Crossover bolt and springs experiments

[FlightMedic938]

Awhile back I had the idea of creating a slip sleeve to go over the stock powertube so the Crossover could use aftermarket bolts for the Phenom and maybe even Automag. I got my hands on an MRT TechT bolt so that all kinda stopped until today. I’m mainly doing this for people that have Crossovers but don’t have a way to get an aftermarket bolt to increase performance.

I ordered a ANS Phase 2 Automag bolt from Bacci paintball today. Looks rough and heavy but if it has a good fit over the Crossover powertube I’ll clean and polish it up. From what I’ve read this bolt is roughly 45mm and the Crossover is 55mm.

I created this little spacer using an old .691 Freak insert. I still need to make it perfectly flush so I cut at 14mm so I can file it even later. A front bumper was put on for this picture so you all will have an idea of what it looks like. Its secure but I need to make a channel for the bumper to sit in so it’s more secure. Inside the freak spacer are 2 O rings that secure it tightly to the power tube

I also have a spool spring for an Emek and a low pressure TechT spring kit for the Tipx coming today so hopefully I’ll get to mess around with those soon as well

[Jonnydread]

This right here. This is the spirit.

[FlightMedic938]

Emek spool spring vs Crossover spool spring.

It’s a touch longer, thinner gauge, and much lighter. Hopefully I’ll be able to drop the operating pressure further and it’s not too light which could cause a leak. ID is almost identical.

I’ll keep the length untouched accounting for the slightly thinner gauge.

[FlightMedic938]

Edit- Actually had it ass backwards. Did a compression test and the shorter spring decreases travel inside the barrel. This actually might be a good thing. It looks like the bolt will stop traveling right before the bore change most Tippmann barrels have so less chance of bolt stick. I removed the teflon bumper. Now I know I have a tool in the toolbox if I test a bolt that is longer than 55mm

Stock spring vs TechT low pressure spring for the Tipx.

The spring is shorter and much lighter. Thinner gauge as well which will allow more compression than the stock spring which will make the front bolt travel further in to the barrel. That doesn’t sound good to be honest. I’ll have to be careful with this. Could cause bolt stick.

To account for the shorter length and thinner gauge I put in a high quality teflon bumper. I’m thinking this could prevent any problems from arising. You can kinda see it in the last pic. Hopefully it prevents the bolt from slamming inside the barrel and it’s adding preload to the spring to stiffen it up a little.

Also, these springs are positional for proper installation. The narrow ID end of the spring goes over the bolt and the larger end goes against the bumper.

[FlightMedic938]

All back together

[lhamilton1807]

Subbed
cool experiments!

[Trbo323]

Subbed

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[FlightMedic938]

Anybody have experience with nesting front bolt springs on a blow forward? I’ve been studying various posts on multiple different forums and it seems that these springs are considered very light and from the little data I’ve been able to interpret the recommendation is to use the “heavy” spring.

Now, I know the Mini GS stock spring is lighter than the stock Crossover spring so to use the heavy TechT spring isn’t as drastic of a change compared to the Crossover. So I nested the light spring inside the heavy spring. It’s still much lighter than the stock spring so I think this is the configuration I’ll try first. I love a good experiment but I definitely don’t want to break something that’ll be a headache to replace.

I did an extensive compression test by hand (seating the springs/bolt in the body and using a barrel swab to forcefully push the bolt forward vigorously) and the bolt moves super smooth with no complications. I think it’ll work just fine and if I’m happy with the results I may try just the heavy spring in the kit.

[FlightMedic938]

Nesting the heavy spring with the light spring worked great. I was able to drop the operating pressure from 180psi to 160-170ish psi. I tried just the heavy spring by itself and the kick felt unhealthy for the gun with a faint metallic clink sound after every shot. With a lighter bolt it would be possible but, at this moment, the 2 springs nested is currently the lightest possible spring(s) without sacrificing durability.

The spool spring, on the other hand, did not work. It’s too light. I even tried using a small guide but no dice. The spool itself is too heavy. I guess it could be lightened but that’s not something I want to do so it’ll stay the way it is.

