Got my UMP from Mastr Blastr for $85 two years ago. Out of the box was shooting 280fps. If I’m not mistaken, Julian the owner swapped the barrel out and put in a smaller I.D one, which gave it the increase to suit newer smaller gels.
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Are the Gen 8 UMP45s sellers are offering now using the same shells that were being sold without gearboxes a few years back?
I’ve never handled one but I remember hearing that those UMP kits were very solid units. 
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Yeah @Friendly_Fire , they are fkn awesome, probably the very best blaster that you could ever own 
The very first versions were just a bare shell that you had to build yourself and add your own Gen8 Gearbox.
This was purely for the fact that they were very tough and high quality blasters which all of the costs were put into designing/producing the most solid platform available at the time.
In the years since, as prices/demand declined, suppliers simply fitted stock generic aftermarket Gen8 Gearboxes and then sold them as complete ready to run units straight out of the box.
They are still one of the most important and relevant Gelblasters to ever be released in my opinion.
The 7.3mm barrels have been my tried and true best performance barrels when running specific hardened gels……. Simply the magic size for decent modified blasters and smaller hardened gels 
I still built many 7.5mm blasters whose gearboxes were set up specifically for that ID and barrel length, and they performed absolutely brilliant for running just the generic milky’s, Orange, Red , Yellow, Blue, Green or whatever 7-8mm common gels without any growing issues for reliable high performance and feeding
My biggest takeaway from Gen8 performance is the size difference of the cylinder head/nozzle.
Much larger diameter than the newer models designed off the 6mm Airsoft gearboxes with much smaller diameter heads/nozzles.
You can really ramp up a Gen8 to push an insane volume of air through their much larger heads/nozzles than the newer restrictive Airsoft design equivalents.
Choking down a Gen8 through a 7.3 barrel can provide insane amounts of FPS if you get your calculations right, whilst still maintaining a “soft” action due to the final last stages of the piston/cylinder volume actually cushioning the impact on the cylinder head due to the increased back pressure on the piston at its full force.
You can achieve the same effect with later smaller V2/3 style builds, but their FPS can’t match the same level of performance as the larger Gen8 outputs.
Of course any modern V2/3 Airsoft sized design replica gearbox/barrel combination can be fine tuned to the optimal performance allowable, but the basic physics standards state that all blasters are primarily hobbled by the swept volume of the cylinder.
The huge difference between the Gen8 and more modern models is that the Gen8 can move a much larger amount of volume/pressure/velocity than any modern small diameter blaster can achieve.
I was getting 430-450 FPS out of a nylon Gen8 way back when the Gen9 and WELLS M401 models were very first released and being touted as absolutely insane blasters because they could produce 239-240 FPS as standard 
What exactly am I rambling on about here?
Dunno, maybe just reiterating the fact that there was a particular time in history where Gelblaster gearboxes/components were specifically designed for the whole 7-8mm Gelblaster market…… but then the manufacturers decided that instead of spending heavily on Gel specific components that were designed exclusively for gelblasters, they simply saved a heap of money/research/development and just copied the 6mm standard design and parts from Airsoft and made it into the standard design for gelblasters
Was that a good idea performance wise for soft 7-8mm gels to be powered by gearboxes designed for rock hard 6mm BB’s?
NO…… it certainly didn’t translate in a physics/engineering sense, but it certainly allowed them to reproduce a shitonne of parts/designs across both platforms worldwide.
Can’t blame them, makes perfect business/manufacturing sense to combine the two together into the same product design.
My personal opinion?
Why do you think that I love the original genuine gel specific designs over the new generic Airsoft crossbreed half arsed designs.
Yes the modern V2/V3 etc are awesome, but yet they are not gel specific and have their flaws in their designs that certainly show up in many Gel related products
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100% agree 
It’s easy to build a Gen 8 box that acheives 280-300fps plus with minimal upgrades and just attention to good air sealing.
A great option for newbie builders and builders on a budget.
