Disco .177 project 10/24/15

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CampFussell

CampFussell

Member
Apr 1, 2015
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Burgaw NC, United States
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Figured I'd share a little info on my Disco experience. Bought this Benjamin Discovery a while back from Norm at Disco's R US. He had some refurbs on sale for $180.00

When I got her she was shooting about 15 FPE, wouldn't group worth a crap and only got around 16 shots or less before POI started to drop. Bought a $50 TKO to quiet her down and groups seemed to be worse with it?

Had my friend Paul ( AKA Strikefast ) install a Lane regulator for me. This involved taking the pressure gauge out of the rifle as the regulator took up the room where the gauge block was located. I must confess I miss having the pressure gauge if nothing more than having a good visual in case of an air leak? But, so far, so good without it.

With the regulator installed and FPE lowered to roughly 9.5 foot pounds, I now get over 40 good shots before noticeable POI drop. And that's with a single air tube!

OK now I have a nice respectable shot count with a 2000 psi fill, and found it was easy to Hand pump from 1000 psi to 2000 psi with only 30 to 40 strokes being needed to top her off. So, I was thinking this rifle would make the perfect loaner to get newbies interested (hooked/addicted) to PCP airguns? Only problem is she still grouped like $hit?

I had heard on the forums about adding a second barrel band and figured I would try it? Holy Sheeeeeee Hight...was that the trick!!!!!! Now I have a nice loaner that is accurate and has a decent shot count and easy for a newbie to hand pump at only 30 to 40 strokes!!!!

I put one barrel band tight against the stock forearm and the other about 3.75 to 4 inches back from the end of the barrel. Now adding the TKO made it impossible to put the fill cap back on, but I found a nice rubber nipple in my junk drawer that seemed to get the job done for me. Can't remember what it was on originally or where it came from?

Anyway I zeroed her at only 20 yds as I have no plans to shoot much past 30 yds with her. Pics below

In the beginning


Now with TKO and two barrel bands


Close up of TKO and Fill nipple cover and barrel band
Forgot to mention I have a rubber o-ring snugged up behind the barrel band to help with keeping the barrel centered as it free floats in this band.



Targets self explanitory. It was windy and at only 9.5 FPE, the wind has quite an affect on it
Yellow dots measure 1/4 inch to help show center to center of group




Waited for the wind to die down


 
Thanks AJ, I forgot to mention ....... Paul did a little tweeking on the trigger too, swapped out a spring etc. and it's much better than a stock trigger.
Now that she's shooting so well, I just might have to send her back to Paul for the Marauder trigger group.

I don't know what Greg Davis did with the trigger on my M-rod, but that thing is sweet. Best trigger out of all my rifles. OK,ok, it's a tie with the Rowan trigger on the S500
Haven't shot the M-rod in forever. Took it out the other day and have a slow air leak? Gotta find the time to take it out of the stock and see if I can locate it? Loses about 400 psi in a week's time. Been meaning to get some balloons and stick one over the end of the barrel but keep forgetting to pick some up?
 
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Jimmy, the trigger alone is one of the reasons I am such a Marauder fan!! By removing the lawyer spring and tweaking to one's liking, it is one of the best triggers in my opinion. After owning Daystate, AA, Kalibrgun, and many others, I still prefer an Mrod trigger over all the rest. I also like a single stage trigger which the mrod can easily be setup for and still have a solid crisp pull well below 10oz!!
 
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AJ, I know nothing of trigger mechanics, but would say my M-rod is set up the way you mention as single stage? It's a hair trigger and everyone who has shot it that knows anything about triggers says it has to be 9 oz or less?
Paul put a Marauder trigger group in his Disco. I'll have to borrow it from him and see how I like it ;-)
 
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"CampFussell"
With the regulator installed and FPE lowered to roughly 9.5 foot pounds, I now get over 40 good shots before noticeable POI drop. And that's with a single air tube!

