Barrel length relationship with the same other factors

Jump to latest Follow Reply
SvilenP

SvilenP

Member
Feb 25, 2018
244
1
Gabrovo, Bulgaria
Hello colleagues,

Maybe this topic has been chewed countless times in different themes and on different occasions do I want to get more clarity about the influence of barrel length on the general "picture" in PCP? 

Where did everything start ...

After many thoughts, tips, asking everywhere, watching hundreds of videos and experience with Hatsan 125, I finally decided to buy my first PCP in the form of a bullpup.

However, here I came across three choices - Short, Standard or Long.

As a person who likes type "carbine" rifles, I immediately decided to choose "long" but then I thought that why I would choose a "long" variant as I once again turned to a "carbine" type...So I decided to choose a "Standard" bullpup length option.

However, it happened so many people advised me to choose the "Short" option and then I decided to figure out what would change if I chose each of the three possible options = barrel length?

If you ignore:

1. personal preference for gun size;

2. the shape, material and weight of the pellet;

And let us assume that we have exactly the same barrels with a difference in their length only, what should be expected to happen?

I personally assume that the difference will be in long-distance traffic, but even I'm not sure ...

What do you think?

The pellet area on which the pressure and volume of air flow is the same in all three cases and then it is clear that only the length of the barrel will influence and that's what I'm looking for !?

Greetings. 
 
A longer barrel simply gives the opportunity to increase velocity. The gains can be especially beneficial to heavier projectiles like shooting solids from big bore rifles.

It also enables better efficiency (air usage) for a given power level.

There are a couple of potential detriments to longer barrels. One is that a longer barrel is more subject to harmonic deflection, all other things being equal, and that may make for greater dispersion of groups. Usually that's mitigated by making it sufficiently thick, by sleeving it with carbon fiber, or by tensioning it. The other thing is that a longer barrel means a longer lock time...the time between when the sear breaks and when the pellet leaves the barrel. That represents a time in which the shooter may pull the gun off the point of aim. Proper follow through mitigates that potential issue.
 
Upvote 0
So it's all down to Engineering Compromises, Murphy's Law of Gun design, if it doesn't work the first time, spend more money 😃

Lots of variable and several ways to skin the cat (not that the cat will be happy.).

But if all your looking at is Barrel Length and all other things being equal, I think you just deal with Increased lock Time and some additional power.

Smitty
 
Upvote 0
You asked about barrels but take it a step further.

Using your bullpup example, the longer gun with the longer barrel probably also has a longer air tube. Since a longer barrel will let you get more potential FPS/FPE from the same air blast.... a larger air tube will yield a larger potential shot count if set up to shot the same power (flip side = you'll' need a bigger air blast to produce the same power with a shorter barrel, so more air and from a smaller air tube).

That doesn't make a gun better or worse, just something to consider for you intended use. I'm stuck in the middle. I like small guns but I also like high shot count...
 
Upvote 0
Ok now I am confused. I knew it would make it more powerful (up to a point of diminishing return) but wouldnt a slightly longer barrel make it more accurate (minutely i understand)? Then why have all these different barrel sizes? Wouldnt they all be basically the same for the same caliber? If say the best length is 12 inches why not make all the barrels 12 inches and just the moderator longer for the looks and sound? There has to be more than that right? Im not second guessing you guys. Im just pondering the question out loud. Im trying to get an education.
 
Upvote 0
Something to consider Crittahitta, is barrel length is only part of a system. When you pull the trigger the air is forced down the barrel behind the pellet, The force will look like a sine wave acting on the barrel, the shorter barrel will be affected by the higher pulse, of course these pulse will be smaller each cycle. So I believe you are looking for that sine wave to cross the center of the barrel at the end, at the same time as the center of balance on the pellet passes through. That way the pellet is not being affected by the harmonic cycle of the barrel. So that were I believe the pellet weight effects the accuracy. The length of the barrel would probably need to be modeled to figure out the pulse length and shorten it to a smallest movement. Probably on the forth or fifth cycle. We'd need some really interesting test equipment to measure this modes, and that would only take out one part of the "system".

Of course I could be wrong, I've been wrong before and possibly will be again.

Smitty
 
Upvote 0
Something to consider Crittahitta, is barrel length is only part of a system. When you pull the trigger the air is forced down the barrel behind the pellet, The force will look like a sine wave acting on the barrel, the shorter barrel will be affected by the higher pulse, of course these pulse will be smaller each cycle. So I believe you are looking for that sine wave to cross the center of the barrel at the end, at the same time as the center of balance on the pellet passes through. That way the pellet is not being affected by the harmonic cycle of the barrel. So that were I believe the pellet weight effects the accuracy. The length of the barrel would probably need to be modeled to figure out the pulse length and shorten it to a smallest movement. Probably on the forth or fifth cycle. We'd need some really interesting test equipment to measure these modes, and that would only take out one part of the "system".

