new mag body will not shoot

[LK-13]

working with my prototype mag unibody
while un-gassed the sear has the normal loose feel
when gassed up the sear is rock solid and will not move at all even with
200+lbs pushing on it.

any ideas what may be causing this lock up?
the sear is in the correct position on the on/off and while un-gassed you can feel the on/off move.

I have tried 4 valves, all do the exact same thing.
But, all of the valves shoot just fine in 3 other factory body/rail combinations;
all 4 valves also function fine in my prototype unibody but not in this one copy
and all measurements are identical.
I can't figure out just what I've done here that would yield this result.

Ratzo has suggested that the on/off pin maybe the wrong size and I may need to grind it down slightly.
but I want more options before I go grinding on valves that work fine in other bodies.

if possible can someone out there check my measurements:
http://i169.photobucket.com/albums/u215/LK-13/Paintball%20Guns/unibodymeasurementssection.jpg

[Ando]

Can't trip it by moving the sear with your finger?

[LK-13]

Can't trip it by moving the sear with your finger?

that is what I was attempting, can't move the sear at all once gassed up.
not even putting 200+lbs on the sear (full body weight) could we get the gun to shoot.

[reckid1986]

is it by any chance binding in the body maybe the sear pin isnt straight and the pressure is making it bind. i remember one of my mags doing this once but i cant remember why it did it.

[Spider-TW]

put some blue on the sear back under the on/off pin and see if it is landing on the middle of the pin hump?

[XM15]

When making a mag body the three bores for the valve are very critical along with the sear location in relation to the thumb screw. I don't know how you machined the body or what your tolerance were but the 1.125" diameter of the valve I hold to +.002"-+.005. The bore for the front section of the valve I do at 1.01 +.005. and the breech bore is .690. The back portion of the valve sits in contact with the rail and the rest should have clearance around the diameter. If your bores are not concentric with one another and straight it's going to bind. If the sear and thumb screw relationship is off the sear is not going to work. If all the above is happening it's not going to work at all. Another possible problem is with your design. Since the back half of the valve is like the foundation of the valve your only locating on a 1/2" of the valve. The majority of the valve along with the valves weight is unsupported. The valve can cock many different ways. When I do the bores I do them in the lathe all at the same time rough drilling them and then boring them with boring bars to finished dimensions so I now they are all straight and concentric.

[LK-13]

When making a mag body the three bores for the valve are very critical along with the sear location in relation to the thumb screw. I don't know how you machined the body or what your tolerance were but the 1.125" diameter of the valve I hold to +.002"-+.005. The bore for the front section of the valve I do at 1.01 +.005. and the breech bore is .690. The back portion of the valve sits in contact with the rail and the rest should have clearance around the diameter. If your bores are not concentric with one another and straight it's going to bind. If the sear and thumb screw relationship is off the sear is not going to work. If all the above is happening it's not going to work at all. Another possible problem is with your design. Since the back half of the valve is like the foundation of the valve your only locating on a 1/2" of the valve. The majority of the valve along with the valves weight is unsupported. The valve can cock many different ways. When I do the bores I do them in the lathe all at the same time rough drilling them and then boring them with boring bars to finished dimensions so I now they are all straight and concentric.
good points all of them,
but I have checked and rechecked the measurements against the rails I have in hand, and against the prototype unibody and everything matches up.
as for the fact the valve is not 100% in contact with the rail;
the prototype functions perfectly; so it's a non-issue.
I'm actually thinking that it may be the sear itself that is the problem.
the sears that seem to work are the big triangle shaped ones that take a 3/16" pic/axle;
but in the unibody I'm using the same sear used in the Micromag with the brass bushing accepting a 1/8" axle/pin.
is the axle to thumb screw center distance different for the different sears?

[XM15]

One thing I forgot in my post is the sear depth in the rail. It has to be correct too. As far as the micromag sear it should be the same. The valve other than being laser engraved differently is no different than any other mag valve and mag on/off. I use the standard 3/16 sear in all my bodies except for my emag which is a similar sear and pin set up to yours. It's the same as the other guns as far as sear location. Have you checked to make sure the sear pin is straight and not at a angle? Is there any chance the sear you are using is bent or out of spec in some way? I don't know what trigger frame your using but is there any chance it's some thing with the frame and not the body at all?

