Kral Arms Going up from 25 to 357

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Dr. Kralenstein said:
Hopefully you can get that thing up to 150 fpe or so. 21" isn't a bad length, but most of these big bores are 28" or so to get that higher power.
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So I had a little time to do some more testing and was able to get 120fpe out my mini, that was with an 85 grn nsa slug at 800fps!

I cranked the up to 2750 psi according to the gauge to achieve this.. reg can go up to 3100 psi and I still have heavier ammo to try and sling 😁 so this Raptor of mine has more heart than I was expecting from its 60ish cc plenum..
Still awaiting the piece to run it unregulated and see what kinda power it can achieve in an unbridled configuration..

Also interesting is that I found out through searching old posts that AEA challenger mags will work on these Raptors! So I ordered up a $20 .357 mag from the pellet shop and it fits and functions great!

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Little bit of progress. Got the rear shroud bushing made, and shroud tube cut to length. Need to make the front end cap for the shroud still. Polished up the lip of the barrel at the breech end so it feeds much better now.

I have to run out and find some stiff springs, I'm all out and the one I ordered from China is THICK. I ordered a 2mm wire diameter spring, and it's way too stiff. I didn't think 2mm was that thick, but im American and don't work well with that silly metric stuff!

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I also have some barrel droop which needs to be addressed. It might be some bottle tilt upward too. Either way, I will make a spacer to help hold it up like how the gen one gauntlet has. Don't want to get or make a bottle/barrel band, I've had bad accuracy issues using those.

I also have a Biathlon lever for it, but Kral didn't thread the hole for the lug 🙄.

Anyone know the thread size for the lever screw? I don't have a metric tap or die that small to check it. It's gotta be like a 2 or 3mm, it's pretty small.
 
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Got some springs from the hardware store and removed the valve spring, ported the transfer port in the drop block, and filled it up to 250 bar so far.

Got this which is over my goal of 700 fps, and I achieved just over 100 fpe with 80.87 grain pellets.

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I have some springs on order from China that I will try when they show up, but the dual spring I have is already a mother bear to cock. It'll help out once I get the Biathlon done and drop it in a stock.

Going to finish up the shroud and male a stock for it, hoping to try for some accuracy tests after the shroud is done. I can set the action in my gun vise and test it in the basement to see if it will even group. If it won't one hole at 25 feet, I have problems.
 
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Got the shroud finished up. The muzzle report is almost non existent! The bottle/hammer ping is pretty loud, but I can just tell my neighbors I took up blacksmithing!

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Just need to sand the carbon tube back to the end cap, and then polish it up nice. I did mount it in my gun rest and put my hawke 4-12x40 on it for preliminary accuracy testing. JSB 81s were shooting a single hole at 25 feet.
 
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Dr. Kralenstein said:
Got the shroud finished up. The muzzle report is almost non existent! The bottle/hammer ping is pretty loud, but I can just tell my neighbors I took up blacksmithing!

View attachment 441824

Just need to sand the carbon tube back to the end cap, and then polish it up nice. I did mount it in my gun rest and put my hawke 4-12x40 on it for preliminary accuracy testing. JSB 81s were shooting a single hole at 25 feet.
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Looks like It’s coming together nicely!
And making more power than anticipated.. that never a bad thing lol
What kinda stick are you going to fit it with?
 
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Rvaughn said:
Looks like It’s coming together nicely!
And making more power than anticipated.. that never a bad thing lol
What kinda stick are you going to fit it with?
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I've got some cheap wood boards that have good grain, thinking I'll glue them together and cut/inlet for the action.

Or I may just get lazy and buy a bighorn stock. Issue there is the action block is about 1/2" shorter, but I could just glue in a block of wood in the stock and it'll be solved. Other issue, I think the bighorn stock us FUGLY lol.

I'd much rather have a stock similar to a theoben rapid or RAW 1000.
 
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Well I gave up the idea of the custom stock for now and bought the only bighorn stock they had at Canada shooting supply. 80 bucks, why not make life easy?

Turns out, it has very nice grain! I had to clearance the safety and gauge to get it to drop in the proper location since the NP03 block is smaller than the bighorn. Nothing you'd notice if I didn't point it out, especially after I touch up the bare wood.

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I got some 35 yard shooting in, and it's landing JSBs on top of each other, but the drop is significant with only 750 fps.

She is LONG. 49" OAL. Not terribly loud report, but definitely has a loud ping and you know something is being shot. Not as bad as say an unshrouded discovery rifle or similar gun, but it sounds like I'm forging horse shoes lol.

It developed a leak at the valve/block seal, so I gotta get in there and fix that. I like the side fill port, will make tethering a breeze. Currently looking at maybe 6 mags/42 shots in its peak.

I might order another 357 barrel and cut it down and see what it does, because this thing is stupid long for my liking. If I can keep it in the 600-650 fps range with 8" less of barrel, I'd be happy. That'd put it around 40"- 41", which I could tolerate. Not too concerned with losing the power, it would still be in the 80 fpe range, and that's plenty for smacking pests and dumping the energy.

Don't mind the chunk of cardboard between the bottle and shroud, thats a temporary spacer to get rid of the droop it has. Guess the shroud/baffles at the end is pulling it down. I will make a spacer from black rubber, or have a band 3D printed.


I just added it all up, and im right about $525 for the entire build which includes the carbon fiber shroud kit. Much cheaper and more quiet than buying the bighorn, and I think I'm close to the same power as the stock 357 comes.
 
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