FPS and Accuracy

Hey gang,

Was hoping to get your ideas on where your sweet spot is for decent FPS and accuracy. I get that we can only hope for so much, and what we call accurate might be different to each other, so:

Assuming the Volume Ratio is in a good place, a hopup, decent gels, and everything else is running fine; what FPS do you think leads to the most consistent accuracy over the longest distance before deviation? I’m excluding gel choice here, I’m assuming it’s whatever gel your blaster enjoys the most, may be worth mentioning if you think it’s important though.

My personal best experience is at 290FPS average, using LDT hardened milkies through a 7.4mm ID barrel with the VE Ratio at 1.68 with a rizer hopup. Gels were deviating maybe 1.5 ft at most at around 30m (eyeballing, not measured) before they lost most of their energy.

Anyway, hope this is productive


That is exceptional accuracy.

At a measured 30m, with similar blaster specification, the best I have been able to achieve is a deviation of around 1.5m either side of a centre-line. I’m using the Hills Hoist measure


I was a member of the Metal Power Pole in the backyard Club :+1:
It made a beautiful thump sound and reverberated nicely after each hit :ok_hand:
Very handy when I couldn’t see the gels at longer distances at night :joy:

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Hi all,

Going through the FPS vs accuracy thing at the moment with a couple of SRC SR4 Blasters. I don’t have the barrel lengths with me at work but mine is a full size M4 that puts out 370 fps with the Tactical Edge hardened gels, my sons SR4 is a compact model and puts out around 340fps with the same gels.

We’ve tried a couple of different hop ups and 5-6 brands of well know gels however accuracy is pretty darn far from a 1.5m spread at 30 metres. Need to do some research on volume ratio…

For the mean time, would the next logical step be to drop the FPS and re-test? Any other tips appreciated.



Hop ups may correct the accuracy. Most likely the VE is full cylinder and although they are great numbers you want around 300 for the best accuracy.

You could try for cheap quick change the spring out for a 1.18mm ausgel.

Hard to say with certainty as I’ve never pulled an SRC down yet, but going by @BradleyPhillipsYT video review on one, it looks to have a full cylinder for the full length barrel which is probably around 380mm long, which would be perfect for 7.5mm inner diameter barrel, however, in the video it is stated it has a 7.2mm inner diameter barrel with 8.6mm outer diameter. The volumetric efficiency is probably pretty good on them, but can’t say for certainty.

The only hopups I could recommend are the ihobby threaded riser style
HK Metal Flash Hider With ihobby Hop Up Unit 14mm CCW - ihobby Invention - iHobby Online (there are a few other versions for if you want your own 19mm flash hider or suppressor, or you can choose a few of theirs)
as this hopup comes with tongues to suit 8.6mm barrels as seen on double bell… which is the other hopup I could recommend Double Bell Flash hider/Hopup Combo 14 mm - X-Force Tactical

They both may require the end of the barrel to be trimmed slightly for a perfect fit on the outer barrel if you are fussy, but both will keep the inner barrel snuggly in the hopup, and give the benifits of a correctly aligned to barrel hopup.

The main problem with normal 9.5mm barrel hopups is it won’t be aligned and true to the barrel which will never help getting it accurate. A piece of coke/beer can etc can be cut and wrapped around the inner barrel to help, but it is still a good amount of fit and fiddle.

Also, gels for a 7.2mm inner barrel are going to be limited to control grown (which I don’t advise) or I would try the x-force predator v2 gels Predator V2 Ultra Hard Gel Ball - X-Force Tactical as these average around 7-7.1mm when I soaked them for 4 hours.

Finally, in Brads video it has a quick remove buffer tube then change the spring option, fire it on 7v battery and semi to ensure the piston is forward before attempting this… I would recommend an m90 spring as this will bring the power down and help accuracy loads. Once dialed in with m90 hopup and gels, you could change back to original spring, or an m100 for a bit more punch. After seeing the spring in Brads video I wouldn’t recommend changing back to it as it is a equal spring, unequal springs are much softer on the pickup teeth of gears and pistons, and only benifits can be had here.

Hope it all helps.


Try this spring. 1.18mm Unequal Spring | Ausgel

M series springs are equal, or has that changed now. I never use them as they vary wildly through the many manufacturers . Loose their tension and are harsher on the gearbox.

Yep, it’s all about trial and error. :+1:

Testing different barrel lengths, cylinder porting, hop ups and piston springs is the well trodden path we go down in the elusive search for accuracy.

Not all of the above applies to your SRC… from what I’ve seen on Brad’s review, they’re pretty damn well dialled in from the get go. As suggested above, a spring change to an M90 is easy enough… maybe a barrel swap if that 7.2mm one proves finicky with gel sizes. Making sure everything’s firmly stabilised is important too.

As an example, I have a CYMA CQB with a short 7.3mm IB running around 320FPS. No amount of stabilising and hop up gave me any accuracy at all… VE was terrible. Instead of porting the cylinder I ran a longer IB through a mock suppressor, gained accuracy and about 5FPS in the process.

Fettling, twiddling, mucking about, problem solving and improvising is, to me anyway, the best part of being in this hobby. :+1:

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Handy tip for parents with young kids too…

I’ve got a couple of inner barrels that are about 8mm ID (tube from Bunnings) on CYMA t pieces.

When the young grandkids come over and want to play skirmish with my blasters I swap out the IBs on my 280FPS CYMAs for the 8mm ones, drops the FPS down to about 150… perfect for sensitive little munchkins, no barrel jams and no welts to take home to mum. :wink:

Helps me maintain my status as the fun poppy with all the cool toys. :rofl:

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I’ve gone back to M springs. Found that the unequally wound springs would compress and shorten quickly and loose performance.

The most accurate blasters at 30m are an overpowered BF AK74U with AKA hop-up in an extended flash hider (think the cone of the flash hider evenly distributes the air at the muzzle) and my gen 8 modded A1 AUG with Ubend hop-up, M100 and v/e of 1.75(probably because the end of the barrel is stabilised in the blaster body). Given up trying to get accuracy from the ACR/R.


What brand of M equal spring?

Strange, Never had a problem with my AG 1.18’s some are 5 years old :person_shrugging: and many millions of balls. I bought extra springs expecting to need to replace them at some time but they are just collecting dust on the shelf.

Maybe yours were stored cocked or the spring guide was uts will ruin any spring in short time.

Using M100 SHS springs. Ausgel 1.28s were compressing. Happened in Gen 8, CYMA and Gen10 ACR.

I also exclusively used AUSGEL 1.18/1.28/1.38 springs wherever possible and never had any issues myself, which got me wondering if yours were being effected due to retainer tilt in the gearboxes?

Nothing wrong with M springs, I just found them very harsh on the internals, like somebody inside smacking the cylinder head with a hammer :frowning:

The best M rated springs I had managed to try out were the Guarder and Solink brands for smoothness and reliability.

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I always thought that this was a good explanation for showing the importance of finding the best volumetric efficiency and its effects on the gels/bb’s accuracy :sunglasses:

I always found out when building stupid high FPS experimental blasters back in the day that higher FPS was inherently more difficult to get accuracy due to the incredibly high air pressure behind the gels as they left the barrel.

Hop-ups were less efficient the higher the pressure rose, very likely due to the speed/force/exposure of the gels through the hop tongues making their effectiveness much more unpredictable.

I also found great results with fitting different types of hop ups and muzzle breaks/flash hiders/suppressors etc. that gave tight control over reducing the air turbulence surrounding the gel as it exited the barrel.

The ideal solution was to use slotted barrels/hop ups and flash hider designs that bled of air pressure behind/around the gel before it fully exited the barrel, which greatly reduced turbulence and allowed the gel to enter the surrounding air stream with minimal interference from the high pressure turbulence exiting the barrel :+1:

Great examples of air pressure reduction through hop up and muzzle brake designs to reduce air turbulence.

Old Rizer had tiny side air slots, but they then increased their size in updated versions possibly due to their design testing showing improved performance with larger cut outs……. though were primarily put there to expose the gels to tracer units, I wouldn’t be surprised if it also improved bleeding off air pressure at the same time :thinking:

Slotted barrel hop ups gave a similar result:

As did these types of Muzzle Brakes for greatly reduced air turbulence and highly improved gel flow/accuracy :ok_hand:

Yes these are real steel flash hiders/brakes, which I purchased from the USA, because they were much cheaper than Gun Shops in Australia, which allowed me the funds to be able to buy/test quite a few of them :+1:

Just some ideas for you to try out and let us all know if you have any improvements :sunglasses:

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The later Rizer/Ubend are superior to the earlier Rizers. Did back to back tests with my Gen 8 Aug and the latest Ubend reduced the horizontal spread by about half at 30m


Like Doc says, unequal springs tend to be a little gentler on internals than M springs.

I just put a 7.3 inner into an M4/M203 build and on test was getting woeful FPS and the whole thing sounded very anemic… no balls at all, 150FPS and I was scratching my head over it.

Turns out that on my last service on this gearbox I put a very short 1.1mm factory spring in it… dunno why, must have not been paying attention. Whacked an Ausgel 1.28 unequal into it, test fired it before assembly. My first thought was that it sounded just as shitful with the new spring in, but the first gel through the chrono showed 272FPS. Not what I was expecting at all.

Unequals feel soft and understressed and it can take a bit of getting used too… especially when your VE’s spot on, you end up with such a quiet blaster when it’s all correct.

That’s quite a jump from 150fps to 270fps with a spring change, that would make me think the air seals were skew-whiff rather than the spring. Glad it worked out though, must have been a very sleepy spring :joy:.

I love a quiet blaster, it’s a sign to me that ‘everything is in harmony’ :sweat_smile:

Some stronger people might be able to ignore it, but when I can hear the internals slapping the shit out of each other in the gear box, it’s not great for my peace of mind, especially knowing the origins of some these parts.

Information only

Dragged out the measuring stick to see what variation there was in the length of springs

Ausgel 1.18

  • new -167.5mm
  • used - 160.5mm
  • used - 161mm
  • used - 164mm

Ausgel 1.28

  • new - sorry didn’t have one
  • used - 155mm
  • used -157.5mm

Be interesting to see the length in the M series.

None the less I tried some of the no name brand M springs from the shop in early days and they’d loose their tension in minutes kinking up and giving free piston bounce. Probably cheap shit springs. Got on to the AG and never looked back. Can get 320fps out of a 1.18mm with a good setup easily. Plenty enough zap and accurate too.