Crosman 140 and the 12 ft/lb limit

[Phil B]

Just bought one and really love it. An interesting and accurate rifle.

However....

I know you can pump these and fill the "tank" and on trigger release, ALL of this stored air is sent down the barrel.

Questions.

Before I design/make a new piston with a blow off valve to set at the pressure that produces say, 11 ft/lbs, has anyone done this before?

Any designs out there?

Is there another piston out there that fits/can be modded to fit, that has a blow off valve built in?

Long shot I know.
Thanks for reading.

[crowbar]

Shorten the piston stroke so it will only pump to required pressure and any extra pumps will not open the fill valve .

[crowbar]

As less air is required a sleeve can be made to reduce the volume of the firing pot which will reduce
the amount of pumps .

[cringe]

As less air is required a sleeve can be made to reduce the volume of the firing pot which will reduce
the amount of pumps .

if you disassemble the air reservoir you can insert a small cylindrical piece of aluminium I guess about 8 millimetres diameter x 6 to 8 mm long?, this will limit the amount of air you can compress. hope this helps.

[Phil B]

Great ideas chaps and all easier than making a valved piston. I wanted to avoid mumping say 10 times to get maybe 10ft/lbs. Rather five and get to max and the valve blows off telling you it's maxed out.

Please keep the ideas coming. I'm new to Crosmans, all my other pumpers are Sheridans (1963, '68, '73 and '85). Totally different system, easy to pull back to the UK limit.

[averageplinker]

Whatever solution you find, take care not to make the pumping action to hard/stiff for fear of bending or straining the pump links.

[cinedux]

'cringe's idea.A wee cylindrical block of aluminium!

[Mark D]

Keep it simple - just put less pumps in it

[T 20]

Great ideas chaps and all easier than making a valved piston. I wanted to avoid mumping say 10 times to get maybe 10ft/lbs. Rather five and get to max and the valve blows off telling you it's maxed out.

Please keep the ideas coming. I'm new to Crosmans, all my other pumpers are Sheridans (1963, '68, '73 and '85). Totally different system, easy to pull back to the UK limit.

The later Crosmans had a sprung piston head, when the pressure in the system reached a certain point the spring pressure was overcome and the piston head moved forwards so limiting pressure and velocity.



All the best Mick

[45flint]

I've got two Crosman pumps and it would be very difficult to get them past 12 FP? There are sterioded Sheridans that push it easily but your normal Crosman I think would be really forced to get there. What will happen if you use it normally and fire it in legal limits. Is some official going to come ever and pump the cramp out of it and chrony it?

[--ped--]

A few options but if you can make a blow off piston that is the best way,I made one as an experiment for one of my pump pistols but finding small springs that were strong enough was a problem
You could also go down the route of a valve blow off as used in UKspec 2200's but this would take more work to do
The valve volume reducer from a 1322 or a 1300 could be used but I think you'd just create higher pressure in the valve faster
A smaller tp could be used but simply adjusting piston so as to leave head space will lower power but the pump arm won't stay up unless the gun is charged with air

[Phil B]

A few options but if you can make a blow off piston that is the best way,I made one as an experiment for one of my pump pistols but finding small springs that were strong enough was a problem
You could also go down the route of a valve blow off as used in UKspec 2200's but this would take more work to do
The valve volume reducer from a 1322 or a 1300 could be used but I think you'd just create higher pressure in the valve faster
A smaller tp could be used but simply adjusting piston so as to leave head space will lower power but the pump arm won't stay up unless the gun is charged with air

I've ordered some Belleville spring washers, so hopefully that'll give be great spring resistance in a compact space, ie in the piston head.

I like the idea of reducing volume, even at max pressure it should reduce available volume at that high pressure, equating to lower ft/lb energy and also quicker pump up.

This rifle would be likely capable of as much as 20 fpe apparently!!

As an aside, every Sheridan I've ever owned arrived capable of 15-16 fpe and had to be tamed to suit!

Thanks again for the interesting and informative replies.

[--ped--]

I used die press retun springs for the prototype I made
I've only tested it in a 1322 pistol I made and it keeps it under 6 but not had time to test in a 140 as yet but recently got a scabby 4th model so may use it as a test gun

[Biker_Bob]

I played with a 140 for the exact reason you're playing with yours.
I tried shortening the pump stroke, this did limit the power but also made pumping much less efficient. To shorten the pump enough ensure it didn't go above 12 ftlbs, you were then looking at 20 odd pumps to get to 11ftlbs.
I tried reducing the valve volume by putting a slug inside it, it did yield a reduction but not enough, it would have needed a new valve making.
I think the only way to go is to make a blow off pump head similar to Sharp and later Benjamins. In my experience these types of valves are quite variable.

[Phil B]

What will happen if you use it normally and fire it in legal limits. Is some official going to come ever and pump the cramp out of it and chrony it?

Yes they will. It's happened before.

Dependiing on your history, it could get you up to 5 years of free poridge as it will be deemed you are in posession of a Section 1 firearm.


Biker Bob, thanks, sage advice too.