Freak barrel style insert systems

[Deerslayer]

I've seen short (5") and longer (8") tubes that insert into a barrel to give you different bore sizes. I think I also saw one system that uses a 1 1/2" (guesstimate on my part) bushing at the gun end of the barrel to do the same thing. Firearms - even old muzzle loaders that took a lead ball - have a constant bore diameter over the length of the barrel.

Doesn't anyone think this is strange? We size the insert/barrel back to fit our PB, then let said projectile rattle around loose once it goes past the 5" or 8" point on its way out of a 12, 14, 16" barrel (whatever length). I won't argue that a few thous hardly lets the ball 'rattle around loosely' but you get my drift. Does the length of the insert matter from 1.5 up to 8"?

Has anyone seen any studies showing these systems are no less accurate than a constant bore size for the full barrel? If your PB is slightly out of round, is it forced into spherical shape by traveling through a short, tight barrel? What happens when it gets beyond the Freak insert?

[iamthelazerviking]

Yes plenty of studies done. The old cockerpunk tests, and Simon at Inception Designed the Stella barrel the way it is based on (his claims) thousands of rounds of paintballs with slow motion forensic cameras or something like that. That's how he came the 8" control bore being ideal, before the barrel front of a larger diameter for the glass to release etc.

However, the average player won't notice massive differences in a 5-6" control bore vs longer. The longer have claims of being able to turn pressure down and seeing some slight efficiency improvements.

But for me, a barrel is a barrel. Just an aluminum tube, but what matters most is everything lining up as concentric as possible, and a good internal polish. I mostly use an Emek. With a 4500 fill in a 77ci and a 688 or bigger UL back (14" total), that fill usually lasts all day or close to it. That's mostly tanks to the Gammacore being well designed, and just not shooting a ton but the barrel doesn't have a huge impact on that efficiency.

We can't bring firearms into it though, totally different world compared to imperfect spheres full of liquid being launched down a ln aluminum tube with compressed air.

[Jonnydread]

I recall hearing that the bore size and porting in the post-insert portion of the barrel can help provide an "air-cushion" and stabilize the flight path of the ball and that the bore length has more to do with efficiency than anything. That said, I have no studies to back this up.

In general, barrels don't matter nearly as much as people think they do.

[The Great Equalizer]

Keeping in mind bore matching is very helpful in most closed bolt guns to prevent roll-outs. All my pumps have Freak sets, but I've never gotten any type of bore kit for my semi's.

[Jonnydread]

The Great Equalizer For sure. Personally I try to either overbore with wedgits or underbore. For anything open bolt I usually just go mid bore-ish and let it rip.

[Grendel]

IIRC bore matching was the worst combination in cockerpunks tests. You want to Under or Over bore but not match bore. I'm like Jonny Over-bore with wedgits is the most forgiving and least amount of hassle.

[RAZRBAKK]

Honestly man, I'm just happy if I get paint thats mostly round.

[Trbo323]

Simon at Inception Designed the Stella barrel the way it is based on (his claims) thousands of rounds of paintballs with slow motion forensic cameras or something like that. That's how he came the 8" control bore being ideal, before the barrel front of a larger diameter for the glass to release etc.

That's kind of funny because he could have just read a post from 2001 to come to the same conclusion (see below)

Ok, there's 2 issues at play here, accuracy and efficiency, I'll tackle efficiency first for no particular reason. Following is Tom Kaye's tech tip #1 from 2001. Deerslayer just in case you don't know, Tom Kaye is the Creator of the adg automag and in my opinion one of the smartest people ever involved in paintball. His exit from the sport is another very long story entirely but he really did some cool stuff for paintball that was not entirely understood/appreciated at the time.

Guys,

I have decided to do a tech tips series of posts so you will understand certain technical processes that go on in the paintball gun. We have tested everything I will talk about and any speculations will be pointed out.

In the tech forum there is a long post on what is the most efficient barrel so here are the facts.

Barrel Efficiency, Tech Tip #1

Barrels are only there to accelerate the ball from a standstill to 300 fps. In theory they also help with accuracy but that's another post. The ball goes through incredible acceleration on its way down the barrel. The balls acceleration rate is approx. 50,000 feet per second to get to 300 feet per second in 10 inches. The entire barrel travel time is about 6 thousandths of a second and this means the ball is seeing about 1500 G's when its getting pushed out the gun. Although this may sound incredible if someone out there would like to do the math you will see that I'm close.

