What are shims for?

[Carbon Blue]

Ok, I must have suffered some sort of memory loss or something because Ive tuned my Level 10 perfectly with the 2.5 carrier and no shims. Now here comes the question what are the shims actually for? If the purpose for carriers is to run the biggest size that does not leak, then what do shims do?

[st6212]

From the lvl10 guide:
" Put a squeegee right in front of the bolt and pull the trigger. With very little clearance between the bolt and squeegee you will notice that the bolt comes forward and just stops on the squeegee. Then nothing else happens. Pulling the trigger does nothing to reset the bolt. In order to get the bolt to reset when it pinches a ball, we have to let the air out of the air chamber. The shims (5) control where in the forward stroke the air chamber starts venting. Its works a lot like the spacers in the original Mags. We left them out before so you could tell the difference between a carrier leak and a shim leak. "

[Carbon Blue]

so if i want a more sensitive bolt, add a shims one by one? or are they used to reset the bolt? just trying to clear it up a little bit

[athomas]

Well explained by RogueFactor.

Furthering the explaination, the shims control how far the bolt can move forward before it will vent the air from the valve chamber. There is a physical measurable distance between the point where the sear will catch the bolt and where the bolt vent hole will be exposed. This distance is adjustable by adding or removing powertube carrier shims.

If the bolt has to move too far, there is a chance that a pinch or blockage will prevent the bolt from moving far enough to vent, but will move far enough to prevent the sear from resetting.

[Carbon Blue]

thanks you guys, now that we have shims explained (to which they cure bolt stick) does anyone want to explain what the carriers actually do? I could setup a Level 10 bolt perfectly but I really have no clue what they exactly do. :confused:

[athomas]

thanks you guys, now that we have shims explained (to which they cure bolt stick) does anyone want to explain what the carriers actually do? I could setup a Level 10 bolt perfectly but I really have no clue what they exactly do. :confused:

Carriers allow you to adjust the inner diameter of the powertube carrier oring. A loose carrier reduces the friction by allowing the oring to be loose on the bolt stem. Too loose, and it will allow air to seep past. The tighter it is the better it seals against the surface of the bolt stem. However, being tighter means it increases the grip on the surface of the bolt stem so that more force must be applied to it for it to move. Since the smaller size of the bolt stem reduces the amount of actual force applied to the bolt, a carrier that is too tight can increase the amount of required force to a value greater than the chamber pressure can exert on the bolt stem. Thus, the bolt sticks and won't move when you fire the gun, or the gun fires and the bolt won't quite reset to the reset position.

[Dayspring]

http://www.airgun.com/xmag/html/graphics/carrierlengths.gif http://www.airgun.com/xmag/html/graphics/carriersizes.gif

[Carbon Blue]

thanks again for the help you guys :)

[Cpt Black]

hi everyone

sorry if I'm jumping in on this thread uninvited but.......

the problem I am having with my minimag sounds like what Athomas just described.......

sounds like my bolt may be sticking, here is as best as I can describe it( oh ya I am a noob when it comes to automags so please don't flame me for being stupid) I have alot of experience with spyders and the like but I traded this minimag for a pistol I had and now I need to try to get it working properly.

anyway here is what is happening.

#1 before I got the gun from my buddy he replaced all the Orings and seal and we did a complete lube job to the marker.
#2 it has a ventury bolt, I don't think it's ANS but can't be sure there are no makrs of any kind on it that I can find.
#3 when I air it up it's great, no leaks and the sear is ingaged(pushed forward into the trigger)
#4 it's a minimag right fed body with a classic valve#7, with a 220 spacer (the only spacer I have) single trigger wood grips, unimount, expansion chamber. not sure if any of that matters but there it is.

Ok on with the story.
gases up fine...
I pull the trigger and it fires but the sear doesn't return, and it leaks down the barrel, then you mess with the trigger trying to fire it again and it will eventually return but sometime it's like it doesn't return as far as it does other times. also the sear will sometimes be high on the trigger and other times it lower, there seems to be quite the slot in the trigger frame for the sear to move in.

my future hopes for this gun..... want to get it working well, then change to a power fed body, and go to a trigger frame that will allow me to walk it. the mech triggers on these are very tight from what I am used to, I am not normally a speed baller, I am a woodsballer but I want a gun that I can play speedball with from time to time just for fun.

anyway sorry if I've put too much in this tread
thanks for all your input and help
Cpt Black

[athomas]

Cpt Black:

The bolt you have is probably an ANS bolt. I think they were the only ones to make a ventury design for the automag.

If the bolt won't reset properly in a level 7, then you are definately getting bolt stick. First order is to change the bolt spring. It may be worn out. Then, if it still sticks, you need to get a longer powertube spacer.

Don't worry about the trigger rod bouncing around. They all do that.

[Cpt Black]

the bolt spring is new it was replaced with the seals from the kit

Cpt Black