Filled Level10 bolt to improve efficiency?

**Dayspring** · 04-09-2004, 10:48 AM

What you're filling in doesn't do anything. The actual seal for the air chamber is at the small piston end. (The carrier oring seals around this.) Then the larger piston section seals against the powertube tip and propells the bolt at full speed.

The vent hole is what allows the bolt to reset on a pinched ball by venting the pressure pushing behind it.

It is this venting (as it vents the entire time in motion- pinched ball or no) that causes the efficiency drop.

**WetPaint** · 04-09-2004, 03:03 PM

Originally posted by Dayspring
What you're filling in doesn't do anything. The actual seal for the air chamber is at the small piston end. (The carrier oring seals around this.) Then the larger piston section seals against the powertube tip and propells the bolt at full speed.

The vent hole is what allows the bolt to reset on a pinched ball by venting the pressure pushing behind it.

It is this venting (as it vents the entire time in motion- pinched ball or no) that causes the efficiency drop.

True, but once the the main gas release happens at full bolt extension, then the gas has to pressurize all the open space inside the bolt, as well as the space behind the paintball. If you minimize this extra space, then more gas goes to propelling the ball.
It's not much compared to the rapidly-increasing space behind the ball though.

**BlackVCG** · 04-28-2004, 11:34 AM

I've had this idea over the last year and just have never got around to it. There's a few other sources of inefficiency that need to be looked at also.

One thing you stated that can not be done is capping off the inside hole of the piston. The air needs to be able to go down this hole so it can vent when the bolt pinches a ball. If you plug this hole, it will pinch the ball and then lock up on it because the air has no way to vent.

Originally posted by WetPaint

True, but once the the main gas release happens at full bolt extension, then the gas has to pressurize all the open space inside the bolt, as well as the space behind the paintball. If you minimize this extra space, then more gas goes to propelling the ball.
It's not much compared to the rapidly-increasing space behind the ball though.

**Cristobal** · 04-29-2004, 09:24 AM

Originally posted by BlackVCG

I've had this idea over the last year and just have never got around to it. There's a few other sources of inefficiency that need to be looked at also.

One thing you stated that can not be done is capping off the inside hole of the piston. The air needs to be able to go down this hole so it can vent when the bolt pinches a ball. If you plug this hole, it will pinch the ball and then lock up on it because the air has no way to vent.

I think what he meant was capping off the hole at the forward end of the bolt -- not the the venting hole. See the little green line in his drawing, right where you'd glue on the foamie.

**BlackVCG** · 04-29-2004, 01:12 PM

Well that would be a total waste of time if you have the foamie in place since no air is going to be going back into that cavity. You do need the foamie in place on any vertical feed gun to keep the ball stack inline. Since almost everyone is using a vertical ULE body anymore, I assume everyone is keeping the foamie on their bolt.

Originally posted by Cristobal

I think what he meant was capping off the hole at the forward end of the bolt -- not the the venting hole. See the little green line in his drawing, right where you'd glue on the foamie.

**RRfireblade** · 04-30-2004, 05:52 PM

I can't see where decreasing the internal volume of the bolt by such a tiny amount will make any noticable difference.

IMO,the primary cause for a decrease in efficiency in the Mag valve is the "cork in the bottle" design in the first place.

**unseenunheard** · 04-30-2004, 10:01 PM

it seems to me that when you decrease the volume of air behind the bolt you will in turn have to increase the pressure to counteract it

**the electrician** · 05-01-2004, 11:32 AM

now this is an interesting subject.

black vcg is right about the hollowed out front of the bolt. there's a rubber bumper in front of it!

I've been looking at the mag, dying to get the efficiency up, and the operating psi down inturn, making the recharge rate a bit better.

notice the three "supports" of the center tube of the bolt, up near the tip, inside. the back of them are flat, and so is the front. seems to me it would be better to have them more areodynamic if you will. don't know what, if anything, that would help.

the other thing I thought about was that front "hollowed out" part of the bolt. what about putting it to use for air flow contact on the ball? only drilling it back enough to have a hole milled to connect it to the gas flow area. perhaps this combined with wetpaints idea of reducing the uneeded volume of the gas flow area would allow the air to expand more at the ball and not so much before.

perhaps a combination of all these things would help?

where does the "blowback" come from in a mag? air coming out of the bolt before it's past the feed tube?

**Cristobal** · 05-01-2004, 09:24 PM

My initial reaction is that compared with the total volume inside the bolt and dump chamber, the hollowed out part of the bolt seems pretty minimal. However its not too hard to get an idea if this is the case.

Using Photoshop to scale the cutaway of the superbolt we can get some approximate dimensions for its internals. The expanded inner diameter is about .625" compared with about .500" at the back of the bolt, and extends for about 1.150". The inner plunger has a diameter of about .250" extending for .950" and .170" for .200" before the inside of the bolt widens back out at the back. This gives an interior volume for the hollowed section of 0.3 cubic inches. Assuming the bolt wasn't hollowed out, the internal volume in that section would be 0.175 cubic inches. So hollowing out the bolt adds about .125 cubic inches to its internal volume, which is about a 70% increase in internal volume.

