Mac 1 USFT ???

 Decent valve design and if it is the tube version doesn't really get bthat many shots. If shooting 18+fpe in .177 you cant finish an FT match on a single fill. With the Ninja paintball battle used on some the fill is to 3,000psi and yes you get a lot of shots.

It takes less than 1,100psi to shoot 900fps+ in .177.

John

I have never shot or even seen a USFT in person, so I am answering based on experience with other lower fill pressure guns. As an example, the Benjamin Discovery is a 2000psi gun, yet it can shoot .177 and .22 cal pellets just as fast as a gun that is filled to 3000psi. But, if the disco was safe to fill to 3000psi, it wouldn't fire or atleast not very fast anyway in stock form, as the valve would probably lock due to the much higher fill pressure. It takes a certain amount of hammer inertia to over come the valve poppet based on how much pressure is in the storage side of the tube or bottle. This sort of illustrates the basic principle that fill pressure vs hammer weight combined with hammer spring tension is a balancing act of sorts.

Valve porting and a whole bunch of other variables can contribute to the success level of tuning and or designing a gun for certain pressures, speeds, etc. The increased shot count I assume comes from some sort of anti hammer bounce design coupled with a very efficient gun to start with. 

Just my 2 cents worth, but I could be totally wrong as i have no clue how the usft was built.

you have described the USFT Richard
even with the Ninja regulator it has the biggest plenum i know of

I have a first gen USFT Hunter in 20 cal. The USFT hqs a huge reservoir that would be impractical for most airguns. 

David Enoch

This is my friend Pat's Mac-1 Hunter: (old style here, I think-?- it comes with a ninja bottle now as one way to go?)




And just for fun Pat sighting in at the 2010 GOB event:


Sorry not sure what size the tank is, no one seems to know/care ( out of the half dozen usft owners I know), you either like the bag-o-pipes aka rifle, or you don't. Darn nice triggers and shooting Pat's rig off a bench I must say this particular example does group. HUGE dia. low pressure tube with burst disc ( maybe an 1,800psi disc ?) It is set for about 18fpe using 10.5g and gets 36 to 40 ( heck if I know why except maybe an unseen difference in the rifles gauge ) shots per fill.
Or you are looking for information on the ninja airtank type?

John

 Learning is just one more great thing you can do with airguns. You wont find a diagram, not that many made and really not needed. Any Field Target near you? If so someone will have one you can look at. You might try surfing for the Simple Simon- the firsat 7-8 that LD made- which became the USFT when timmy started making them for sale.
Leonardj ( maybe on the Canadian forum) made a copy, the pictures seem to be gone though. You could ( hehehe ) join LD's private pay top play forum, might be some information there.
Really if you looked at one in person, every part is viewable, except the check valve and valve stem head. 3,000psi burst disc, thought I should correct that.
The low pressure thing is no dofferent than other pressures, some ole principals apply. The big difference is a much ( MUCH)_ lighter hammer and the dwell achived . Balancing the psi/hammer/springs principal is the same ideas You could have fun tuning any rifle you might own to low psi if you had a scuba tank that was down to say 1,500psi and tethering to it, HUGE volume low pressure. 
A QB78 ( converted to HPA with a ninja tank) using 1,100 psi, with the tank tuned off will give you two shots at 12fpe, it was more fun than it sounds like playing with it.
You might in fact enjoy tinkering with a QB78/79, totally different design that the USFT but still the same theorys apply.

The USFT model that got 60+ shots per fill had a HUGE airtube , you could drop a few 500cc airtubes inside it. To get more power and keep the total fps spread reasonable a regulated HPA tank was needed, thus the newer ones with the ninja tank.

Really want to get into the USFT that Red one might be for sale - it is not mine but I do know where it lives.

Keep us posted as you move through this exploring lower psi thing.

John

they use weights on the hammer to adjust power his 30 cal lone ranger has stacks of weights on the hammer

I have a regulated USFT. I get 120 shots on a 3000psi fill at about 18 foot pounds with my .177 FT rifle before it gets close to falling off the regulator. The regulator is set at 1200psi. I have never shot a non-regulated version so I can't comment on that. This has been my favorite FT rifle out of many different brands I have owned.

They are simple rifles in operation and to work on. The hammer strikes the valve and the air from the regulated pressure goes through the swing breach to the back of the pellet. The hammer force can be changed by adjusting the hammer spring tension with a 4mm hex. Tim sells two different sized valves. Weights can be added or removed from the hammer on later models. The Gen 3 swing breach also has a port restrictor that is adjustable.

this is the closest to a diagram i have seen for a USFT

http://gunnutt.com/usft/002-layout.jpg

Scott Allen what did that Mac cost? It looks amazing.......I would probably use it on some pigeons at the farms also .

3500 is what mac1 told me for a .30 cal usft

Who shoots field target with a 30 cal? Doesn't seem like many even shoot 22

Its for the extreme benchrest shoot at 75/100 yards