Benjamin 397P Phase 1

[ratbuster2240]

Excellent work Louis that's a really efficient modification and good performance from a rifle that might have been binned.

It could also be used then to de-tune the power if it's too close to our UK limit. Without having to cut springs down and leaving residual air after each shot it will be more consistent.

I wouldn't worry about causing damage to the valve a few millimeters of adjustment is probably just taking up the slack of a compressed rubber pump cup.

[--ped--]

it is Louis
i once removed a soldered in valve from a gun i bought that had been cut in half,and once soldered i have no real concerns about the valve breaking free
i have made adj piston rods for a few of my c series and whilst inc head space will lower power i prefer to use my lighter springs and adj spring seats


the adjuster

[ratbuster2240]

Very cool! I read a post on here that someone cut up his old Sheridan because it was over the limit. It's shame he didn't just fit one of these.

[--ped--]

i think i got it off the other forum and the lad had put an hacksaw through it before he could be talked through reducing the power
it was a real shame as it had a real nice stock and was in fair condition ,still the parts were used to fix 3 other sheridans and the barrels pieces made a couple of .20 crosmans

[ratbuster2240]

That was probably the one I saw, glad you got it off him to fix up the others.

i think i got it off the other forum and the lad had put an hacksaw through it before he could be talked through reducing the power
it was a real shame as it had a real nice stock and was in fair condition ,still the parts were used to fix 3 other sheridans and the barrels pieces made a couple of .20 crosmans

[ratbuster2240]

I knocked the original rear sight off and mounted the Williams peep. It took a bit of time to zero and I prefer it over the scope, it's lightweight simple and fun to shoot.



I had issues with modern silencers blocking out the foresight and I was grateful to find a Parker Hale MM1 in the wanted section. This one is lightweight aluminium and is approximately 22mm in diameter, for the size does a very good job. You use to see them everywhere but have now been superceded by more efficient mods like the HW. It was interesting to read the design goes way back to the original Maxim silencer in the early 1900s.



I like slings to keep my hands free and I don't like putting my rifles on the ground or leaning them against a tree to potentially get damaged. Without the need to drill holes I put on these inexpensive universal slings that cinch down and can be slid out of the the way when pumping.

[--ped--]

looks good with a peep on i have one on one of my later rescue c series

[ratbuster2240]

looks good with a peep on i have one on one of my later rescue c series

They are great sights Ped, I've been getting some tight groups with it. This is a no frills one but I like the fit and forget style. I have had to adjust the windage quite far to the right, I've still got some more room for adjustment but anymore and I'll have to shave a mm or two off the attachment.

[ratbuster2240]

I had some fun earlier dialing in the Williams peep and using an advent calender as a shooting card. Rested and kneeling at 10 meters I got just over 1/4" group with 5 shots using JSB's.
The peep sight seems much more precise than the standards sights.

[jirushi]

Wow very nice!

Same here, I have tried a scope on my Blue Streak but I took it off quite quickly. Standard opens are ok, but indeed the peep sight is great.

This is a great thread, thank you for the updates.

[ratbuster2240]

Thanks Louis. I'm glad you enjoy it, it's keeping me sane playing around and shooting these fine airguns.

Wow very nice!

Same here, I have tried a scope on my Blue Streak but I took it off quite quickly. Standard opens are ok, but indeed the peep sight is great.

This is a great thread, thank you for the updates.

[ratbuster2240]

Tonight I stripped the Sheridan C-Series down to try and find out why it's only producing 7-8 Ft-lbs. I am hoping fresh seals and a thorough clean will bring the power up. I would appreciate any suggestions.



All the seals looked original so it was due a refresh. It did strip down quite easily apart from the end plug which was in tight and I had to be careful not to damage the finish. A hair dryer, WD40 and gentle tapping eventually got it moving. Thankfully the valve nut and valve thread was in good condition and unscrewed by hand using the valve tool. Perhaps it may have been a little too loose and allowed air to escape away from the port?

The front valve seal (black plastic) was in pieces but I don't think it was a problem because it held air for months, but could it allow air to escape back down the cylinder when the valve is unseated?



The hammer was covered in thick hardened grease, although it may have slowed the hammer it wasn't an issue because it dumped all the air on firing.

I noticed there are two holes at the back of the valve and I wondered if this is for a lower power/restricted model?



The inlet seal was in good condition and the usually heavy oxidation was present over the internals.

The trigger looks like it has been modified to lighten It, I don't remember seeing later ones with these fitted?

[jirushi]

Hi,

I have never seen the two holes in the brass valve part before. Perhaps indeed a modification to make the Streak UK legal? Probably Ped knows.

I might have a spare one here without the holes; if you can use it, I would gladly send it to you. I think I also have a spare valve stem which was resealed by Lawrie a few months ago. He punches the stem out and fits a high quality polyurethane seal, which should last a very long time. Ped sells seal kits. I would re-use the lead seal, as I have found that they work best. With non lead replacements, it is often extremely difficult or impossible to get the valve nut on again.

With the sticking trigger block, I usually remove the trigger mechanism and stick a punch pin in the trgger axis pin hole, and then turn. They always come loose easily that way, but perhaps you did this, and in any case your method worked too.

Are you going to use the Mac1 adjustable pump arm? That will have a good, new pump cup. And you can make it touch the valve face nicely. Ped has given guidance above on how much you can make it cam over without causing damage. UJ Backus, the Sheridan guru from the USA, advised me that he adjusts to half an inch between pump arm and bottom of cylinder when the pump cup first touches the valve.

Are you also sure that there is no air leaking from the sides of the breech? My Silver Streak had hairline crakcs on either side of the breech, a result from the previous owner using the infamous intermount. I had to separate the entire breech in order to re-attach it firmly so that the tp would seal again. This gave a dramatic power rise.

Have fun!
Louis

[--ped--]

the two holes in the exhaust body are what is causing the power to be low and it is what croaman did with the 1377 UK/Can spec guns-the earlier 1322 had it's power lowered by the same idea just it was an alteration to the stem
for the stem don't bother trying to put a new seal on replace it with a as2250 one or a shortened 22xx one -you can also fit a discovery one which is what is fitted in a Mac1 steroided gun
to fix the exhaust body just thread the holes and fit small grubscrews

[ratbuster2240]

Thanks guys that's very helpful!

I've shone a torch around the soldering and I can't see any cracks or light coming through. It didn't come with an intermount and I can't see any tell tale marks one was used. In comparison the the Racine 397P has a much longer and chunkier breech.

It looks likely that the exhaust body is the cause then, The 397 didn't have the holes and probably didn't need it being .177. Thank you Louis for offering me a spare, I will be in touch to buy it off you. I doubt a reseal will increase the power enough with the restricted valve.

I have spare AS2250 (king ratcatcher) and Benjamin Discovery valve stems. I used a Discovery stem in the 397 and I have been happy with that. I also have spare Ped seals to go in.