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MrJR 03-28-2008 09:32 AM

Sniper build woes.
I'm having one horrible time trying to get my Sniper up and running. Long story short, I can't get usable velocity.
Here's the setup:
  • Psychoballistics Superbolt body, half blocked by hvacman250
  • White Wolf Airsmithing premium mini pump kit
  • Sidewinder reg
  • Benchmark slider
  • pbmodshop (hvacman) halfblock kit
  • jcurt halfblock kit
  • Stock valve
  • Stock slotted hammer
  • Using 13/3000 with Nitroduck I-reg (800 psi output)
  • Also have a WGP valve and a Shocktech Phat hammer that I just slotted

Here's what I've tried so far, all using stock valve and Sidewinder reg:
-Stock (slotted) hammer, light green springs
-Stock (slotted) hammer, light valve, medium hammer
-Phat hammer (slotted), green springs

Then I'd sweetspot the reg with the ivg in 2-3 turns. Never saw anything approaching usable velocity.

Even modified the air passage on the White Wolf mini pump kit because of potential flow problems. Pretty sure I can rule that out.

I have 2 halfblock kits now, and both allow more blowback than I'd like. Especially with the pbmodshop one. The second one I got seemed to be a bit better. It makes me wonder if these bodies use different internal specs than the WGP ones, perhaps.

Next up, I'm going to throw in a WGP valve, and maybe heavier springs, at least for the hammer. And then maybe a different bolt? Like a Shocktech superfly bushmaster bolt? I'm running out of options here. What suggestions do you have? Thanks,


sdawg 03-28-2008 10:56 AM

What pressure are you sweetspotting at (do you have a gauge)? Are you sure that you haven't over-pressurized the valve? That was my mistake a couple of weeks ago. I was starting way too high, assuming my marker needed 200psi+ when I really needed to start at 0psi and work my way up.

It sounds like you know what you're doing and you have the right parts. So, my only advice is to go to your field with a bag of paint and a reliable chorno and take the time it needs to get your rig going.

MrJR 03-28-2008 11:06 AM

I don't have a gauge on it, but I think I'll rig one up. I was curious to know what the post-reg pressure was.

Haha. I'd like to think I know what I'm doing, but it just doesn't add up. Starting to think the blowby is much worse than I thought and is robbing me broke...

hvacman250 03-28-2008 02:05 PM

The problem is the pump kit. The air passage holes in the kit are way too small and dont line up. Take the pump kit apart and carefully inspect it. You'll see what I mean.

You need a small set of drill bits and a drill to fix it. PM me if you have any how-to questions.

hvacman250 03-28-2008 02:08 PM

And is that my HB kit os someone else's? I rememebr the body, but dont know if its my kit.

MrJR 03-28-2008 05:56 PM


Originally Posted by hvacman250 (Post 354697)
The problem is the pump kit. The air passage holes in the kit are way too small and dont line up. Take the pump kit apart and carefully inspect it. You'll see what I mean.

The scary thing is that I've already modified the pump kit. I drilled a new hole aligned with the vert asa that is about 2x the size of the original hole. That should do it, right?

And yep, the kit in the picture is yours.

hvacman250 03-28-2008 06:37 PM

In my experience, the main problem is the hole in the threads has to be perfectly on the bottom to line up with the hole in the ASA. I made a mark whre they lined up, and when I tightened it up so it was tight, the hole in the threads was about 10 degrees past bottom. No air getting in the body.

Also check that the hole in the bottom of the bolt is lining up witht the air passage hol ein the bottom when the sled is in the forward/firing position.

MrJR 03-28-2008 06:56 PM

Yep, so I'm pretty sure the hole in my guide rod is aligned fine. I'll check the bolt hole too.

thumper 03-28-2008 07:49 PM

pressure -- I would guess starting at around 500psi given the lack of volume in the mini. -- work it 100 psi each way from there.

also: make sure the jam nut is snug and the valve is aligned correctly...

Ive seen an xtra oring on the loose back in a valve chamber create havok

Smiley 03-29-2008 01:35 AM

I did some Mini-Halfblocks a while back.Get a gage,start at 500 and work down,the last one worked best between 250 and 350 psi.
Use the phat hammer, start with the heavest hammer spring you have and screw the IVG half way in.
When halfblocking a mini you need to make up for the weight you loose milling the slot in the hammer and the weight lost by not having a cocking rod and nut screwed into the back of the hammer.
You can also add a little more weight to the hammer by using a fully threaded 10 x 32 allen head capscrew 1 inch long with 3 nuts on it screwed into the hammer.Check it for clearance by remvong the IVG and the hammer spring,thread the 1" capscrew all the way into the hammer the put it in the body and screw the IVG all the way in.Cycle the pump and make sure the hammer will catch the sear,when it does back out the 1" screw untill it touches the IVG.Remove the hammer and measure how to determine how many nuts you can use(unless you have a lathe and some 5/16" brass rod to make a solid bushing).
Raceguns use bronze hammers with a steel pin at the rear of the slot for durability.
For a pump gun it might not be needed.
Stock hammer with capscrew and brass bushing:

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