Of course I could be wrong, I've been wrong before and possibly will be again.

Smitty
 
Upvote 0
Something to consider Crittahitta, is barrel length is only part of a system. When you pull the trigger the air is forced down the barrel behind the pellet, The force will look like a sine wave acting on the barrel, the shorter barrel will be affected by the higher pulse, of course these pulse will be smaller each cycle. So I believe you are looking for that sine wave to cross the center of the barrel at the end, at the same time as the center of balance on the pellet passes through. That way the pellet is not being affected by the harmonic cycle of the barrel. So that were I believe the pellet weight effects the accuracy. The length of the barrel would probably need to be modeled to figure out the pulse length and shorten it to a smallest movement. Probably on the forth or fifth cycle. We'd need some really interesting test equipment to measure these modes, and that would only take out one part of the "system".

Of course I could be wrong, I've been wrong before and possibly will be again.

Smitty
 
Upvote 0
From the perspective of a guy who doesn't get into the science of why things work, but shoots short (Leshiy with 250mm barrel) and long guns RedWolf HP with 23inch barrel). I can tell you shorter doesn't really matter on accuracy. What you get into is gun weight and how steady can you hold a 3lb gun compared to a 9lb gun. My leshiy will shoot as good as I want but getting it locked in a bench is required. 
 
Upvote 0
Thank you colleagues!

It's probably hard to understand me because I use a Google translator when I write otherwise I understand 95% when I read ...

So ...

My question was how only the length of the barrel influences under the same other conditions?

It's about Taipan Veteran who has it in three versions: Short, Standard and Long.

I was interested in what is the difference in the technical data for the three different lengths of the barrel in the three variants of this bullpup.

Of the posts here and in the GTA I have already understood what I was asking.

In short, the long barrel provides more power than the shorter barrel, but there are other factors that matter and this leads to my new questions:

1. What should be the barrel twist rate for pellets and for slugs? Is there a universal twist rate of the barrel for firing with pellets and slugs?

2. Which type of barrel - polygonal, fully cut (as with firearms) and smooth with and without cuts at the end of the barrel is suitable for pellets and which for slugs? Is there an almost universal barrel with which to shoot both pellets and slugs?

Greetings .
 
Upvote 0
Hello colleagues I am again with my annoying questions :)

I will try to be specific with the hope of getting an answer ...

I ask about two cases:

1. Taipan Veteran Standard 25 - barrel LW (or CZ). Here I found it interesting that in Balistas.com the new shotgun put on sale soon in 25 caliber has a barrel CZ assuming that up to now in 25 caliber has always been with LW barrel ...

So I wonder if he shoots the same well with pellets and slugs?

As I have already written one of the main reasons for choosing another brand instead of FX is the ability to shoot both pellets and slugs.

2. FX Wildcat MKII 25 (or Compact 25)

I have already seen somewhere that the FX Wildcat MKII 25 is being sold with the new X barrel and my question is: How will the new barrel be shot when shooting with slugs besides the usual JSB pellets?

I have already read at least about the ST type barrel and perhaps for X barrel is the same that for pellets and slugs is used different barrel with different twist rate but still ask?

Greetings.
 
Upvote 0
I see you are confused about several points. I will try to explain briefly, but there is a great deal of information on this subject as it has been accrued over more than 100 years.

Can barrel length affect accuracy? Yes, not so much in a PCP weapon, but certainly with a springer with the very rapid pressure rise but low air volume. There is an optimum length of about 30 CM. Lengths beyond that causes loss of velocity due to barrel resistance and air pressure drop.

What is the correct rate of twist? It is determined by the sectional density of the projectile. (length). The longer the projectile, the more rpm is required to stabilize its flight. Too little rpm and the projectile wobbles and tumbles. Too much rpm causes the projectile to pancake in flight, like a spinning stone skipping across water as it engages different air densities in flight because the projectile will not pitch over at the apogee of its flight path. So, if a heavier projectile is wanted in a given diameter, it must be longer with a greater sectional density. This requires a higher rpm. We can increase the rpm in two ways, shoot the projectile faster or increase the twist rate. There is a practical limit to speed called physics, so that leaves increasing the twist rate as the projectile increases in weight. Diablo shaped pellets do not need spin at all to be stable. They are inheritably stable, but do shoot more accurately with spin than without. Slugs are like bullets and require spin to be stable in flight. Air guns are designed for Diablo pellets, so if slugs are required, barrels need to be designed for them with less choke and greater spin rates. Another limitation to the maximum length is magazine depth and the available space to actually load the projectile in the breech. So, in conclusion, should you want to shoot slugs, get a slug gun optimized for slugs. The same goes for pellets. There is no gun that will shoot both as well as a dedicated gun for either.
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu