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Mac 1 USFT ???

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Richard300

Member
Dec 2, 2015
243
1
Wi, United States
Hi got another question.
How does a Mac 1 usft Airgun use only 1500 psi and get the same fps as a air gun at 3000 psi?
And I read that they get a lot more shots per fill at the 1500 lps.
How does a low psi Mac get to be more efficient then a higher power target rifle.
If this is true why dosn't all the airgun companies do this...Is it a high cost to get a Airgun to do this?
If I have this all wrong please let me know.
Thanks Richard 
I found this on the web,,,this is what I'm talking about.
 
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.
 
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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

 
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spysir thanks. I'm just trying to figure out the working of the gun. Sure would like to see a schematic of the mac 1. It is interesting '''to me''' how these guns work so well at a lower pressure. And maybe someone else will learn like me along the way. Great looking rifle. Why is it I"m asking.. about the size of tank..... and the accurate shot count of the Mac.. Its just for me to compare a high pressure airguns... against the low pressure mac 1. This is just something that is stuck in my mind.... : ) that I want to figure out and learn along the way. And there are a lot of knowledgeable people on here ....to find out. : )
Thanks Richard
 
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 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
 
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Thanks john...very interesting read. I like how everything is in the open on the mac1. There great looking guns. Not many around here that shoot pcp's. I work most week ends so seeing any at a shoot is slim to nun.... for me.
[ untell retirement in a year and a half]..... then I can do some compition shooting. I will just learn and practice untell then.... : )
thanks richard
 
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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.

 
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