GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Tack Driver 10 on January 23, 2021, 02:59:32 PM
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Had a spare 1377 gun and with all the chatter about pcp guns decided to convert it.
Made a drop block and slid it into the tube.
Left the rest of the gun stock and pumped the bottle to 2000 PSI, regged at 1500.
Wasn't sure how the gun would respond but it fires just like a pumper.
Got 22 shots from 2000 psi to 1500 psi.
Too late to run it over the chrony last night though.
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very compact , i like it !
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I like it too! I'll be waiting for chrony results.
Meanwhile I'll post a 1377 you might like.
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that is AWESOME!!! 8)
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The "short and sassy" (SS) gun has a 17 cal 12" LW barrel, measures 23".
The Ratcatcher (top gun) makes 750 FPS in 22 cal with a 14" LW barrel so should get around 850ish FPS???
May need some tuning but I'm going to run it as is to get a baseline.
Hopefully rain and clouds should clear out later today for chrony test.
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The best I could ever get from a 2240 and regulated 850psi air, was like 840 fps, 24" barrel.
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Moving thread to the Darkside
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Very interesting. I have a 1377 gathering dust and no 177 PCP.
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JimD....Tons of options modding a gun like this.
If you want to use a 13 ci tank, just machine a 2100 tube to fit the 13xx frame.
more here:
https://www.gatewaytoairguns.org/GTA/index.php?topic=155629.msg155718495#top (https://www.gatewaytoairguns.org/GTA/index.php?topic=155629.msg155718495#top)
So ran the gun over the chrony wih 7.9 CPHPs:
1 shot 17 cal 11" LW barrel, .134 port, reg 1450 psi
650 FPS 07.41 FPE
The 11" barrel choke is extremly tight and kept getting errors.
Possibly bits of pellets?
3 shots 17 cal 14.5" LW barrel, oval port, reg 1450 with 7.9 CPHPs:
1. 722
2. 717
3. 719 average 9.07 FPE
The 14.5" barrel was fine with no errors.
Ran a 10.65 g Barracuda Match pellet
664 FPS 10.42 FPE
The pumper valve has the Teflon check in it etc and reduced volume so mostly stock.
Next need to take the gun apart and modify the valve to take advantage of the 3" plenum.
An SSG and power adjuster are also needed.
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What are you using for exhaust/transfer port? Is it custom or still original?
I'm really curious what sort of numbers you would get from a 21" barrel.
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The valve and transfer port are .157".
I don't have a 21" barrel but put a 24" barrel on the gun.
This is a non choked Crosman barrel.
The LW choke usually takes about 20 FPS off.
CPHP 7.9= 793 FPS 11.03 FPE
BM 10.65=717 FPS 12.15 FPE
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very good numbers.. with the 24 incher, and the front of the 1377 valve opened up , im thinking the sky is the limit.
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By the look of things, I think simply opening up the ports will help performance a lot. Then play with a hammer spring adjuster to out it where you want it.
I know it's not the same thing... But I have a 1400 doing 900+fps in 177, the thing is I have no way of knowing what sort of pressure I'm playing with.
Not sure if you're after max power or what...
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I'm really beginning to love this gun.
Why I love this gun so much that I made the valve opening in the shape of a heart....LOL
Isn't that special?
But seriously folks:
Took the gun apart and modified the valve.
It had a big spacer in it that restricted the volume.
Took the stem and cut a goove in it for an external spring and clip.
Added a poly bumper to the back of the valve to limit stem travel to .090".
Put the gun back together with the same back end for now.
Ran it over the chrony and believe me Cleveland has nothing on this gun because it's rocking out with the band.
14.5" LW barrel, reg 1450
945 FPS 15.66 FPE with 7.9 CPHPs
885 FPS 18.52 FPE with 10.65 BMs
24" Crosman barrel, reg 1450
1030 FPS 18.61 FPE with 7.9 CPHPs
958 FPS 21.70 FPE with 10.65 BMs
The gun is VERY LOUD (93.7 dB) as expected so need to tune it for power and shot count.
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yes , that thing is cooking now !!
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That is awesome!
Are the exhaust ports still the same size or did you open it up?
By the way... I'm borrowing your external spring idea
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That is awesome!
Are the exhaust ports still the same size or did you open it up?
By the way... I'm borrowing your external spring idea
The ports are the same as before.
Only change was to gut and open the front of the valve.
Sadly it's now just a shell of what it once was....LOL
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I know what you're thinking.
How much power would a 24" Crosman 22 cal barrel make?
Swapped one in from one of my pumpers, .135" barrel port.
The barrel port is a little small but it is what it is.
Since I'm expecting explosive power used the Grenade bolt to help tame this beasty boy....LOL
Still just as loud at 93.6 dB.
