Benjamin 397P Phase 1

[AllanM]

As you say, you don't see many Model F's in the UK and they are starting to fetch high prices in the states -- they are my favourite CO2 rifle although I would dearly like to get my hands on a Howa 55G.
I am not a fan of scopes on pumpers but, if you feel the need, the only way to go (IMO) is the long eye relief scout type like your nice little Weaver -- better still, forget the scope and use a Williams peep sight!

[ratbuster2240]

Thanks AllanM

I have seen the Howa and it looks like a full bore rifle. Great quality

I agree with you on not scoping them, nice and lightweight and easier to pump without an optic. I have a Williams peep sight on it, I had to file down the screws as they were touching the bolt I may transfer the peep to the Sheridan. Although crude, the original sights work just fine.

As you say, you don't see many Model F's in the UK and they are starting to fetch high prices in the states -- they are my favourite CO2 rifle although I would dearly like to get my hands on a Howa 55G.
I am not a fan of scopes on pumpers but, if you feel the need, the only way to go (IMO) is the long eye relief scout type like your nice little Weaver -- better still, forget the scope and use a Williams peep sight!

[MartynB]

Thanks AllanM

I have seen the Howa and it looks like a full bore rifle. Great quality

I agree with you on not scoping them, nice and lightweight and easier to pump without an optic. I have a Williams peep sight on it, I had to file down the screws as they were touching the bolt I may transfer the peep to the Sheridan. Although crude, the original sights work just fine.

Googled and seen some pics, a bit of stunner

[jirushi]

I eventually found a nice quality used pistol scope in the sales section for my scout set up.
It's a nice Japanese made Weaver 1.5-4 x 20 and well cared for by the last owner.

The original Sheridan barrel mount is surprisingly sturdy and I havent had any issues with these or the Benjamin 4 piece mounts moving or causing barrel separation. I have ordered a Mac1 airguns mount which supposedly clamps to the barrel without making contact with the cylinder.

Another recent addition is a really compact Huggett Atom Belitta which is the smallest in the range at 89mm and weighs just 70g. Sure my other mods Sak, HW and Logun are quieter, but the Atom reduces the snap at the muzzle without adding too much length.

Looks cool, ratbuster2240
I have seen three Sheridan/Benjamin pumpers with barrel separation over the last six months or so.
All had been used with the Intermount lol.
It isn't a problem on a Model F when not overtightened.
However when the scope is held during pumping, which is often the case, then even without overtightening, the barrel can come loose.
Two had barrel and breech separation.
The last one was a nice looking Silver Streak from the first owner's grandson, complete with the manual, for 150 euros.
It was scoped. I should have known....
At home it turned out to be very low on power. Plus I felt a whiff of air on my hand during the shot.
A crack on both sides of the breech.
Had to separate it completely, plus the first half of the barrel, to repair it.
Now shooting good, 200 m/s on 8 pumps (thanks to Loctite 380; works much better for me than JB Weld).

[ratbuster2240]

Thanks for sharing your experience Louis. It looks like pumping whilst holding on to the scope now goes to the top of the list of likely causes.

[ratbuster2240]

I have just fitted a nicely made Ped moderator adaptor which is a lovely snug fit. The rifle came with a female adaptor which I have now passed on to another member. The only issue is I will have to get a slim Parker Hale sized mod as the others block out the foresight.

[ratbuster2240]

With not a lot else to do at the moment, I've spent some more time on the lockdown 397P.

I've now got a good supply of the famous MAC1 airguns Secret Sauce and it does seem to help the piston glide nicely. I made up some small needle oil droppers with about 10ml in. Time will tell if it's any better than Pellgun oil or even 30w non-detergent motor oil.

The adjustable piston has a stainless steel head and the original rubber pump cup, but with the 397 making good power I'm now going to install this in my Sheridan C series.

Lastly the IA scope mount which clamps very securely and without risking barrel separation, unlike the original 2 and 4 piece mounts I have previouly tried. A small piece of electrical tape between the barrel and mount helps to prevent it marking the finish and slipping.

[--ped--]

the Mac1 stuff is good and you'll notice it will build pressure up better with an adjustable piston
the green co2 oil i do is not what is sold by Mac1 but is the same oil,i did try to get it shipped over but previously Tim had stopped shipping it to the UK

[ratbuster2240]

great! It's good to know it can be had here. It's meant to be better at reducing valve oxidisation.

[jirushi]

Very nice. Coincidentally, I have also recently received a IA (Ingvar Alm, the late designer and famous airgun collector) mount from Mac1, and the adjustable piston.
Tried to finish adjusting the piston this morning before work, but there's a bit more tinkering to come.
It will be interesting to read your results.
The current length of the Mac1 piston is a tad more than the original one, but it isn't long enough: correct me if I'm wrong, but I think the pump cup should make contact with the valve on closing the pump arm. Just a bit? I can't feel that atm.

[ratbuster2240]

Hi Louis, I remember from other adjustable pistons it can be a bit of a chore getting the correct length. From memory most people find it only needs a few mm, I think the early ones were adjustable to accommodate the slight wearing and compression of the rubber pump cup.

Ped once suggested putting the piston in and marking it through the pivot hole when it touches the valve. This might make it easier getting it there.

The Mac1 website states: Mac1 Steroid Piston Head includes the Factory Pump Cup. (OAL) Length of adjusted piston is 7.25".

I'm sure I've seen a photo of several original pistons in different lengths, so they may vary over the years.

[ratbuster2240]

The Benji is now shooting 11.2 ft-lbs consistently with a Crosman Premier 10.5gr but the .20 Sheridan C- series is only doing 8 ft-lbs. It pumps and holds air fine and it feels like the first 2 pumps are weak, so I'm hoping it just an inlet seal, but I won't know for sure until the valve is opened up.

[jirushi]

Hi, yesterday I finished tweaking the Mac1 adjustable pump rod for my Blue Streak.

I increased the length with about half a cm, from how I got it from the States.

A lucky shot: it seems to be perfect now. It makes contact with the front of the valve, and then cams over. I am a bit worried that it might damage the valve when all this force is put on it with each pump, but I think it will be ok? Ped, may I ask you advice on this?

The power increase is nice.

3 pumps: from 124 to 139 m/s (456 ft/s). 6.3 ft/lbs
4: 140 > 157 (515 ft/s) 8.1 ft/lbs
5: 150 > 173 (568 ft/s). 9.8 ft/lbs
6: 162 > 185 (607 ft/s). 11.2 ft/lbs

In other words, be careful in the UK.

I was using 4 pumps for plinking, now I get the same velocity with 3 pumps.

I bought this Streak for 35 euros; it had breech and barrel separation (about a third of the barrel).

[--ped--]

i set an adjustable piston on solder valves so it has about 6-10mm clearance between the tube and arm

[jirushi]

i set an adjustable piston on solder valves so it has about 6-10mm clearance between the tube and arm

Hi Ped is that the distance between de end of the forearm (approx at the rubber shock absorber) and the cylinder at the moment when the pump cup makes contact with the valve? Cheers