[LK-13]

One thing I forgot in my post is the sear depth in the rail. It has to be correct too. As far as the micromag sear it should be the same. The valve other than being laser engraved differently is no different than any other mag valve and mag on/off. I use the standard 3/16 sear in all my bodies except for my emag which is a similar sear and pin set up to yours. It's the same as the other guns as far as sear location. Have you checked to make sure the sear pin is straight and not at a angle? Is there any chance the sear you are using is bent or out of spec in some way? I don't know what trigger frame your using but is there any chance it's some thing with the frame and not the body at all?

there is no trigger frame being used at this time.
these are all going into rifles stocks and being fed from below by magazines.
kinda like this:
http://i169.photobucket.com/albums/u215/LK-13/Paintball%20Guns/DSCI0363.png

trigger group looks more or less like this only more refined:
http://i169.photobucket.com/albums/u215/LK-13/PAINTBALL%20GEAR/Picture034.jpg

[athomas]

Without the valve installed, check where the on-off portion of the sear assembly enters the valve cavity of the body. Is it centered properly? If you put pressure on the back of the sear from inside the body, does it affect the trigger movement and feel? ie; does it bind?

[Spider-TW]

From that picture, it looks a little like your linkage could cam-lock with some pressure from the sear. Does the pivot point on the trigger stay below the linkage pivot on the trigger? It looks close.

[BigEvil]

Have you tried it with a grip frame bolted up?

[Xmagterror]

The 1" bore is just for clearance. The 1.125 bore is what the valve really sits on and aligns it. Looks to me like your 1.125 bore is not long enough to make the valve sit right. I bet your valve is sitting at an angle and binding the valve.

[LK-13]

Without the valve installed, check where the on-off portion of the sear assembly enters the valve cavity of the body. Is it centered properly? If you put pressure on the back of the sear from inside the body, does it affect the trigger movement and feel? ie; does it bind?


there is no trigger installed, using the sear only.

[LK-13]

From that picture, it looks a little like your linkage could cam-lock with some pressure from the sear. Does the pivot point on the trigger stay below the linkage pivot on the trigger? It looks close.

that is a completely different build that functions perfectly.

[LK-13]

Have you tried it with a grip frame bolted up?


no, there are no attachment points for a grip frame.

[LK-13]

The 1" bore is just for clearance. The 1.125 bore is what the valve really sits on and aligns it. Looks to me like your 1.125 bore is not long enough to make the valve sit right. I bet your valve is sitting at an angle and binding the valve.

now that is possible.
the 1.250" bore is 0.5000" deep and works fine on other versions of the unibody.

I think my 1.250" bore may be over sized.
if it is I may be screwed, because nothing i could shim the valve with would stay in position or stick to delrin.

yes this body is made of delrin.

if it comes down to it I may cut a rail to size and key hole inlet it into the body to solve the issue.

it's cheating but it will work and put me back on schedule.

[LK-13]

after examining 6 different Automags of differing flavors, looking over any and all diagrams I could get my hands on and measuring and remeasuring till my caliper's battery needed changing...twice...
I believe my sear may be out of position by half the width of the on/off pin.
in the diagram below the red/yellow sear foot print is what I'm currently getting;
the rear most point on the sear pressing the on/off uh.. button before the sear connects with the on/off pin.

what I think I need is more like on/off #2 where the green foot print shows the on/off pin being pressed by first contact with the sear and the on/off button being kind of secondary.

for those of you that know better than I;

does this supposition seem correct?

Mr. Kaye where are you when I need you!! (I've got a couple dinosaur questions as well Mr.Kaye if your out there...)

http://i169.photobucket.com/albums/u215/LK-13/Paintball%20Guns/onoffnotquiteright.png

[athomas]

What does each color represent? It looks like the black is the hole in the body, the grey is the on-off pin, and the color is the back of the sear. Is this correct?

