GTA
Airguns by Make and Model => Crosman Airguns => Topic started by: mooseslayer on March 02, 2013, 02:49:20 PM
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First test of the ProChrono Digital with pellets that I had. Hadn't a clue how fast the gun really was so this is to get a base.
Seemed when shooting in basement that POI changed if I went to change target or waited for some reason.
So...I did 3 tests with CPUM 10.5gr pellets (that usually shot well at 10yds) with different spacing between shots.
Five shots each 2 ft away from chronny.
Predator Polymag 8g 4.5mm 875 900 885 891 875 avg 885.2 spread 25
Crosman Pointed Hunting 7.4g 4.5mm 902 891 911 911 890 avg 901 spread 22
Crosman Destroyer 7.9g 4.5mm 903 913 901 903 916 avg 907.2 spread 15
RWS Superdome 8.3g 4.5mm 908 912 911 919 918 avg 913.6 spread 10
RWS Meisterkugeln 8.2g 916 917 917 911 920 avg 916.2 spread 9
RWS Superpoint 8.2g 917 915 916 917 922 avg 917.4 spread 7
Crosman Prem Ultra Mag 10.5g 4.52 796 793 778 780 795 avg 788.4 spread 18
- same 2nd test quick reload 790 773 793 785 796 avg 787.4 spread 21
- same 1 minute between shots 796 794 791 801 799 avg 796.2 spread 10
Not sure what to make of it yet...want to do a lube and tune, brass breech washers etc.
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Notice the spread is lower on the pellets with the higher averages. Says to me they are sealing to the barrel better and more consistently. Almost willing to bet they'll be more accurate too. Looks like a healthy powerplant.
You're getting about 15 FPE, which is average and good.Lube tune and new seal will probably push you near 16 FPE.
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How do you like that venom nitro dusk? I have one in lay away at dunhams.. 139.99 tomorrow and Monday
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what about spread tighter and FPS higher if I wait a minute between shots...same pellets?
Will a lube and tune help?
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Not sure about that, but I would GUESS it has to do with heat. Might be the heat from compression is affecting the seal causing slight pressure loss. Hard to tell.
I would think a tune would help tighten things up. The seals from Vortek and Air Rifle Headquarters are higher quality, and some smoothing and good lube should improve consistency. I would definitely get the brass washers and CDT trigger.
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Thanks Paul...trigger done, got brass washers yesterday... looking at DIY piston compressor posts... and ordered Moly yest.
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Still baffled why spread lower and fps higher when waitin glong between shots. Anybody got a theory? Somebody suggested heating cooling of lube maybe. Going to try a lube and tune.
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I really think there is insufficient data to make any conclusions. If you have not had the piston out then you need to get all the "chinalube" outta there and re-test. Actually suprized the spread is that tight if you haven't been into it yet. You didn't mention how many rounds you have thru the gun? I had the same thing happen where it would just change poi from day to day, or even between shot groups. I have had an NV .177 for a little over a year now and after learning lots from this site and a lube/tune, new scope, seal, Tuna trigger, washers and over 10,000 rounds.....(lost count of nutters starlings and HOSP's) .......It turned out to be a great shooter, with cphp and FTT 4.52 being the most accurate.
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Here is a thoery!
When rapidly shooting, the air is slighlty warmed when entered into the compression chamber. Warmer air is not as dense as cooler air.
Allowing the action to cool, keeps the ambient temperature down, keeping the air cooler. When rapidly heated, the denser air creates more pressure.
Just a theory!
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thanks treb..figure I have 1000 shots thru it and agree my next step is lube
kid...thanks. but when I bought the gun the one theing the guy at the Gun shop said was because it was a nitro piston it is not affected by outside air being pulled in if hot cold outside.
Thanks guys
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thanks treb..figure I have 1000 shots thru it and agree my next step is lube
kid...thanks. but when I bought the gun the one theing the guy at the Gun shop said was because it was a nitro piston it is not affected by outside air being pulled in if hot cold outside.
Thanks guys
That's in regards to the nitro piston operation moose. Kid is refering to the density of the air itself. I'm leaning towards the seal become harder or softer from heating cooling, or the lube loosening a bit between close together shots. As it is, I don't see enough variation to worry too much about.
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The chrono tests were done because I was baffled why the gun shot better when I left it to go change targets. The tests (although preliminary because just got chrono) seemed to confirm it. I am hoping a proper lube with the Moly I just ordered will help and the pisten will move more freely and nore consistent. Now that I have the chrono I will do more thorough testing.
Thanks again. everyone. I love this site.