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I loved how easy it was to get 300fps from gen8/9/10/11/12 boxes. Barrel, airseals, m90, 11v, done. and stupid reliable. I recommend newcommers cutting your gel teeth on them highly 
Or the Jingji SLR, not as cheap but all the same applies, and if you want you can easily metal gear and stronger spring and motor it and still have it reliable too.
@DocBob has a very valid grasp on the nozzle. Part of the reason also love the JingJi SLR and JG v2 nozzle is they are “gel” size nozzles. My personal favourite nozzle is the SLR, as it seal against the barrel, not the tpiece. It also allows for a great seal with no need for glue, you can swap and test barrels until happy, then a drop of glue on each of the t-piece halves and screw it on the barrel.
The SLRs tappered/pointed nozzle tip, you also can have the tappet to not be pulled back for as long as other gel style nozzle/tappet combinations, and still have the gel feed, slipping past the tip into the chamber. 30-40rps is quite easy, just a shorter stronger tappet spring, and trim the tappet tail 2-5mm, and it works. It is a delight to me.
I do find the smaller nozzles have a place, if you are doing a barrel longer than 400mm, the extra volume that isn’t lost in the nozzle area helps, or if you are doing a high rof blaster over 40rps, the nozzle doesn’t travel quite as far as the JM “gel” tappet plates. That said I have had my gen9 with MK box doing 42rps while feeding and sealing in auto, but it was a headache, taking down and shaving the tappet numerous times. And if you want to DSG, it just will not play nice unless it is doing 30ish rps, defeating the purpose of doing DSG. Though, with short stroking and a brushless motor, DSG is becoming a bit moot imo, but I digress… (frequently!)
I also agree with the 7.3mm barrel, in part. In barrels over 400mm, a 7.3mm with slightly smaller grown gels is very consistent, and accurate still. 7.5mm though for me, is just easy as I feel that full size weight gels are worth it, just limit the inner barrel to around 380mm and it goes well.
M4a1 recently got a bunch or 9mm od barrels that were 7.4mm id, and I love them. I did kinda buy out alot of my local stores limited stock though lol. I found they were still great with full size gels, with the benefit of the 7.3mm if barrels. Bit more work to get in 9,5mm tpieces, a couple of alumminium tape wraps and its good. it then has the bonus of easier to stuff o-rings in the end of the outer barrel to stabilise it, but then makes mounting hopups harder. It has given me the idea of lathing a couple of 9mm diameter rings in barrels for orings to stabilise it, but yet to try it out.
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Awesome informative reply!
I left out the part about barrel lengths, so good of you for the advice on what works best at different lengths.
I found the same, using the different diameters for different length barrels and also when balancing out volume ratios.
Loved the SLR for the same reasons, yet out of all of the many different models in collection, I only had a single lonely SLR!
Good luck with the barrel stabilisers, sounds like another good project to play with and knock out some swarf!
7.3 IBs are my go to as well… especially on something like a bullpup where optimal VE is tricky to acheive.
Every barrel swap I’ve done from 7.5 to 7.3 saw an increase in velocity of about 20-30fps, well worth the hassle of building up the 9.0mm OD for the t piece, outer barrel and hop up.
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mmmhmm one of the old GBF members taught me this 7.3, way to be
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Get 'em while they’re young!
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I weakened and bought one, just to fill the gap in my life This 26 is so much better than the old plastic one I had. Really nice quality as a collectors piece. The little foam darts it comes with are interesting too.
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Yeah, they’re quality for a manual springer…
Those little foam darts sting like a mofo, I can tell ya! 
Need a little ankle holster for it.
Get a fashion co-ordinated one…!! 
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You would NOT want to get busted by the rozzers wearing an ankle holster sporting a G26… 
Maybe just a nice set of cowboy boots to slip it down … right at home!
Hehehe
Bonuscharsssssss
Suppose you’re going to say you are 007 next. They need a new actor anyway 
Never said it was mine…!
Random image , off the net…
I call it, “The Tiny Tiger”…
Be cause, yknow, the colour and themes…
HAHA, now that I like