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Author Topic: Benjamin Discovery Chorny  (Read 8042 times)
jrboon
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« on: February 11, 2009, 09:47:21 AM »

What kind of fps and fpe on the Benjamin Discovery with  the mods. and in what cal..
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ribbonstone
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« Reply #1 on: February 11, 2009, 11:54:24 AM »

With a power adjuster (which pretensions the hammer spring so it could be called a spring pre-tensioner), in .22,  could crank it in to get just at 900fps with 14.3gr. pellets but get very few shots before the vel. drops off enough to be noticable even WITHOUT a chronograph (at this setting, is better to fill to 2000psi and  stop shooting at 1500psi and refill at that point and avoid the drop off at low pressure).

Cranked all the way out would be at 810fps but it kind of builds up to that speed after a slow start (at this setting, is better to fill it to 1700psi  and refill at 900psi).

Normally keep it running at 830fps, short run up to "normal" speeds, longer shot count....refill at 1200psi.
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If none of this makes sense (yet().

Unregulated PCP's have a pressure range that they work best in (often called the "sweet spot)".  Strong spring tesnions/strong hammer strike lets them go fast, but workat high presser and slow down as pressure drops.  Light hammer strike lets them work best at lower pressure, with a long climb of increaseing vel. per shot until you get to that ideal pressure.  Someplace in the middle seems to work best, giving the most consistent shots per fill up.
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Robert
jrboon
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« Reply #2 on: February 11, 2009, 12:58:26 PM »

Thanks ribbonstone for the info. I will admit that I am new to the pcp side.
How many shots at 900fps?

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ribbonstone
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« Reply #3 on: February 11, 2009, 01:59:04 PM »

Will have to look up the exact test data, but something like 11 or 12 shots before falling to 850fps, from there is was down hill fast...could shoot another 25-30 hots, with each slower than the last, until the pellets wee going about as fast as you could throw them.  WAY too much work getting it up to pressure to get less than a dozen good shots.  Considering that just 60 or 70 feet per second less speed can give twice as many good consistent shots.

On a stock Disco, the factory setting isn't far off the best setting for a large number of reasonably consistent shots at about 810fps...I'd not look to change anything until i'd tested it pretty well as issued.
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Robert
melloroadman
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« Reply #4 on: February 11, 2009, 03:34:58 PM »

http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=8956&posts=19&highlight=lower%20link%20mod&highlightmode=1#M79112
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jrboon
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« Reply #5 on: February 11, 2009, 10:12:49 PM »

Thanks Marvin for the info. I going to order the disco today and when it gets here do a good clean on the barrel and wait a day or two before doing a mod on the lower link to make sure that the disco does not leak and the rifling is good.
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melloroadman
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« Reply #6 on: February 12, 2009, 03:24:20 AM »

Just so you know I have since put the trigger back to stock except for a real light return spring out of a ink pen and had good groups at 50 yards . I did this not because the mod had a issue but I wanted to get use to heavier pull triggers so that when I shoot my Career 201 S it would not be such a big change . The trigger is not that bad in stock forum . It is the person pulling the trigger that needs to be adjusted IMO . There are pistols with 15 pound pulls and people do just fine . Marvin
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jrboon
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« Reply #7 on: February 13, 2009, 11:08:16 AM »

Well I checked today with UPS and they say that my Benjamin Discovery is to be here on Monday.
Just trying to see what to look for and what works and is safe.
Do you leave air in the rifle or decompress after shooting?
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ribbonstone
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« Reply #8 on: February 13, 2009, 11:24:34 AM »

The way mine is set, the best shots are from 1700PSI to 900PSi, so I usually store it with  900PSI still in the tank..
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Robert
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« Reply #9 on: February 13, 2009, 11:40:10 AM »

You should leave air in the rifle when stored . This will give you a lot of info if you read it while you wait till Monday .Marvin
http://www.pyramydair.com/precharged-pneumatics-basics-article.shtml
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Gunby
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« Reply #10 on: March 22, 2009, 06:33:05 AM »

See attached table(jpg image) I made after testing my .22 Discovery.

Pellets used:
- Beeman Kodiak
- JSB Exacts
- Crosman Premier

Table shows "sweet" spot was the same on mine as I have seen in many reports.


* Chrono_Discovery_20percent.jpg (91.29 KB, 435x961 - viewed 474 times.)
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waunderin
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« Reply #11 on: March 23, 2009, 06:46:59 PM »

with the .22 here's some averages

crosman pointed 14.3gr.    1st string, avg. 873.7, 2nd avg. 885.1, 3rd. 845.0.and down from there
cavela's 14.3 hp   1st 873, 2nd 881
kodiaks    21.1gr  1st. 742
bee fts   1st.  860, 2nd  870, 3rd  862

with the .177
 cphp 7.9  1. 993, 2. 1032, 3. 1008, 4. 944
cph 10.5,  1.916, 2. 938, 3. 910
c pointed  1. 1040,  2.1046, 3.1005
disc 10.5 hp  1.  874,  2. 915,  3. 938

and that's as much as i've done so far with the discos. i test several pellets, and these are the ones that were the most accurate, so were the ones i chronyed so i could use the ballistic charts.   john
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Gunby
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« Reply #12 on: March 25, 2009, 04:34:59 PM »

Well, it did it again last night. I put 75 pumps into my Talon SS tank, opened the pump bleed valve to expel the pressure and moisture, and all seemed well. I then went to put the pump away, and extended the pump handle to make one, last and final stroke to make sure everything was ok and it froze.

The pump outer shaft remained stuck about 8 inches from bottom. You could push it down by putting your weight on it, but it would spring back up when you let go. It would pump no air.

The next morning, all was fine again. What the heck is going on?
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