Ran 3 shots with different pellets:
14.3 CPHP 926 FPS 27.22 FPE
25.4 JSB Monster 748 FPS 31.55 FPE
34 JSB Beast 641 FPS 31.01 FPE
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Nice! That's pretty good power for a 1377 haha.
I need to get me a pump and a bottle...
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Time to get serious and tune this gun.
Put the 17 cal 14" LW barrel back on.
Took the stock off and installed an SSG, now it's a pistola.
Tried a 2300 spring too soft, hammer had too much bounce.
A 13xx spring works really good with the 13xx hammer.
Was able to adjust the hammer free flight from 800- 900+ FPS.
Settled on 900 FPS 14.21 FPE for now to see what the shot count is.
That's about what a hot 2100 pumped 15 times makes.
Thinking should get 22 shots per 500 psi or 66 shots from 3000-1500psi.
At one point I'd like to drop the reg pressure down to around 1200 psi.
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Dry fired the gun from 2000 psi to 1500 psi and got 23 shots.
So should get around 70 shots from 3000 to 1500 psi.
As an experiment swapped in a 14 1/2" Crosman 22 cal barrel.
Want to see what difference the caliber swap makes with all else equal.
07.9 CPHP 882 FPS 13.64 FPE
14.3 CPHP 733 FPS 17.06 FPE
The 17 cal LW barrel is choked so normally cuts velocity by about 20 FPS.
Adding 20 FPS to the 17 cal barrel= 902 FPS 14.27 FPE
Good numbers with both calibers, I think I'll leave it there (for now).
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The reg on the gun was set at about 1475 psi.
Set up another bottle with a reg pressure of 1200 psi and installed it on the gun.
Left everything the same and was expecting a decent drop in velocity.
Dropped less than 10 FPS with the same sound level, 91.5 dB.
14 1/2" 17 cal LW barrel
7.9 CPHP 877/875 FPS 13.45 FPE
The gun has a stock 13xx hammer that weighs 38 grams.
Made an adjustable 24 gram hammer to further tune the gun.
The poly bumper on the back of the valve limits stem travel to .100".
With this hammer stem travel can be adjusted lower until power drops off.
Wagged the shot count to be 80 shots from 3K down to 1200 psi at this power level.
Should be able to increase it if the new hammer works out.
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Well.... that hammer didn't work out.
Regrouped and made a new valve bumper from Teflon.
The valve stem protrudes .500" from the back of the valve.
Made this bumper .450" so the stem has .050" of travel.
Same stock 13xx hammer and SSG.
07.9 CPHP 859 FPS 12.94 FPE
07.9 CPHP 855 FPS 12.82 FPE
10.65 BM 763 FPS 13.76 FPE
The word on the street is if you want to succeed then dress for success.
Dressed up the gun with a stock and other items from my collection.
If loving this gun is wrong, I don't want to be right....LOL
Here it is all gussied up.
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very cooll probably serious efficiency with thaat set up.. ( regged and limited stem travel
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Sighted the gun in and it's very accurate with 7.9 Crosman CPHPs.
Ran some extra shots to run the reg down from 2K to 1500.
Got 25 shots at the same power as before, 855 FPS 12.82 FPE.
So if the gauge can be trusted, should get 90 shots from 3K to 1200 psi.
Makes it easy to calculate, 10 shots per 1 ci and 5 shots per 100 psi.
With the power set at 12 FPE should get close to 100 shots.
A 13 ci tank at 12 FPE possibly 140 shots.
When I was in the Air Force the saying was, "The job's not finished until the paperwork's done".
Glad I only did one hitch....LOL
The PCP conversion cost me about $100.
$50 for the tank/reg and belleville washers. (ANS Gear, McMaster Carr)
$35 for the drop block, ASA adapter and gauge.
$15 for the SSG.
This is my cost for basic materials assuming you have a 13xx gun (who doesn't) with a steel breech and good barrel..
I'm not factoring my time etc.
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For all the tree huggers (you know who you are), here's a green version....LOL
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Where did you buy the drop block?
Can you post a link?
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Where did you buy the drop block?
Can you post a link?
I made the drop block from basic aluminum stock and an ASA adapter.
Got everything off EBay.
Maybe someone with a CNC setup will make a run of these and sell them.
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Another option is to use a spent 90 gm CO2 bottle.
Wouldn't be regulated but would fit nicely on a 13xx gun.
Just add a gauge and fill port on the drop block.
Could also be used on a 760, 2100 etc.
Here it is mocked up on a 13xx chassis.
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Here's the 90 gm bottle drop block, nice little afternoon project.
The bottle screws into the block so no adapter needed, I cut out the middle man....LOL
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Here's the 90 gm bottle drop block, nice little afternoon project.
The bottle screws into the block so no adapter needed, I cut out the middle man....LOL
that actually looks like it belongs there ..
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Some pics of the drop block.
Mounted the drop block on my test gun.
