Magnets are brittle and break like glass. You can use lead by compressing a fishing sinker to form the shape or purchase tungsten rod in the diameter you need. Pure tungsten is by far the best for adding weight.
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Chokes and velocity
- Thread starter Dr. Kralenstein
- Start date
Troy Hammer has mentioned in other threads needing more hammer weight than factory provides for some kral .357 builds.
I'd personally increase the throw if possible, then add weight if necessary but that is just me. Maximizing throw (kept within reason) in conversions such as a small caliber to big bore should be a top priority. The difference in say .6" to .9" throw is tremendous.
-Matt
I'd personally increase the throw if possible, then add weight if necessary but that is just me. Maximizing throw (kept within reason) in conversions such as a small caliber to big bore should be a top priority. The difference in say .6" to .9" throw is tremendous.
-Matt
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Funny part with that, is he actually cut down and drilled out the stock hammer on the bighorn to get the power increase he achieved. Cutting it down from the rear does me no good, since the sear engages the hammer in the same spot no matter what. The only way I see I can get more dwell is shaving down the rear of the valve and adding length to the front of the hammer.
This is how the jumbo hammer looks, the mega/np03 hammer is what I have which weighs less but has a larger spring cup for bigger springs. 12 mm for np02 vs 8mm on the jumbo.
The front section stops at that lip and engages the sear on that edge. The section that is turned down does into the valve cavity of the block and hits the stem.
If I add to that section and shave the valve to let more stem protrude, it would open the poppet more.
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Yes, I will check the seated depth and also push the pellet to see how much drag there is. Usually there will be accuracy issues if the skirt is over the port, since the blast of air usually deforms the skirt. That's one thing I have going for me, it's pretty accurate.
The barrel and probe are same length as the other kral guns which I've had no issue with, but anything is possible.
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I'll assume he drilled / cut down the rear of the hammer to allow a longer spring.
If your stem protrudes enough for the hammer to open it ~5mm then it should be fine, if not then its definitely worth exploring exposing more stem. Otherwise you want to expose more of the stem so you can trim it down while retaining that minimum necessary ~5mm travel. Other modifications may be needed to allow the hammer to travel forward more, or it may just prove to be too challenging.
If that is the case I'd recommend sourcing a poppet made from peek slimmed down to have .5mm sealing margins, so 1mm over the seat/throat OD.
Although I'd personally throw it all at it, a peek poppet, eek out whatever extra hammer travel one can manage, and maximize that hammer weight, the trifecta here will certainly reduce the cocking effort from what it is while very likely achieving far more fps than 750 from 81 gr.
-Matt
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Got some rough specs on hammer travel. Looks like 40mm.
Here's the hammer not cocked
Hammer cocked
Here's the hammer not cocked
Hammer cocked
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Here's spring travel.
Not cocked.
Cocked.
With roughly 5mm of spring seat/adjuster that threads in flush to the end. Plus whatever the spring cup in the hammer is, I don't have a gauge or ruler to get in there.
I need more weight and valve lift.
Not cocked.
Cocked.
With roughly 5mm of spring seat/adjuster that threads in flush to the end. Plus whatever the spring cup in the hammer is, I don't have a gauge or ruler to get in there.
I need more weight and valve lift.
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How do you plan to get that pellet seated properly and get your port volume back to where it should be? How many FPS are you loosing? Curious if it’s small or if it’s substantial. For testing you can just make a tool to reach in there a seat the pellet. Then you’ll know. Also check the probe with the gun cocked to see if you have room to move it forward and still be able to use a magazine.
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The factory probe goes back far enough that I can cut the tip off and drill it out and seat a pin in it that is longer. I used to make extended probes form my crosman guns like that.
I have about 1mm I can shave off the valve to get more valve lift. The stem has an o-ring it that will pop out into the exhaust port if I go past that. Then I would need to add 1mm back to the hammer face.
Not sure how much that will give me, but roughly an extra 1/16" of an inch should do something. Need to get a tungsten rod and make a hammer weight as well. Cutting that should be fun. Probably need a diamond cut off wheel.
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The key to shaving off the back of the valve and some of the stem is to increase hammer travel/throw, so you wouldn't want to add length to the hammer where it makes contact with the valve stem (the striker), only the face of the hammer which doesn't contact the valve stem nor limit it or the valve stems travel.
Shaving off the back of the valve while increasing the distance the valve stem protrudes would allow for potentially more valve lift but that is only concerning if the valve stems travel/lift currently under the ~5mm mark, in this case you'd be removing say 3mm from the valve rear and 1mm from the stem, adding 2 extra mm, but I don't think your current valve stems travel is limited.
Other modifications may be necessary to allow proper hammer/valve stem travel, hammer lip reduction, extending a notch, ect, I don't know for sure as I have never messed with this gun, either way take your time, I have no doubt the mods can be done its just how they should be done that matters.
-Matt
Shaving off the back of the valve while increasing the distance the valve stem protrudes would allow for potentially more valve lift but that is only concerning if the valve stems travel/lift currently under the ~5mm mark, in this case you'd be removing say 3mm from the valve rear and 1mm from the stem, adding 2 extra mm, but I don't think your current valve stems travel is limited.
Other modifications may be necessary to allow proper hammer/valve stem travel, hammer lip reduction, extending a notch, ect, I don't know for sure as I have never messed with this gun, either way take your time, I have no doubt the mods can be done its just how they should be done that matters.
-Matt
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Why don’t you just try a brass hammer weight. See if it gets you there or almost there before you get all exotic with tungsten.
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I could just smash a 357 pellet down and shove it in there. That's roughly 5.25 grams of weight.
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I’ll make you a brass one but I’ll need some measurements pronto. I’m headed out of state for the weekend. I can turn it this evening and drop it in the mail in the morning.
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Sweet! 12mm diameter seat to fit in the hammer. 2mm hat thickness spund good. The shaft max length is 10mm from the 2mm hat for a total length if 12mm, and 5mm diameter. That should work.
How much you think that would weigh?
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I can't picture this shape in my head so you could calculate it at this link. Edit: link not working.
Calculate the volume and then brass is 8.6 grams per cc
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I’ll let you know. And if I have any questions, keep an eye on your PM’s for the next hour. Heading down now. So this is what you want?
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That is spot on man. That should let me cut the spring guide off the adjuster, leaving about a 2mm nub to hold the springs.
Thanks!
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