If I was correct in the color scheme, then your problem is probably due to the back of the sear not contacting the on-off pin squarely enough. When the pin pushes down on the back of the sear (which is not perfectly flat on top), it will be forced to the front/back and could bind, especially when the sear is fully reset. When attempting to pull the trigger, you would be pushing the pin sideways rather than straight up. This could be the lock-up of the trigger you are experiencing.

[LK-13]

What does each color represent? It looks like the black is the hole in the body, the grey is the on-off pin, and the color is the back of the sear. Is this correct?

If I was correct in the color scheme, then your problem is probably due to the back of the sear not contacting the on-off pin squarely enough. When the pin pushes down on the back of the sear (which is not perfectly flat on top), it will be forced to the front/back and could bind, especially when the sear is fully reset. When attempting to pull the trigger, you would be pushing the pin sideways rather than straight up. This could be the lock-up of the trigger you are experiencing.
guys, read this carefully,
there is NO TRIGGER, OR TRIGGER FRAME involved at this point.
we were manually pushing right on the sear itself.
additionally there will NEVER be a TRIGGER FRAME attached to these guns.
these bodies have been designed for use in RIFLES STOCKS with no allowance being made for the use of a trigger frame.
note the sear sticking out the bottom, and no trigger.
http://i169.photobucket.com/albums/u215/LK-13/Paintball%20Guns/DSCI0353.jpg

in the diagram below the red/yellow sear foot print is what I'm currently getting;
the rear most point on the sear pressing the on/off uh.. button before the sear connects with the on/off pin.

what I think I need is more like on/off #2 where the green foot print shows the on/off pin being pressed by first contact with the sear and the on/off button being kind of secondary.
http://i169.photobucket.com/albums/u215/LK-13/Paintball%20Guns/onoffnotquiteright.png

sorry if it comes off as me getting huffy about it, but people are posting things that were suggested and ruled out, with the reasons posted in the thread.

[Drix]

Whats the orientation to this body wise? Is the pin offset to the sear front to back or left to right? If it's offset left to right I would imagine that you might be catching the sear on the body, front to back shouldn't matter too too much?

Edit: How are the measurements on the gassed body? I'm assuming you're measuring un-gassed, is it possible that the body is distoriting slightly with the valve and springs and wotnot inside?

[athomas]

When you pull back on the bottom of the sear, it becomes the trigger. It just refers to the action of pulling/rocking/activating the sear.

I just wanted to know what you were referring to with the colors and you still haven't indicated it. You just reiterated the same explanation as previous. I know you are referring to back of the sear where it hits the on-off, but you haven't indicated what color represents the back of the sear or what color represents the hole or what color represents the on-off pin. Its probably obvious to you because you already know. Its not obvious to others looking at it with different thoughts than yours. It just needs clarity to make sure we are all seeing the same thing.

If you get snippy in your answers, we won't help at all.

That being said, you haven't indicated whether the back of the sear is in contact with the pin as I mentioned earlier.

[LK-13]

light grey dot is on/off pin
dark grey "doughnut" is on/off uh... button(?)
red section of sear foot print is engaging first
green foot print engages all at once

But,
thanks to Cougar20th I've now determined what the problem is.
Returning to the slugbody drawing and by turning different layers of the drawing on or off
I was able to get the measurements I needed and correct my own cad drawings.
saddly I don't know if I'm going to be able to save this particular body.
the errors while being tiny, only .023", are accumulative and become a large error 3 or 4 steps down the line.

1)thumbscrew hole should be at .347" not at .169"
2)sear should be located at 1.523" x 0.223" not 1.549" x 0.250"
while they sound small, relative to the size of the on/off pin, the errors combine to put things out just enough to not function.
to put this all in perspective a sheet of computer paper is approximately 0.001", a single human hail is approximately 0.003", so as you can see an error of 0.026" x 0.027" in the case of the sear can add up; particularly when the valve is 0.187" out of position.

oops!

guess I need some more bar stock to make another body...
back to the shop I go! :rolleyes: :D :cool:

[athomas]

Yeah, the location needs to be pretty specific. Its good to hear you found the problem. Now you know how to correct it.