FX Impact barrel lenght

[AirSupply]

In one of the video's about the new FX Crown they mentioned not only could you swap caliber and twist rate but also barrel lenght. 
600mm seems to be the maximum length on airguns and so I guess they mean shorter barrels. 
On a traditional rifle with a 600mm barrel it is a bit like a javlin especially with a moderator on the end. 
The impact on the other hand is not much longer than the 600mm barrel. If you where to set it up to shoot from a bench could you use say a 700mm barrel?
Would you gain some fps? Maybe not have to max everything out with heavier pellets and possible low 
SD? Better shot count?
Is a little more weight forward of centre a help?
Is there a down side when barrels get this long?
Thanks Michael

 

[weatherby]

Hi Michael,

Longer barrels will in almost all cases increase velocity of high power pcp's if shot with the same settings, but they are also less stiff if the OD remains the same.
For instance, the ST barrels are only 14mm OD, and when you increase their length to 700mm, this will have a very negative infuence on barrel stiffness, in that case it must be supported in a proper way. 
Dwell time will also increase, the pellet will be in the barrel for a longer period before it exits the muzzle, which may be a disadvantage as well.
Besides that, 700mm barrels are not very common, so you will probably end up with a custom barrel.
I think 600mm is a good compromise for speed and stiffness

kind regards,

Gijs

 

[AirSupply]

Gijs. So if I understand correctly the pellet being in the barrel longer means more time to have recoil ect move things before it exits and spoil the shot. "Dwell time"
I understand the stiffness requirement. Could a carbon shroud support the barrel?
I'm not going to run off and try this of course. Just 
interested. Short easy to handle guns are great but from what I've seen the difference in efficiency in some models between full length and carbine is substantial. 
When I look at the impact I think yeah I could cope with another 10cm. Seems like an easy way to increase power. Green power, more for less!
Im sure if it where that easy manufactures would do it! 
Thanks for your reply. Always enjoy reading your posts. Appreciate your true hands on experience. 

 

[weatherby]

Thanks A longer barrel doesn't necessarily mean more or less recoil, there are more things to it.
A long dwell time means that the pellet takes more time to exit the barrel, and with airguns it also means more time that the shooter can pull a shot after pulling the trigger.
Firearms ofcourse have a very short lock time and dwell time, with lighter loads of my 300wby magnum travelling at +3300fps I could see the impact in the sand through my scope at 100m before even feeling the recoil. It all happens in a split second, and there is less chance to pull a shot.
With airguns running at relatively low fps, it's a lot more important to keep the crosshairs at the target even after squeezing the trigger to prevent pulling a shot.
Beefing up a barrel with CF tubing works well, but there has got to be room for it to do so

cheers, Gijs

 

[GQ]

According to the Canadian regulation our FX Impact barrel and shrouds here in Canada are fixed and are 725 mm long.
I think it is a reason why I get an average of 880-890 fps wit a 25 caliber 33.95 JSB MKIi pellet.
And accuracy is more than excellent at 50 + yards.

 

[weatherby]

"GQ"According to the Canadian regulation our FX Impact barrel and shrouds here in Canada are fixed and are 725 mm long.
I think it is a reason why I get an average of 880-890 fps wit a 25 caliber 33.95 JSB MKIi pellet.
And accuracy is more than excellent at 50 + yards.

What do you think should make the difference?
You actual barrel length is also 600mm, just like all other 25 cal Impacts. A fixed shoud has got little to do with muzzle velocity, it's the barrel lenght what counts.
Ofcourse there will always be sample variation, I think you just have a healthy one regarding speed
Mine does over 900fps with a CZ barrel if I want, but I made a oval transferport for my .25 barrel. Not comparable to stock configuration anymore unfortunately.

cheers, Gijs 

 

[GQ]

Weatherby, no the Impact barrel are not all the same.
For example , whatn Ted have set up on his Impact is way longer than the usual Impact barrel. I am not talking about the silencer he use at the end of his barrel.

 

[weatherby]

"GQ"Weatherby, no the Impact barrel are not all the same.
For example , whatn Ted have set up on his Impact is way longer than the usual Impact barrel. I am not talking about the silencer he use at the end of his barrel.

As far as I know, only the shroud is longer, the barrel inside is still 600mm like all other FX .25 barrels
You can't say anything about the lenght of the barrel when it is shrouded. Might as well be a 300mm barrel in a 700mm shroud
AFAIK, FX doesn't make .25 (or any other caliber) barrels longer than 600mm. So I am pretty sure that your Canadian model also has got a 600mm barrel.inside the shroud.

 

[AirSupply]

Got to say though Ted's impact is looking less like your easy to handle bullpup and more like a bench rest machine! In his last video it was preferable for him to grab his streamline to finish off a winged pidgon than take the impact!!
Sure it was probably an opportunity to plug the new rifle. 
Why not make the moderate section longer get more volume there and reduce overall length? 
Anyway it work!!
Here in Oz we can't have any form of sound moderation and have a similar rule to GQ about overall length. Guns come in with bare barrels. Because of this our .22 barrels are 600mm. 
You should have a look under that shroud GQ. 
I also think you will find a 600mm barrel. Because you can have shrouds that's how the rifle has complied to your laws on length. 
Im going to look at some figures and try to work out 
how much improvement in efficiency might be gained per 1cm in barrel lengh. Probable won't be linear gains but I'll get back with some numbers. 
Gijs your CZ barrel is 600mm? Also you made a new thimble for your gun. Do the fx thimbles screw off the barrel? Sorry to bombard you with questions but I know you'll know the answers. 
Michael

 

[broekzwans]

"AirSupply"Got to say though Ted's impact is looking less like your easy to handle bullpup and more like a bench rest machine! In his last video it was preferable for him to grab his streamline to finish off a winged pidgon than take the impact!!
Sure it was probably an opportunity to plug the new rifle. 
Why not make the moderate section longer get more volume there and reduce overall length? 
Anyway it work!!