The Automag bolt hasn’t arrived yet. I’m not sure it’s even shipped yet which sucks. I did think of an alternative method instead of the freak spacer with a bumper. Researchpaintball.com sells fatty Spyder bumpers and Evil Omen bumpers that are 10.3mm thick. I got them in the mail today so I’m just waiting on the bolt to get here.

[Trbo323]

Do you have a goal here? I'm just curious if you are aiming for anything in particular

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[FlightMedic938]

My goal was to maximize the performance of the Crossover using only mech mode. The only thing left to do is to try the thick bumper to see if I can use a shorter bolt effectively and see if it increases performance. So the MRT Crossover bolt weighs roughly 16g and the MRT Phenom bolt weighs roughly 10g and it’s delrin. I think with that bolt and just the heavy low pressure spring from the kit I can get the operating pressure down to 150psi or so. Everything I’ve done so far has made it more efficient, more quiet, and smoother.

[FlightMedic938]

I did a fit test with the new bumper and it feels like this’ll work. I won’t know until I get the bolt to test it. The bumpers are 9.5mm and the stock Crossover bumper is 3mm.

I was off a little with my measurements initially. The Crossover bolt is 2 1/4” and the Phenom bolt is 1 3/4” (from what I’ve read). So I’m looking at a 1/2” difference here or 12.7mm. The fatty bumper from researchpb.com and another stock bumper gets me to 12.5mm. I think with another stock bumper spacer on top, it should be as close to 12.7 as I can get right now.

The Automag bolt hasn’t got to me yet but if I remove the top stock bumper I’ll be at 9.5mm. So .5mm off. I won’t know until it gets here if that’ll be an issue or not but a bumper spacer should fix it if it is a problem

[Trbo323]

My goal was to maximize the performance of the Crossover using only mech mode. The only thing left to do is to try the thick bumper to see if I can use a shorter bolt effectively and see if it increases performance. So the MRT Crossover bolt weighs roughly 16g and the MRT Phenom bolt weighs roughly 10g and it's delrin. I think with that bolt and just the heavy low pressure spring from the kit I can get the operating pressure down to 150psi or so. Everything I've done so far has made it more efficient, more quiet, and smoother.

Worthy goals. To me the trigger was one of the biggest problems when I had one. It just never felt good. I found I was always comparing it to my automag and if that's the case, I might as well just shoot the automag

One other thing that always annoyed me, won't affect you if you are aiming for mechanical only but it was that you had to have the trigger activation point in 2 separate spots for the electronic mode and mechanical mode. So if you flipped modes the trigger would fire at a different spot in the pull. You could get them close but for it to function as intended the e frame spot had to be in front of the mechanical spot.

Also that thing has the worst programming sequence I have ever come across by a pretty good margin.

I think mechanical only is a good choice. Wonder if you could use a mag RT pin .....

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[FlightMedic938]

I haven’t shot an Automag in decades so I can’t really remember but the Crossover has a really nice pull in mech if you mess around with a little. I think I’ve already posted what I’ve done but I polished the trigger and trigger lever (sear) and the firing valve assembly. I was surprised to find as many burrs as I did. I also doubled up on the frame magnet to increase the return and adjusted the “forbidden” adjustment screw to make it mech only, which shortened the pull by a lot!

Now I’m thinking. Since I’m only shooting mech I really don’t need the trigger lever. It just acts as an intermediary at this point. I could replace it with a magnet on the pin and trigger landing (opposing) or a compressible polyurethane to engage the pin.

[RhoXi]

I only shoot mine mech too. The board in these leave a lot to be desired and I find it easier to walk the trigger in mech mode.

[FlightMedic938]

I did some trigger work today and I’m really surprised on how in turned out. It only works for mech and the electronics have to be removed.

I removed the trigger spring, super glued a magnet over the trigger spring hole with attracting polarity to the trigger set screw magnet, and then placed a larger magnet from an old Tippmann Egrip over the the screw that secures the valve body with opposing polarity to the magnet over the trigger recess.

It made the trigger pull very crisp and easy to walk! The magnet over the screw needs a piece of hockey tape over it but everything works perfect. I need to try it with air because I used most of it tuning other markers and trying to figure out why the Crossover sprung a leak. Turns out, you need the trigger lever (sear). If it’s not installed the trigger pin comes too far out of the core and past the first valve core o ring creating a leak.