OK now I have a nice respectable shot count with a 2000 psi fill, and found it was easy to Hand pump from 1000 psi to 2000 psi with only 30 to 40 strokes being needed to top her off.


Click to expand...
Honestly while 40 shots seems nice, there should be over double that and more.

If you are shooting those 8.64 pellets at 9.5FPE that's 705fps. Your tank volume should be around 215cc. Using these numbers and shooting from 2K down to 1K your efficiency is a dismal .42FPE/cuin. At that power level the Disco is capable of 1-1.5FPE/cuin, meaning when tuned efficiently you should be getting 80-120 shots.

Here is a great calculator to figure out your gun's efficiency

http://www.calc.sikes.us/1/index.php

As an example my .22 Disco shoots 30 shots at 23fpe from 2000 down to 1200psi for an efficiency of .94FPE/cuin. The lower the power level the more efficient you can tune the gun.

Sounds like taking a bunch off the hammer spring would be a good starting point.
 
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For a third option you can try an Alliance Hobbies trigger. It's a drop-in unit, replaces one spring, and is a big improvement even over the three screw/polish mod. I have one and love it, though I will admit that it isn't as nice as an Mrod trigger.

BigTinBoat: wow, nice! I'm getting maybe 12-15-ish shots before I notice a decline in POI (.22 Disco, stock gun). Would you share what you did to yours/how to increase efficiency without losing significant power? All the mods I've seen (so far) for the Disco have involved either increasing power (which for my purposes I really don't need), increasing shot count by lowering the velocity (which for my purposes I really don't want), increasing the operating pressure (2000 psi fill pressure is one of the reasons this gun appealed to me), or just throwing tons of money at it (double kits, multi-shot kits, etc...which would beg the question: why not just buy a better gun?).

almost forgot, CampFussell: my TKO definitely effects point of impact. Each time I install it for backyard shooting, I have to re-zero. It is especially pronounced now that I added the second barrel band (would have expected the opposite). Pellets aren't "clipping," may just be the difference in weight at the end of the barrel (between the stock weight and the TKO)?
 
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"Honestly while 40 shots seems nice, there should be over double that and more.If you are shooting those 8.64 pellets at 9.5FPE that’s 705fps. Your tank volume should be around 215cc. Using these numbers and shooting from 2K down to 1K your efficiency is a dismal .42FPE/cuin. At that power level the Disco is capable of 1-1.5FPE/cuin, meaning when tuned efficiently you should be getting 80-120 shots.Here is a great calculator to figure out your gun’s efficiencyhttp://www.calc.sikes.us/1/index.phpAs an example my .22 Disco shoots 30 shots at 23fpe from 2000 down to 1200psi for an efficiency of .94FPE/cuin. The lower the power level the more efficient you can tune the gun.Sounds like taking a bunch off the hammer spring would be a good starting point."


Sorry, but the airtube volume of a disco is not 215cc. That is the volume of a Marauder. The Disco has a 126cc airtube. What is your ES for those 30 shots?
 
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Thanks for the input Tinboat. I'm sure it could use some more adjusting, but it's shooting so well right now, I just got to leave it alone.

Thanks Mentolio, I'm familiar with the Alliance Hobbies trigger also. That's always a good option too.
As for your TKO......why don't you just leave it on the gun all the time? Yes, it will change the point of impact with and without it.
 
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Just wanted to add some info on Jimmys gun. The regulator I installed in his gun is the same as I did in mine. I get over 60 on target bull FULL power shots at just under 12 fpe. I mean under a dime at 30 yds for 5 shots. Jimmy can verify that as he shot my Disco doing it. Both his and mine are .177 guns.

The regulator is set at 100 bar. I used a Maruader trigger from Norm with the 0.30 spacer he provides. An aluminum can would not be thick enough as a spacer unless doubled I believe. Either way that is the best way to go IMHO. It is a drop in mod and when adjusted will make all the difference in helping accuracy.

