All About Bolts
What is it?
The bolt is the long cylinder that pushes the paintball into the chamber. On the impulse it is connected to the hammer by the pull pin and moves forward when the gun is fired and back when the gun recocks.
What does it do?
The bolt actually does a number of things. Its primary job is to act as an extension to the valve. When the gun fires, the valve opens and high pressure air is passed thru the body into the bolt and on to the ball. The air that pushes the ball actually does a “U” turn to get there. Before the gun is fired, the pressurized air is stored in the front of the gun (behind the “valve cap”). When the valve is pushed open by the hammer, the high-pressure air makes a 90* turn up into the body. The air passes into the bottom of the bolt, makes another 90* turn and pushes toward the front of the gun, pushing the ball in front of it.
The second function of the bolt is to load the paintball into the chamber. The paintball lays in the body between bolt and the barrel. It is stopped from rolling forward by the ball detents. As bolt comes forward, it forces the paint ball by the spring loaded ball detents into the barrel.
The third function of the bolt is to act as a ”door” to allow the paintball to load. When the bolt comes back it “opens” the passage of the ball to fall down into the body. If the bolt doesn’t come back far enough, the paintball can’t feed freely. On an Impulse this last will only be a problem if the bolt is drilled incorrectly- there is no “bolt adjustment”
The forth function of the bolt is to seal the back of the barrel. If the back of the barrel were not sealed, the air pressure would leak out and not drive the paintball forward.
The original bolt in the Impulse is made of Aluminum. Early models had a single round hole all he way down the center. Later models have a “head” on the bolt with three large holes. There is really no performance difference in these bolts. All of the stock bolts are made of aluminum, and relay on o-rings to seal the gas. There are three o-rings on the stock bolt. One on either side of the air transfer port (where the air flows into the bolt from the body) and one at the front of the bolt to help seal the back of the barrel when firing. Stock bolts have few failures. The only problem I have seen in hundreds of stock bolts is the very front of the bolt breaking off at the o-ring grove. Stock bolts must be properly lubed. Too little lube could result in seizing the bolt and too much lube will result in inconsistent performance and decreased accuracy .
Something else you may see is the black anodizing wearing away on the top of the bolt. This actually isn’t a “bolt” problem- it a body problem. Most don’t realize it, but when you install the feed tube, you are only supposed to make it “hand tight”. The Loc-tite is what holds the feed tube in place- not being overly tightened. When the feed tube is screwed in really tight, the top of the body can actually be deformed slightly to interfere with the bolt.
The is almost nothing you can do to a stock bolt to improve the performance. Most bolt mods simply involve replacing the bolt with one made of a different material. The most used material is Delrin.
Delrin bolts will be much lighter then the stock bolt. More important Delrin is very slippery and requires no lube. Most delrin bolts are designed to be used without o-rings. This is a “good news/bad news” thing. The good news is, of course, that you need no lube and maintenance is very simple. The bad news is that there are no o-rings to compensate for a “too big” chamber. While machining can be kept to very tight tolerances, the honing and polishing and anodizing will introduce some variables. The English version of that is that some guns will simply have bigger chambers and there is no way to compensate for this with a Delrin bolt. The net result of this is that there are simply some guns that will not benefit from a switch to a Delrin bolt and the only way to really find out is to try the new bolt and see what it does.
The drilling of the front of the bolt has far less effect on performance then many think. Regardless of how many holes there are, or how they are arranged, within a very very small amount of time (maybe 1 to 2 milliseconds) the air pressure will form a perfect “air cushion on the back of the ball. 5 milliseconds into the firing cycle every point on that half sphere that represents the back of the ball will have exactly the same pressure pushing on it.
Factors what will have an effect on performance include the volume of the inside of the bolt, the “flow characteristics” of the bolt, the bolts ability to seal the back of the barrel, the bolts ability to seal the area where the air is transferred into the bolt , and the weight of the bolt its self.
The Werm bolt is unusual in that it directs the air only to the bottom of the ball. This is designed to effect the spin the ball normally picks up as it rolls down the barrel. When used with a larger then normal barrel, many users report this bolt will affect long-range performance.
The New Designz bolt has one of the smallest internal volumes. It also seems to have better flow then most. Most users that have compared them find that the new designz bolt gives some of the least shot to shot variation of those tested.
The VooDoo is basically a copy of the stock bolt only made from Delrin. This is by far the most used after market bolt. Most of the custom Impulses are sold with this bolt. There are hundreds of users that swear by this bolt.
The Evolution bolt uses a head with a number of small holes all around the outside. This gives the “diffuser” effect to the first few milliseconds of the firing cycle. Users have reported this bolt to improve efficiency in most guns especially those using LPRs
Like so many after market accessories, there is no one “best” bolt. And unfortunately the results cannot be accurately predicted, as every gun is a little bit different. One should not believe some of the rather outlandish claims of some people. A Delrin bolt is very worthwhile upgrade- if only for the reduction in maitanance. One should not expect a change in bolt to make some magic change in an other-wise so-so gun. It is best used in conjunction with other changes to get a balanced package. Remember, the delrin bolt is lighter then a stock bolt. If you choose to make other changes that lighten the bolt/pull pin/hammer/ram assembly, you should watch that you don’t make your assembly “too light” (which will require increased dwell) Most users combine the bolt change with a change to a heavier hammer (like Ti or SS)
ND Short bolt -378grains -24.5g
Werm GFB -445grains -28.9g
Voodoo -488grains -31.7g
Eclipse Dart -493grains -32.0g
Evolution -507grains -32.9g
Sp Stock -873grains -56.7g -(stock)
Courtesy of http://www.mipaintball.com/bolt.htm