600mm or 700mm in FX Impact MKll in .25 cal

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No suppressors in Canada so it isn't an issue. Get the 700 ;) 34 inches total length.

Hey from Burnaby BC

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From my experience the increase in velocity (for the same gun parameters) seems to always be in the 40FPS range of a 700mm over a 600mm barrel, regardless of caliber.

Accuraccy as above is not a direct effect of the barrel length, unless of course the added velocity serves to keep the pellet stable over a longer distance, it could be though that the shorter stiffer barrel is less affected by the harmonics Bob has been talking about, this can certainly be a factor (barrel whip) in centerfire guns.

Secondly as mentioned above the longer barrel (up to a point) should make the gun more efficient, that is you can set up the gun to give you more shots from the gain with the longer barrel but still maintain the velocity you would get from a 600mm barrel (I hope that makes sense).

So my answer to your question is buy the Impact now and get the 700mm barrel later, thats the fun with the system, to have all the different set-ups and experiment.


 
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No difference in accuracy if tuned right, best projectile match to barrel, good scope, repetitive hold/eye placement & you can shoot. 

You concerned with most power for efficiency than definitely wait on the 700mm 27.559” barrel liner.

The PCP general rule of thumb that 10-15fps is gained per inch is a rough estimate but good. Here’s what you need to know on length in PCP’s

After 24” (23.75 LW) the gains increase significantly. Throw a 26” Maximus barrel on a Discovery & do the math with a chronograph but you’d have to test both at OEM specs then cut an inch or even 1/2” off & test backwards on old barrel. A 23.75LW in any caliber PCP set at 880fps. Put a 28” barrel on same gun, same settings. It won’t be optimized timing wise but those 4.25” will gain you at least 80-100fps, possibly more. So, I say wait & be happy. Bull pups are the desired item for many. FX is aware a long barrel is needed. Run at 2100psi and making good power but a longer barrel at 1200psi can make more. Problem is very few people want a heavy BR target style 3-4’ barrel on their bull pup let alone a traditional rifle. I’m one of those rare weirdos that do want that but; I also see the appeal of something like a Leyla or Vulcan Gen 2. They would make AWESOME back packers or mountain bike guns. 
 
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I would have to say in my opinion the 700mm barrel is more accurate. This is because you can obtain your optimal velocity with lower regulator pressure and less hammer spring tension. Less air means less turbulence behind the pellet as it exits the barrel.

Quote from FX

It is 100mm (3.9 inches) longer and provides higher accuracy due to its more efficient air consumption and stabilizing power imparted by the length of the barrel.
 
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I would have to say in my opinion the 700mm barrel is more accurate. This is because you can obtain your optimal velocity with lower regulator pressure and less hammer spring tension. Less air means less turbulence behind the pellet as it exits the barrel.

Quote from FX

It is 100mm (3.9 inches) longer and provides higher accuracy due to its more efficient air consumption and stabilizing power imparted by the length of the barrel
Click to expand...

While I don’t have an impact ( yet) I have done a lot of testing (pellets, not slugs) with short and long barrels. I found no difference in accuracy regardless of length BUT as the distance increased, the longer barrels held onto their accuracy whereas shorter barrels tended to loose the plot. I have no idea why this should be but almost without exception this proved to be the case. Out to 50 or so yards, get whatever feels balanced,.Along with the obvious power advantages, 100yards plus I would choose a longer barrel every time.



Bb
 
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I would have to say in my opinion the 700mm barrel is more accurate. This is because you can obtain your optimal velocity with lower regulator pressure and less hammer spring tension. Less air means less turbulence behind the pellet as it exits the barrel.

Quote from FX

It is 100mm (3.9 inches) longer and provides higher accuracy due to its more efficient air consumption and stabilizing power imparted by the length of the barrel.
Click to expand...


I would agree to an extent, however turbulence is not directly related to the reg pressure, basically it's how much "extra" or wasted air behind the pellet when it exits the barrel that has done nothing to increase the velocity, that is the important factor.

Put another way the volume of air and it's initial pressure are not the same as too much air behind the pellet causing turbulence.

The quote from FX is a sales pitch and the word "potentially" inserted before "provides" would be better.
 
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Well guys thank you very much for such great inputs and advices. I really appreciate it. 

It is now concluded that I will get a 700mm barrel in Impact MKll.

Now this thread/topic brought a new item of 30 caliber. 

Now my new confusion is between .25 or .30?

.25 Impact MKll will take few months and the .30 is in stock and I can get it today.

The slug liner are not available yet here in Canada. 



Thanks again for your time and inputs. 




 
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I have both the 25 and 30 caliber in 700 mm I enjoy the performance of both barrels. I find the 30 is better with the wind over 125 yards at 100 yards they are pretty close. I have the previous model Impact not the Mark ll. Other than the ammo costing less in 25 caliber and there is a slug liner in 25. The choice is yours you will have a nice gun either way.
 
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