How much fps would I lose dropping my barrel length from 200mm to 128mm

[steverebo]

So I'm thinking of reducing the length of my barrel to create a nice cqb size gun and was wondering how much fos I would drop going from 200mm to 128mm I'm currently shooting at 305fps with a .25

[Jez_Armstrong]

Depends, what cylinder do you have in there at the moment, you'd need to match the volume in the cylinder to the new barrel if you want to keep your fps around the mark you have now

[steverebo]

It's ported 3/4 cylinder

[Rogerborg]

"Some" is the most likely answer.  What I will say is that my MP5K with a 110mm-ish barrel shoots at 1J - 1.05J (depending on air seal and mood) with an M100 spring and... uh... 1/2 or 3/4 cylinder, I can't recall what's in there right now.  You're at 1.07J so you might not lose a lot, or nothing that a fresh M100 spring, or an M105/M110, can't cure.  You might even consider short-stroking it while you're at it.

 

[Lozart]

12 hours ago, steverebo said:

So I'm thinking of reducing the length of my barrel to create a nice cqb size gun and was wondering how much fos I would drop going from 200mm to 128mm I'm currently shooting at 305fps with a .25

 

At 200mm it's already a good length for CQB. Going that short you're more likely to notice the complete lack of accuracy than a drop in FPS!

[steverebo]

I didn't think barrel length effected accuracy in airsoft?

[Lozart]

46 minutes ago, steverebo said:

I didn't think barrel length effected accuracy in airsoft?

 

To a point. Once you get below 200mm it can start having an effect. To be fair, at CQB distances it's less of a problem but for example my MP5K is far less accurate than my MP5A3 both have the same hop rubber and similar quality of barrel.

 

Personally, if your looking to modify the sa-e07 you have in your profile description I'd just swap out the handguard for something shorter and ditch the extra length of the amplifier etc. 200mm is plenty short for CQB.

[steverebo]

This for an arp9 I bought that the original owner put a 200mm inner barrel and suppressor covering it and was thinking about going back to stock length 

[Lozart]

32 minutes ago, steverebo said:

This for an arp9 I bought that the original owner put a 200mm inner barrel and suppressor covering it and was thinking about going back to stock length 

 

OK, I'd ask myself why the last owner felt the need to extend the barrel. Have you actually run it in a game as is?

[Fatboy40]

The example I'll give is the G&G Firehawk, a perfect CQB sized AEG, only a 120mm inner barrel but as stock is around 320'ish FPS on 0.20g BB's.

 

It does this as it has both a full cylinder and an M130 spring, masses of air volume and a piston pushed forward like an F1 car.

[steverebo]

3 hours ago, Lozart said:

 

OK, I'd ask myself why the last owner felt the need to extend the barrel. Have you actually run it in a game as is?

I have had a play for a few games and it is very nice but I really dislike the huge suppressor and quiet like the stock look of the arp9. Perhaps I could but a pdw rail and short barrel extention and do it that way

[Lozart]

12 hours ago, steverebo said:

I have had a play for a few games and it is very nice but I really dislike the huge suppressor and quiet like the stock look of the arp9. Perhaps I could but a pdw rail and short barrel extention and do it that way

 

Gotcha, you could absolutely lose the suppressor and use a barrel extension as you suggest but if you're dead set on having the look of the ARP9 then yeah, shorten the barrel. You may need to bump up the spring but I'd try swapping the barrel out first and see if it actually makes for much of a power loss.