FPS increase by tightbores query

[THE FNG]

Hi all, I have a query after my day at anzio camp.

 

I previously was firing a Classic Army UMP/UMC at 330ish fps (0.2g bb's). Stock barrel is around 205mm length IIRC.

 

I have since installed a 343mm 6.03 madbull tightbore barrel and it chrono'd today at very high fps' of up to 372.

 

I was wondering if the tightbore itself had caused the 30+ fps increase or if it was a misalignment in the hop bucking as a quick google search has suggested.

Thanks for you help,

 

Andy

[Elmusie]

TBB do indeed increase velocity, the increase depends on plenty of factors.

 

I recently swapped out my barrel and hop unit but only gained about 18 fps on average.

 

If its causing too many issues on site just have a tech or yourself clip 1 or 2 coils off your spring. 1 coild should bring you down below most site limits.

 

Adam.

[sp00n]

Barrel length also majorly effects fps, my mp5k with a m100 spring and a 110mm barrel can only make 250fps , yet my l85 with a m100 makes 345fps

[Elmusie]

Barrel length on an AEG wont affect velocity to any major degree (not when compared to how tight the barrel is anywho) other than when the barrel length exceeds the intended length for the cylinder you have, at which point you would normally need a bore up kit to ensure you have the optimum volume of air being pushed out of the barrel, too much volume and you just end up with an innacurate gun

 

On gas guns however barrel length can increase FPS massively as there is more room for the gases to expand before the shot leaves the muzzle.

 

Adam.

[THE FNG]

Alrighty, thanks for the quick feedback!

Think I'll switch to the stock barrel for tomorrows game and then look at the tbb at a later date.

 

Thanks again,

Andy

[RR01]

Contrary to Elmusie's response I've proved that increasing inner barrel length can radically effect FPS when using a short inner as standard. I had a G&G CM16 Raider S which had a low FPS of average 265 as standard on a 229mm inner barrel. Without changing anything other than the inner barrel length I substituted a 509mm inner from one of my L85s to see if it was the gearbox sealing at fault and got an immediate increase to over 370 FPS. So going up over 140mm in length will have added the extra FPS to standard. If you tried it with a 500mm barrel you would probably get well over 400 fps, as the spring must be quite strong to give you 330 on such a short inner as standard.

[THE FNG]

Got chrono'd again today after taking the tightbore barrel out and refitting the stock barrel. The fps ranged between 318 and 323. The stock barrel has also increased accuracy noticeably and range slightly...almost to the point of where I don't know how I coped with the tbb!! I have noticed the bb's travelling slower, however they are still hitting where they are meant to.

 

Thanks again for the advice and help,

 

Andy