pre-2k bolt in 2k - higher velocity

[latches109]

I was messing around with my trilogy build and putting all sorts of bolts int here. I found two of my pre-2k bolts 20 & 40fps faster respectively than ALL the 2k bolts.

looking at the two bolts on the right with the pin in both - STO pre-2k (black L) - and a stock 2k trilogy bolt(silver R). The Pre-2k comes almost flush with the edge of the barrel milling, my best guess is a better seal on a smaller diameter of the barrel.

Can someone else test this? pls discuss where the bolt should end and why. Ignoring the back block pin location -> form the valve hole to the bolt tip.

[Ecapnation]

Bolts can and will effect velocity.... But how did you get paint to feed with a pre 2k bolt in a 2k?

[latches109]

Yes there was ~1/8” available. And the valve hole was occluded blocking some of the air.

[iamthelazerviking]

Interesting, using a pre2k bolt with 2k backblock like Ecap mentioned shouldn't really work. But I'd say it has more to do with the pre2k being venturi vs open face.

[capitalpaintball]

I run a 99 bolt on my 2k2 Pump, just need to use a pre2k back block.
I found wide variances in length of aftermarket bolts. it seems there was no exact specs they used. iirc Bob Long bolts were way shorter then everything else.
Because you can "time" a cocker you could adjust how far the breach opened. doesn't change anything when closed though.
I think even the back blocks varied in "size" too

[WORR13]

open face to open face - the bore diameter changed from pre to post 2k. pre 2k were smaller promoting higher psi (within reason). around 2k there was a 'need' or desire to make everything low psi in paintball (also the switch from co2 to hpa), which equated to larger bore diameters on everything, lowering psi but needing higher volume. in everyone chasing the low psi setup everyone wanted larger bolt bore's, bigger is better theory -not always true. same with the valve chambers on pre 97/98 cockers (this more for hpa operation).
the bolt face should sit at the end of the barrel milling, at that edge where the end of the barrel sits in the breech i would think. if you wanted to really go nuts to check this you could disassemble the gun and stick a punch through the valve set screw hole and line up the bolt inlet to see where it lines up in the breech and that would be the ideal spot for that set up.
also there has been many, many bolt comparison tests done -look them up and you'll have hours of reading to do

[Grendel]

I believe this is a correlation vs. causation situation. Whether a bolt is Pre-2k or 2K+ is really a factor of length of the bolt but does not necessarily have any bearing on air passages and efficiencies. You are correlating the change in performance to one of many variables between the bolts vs. actually identifying that actual cause of the variation.

[latches109]

but does not necessarily have any bearing on air passages and efficiencies.

ball is loaded into the barrel completely vs a 1/2 - 3/4 load, with the barrel being a smaller diameter. This bolt is occluding the valve opening too. yet, I am getting higher velocity. does not seem to add up, and I should have feeding issues.

[latches109]

normally there is 1/8" gap from bolt face to where the body meets the barrel

[latches109]

so my thought is, if the marker setup allows for a longer cycle, a pre-2k bolt on a 2k back block could work, especially if the valve opening is elongated.
Benefit being better efficiency.

any downsides?

[WORR13]

give it a try as long as theirs no mechanical clearance issues foreseeable

[WORR13]

you've been using pre 2k and 2k bolts on a 2k back block? or you have been using the matching back block for the bolts? from the diagram above i would think the pre 2k bolt would be a more efficient setup, is this what you've found?

[latches109]

yes stock trilogy back block (2k) with a pre-2k bolt