Of course the total internal volume of the bolt is a bit bigger. At the the inner diameter is about .5 for .5 inch, minus the plunger which gives about .1 cubic inch, minus the three fins and foamie which take up maybe a quarter of the volume. So I estimate about .075 extra cubic inches at the front and a little in back. Plus there's the power tube which is about 1" long (and with lvl10 about .175" in diameter inside). So we end up with an additional .075 plus .025 = .1 cubic inches of "expansion" volume that the gas has to get through before reaching the paintball.

So I figure the total expansion volume without the hollowing out to be about 0.275 cubic inches, and with the hollowing out to be about .400 cubic inches. So hollowing out the bolt increases the total expansion volume by .125/.275 about 45%. Once we hollow it out, this excess volume represents .125/.4 or about 30% of the total expansion volume between the barrel and the dump chamber.

What that means for efficiency is a little less clear to me. But I'll take a shot at it: Whatever gas pressure is left in this volume when the bolt closes is essentially "wasted". As the ball goes down the barrel, the volume expands, so the pressure drops. But this bit of volume behind the ball is excess "dead weight" if you will, and any gas left in it doesn't get to be reused like left over gas in the dump chamber.

If we take the extra volume of the hollowed out section and multiply by the residual pressure left in it, we could estimate the energy penalty we pay by hollowing it out. I have no idea what the residual pressure is at the time the force of the spring pushes the bolt back. Especially with the stronger lvl10 springs though, I imagine that it is not insignificant. Given that the ball sees a peak of about 90psig at the beginning, lets just assume (to see what happens) if we say that there is 10 psig left when the bolt is returned. In this case our wasted energy is .125 in^3 x 10psig = 1.25 in-lb of energy.

As I recall from a thread pbjosh posted a while back most guns average about 250 in-lb of energy used per shot. If we're only wasting an extra 1.25 in-lbs that isn't too bad. Assuming 1000 shots per tank previously, by filling in the hollowed region we just saved 1250 in-lbs of energy: enough for a whopping 5 extra shots.

Of course this depends on my assumption of how to calculate energy loss from this volume. Comments?

* Oh, and BlackVCG, sorry if I was a little blunt above. I agree: with the foamie, the forward part of the hollow plunger ought to already be blocked off from air.

EDIT: Thread with energy per shot calculations is here: http://www.automags.org/forums/showt...threadid=18939

**the electrician** · 05-02-2004, 08:01 AM

that's good work, but I can't say I agree with all of that.

I came up with some different numbers. I came up with a bit shorter distance for the hollowed out part. about 1.04" in my bolt. I'm not saying that's dead accuracte though, because it is hard to get a measurement inside there. also I just figured the difference between the hollowed, and not hollowed. if it wasn't hollowed out, it be .502" aprox.(give or take) but the hollowed out part is about .06 to.05. which takes it up to .562 at most and .552 at least. I figured the difference in volume at about .05 cu in. don't really care about percentages too much, but using your inner bolt piston numbers, everything looks good but the added volume from the hollowed out area. not sure how you got .125 cu in.

that's where my numbers differ from yours, not that it matters too much, I just think the increase in volume wasn't as much as what you came up with.

I don't know, but I think that it is about letting it expand more or less BEFORE it really moves the ball. once the ball moves, I don't think it matters too much.

I'll tell you what, it's not going to be easy to actually try "filling" this area. retro fitting a lvl 10 bolt wth an inner sleeve. to try and test the results. once you get something in there, not easy to get it back out. it would have to be flexible enough to squeeze in there, but it would have to be strong enough to not get torn up when you shoot the gun. turning some plastic on the lathe that thin would be a bit of a pain, but it could be done.

really there's only so much that could be done to the mag to increase efficiency, but it would be nice to get the operating psi down to 300, by means of efficiency.

**the electrician** · 05-02-2004, 11:21 AM

ah crap, I just realized where I screwed up. your numbers are the accurate ones. the hollowed out part has an approx. .625" dia., not .562

I have opened mouth, and inserted reebock.
I have failed misreably, and brought shame to my village.
I will now go feed the others there lunch.

one thousand pardons cristobal.

**Lohman446** · 05-02-2004, 06:38 PM

YOu know.. I was thinking about level ten in its entirety. It is the air that moves the ball, not the bolt.. what if the ball sat forward further, like a half inch, so the bolt never went through the area the ball in. Instead it shoots forward, allows the air out to push the ball out, adn then resets - but never enters the ball chamber itself - would this nto stop chops and be just as quick?

**Cristobal** · 05-03-2004, 02:42 PM

Originally posted by Lohman446

YOu know.. I was thinking about level ten in its entirety. It is the air that moves the ball, not the bolt.. what if the ball sat forward further, like a half inch, so the bolt never went through the area the ball in. Instead it shoots forward, allows the air out to push the ball out, adn then resets - but never enters the ball chamber itself - would this nto stop chops and be just as quick?

Ahh, but unless I read your idea wrong, you still need something to keep the air from going out the feed tube. That's the whole point of having the bolt come forward and push the ball forward in the first place

And no worries electrician

**RRfireblade** · 05-03-2004, 04:47 PM

You know......

All you need to do is enlarge the dump chamber,actuate the bolt with pnuematics and have the chamber dumped by a mechanical/pnuematic valve instead of the "pop the cork" bolt method and your there.