Im going to look at some figures and try to work out 
how much improvement in efficiency might be gained per 1cm in barrel lengh. Probable won't be linear gains but I'll get back with some numbers. 

In his video he says that he takes his streamline because it's tuned to lower power to be able to shoot within barns/sheds/silos to prevent it from damaging roofs and walls


Regarding the barrel length vs. muzzle velocity there is a paper online about this topic: http://www.kiledjian.elac.org/phys%20001/Ballistics%20of%20Air%20Gun.pdf. He makes some assumptions in here which probably will turn out a bit different in reality but it is pretty linear, just slightly curved.


There is a video on youtube somewhere from Edgun where Ed explains why he chooses a certain barrel length for his standard length Matador and the benefits of both shorter and longer barrels.

 

[AirSupply]

Thanks Roekzwans. I have to admit a lot of that article is over my head! Still interesting. Once I started looking I realised there is a lot of info out there. Appreciate your help. 
Michael

 

[Powerbroker]

How long is my barrel?

 

[Hobbyman2007]

That’s a 600mm barrel. The measurement comes after the transfer port . 

 

[AirSupply]

It’s interesting this tread pops up after all this time. Now of course we all know Ted and a few others did have 700mm barrels. I think I had the right idea It was all a secret at the time 

 

[Powerbroker]

Thank you. I cant buy the 700mm slug liner  

 

[Bob_O]

The Impact is the perfect platform for a 700mm barrel. I can hold it by the pistol grip with my arm down, with a suppressor and it still doesn't touch the ground.

I've seen no loss of accuracy with the 700 barrel.

 

[Powerbroker]

A distributor here in the Philippines is selling the .30 cal slug (stxt) barrel kit with probe (set). i want to buy it but i do not know if the present FX Impact x (not mkII) can propel the .30 cal slug properly. Any advise is appreciated.

 

[biohazardman]

In one of the video's about the new FX Crown they mentioned not only could you swap caliber and twist rate but also barrel lenght. 600mm seems to be the maximum length on airguns and so I guess they mean shorter barrels. On a traditional rifle with a 600mm barrel it is a bit like a javlin especially with a moderator on the end. The impact on the other hand is not much longer than the 600mm barrel. If you where to set it up to shoot from a bench could you use say a 700mm barrel? Would you gain some fps? Maybe not have to max everything out with heavier pellets and possible low SD? Better shot count? Is a little more weight forward of centre a help? Is there a down side when barrels get this long? Thanks Michael

The upside

The gain in fps for the 700mm barrel is about 10%. 

There is a slight gain in efficiency so possibly a couple more shots and slightly less noise. But more likely less shots and the same noise cuz you will turn the power up to get more fps for less elevation on the long shots. 

When tuned your SD should be pretty much the same.

I did not notice any difference in the balance of my gun when I installed the 700mm barrel.



Down side;

Dwell time is negatively affected. I don't worry much about dwell time for a slightly longer barrel as it is only a few hundredths of a second.

If you are going to put a 700mm on a Crown, not sure there are kits out yet, then I would highly suggest a barrel band of some sort cuz the barrel is not supported and I think it's pretty flimsy at 600mm.



If you like to shoot long distances of 100 yards or longer then you want a 700mm barrel if not then a 600 will do you fine.

If you are going for the 700mm barrel I would suggest the slug barrel as, once tuned correctly, it shoots the pellets just as well as slugs and the slugs will perform much better than the pellets in wind or at ranges over 100 yards.

 

[Powerbroker]

Thank you. 25 Cal for 700mm slug barrel is the way to go then.

 

[AirSupply]

In one of the video's about the new FX Crown they mentioned not only could you swap caliber and twist rate but also barrel lenght. 600mm seems to be the maximum length on airguns and so I guess they mean shorter barrels. On a traditional rifle with a 600mm barrel it is a bit like a javlin especially with a moderator on the end. The impact on the other hand is not much longer than the 600mm barrel. If you where to set it up to shoot from a bench could you use say a 700mm barrel? Would you gain some fps? Maybe not have to max everything out with heavier pellets and possible low SD? Better shot count? Is a little more weight forward of centre a help? Is there a down side when barrels get this long? Thanks Michael

The upside

The gain in fps for the 700mm barrel is about 10%. 

There is a slight gain in efficiency so possibly a couple more shots and slightly less noise. But more likely less shots and the same noise cuz you will turn the power up to get more fps for less elevation on the long shots. 

When tuned your SD should be pretty much the same.

I did not notice any difference in the balance of my gun when I installed the 700mm barrel.



Down side;

Dwell time is negatively affected. I don't worry much about dwell time for a slightly longer barrel as it is only a few hundredths of a second.

If you are going to put a 700mm on a Crown, not sure there are kits out yet, then I would highly suggest a barrel band of some sort cuz the barrel is not supported and I think it's pretty flimsy at 600mm.



If you like to shoot long distances of 100 yards or longer then you want a 700mm barrel if not then a 600 will do you fine.

If you are going for the 700mm barrel I would suggest the slug barrel as, once tuned correctly, it shoots the pellets just as well as slugs and the slugs will perform much better than the pellets in wind or at ranges over 100 yards.

Thanks for the reply. Take a look at the date I first posted this tread. There where no fix 700mm barrels. I was speculating about the advantages a 700mm barrel may have well before fx ever mentioned producing one. It didn’t exist then.