Air pressure behind the ball is what causes this acceleration to happen. This pressure varies between the different guns but is generally between 50 to 125 pounds per square inch at its peak. The air pressure peaks right when the ball starts moving down the barrel, after that, the ball moving down the barrel creates a bigger chamber so the pressure drops. This is why low pressure guns are a myth, in reality all guns shoot at considerably lower pressure than 200 psi.

Peak pressures above 150 psi tends to break balls down the barrel due to really high acceleration and G forces. If you don't have any way to control the peak pressure behind the ball, the only way you can change it is to go with lower pressure in the air chamber, hence low pressure guns. AGD uses the precise contour of the power tube tip to release air in a controlled manner behind the ball to limit peak pressures to around 60-80 psi..

It is simple to understand that the harder you push something the faster it will accelerate and get up to speed in a shorter distance. So what distance do we have to get the ball up to speed? The effective length of the barrel is from the balls position before it's fired, to the place in the barrel where the pressure gets released, This is usually at the first porting holes or the step in the barrel. Porting is there to release gas pressure!! You are effectively stopping the acceleration at the ports so your 14" barrel that is half full of holes only has an effective length of 7".

Now we understand that we need to limit the peak pressure behind the ball to keep it from blowing up, and that the pressure drops as the ball moves down the barrel. The next question we need to ask is, how far down the barrel does the ball have to go before the pressure gets to low to do anything useful? That answer is 8-10 inches. We know this from looking at the graphs that our gun dyno puts out. If your peak pressure is higher, say over 100 psi you can get away with a shorter barrel, if it's lower then you need a longer barrel. Since AGD is the only gun manufacturer to actually test their pressures behind the ball you might have a hard time getting this info for other guns.

So as far as our guns are concerned, the best efficiency would be had with an 8-10" effective length barrel. Since two piece ported barrels with an effective length of about 5-6" are the rage right now you hear a lot of complaints about gas efficiency. Under some circumstances there is a good reason to use a short effective length barrel. Short barrels cut off the acceleration abruptly by venting and this has the effect of tightening up the shot to shot velocity variation. If you need this at the expense of efficiency then go ahead. Tighter velocity control usually translates into some improvement in accuracy due to better consistency.

So if you want the best of all worlds, limit your peak pressure, let your ball accelerate all it wants, don't follow the crowd and keep asking questions.

AGD

so, 8-10" control bore, everything after that, efficiency wise is moot. Most manufacturers are settling on 8" I think for a number of reasons but mainly that can leave 6" for porting on a 14" barrel which are the most popular.

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[SuperAtomic]

It sounds like he saying that 8-10" is the ideal acceleration distance just for Automags. He mentions that AGD is the only company that tests their behind-ball pressures and that if your peak pressure is higher than 100 psi you can use a shorter barrel (and need a longer one for a lower pressure).

Do we know what the peak pressures are for other guns?

[Trbo323]

I recall hearing that the bore size and porting in the post-insert portion of the barrel can help provide an "air-cushion" and stabilize the flight path of the ball and that the bore length has more to do with efficiency than anything. That said, I have no studies to back this up.

Here's one that refutes the air cushion. This is Tom Kaye's tech tip #2, bore sizing. From what I read elsewhere that was started by tippmann basically as an excuse for why their barrels are so large. Of course they would never admit other reasons being players being able to use literally any paint, even some slightly swollen stuff off the ground that you really shouldn't be shooting but hey, come up with a marketable selling point and you don't have to admit you made your marker able to shoot junk

All,

By popular request I will divulge the inner secrets of bore/paint match ( is was 101 degrees out in the field today so I came in early)

Does having a good paint barrel match improve your accuracy??? YES. How does it do it? Very simple, if your gun shoots with a consistent velocity the paintballs will tend to follow the same arc, thereby improving accuracy. It technically is making your gun more consistent which is a better term than accuracy.

Historically there were many theories about paintball barrel matches. First there was the Tippman theory where they used a very large bore barrel and claimed that the air escaped evenly around the ball and it floated down the barrel without touching anything. They claimed this was the "air bearing effect". Next there was the tight barrel theory that said if the ball seals all the way around the shot will be more accurate. Actual testing has proven both these theories false.

Why match paint to barrel? Going back in time the paintballs were much more inconsistent than they are now, in fact now they are really, REALLY round and half the price. Players found that their consistency/accuracy improved when they used certain size barrels. Unfortunately paint is constantly changing size and this requires different barrel id's to work well.

The technique used to research paint/barrel match is simple and doable by anyone. Testing is performed by blowing a thin powder down the barrel to coat the inside. We used to use Desenex Foot Powder that sprayed on dry. Todays Desenex is a different formulation and doesn't make a powder. Once you have coated the barrel you dry fire the gun once to clear out any extra powder. Lastly shoot one paintball out the gun and inspect the inside of the barrel. The powder will be stripped away everywhere the ball touched. This allows you to see exactly what happened to the ball down the barrel.

If the barrel is too big, the ball ricochets back and forth down the tube. We used to say it looked like Zebra stripes in there. Hence big barrels do NOT create an "air bearing". Barrels that are too small scrape most of the powder off and this creates excessive FRICTION. Tighter barrels that were too long were found to slow the balls down due to this friction. In other words, when you cut these barrels down, velocity went up. Remember the 8-10" acceleration distance, these barrels were 14" long and unported.

The best paint barrel match left two 1/8" wide streaks opposite each other down the barrel. The widest part of a paintball is usually the seam which is also called the equator. With a proper size match only the balls equator touches the barrel snugly on two points. The equator tends not to align itself so the entire seam touches the barrel hence you only get two points touching. So what is happening here that makes this so desirable? We all know paintballs vary in size, this means that there will be slightly more or less friction on the ball depending on how tightly it fits in the barrel. If you use too tight a bore that touches the ball all around, trying to squeeze a bigger ball in greatly increases the friction and changes your velocity. By having the barrel sized to only touch two points, bigger or smaller balls only increase the contact patch a small amount and this gives you better shot to shot CONSISTENCY. To large a bore solves the friction problem but you get back to the ricochet effect.

So this is the story behind proper paint/barrel match. Many of you have commented that the stock barrels seem to work about as good as custom barrels. This is because todays paint is so much more consistent than 10 years ago that the difference between barrels is much diminished. Even the biggest to the smallest barrels don't product that much difference in accuracy IF YOU ONLY COUNT THE SHOTS AT THE SAME VELOCITY. So there you have it, I should mention these studies were done in the early to mid nineties, we have not done any testing lately on two piece barrels etc.


AGD

I will say, I think his point about squeezing the paint is either a little dated in that paint has changed since 2001 or they were REALLY squeezing it because going from a "perfect fit" bore size (which is pretty much what he is recommending) on your paint to a underbore typically results in higher velocities without touching any velocity adjustment. One big difference though is his testing was with 14" constant bore unported barrels and since I'm not sure you can even get that anymore it might be a moot point since you literally can't create that much friction distance with today's systems

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[SuperAtomic]

Realized you can't see comments, Trbo323. Here's what I said 2 posts up:

It sounds like he saying that 8-10" is the ideal acceleration distance just for Automags. He mentions that AGD is the only company that tests their behind-ball pressures and that if your peak pressure is higher than 100 psi you can use a shorter barrel (and need a longer one for a lower pressure).

Do we know what the peak pressures are for other guns?

[Trbo323]

Realized you can't see comments, Trbo323. Here's what I said 2 posts up:

It sounds like he saying that 8-10" is the ideal acceleration distance just for Automags. He mentions that AGD is the only company that tests their behind-ball pressures and that if your peak pressure is higher than 100 psi you can use a shorter barrel (and need a longer one for a lower pressure).

Do we know what the peak pressures are for other guns?

I mean it's not like I know for sure but I didn't read it that way at least

This pressure varies between the different guns but is generally between 50 to 125 pounds per square inch at its peak

That would be a massive range for just automags to cover. Later he mentions controlling this peak pressure using the design of the power tube tip so I'm betting the testing on automags was primarily for that reason and they probably tested some other markers as well to see what the different pressures/designs do at the moment of firing

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