Just pulled off the pump arm and piston and slid the DB in.
I'll run it as a pumper valve and then tune it like a PCP.
Has a 22 cal 18" Crosman barrel.
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Ran 12 shots over the chrony to get a baseline, 1500-1250 psi.
14.3 CPHP, 18" Crosman barrel. 160" ports
635 FPS 12.80 FPE start 1500 psi
644 FPS 13.17 FPE
653 FPS 13.54 FPE high
649 FPS 13.37 FPE
641 FPS 13.04 FPE
25.4 Monster 510 FPS 14.67 FPE
642 FPS 13.08 FPE
640 FPS 13.00 FPE
635 FPS 12.80 FPE
635 FPS 12.80 FPE
634 FPS 12.76 FPE
630 FPS 12.60 FPE low, end 1250 psi
Pretty good for a gun setup as a pumper.
Some tuning and mods should help the gun considerably.
Anyone have a WAG as to how many CI are in a 90 gram CO2 bottle?
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90 gram is aout 121 cc, so whatever that is in Ci
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90 gram is aout 121 cc, so whatever that is in Ci
7.38ci.
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Thank you gentlemen.
The regulated 9 ci bottle has an efficiency of 1.06.
The short 17 cal barrel and low pressure just can't make big power.
I plugged the 90 gram bottle gun values into Lloyds efficiency calculator:
Came out at 1.23 so somewhat better.
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Pumped the gun to 2000 psi.
Took 2 shots:
14.3 CPHP
733 FPS 17.06 FPE
726 FPS 16.73 FPE
Need to take the gun apart and mod the valve.
In the meantime, why not a 760 bottle rocket?....LOL
Made the drop block before the SB kickoff.
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nicce, a real good fit on the 760
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It does look like a nice fit for the 760 and 13xx.
The tradeoff is the bottle is unregulated.
A 9 ci regulated bottle can also be used as seen mocked up here.
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I really like these little bottle projects.
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I really like these little bottle projects.
Right, I can't believe I kept this bottled up inside me for so long....LOL
It feels so good to just.....get it out.
Took the 13xx 90 gram gun apart and replaced the valve front half.
Aluminum version that got FT and bored 3/8" through (crappy picture).
The valve is the Min Max Smoke Pro valve so kept the back half for continuity.
It has a 3/16" throat drilled close to the TP and a small Delrin valve stem head.
Should be able to chrony it tomorrow, it's freezing rain today.
Expecting a good bump in power.
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Ron
Great build/info so far, looks outstanding, I have been following along,
I like the looks of that spring setup on the valve stem........... ;)
Tia,
Don
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Ron what sie e clip or c clip is retaining that stem spring ?
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Ron what sie e clip or c clip is retaining that stem spring ?
Rob,
They're 1/8" C clips sourced at ACE hardware for about 25 cents each.
You can also get them in bulk at McMaster.
https://www.mcmaster.com/c-clips/ (https://www.mcmaster.com/c-clips/)
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Pumped the gun to 2000 psi and ran it over the chrony.
18" Crosman 22 cal barrel.
14.3 CPHP
944 FPS 28.29 FPE
910 FPS 26.30 FPE
906 FPS 26.05 FPE
25.4 JSB Monster
766 FPS 33.10 FPE
33.9 JSB Beast
659 FPS 32.73 FPE
Was expecting more power but not this much more....Yikes!
Wastes a good amount of air at about 50 psi per shot.
Sound test 92.2 dB.
Put a 24" barrel on the gun
14.3 CPHP
980 FPS 30.50 FPE
25.4 JSB Monster
757 FPS 32.31 FPE
What do the experts have to say?
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i noticed the monsters lost a bit of steam on the 24 inch barrel , meaning you could push more air and still make gains with the 24 8)
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I noticed that also.
Possibly the smallish .187" throat is holding it back???
The slot in the tube limits the size of the plenum, more plenum, more power.
Now picture this, a 22 cal 760 PCP pushing 30 FPE.
Same config as this gun .
I'm on it like vomit....LOL
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Did you try the 33.99 beast with the 24”?
You really got me rethinking a small lightweight carbine..
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Did you try the 33.99 beast with the 24”?
You really got me rethinking a small lightweight carbine..
I didn't try the beasts in the 24" barrel.
Figured the monsters were struggling so no need to try them.
I have a difficult time handling rejection...LOL
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I'm deeply saddened to announce that I'll be putting this gun on the back burner (for now).
I want to focus exclusively on the 22 cal 760 bottle gun.
Should get most of it done by the end of the week.
Will be starting a new topic for it soon.
See ya there!
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Aww man, I was enjoying this one.
The bottle adapters look good!
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Very nice drop blocks
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Aww man, I was enjoying this one.
The bottle adapters look good!
Good news, the 760 bottle gun will incorporate a DB also.
One more thing: