with it's o-ring groove) lets you cut away the valve body so the main tube sees pressure, and nearly doubles the storage volume. Nice low pump effort,with an increase in power, at the cost of more pumps. Or set the gun up to retain air, and get as much as 900 fps on five pumps per shot, at similar lever effort to stock.

Not a project for the faint of heart, and Dan(the mod) what it's like.
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Joined: September 2nd, 2012, 9:45 pm

December 14th, 2017, 11:13 pm #9

somewhat similar to making a FT for a 2100.

I cut off about 1/2" from the front cone, then make a new FT cap.
They thread together so the new valve is 3 piece.

A FT adjustable piston compliments the valve.

Easy-Peasy

Ronald
Last edited by GunNut10 on December 14th, 2017, 11:14 pm, edited 1 time in total.
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Joined: April 12th, 2002, 5:26 am

December 20th, 2017, 4:07 am #10

A cutaway valve can be done with a purchased AS rear and a dremmel. .
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