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russc
09-01-2008, 05:25 PM
Hey guys, just wondering if any of you have experience with JAM bolts in pumps. Right now I'm using the matching original venturi bolt that came with my Carter cocker but the plastic/delrin/whatever front is scratched and gets gummed up very easily.

What I'm most interested in is whether the bolt acts to allow for pump blowback (like when you don't hold the pump handle) but when you are holding the handle firmly. Does it act as an internal buffer for the back pressure?

drg
09-02-2008, 10:45 AM
Yes it does blow back when you fire it, pretty massively if you use the stock spring. I put a red valve spring in mine to try to lock it down and it still did it a little.

Whether this is desirable is up for debate in my book ... I wouldn't use a Jam bolt in a pump.

russc
09-04-2008, 06:11 PM
Well, all of my Snipers shoot better when I don't hold the pump handle. My thinking was that the JAM bolt could allow for some internal kickback while the pump handle was held firmly.

drg
09-04-2008, 10:23 PM
Yeah, it could. Personally I think the opposite (not holding the pump costs fps), but I see the idea, you can tune it for a good fps with pump held. I didn't find it worth keeping the JAM bolt because it is not as efficient as other bolts, but your priorities may be different.

You will likely need to tune the spring a little bit, the stock spring is pretty soft for that application, and the bolt has very little mass compared to the pump assembly.

thumper
09-05-2008, 09:49 PM
Hey guys, just wondering if any of you have experience with JAM bolts in pumps. Right now I'm using the matching original venturi bolt that came with my Carter cocker but the plastic/delrin/whatever front is scratched and gets gummed up very easily.

What I'm most interested in is whether the bolt acts to allow for pump blowback (like when you don't hold the pump handle) but when you are holding the handle firmly. Does it act as an internal buffer for the back pressure?

ive played around w/ them - similar effect to not holding the pump handle.

worth playing around w/


ps: try chronying while holding and not holding the pump handle..

and compare

thumper
09-05-2008, 09:50 PM
..You will likely need to tune the spring a little bit, the stock spring is pretty soft for that application, and the bolt has very little mass compared to the pump assembly.

yeppers

r90t
09-12-2008, 04:33 AM
I have one in my Ripper that I just resprung. Afterwards, it was like WTF, I was double feeding. It took me about an hour to realize that I had reduced the hammer spring tension so much that I was getting significant backblock motion. Enough to double feed. Then holding the pump handle forward, it was still doing it. The JAM bolt had enough rearward travel to feed a ball, even with the pump handle held forward. I put a small spacer in under the bolt spring to fix this problem and a stronger return spring on the pump to fix the other issue.

I have had no problems using this bolt in 2 pump guns for 4 years.

drg
09-14-2008, 11:44 AM
At the risk of sounding BST-ey, I may want to part with my 2k spec JAM bolt if you are interested. PM me.

russc
09-25-2008, 03:53 AM
drg, my Snipers are mostly pre2k otherwise I would have taken you up on that offer. I've got a few on the way now to test out, and I'm also considering modifying one of my old Bud Orr quick strip bolts to absorb some of this "recoil."

Freedom_paintballer
09-29-2008, 09:44 PM
I chrono my gun when the pump handle is not being held and my gun will shoot the same if i hold it and i can achieve about 7 to 10 more fps by holding it down to give me that little boost to make longer shots.

russc
10-22-2008, 04:32 AM
I bought a few of these bolts and so far I love them. I can now hold the pump handle tightly and they act as recoil buffers, meaning I get that same nice smooth shot, quiet sound and trajectory. Before, my guns never felt right when I held the handle.

customxphoto
10-22-2008, 04:48 AM
nice i have one of these



ill have to try it in my pump



thanx for the tip

thumper
10-27-2008, 11:50 AM
jam bolt in snipers ...

I messed around again w/ one -- it was a 2k aluminum w/ in perfect condition. I shimmed the bolt spring w/ a wooden dowel to turn it "evo length" (maybe just under 1/2") and then experimented w/ my green rf evo X sni2, comparing shot patterns from my aluminum belsales supercharger venturi bolt to the jam bolt - doing so in every configuration. The pump return spring and bolt springs were tight enough to prevent double feeding and pump slop.

Comparing these using a target at 150'

config1) : supercharger + nail polish wedgeted 14" AA + dont hold handle @ 350 psi female stab = exceptional - (10" pattern @ 150')

config2) : supercharger + nail polish wedgeted 14" AA + hold handle @ 350 psi female stab = 90% as good as config1 (significantly louder than config1 - like a dry fire) (20" pattern @ 150')

config3) jam + nail polish wedgeted 14" AA + dont hold handle @ 350 psi female stab = 80% as good as config1 (similarly quiet to config1)
(30" pattern @ 150')

config4) jam + nail polish wedgeted 14" AA + hold handle @ 350 psi female stab = 80% as good as config1 (similarly quiet to config1 - same sound signature as config3)
(30" pattern @ 150')

My conclusions : Jams go back in the tool box.