I don't know what anyone would expect from these inexpensive guns. A fellow club member has a Discos R Us modded one and shot a 46 at our match in Aug match. On the first time out with the gun. Not too shabby.

Myself, I want a good shot count, but want an accurate shot count more. My gun got 8 on target shots before regulation. Now at 60 accurate shots at FULL power it is perfect . I can go higher on shot count but the accuracy suffers above that. So higher then 60 the shots are usless to me. Again this is my opinion and as such it's what works for me.

Mentolio, I totally agree with you on the TKO. I took minecoff and sold it. I definitely has POI issues with it on. I tried every way possible to make it work. It was not clipping but since it is basically a tube with plastic washers you shoot through, the chambers seem to move the air pressure from the pellet and cause a shift ever so slightly in POI.

I don't know the dynamics butvit may be a crown issue either being too far or too close to the barrel crown. Don't know. But Jimmy must have his perfect as his groups reflect it.
 
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"Mentolio"

BigTinBoat: wow, nice! I'm getting maybe 12-15-ish shots before I notice a decline in POI (.22 Disco, stock gun). Would you share what you did to yours/how to increase efficiency without losing significant power?


Click to expand...
First thing you do is get the "original" Disco spring. Mine is an older gun that I bought used. It was "tuned" by Mike from TKO so not sure what all original mods that were done to it. It is shooting from 780 to 810 and back to 780 for 30 shots.

AJ - I did mistake the volume. It should actually be 135cc even though some sources list it at 126. My FPE/cuin is actually about 1.3
 
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Thanks for your input AJ. My buddy Paul is the gunsmith, I'm just a nut behind the trigger. He and I both bought the refurbed Disco's at the same time, and since he is a gunsmith by trade, he wanted to use these for guinea pigs to practice his craft on airguns.

He put the Lane Regulator in his also with similar results. Maybe he will chime in? I know we both have 2 Discos that have at least a 40 to 50 shot count with the 8.64 gr H&N pellets at roughly 700 FPS. I think his likes the 8.44 JSB's and shoots a little harder than mine? He has the M-rod trigger on his now.
 
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"strikefast"Just wanted to add some info on Jimmys gun. The regulator I installed in his gun is the same as I did in mine. I get over 60 on target bull FULL power shots at just under 12 fpe. I mean under a dime at 30 yds for 5 shots. Jimmy can verify that as he shot my Disco doing it. Both his and mine are .177 guns.

The regulator is set at 100 bar.
Click to expand...
Now this is phenomenal efficiency. If you are shooting from 2000psi to 1450 (100bar) and getting 60 shots averaging 12FPE this is over 2.2FPE/cuin
 
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Ok I think I have it now. If did keep the Pro Chrony results from what I marked "latest shot group" on the Disco.

Al, I plugged it into your caculater you posted ( thank you for that) as well as PA calculator for fpe. It is shooting at 12.6 fpe according to their calculator and my avg fps.

My original out of the box was 14.45 fpe. I wanted to tame it down to a 12 foot pound gun for better accuracy as the original accuracy sucked big time.

I also recorded the low pressure that Jimmy shot it down to a his house.. I used his tank to refill it and the familiar "tick" of the gun and tank equalizing, came at 800 psi!!

Using that low and the 1900 fill, 8.4 pellet wgt, 126 cc tank, 60 ,shots, at 804 average velocity. The Sykes caculator gave me this readout. Please ck me as this is the first time I used it.
1.24 fpe cuin per shot
Avg bar 13.2
Avg fpe per shot 12.1
Avg psi per shot 18 psi

If I read that caculator rt the gun is in the good range even almost to excellent as stated for low power gin. But I don't know where low and med power guns fall...Does this help?
Again keep in mind I only go to 50 shots and the 60 was not normal. The figures would change from there. Now I don't remember if I lowered the 100 bar setting that came set on the adjustable Lane regulator. I am turning 63 and do lapse sometime in my memory.... Just don't tell my wife that.....lol
 
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