Suggestions on building reliable accurate blaster


So, with an M4 base, what would be suggestions for internals ?

Barrel and length ? Is longer better if ROF isn’t the goal ? I understand not all gels work with all barrel designs, eg bruisemaster 7.1
Would SS 7.2 or 7.3 be a better all round option if I don’t want to be locked in to a certain gel?
SHS 18:1 metal gears.
Hop up ?
MK gearbox
cylinder, piston, nozzle, T piece

Would be really nice if there was a list of suggested parts that played well together.


my two best by far to date have been…

a wells with stock compression gear and a slightly oversized 1.4 non linear & some generic hopup
—retired, i destroyed the front of the box so badly no amount of glue will put it back together

a “relatively” JJ SLR with a 375mm 7.2ID FB barrel and a RZ hopup

gel fit is absolutely critical with the 7.2 barrel.

the 7.5 doesn’t really care so long as the hopup is set properly

Thanks zeHamish,

So how does the length of the barrel relate to FPS and accuracy ? I’m assuming a longer barrel will offer better accuracy. But I wonder with gels and a hop up what the optimum length is.
I see on guido chop shop, he saw a higher fps reading with the longer bruisemaster barrel.

longer barrels do indeed produce more accurate results


there is a world of caveats

1: too long and you loose so much air pressure it negatively impact range - volumetric efficiency
2: not all gels are created equally and their distortion is the number one barrier to accuracy
3: not all hopups are created equally and even then they may behave differently at different FPS with different gels
4: the internal finish of your barrel is super important

i have a 495mm 7.2ID FB in another blaster that is “ok” and to be fair its still a relatively new build sooo…fair cop…but its nowhere near as good as my SLR is. But, the SLR has had hours of subtle tweaking that the DMR is yet to receive…

something as simple as your spring size can mess with your accuracy and heavier is not necessarily better

nozzle diameter has also been shown to mess with FPS and by extension, range and accuracy

Low Guido is THE MAN!

Note: i would not recommend the 7.2ID barrels…they are fussy AF about their gels and recently i’ve had a fair bit of issue on this front…so much so that i’m collecting bits to build a gel grader so i don’t have to fk about with T-piece jams on field…

always love it when you have someone dead to rights and you jam…then they unload in your face >/

Thanks for the great info.

If you don’t recommend 7.2mm ID barrels, then what size would you ? 7.3 ? 7.5 ? I’m assuming you don’t like 7.1 either?

i will probably be moving to 7.3ID SS for all my custom equipment.

i have a range of 7.5ID “stock” equipment that will stay that way.

but…and its no reflection on the tighter bores but more a reflection of my limited gives a *** factor where i just really couldn’t be arsed dealing with intermittent and unpredictable ammo issues on field

i am on field to frag you fkrs, not to d1ck about with bad gels.

its a maximum reliability for minimal effort thing i suppose.

1 Like

You really need to have an assortment of barrels… and grade your balls (the gel ones) laughing%20(1)

The barrels are generally pretty easy to swap 205qlh4

I suggest you have a 7.2, a 7.3 and a 7.5 and keep your balls in batches. LowGuido has a video on gels, a device he made to grade the sizes made from two lengths of angle aluminium set at a gap of 7mm at one end and 7.6 at the other on a slight down slope… and bins under it… as the gels roll down, the gels drop into corresponding bins.

So what is the advantage of tighter barrels ?

This might sound silly, but what is the maximum size ball that would work in a 7.3 barrel?

Fair enough! :grin:

I’m assuming if most gels are below 7.3 a 7.3 barrel might perform better than a 7.5.

Oh, and are these the 7.3mm SS barrels from Chenghai ? Or is there an alternative closer to home ?

yes. the 7.3ID SS are from chgbbs

on the performance question - this is a commonly held but inaccurate thought.

my 7.5ID wells performed every bit as good as my 7.3ID SLR

That is correct :+1:

Not with gels below 7.3mm

Haha, well I was about to question that. Otherwise, what’s the point !?

The S/S 7.3mm Chgbb barrels are a good for several reasons…

*High quality mirror finish inside and consistent size bore over its length
*Suits most commonly available milkies
*Very durable and long lasting



my 7.5ID blasters are for gels that don’t feed through my 7.2ID

i probably should have made mention of the two size differences.

great service
reasonable shipping times
friendly and helpful

on chgbbs themselves


Longer barrel is better to a point…
Short barrels below 200mm, poor accuracy and cause piston hammering especially with 100% cylinders.
Long barrels over around 380mm , gel start to slow down and more jamming issues.
I prefer barrels between 250mm to 360mm and choose a cylinder volume to suit…
60% cylinders on 250mm
75/80% cylinders on 280mm to 360mm
100% cylinders on 360mm plus.

A nice setup would be …
MK v2 box
Metal spring retainer
350mm S/S 7.3mm id barrel
18:1 cut or machined steel gear set
80% MST cylinder
SHS 14t piston
SHS anti reverse latch
SHS Pom piston head
Gen9 style alloy cylinder head with o ring nozzle
Gen9 tappet
Gen9 T piece
Rizer R1 or V2 hop up metal or nylon
1.25 unequal spring
Perun v2 mosfet
M150 or similar high torque motor around 35000rpm
2s or 3s Turnigy 1200mah 25-50c Lipo

1 Like

The above setup done right should give you well in excess of 300fps.
I find speeds around 280 to 300fps give the best accuracy and range plus is very reliable and easy on the gearbox and battery so you may prefer a smaller spring to get below 300fps.


people cry less in this range too and are more inclined to call their hits

1 Like

I actually find that at this speed the gels hit harder at 15m plus and is able to put consecutive gels on the same spot.
I can target your earlobes at 15m :eyes:
I would rather take on someone with a 350/400fps blaster any day :rofl: