Review: Mad Bull Black Python 6.03mm GBB tightbore x 4

[Steve_U1S]

Yesterday I acquired 4 Mad Bull Black Python 6.03mm tighbore inner barrels for KSC G-series GBBs from Jugglez - 1 x G17/18 & 3 x G19/23.
I immediately installed into the G18c, which had already proven to be a very nice, straight, well grouped shooter.

First impressions (as it's still early on and no hard measurements, but worth sharing for anyone considering purchasing):

The Mad Bulls are quite light in the hand, attractively anodized semi-flat black with white screened logo info (see following).
Fit and finish are excellent (although it bugs me the slightest bit that, hidden completely under the outer barrel, the G19-size barrels have their Mad Bull logo info screened 'upside down' relative to when installed, whereas the G18's is right-reading =] Strictly cosmetic, but thought I'd mention it).
Installation went very smooth and took single-digit minutes, requiring only a small hammer and pin punches; it too me longer to get the shimming of the O-ring precisely to my liking (see bottom of post), as the unmodified fit was quite close already, and that went quite fast. (I'd just recently gone through bumping the stock inner barrels to minimize wobble, so brought this to the new ones as well.)

Proceeded to 'range' the G18c; after some hopup and sight adjustments to reflect the new part and slight FPS boost, I found a notable increase in accuracy and consistency of shots. Aluminum targets clearly showed the deeper denting and more frequent puncturing from the higher pressure, confirmed by my need to de-elevate my rear sight a bit (note; fully adjustable G34-type sight being used).

Then I did an A-B test; I had along my G19 (again, noticable accuracy and power already), which I ranged, performed the upgrade on-the-spot (again, shimming the O-ring took longer) and repeated the targeting.
As above, the shots were clearly more tightly grouped, and showed signs of a similar little jump in velocity.

I have installed into my two G23Fs, one of which I'll probably be 'ranging' a bit later today - the other is in need of a trigger bar (part #92), so it has to wait until I can acquire the part.
More on those results will follow.

Time will tell about the longevity of the parts. Thus far, though, I can speak highly of the results - I'm sure that anyone going from a stock inner barrel to one of these will note a similar improvement in performance, and at a cost that is very reasonable. Good bang (!) for the buck.

Also worth noting, and this is likely covered elsewhere on the site; if you are either shimming your O-rings, or replacing them with larger outer-diameter ones, make certain to leave enough room in the fit between O-ring and outer barrel to allow the inner barrel/O-ring combination to move back and forth when in its correct position, where it's at its tightest, without too much drag. Too tight a fit will absolutely affect the slide's action, specifically, hindering return to battery. A light wipe of silicone oil on the O-ring helps keep things moving as well.

Hopefully this info proves helpful to others.

[Steve_U1S]

I'm investigating further, but I've had an apparent failure with the G17/18 tighbore after roughly 400-500 rounds through - suddenly developed a stray shot problem that was not from contaminants, dirt, damaged hopup rubber (replaced to test that, too) etc.
Swapping back in the original inner barrel brought it back to previous spec.

This type of failure has apparently not been reported previously - suggesting that I possibly got a below-spec specimen (that did, however, group very well initially).
I'll continue to observe the other 3.