[pestobanana]

People often approach me with the exact same questions, and it has gotten quite tiring trying to re-explain to people why they should stick to VFC instead of their Krytac or G&P when it comes to extensive upgrades on an M4 platform.

VFC:

VFC is my preferred upgrade base. All of my personal AR builds have been VFCs, simply because VFC tolerance and spec are much better than the other brands, so they accept aftermarket parts more easily. Any part that needs replacing on a VFC is easy to remove and replace, and the sizing is fairly standard.

Older VFC gearboxes suffer from narrow piston guide rails, but that is a fairly simple fix with sandpaper. Aside from that, VFC does not suffer from any major compatibility issues. Bushings are easy to replace, aftermarket gear sets fit well and are easy to shim. There is plenty of space to wire up a 3034 FET or drop in a BTC unit. VFC motor angle is usually good using the stock grip unless you have a 416 grip, in which case it is off by a bit but it is not terrible by any means. People complain about the self shimming gear set, there is actually nothing wrong with it and I doubt the people complaining know what they are talking about. VFC air seal components seal very well out of the box. Best air seal of any stock gun.

Hop up alignment is almost never an issue in VFC unless you start messing with too many off spec aftermarket parts such as a ProWin hop up unit. The stock VFC hop up unit is actually quite good, though my only major complaint is the lack of rigidity in the VFC arm. I often replace the hop up unit in VFCs with a Lonex chamber, which will require the top of the mock bolt to be bent slightly in order to clear the middle hop up gear.

With a VFC, they typically work as expected after upgrades are installed, and I typically do not run into bullshit tolerance issues. VFC receivers also accept most real steel handguards without modification.

G&P:

People seem to get this idea that G&P is such a great platform, especially since there is a well viewed review of my work on YouTube using a G&P as a base. G&P is not a good upgrade base, but is still workable. The tolerances are pretty bad, but it can be made to work without expending too much effort.

Their stock components are pretty shitty. They took components that seem like upgrades at first, but them implemented them very poorly to the point that they are actually worse. G&P piston assemblies are not great, air seal is very poor out of the box. The concept of non porting cylinders and tapering the rear instead relies on the gun's poor air seal to function and is far less than ideal. Their stock nozzles seal well, but wobble way too much due to G&P's extremely poor tolerances. Their bearings are okay, but will inevitably break. Their gears are not great, but not the worst - famous for weak gear shafts. G&P motors are also some of the shittiest on the market. There is also too much gearbox reinforcement in useless areas, so it is not possible to install a 3034 MOSFET inside the gearbox without extensive gearbox modification.

G&Ps can be made to work, and work very well. They simply require more work due to their extremely poor manufacturing tolerances. They almost never work properly after the first try once extensive modifications have been completed and usually require troubleshooting.

Krytac:

I have gotten to the point where I am outright refusing to upgrade Krytac AEGs aside from simple air seal component swaps and barrel group upgrades.

The U.S. airsoft marketing machine has made it seem like Krytac AEGs are amazing. They aren't. They're quite decent out of the box, because they did take feedback from the U.S. teching community in that they have a built in 3034 MOSFET, better wiring, upgraded motor, etc. The problem is the implementation was quite poor. For example, the motor magnets are better than most stock guns, but they are still quite weak as far as proper motor magnets go. I would not run that stock motor in a highly upgraded gun.

Krytac nozzles do not come with O-rings so they leak out of the box. Krytac often also has hop up related issues that cause misfeeds and jams. The rest of the internal components are not terrible, but best left stock.

The biggest issue with Krytac is that they are based on the V2 design, but the spec is off enough that a complete re-build does not quite work out well. Krytac motors seem to be slightly shorter than standard long motors. Their gear sets are also narrower and their gear shafts are shorter than standard. The reason for their off spec gearing is their ambidextrous selector design that goes on top of bushing holes. If you shim a Krytac gearbox and the gear shaft sticks out a bit more than it comes stock, it will interfere with the selector mechanism. After gear shafts are cut shorter to prevent that interference, aftermarket gears are still too wide to even fit in a Krytac gearbox. The bushing holes must be re-milled to be recessed deeper and allow for a standard gear thickness. The bearings will inevitably break under high stress, and should be replaced with solid bushings - partially due to durability concerns, but mostly because recessed bushing holes will cause the bushings to stick out of the gearbox and jam the selector components. Therefore, in order to perform any major drivetrain upgrades on a Krytac AEG, gear shafts must be cut shorter, bushing holes must be drilled deeper, bushings must be cut thinner.

Krytac definitely took a step in the right direction and forced other companies to do things like include better motors and MOSFETs out of the box. They look good on paper but in implementation, are really not that great as upgrade bases. They are better left stock or with minor upgrades.

TLDR:

VFC - Easiest to upgrade, highest performance potential.
G&P - Annoying to upgrade, but will still perform well once tolerance and other bullshit issues are resolved.
Krytac - Best left stock or with minor upgrades, too off spec to be worth heavy upgrades.