-----------------
As for the guys who experiment w/ hold vs don't hold and velocity : I now believe there is a great deal to be said for the venturi effect and an elongated bolt air inlet hole - both of which effect velocity, initial drag and acceleration.

I think the venturi effect accelerates the ball slower thus creating less drag (as the ball retains its shape). I believe this effect to be multiplied when not holding the pump handle on a low pressure sniper II - thus causing the muzzle velocity to climb a few FPS.

It would be very cool if someone would make a 6 hole venturi styled jam bolt w/ elongated inlet hole.. with adjustable pull pin hole location and a variety of bolt springs to tweak the recoil absorption... (now there is an idea) (shims are easy -- 3/8" wooden down w/ rubber bumper cut to length and large rear set screw to adjust)

test marker:
http://www.teamsection8.com/collection-2008-07/0771.jpg

k.macocker
10-27-2008, 01:20 PM
nice test. but...
I thought over the chrono would have told me more to be honest. lol

and didn't tom kaye with kodac prove that paintball maintain their shape in the barrel?

kmac

sorry if im coming across negative, im not just accuracy has soo many more factors than a chrono.

thumper
10-28-2008, 08:01 PM
nice test. but...
I thought over the chrono would have told me more to be honest.

and didn't tom kaye with kodac prove that paintball maintain their shape in the barrel?


no prob.. ill measure 4u

k.macocker
10-28-2008, 10:04 PM
no prob.. ill measure 4u

you da man...
Kmac

drg
10-29-2008, 08:09 AM
How did you stabilize the gun during firing?

thumper
10-29-2008, 10:14 PM
How did you stabilize the gun during firing?

4 moa red dot --

drg
11-03-2008, 08:14 AM
Wait, you handheld the guns?

k.macocker
11-03-2008, 12:56 PM
Wait, you handheld the guns?

thus why I asked for over the chrono :)
Kmac

thumper
11-03-2008, 08:58 PM
Wait, you handheld the guns?

lol - well I haven't mastered shooting with my feet..

k.macocker
11-03-2008, 09:03 PM
lol - well I haven't mastered shooting with my feet..

haha, all accuracy tests should be done in a vise of some sort to remove human error. indoors would be preferred to avoid wind, lol.
thanks for what you have done so far..
Kmac

tonloc91483
06-12-2009, 02:07 PM
wondering if anyone else has any feed back on jam bolts in pumps?

russc
06-12-2009, 05:50 PM
I'd highly recommend them for people who keep their hands on the pump all the time. It pretty much just makes your gun shoot the way it would without holding the pump. I think a slightly stronger spring should be used in snipers since you aren't actually using it for anti-chop.

Dr. Isotope
06-12-2009, 10:06 PM
Just for giggles, I built one for one of my nephews pumps (2k3 fullsize body).

http://img.photobucket.com/albums/v307/DrIsotope/Random/jambolt.jpg

Works pretty good. The slight recoil action makes the gun quite a bit quieter.

thumper
06-12-2009, 10:25 PM
wondering if anyone else has any feed back on jam bolts in pumps?

ive tried on and off for a few years -- like the man said, go w/ a stiffer spring and hold the pump handle...they are fun to mess w/.

I keep a few jam bolts stashed away for when the mood strikes, but lean towards the belsales 6 hole aluminum venturi to deliver the goods.

pump
06-13-2009, 01:03 AM
At the risk of sounding BST-ey, I may want to part with my 2k spec JAM bolt if you are interested. PM me.

you gave it to me for trade for a ccm already
but ill give it back, i still want an evo for my STO bellows special

tonloc91483
06-13-2009, 03:09 AM
ive tried on and off for a few years -- like the man said, go w/ a stiffer spring and hold the pump handle...they are fun to mess w/.

I keep a few jam bolts stashed away for when the mood strikes, but lean towards the belsales 6 hole aluminum venturi to deliver the goods.



Alright I guess I'll have to buy a 2nd bolt for my sniper and play around with both and see what works.

drg
06-13-2009, 03:54 AM
you gave it to me for trade for a ccm already
but ill give it back, i still want an evo for my STO bellows special

Check the date I posted that lol

russc
06-13-2009, 04:38 AM
Just for giggles, I built one for one of my nephews pumps (2k3 fullsize body).

http://img.photobucket.com/albums/v307/DrIsotope/Random/jambolt.jpg

Works pretty good. The slight recoil action makes the gun quite a bit quieter.

That's a sweet little piece of equipment you've made there. I'm actually interested in figuring out how to make a recoiling bolt for my Buzzard to get rid of the Nelson "fart." I think it comes from disaligning the transfer ports, so it could probably be done by having a spring loaded venturi that closes the ports when pushed back by air pressure.

cockerfanatic
06-13-2009, 04:55 AM
yea i like the look of that bolt!

you should make a few and sell them ;)

pump
06-13-2009, 06:49 AM
Just for giggles, I built one for one of my nephews pumps (2k3 fullsize body)make me one


Check the date I posted that lol

yikes hahahaha