1377 Transfer port options?
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1377 Transfer port options?
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Topic: 1377 Transfer port options? (Read 2691 times))
Wolfer
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Posts: 1214
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Real Name: Mike
1377 Transfer port options?
«
on:
March 24, 2017, 05:33:37 PM »
Have a new 1377 torn apart and not able to come up with what to do with trans port. Open up stock port, poly tube port or come up with something new perhaps. Used brass tubing on a 2100 and worked pretty well. I am using stock plastic breech. I have read somewhere that someone used a ink pen tube. Thanks for any tips. Valve mods are going to be pretty simple angle port and open up exhaust port just slightly. Wolfer
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Dos Palos CA.
Bentong
GTA Senior Contributor
Posts: 2592
Real Name: Leo
Re: 1377 Transfer port options?
«
Reply #1 on:
March 24, 2017, 08:05:23 PM »
1/4 ice maker poly tube is all you need. To benefit from this you need to squeeze more air into the valve. You can't do this with stock piston, you need a flat top set up. Then you can up your velocity with longer barrel. All these needs a solid breech and stock plastic breech can't offer that. With all the pumping you will do, the roll pin holding your pivot arm will have a tendency to roll out...you will need a solid pin with a guide washer to have solid pumping with no side wobble. On my 1377, i can squeeze 7.9 cpl to 708 fps with 10 easy pumps.
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B3c👀l Oragon
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26956
GTA Forums Person of the Year 2017
Real Name: Bob
Re: 1377 Transfer port options?
«
Reply #2 on:
March 24, 2017, 10:47:04 PM »
Personally, I would not increase the port diameters in a .177.... The only thing I do to the valve is round the bottom corner where the exhaust port meets the valve throat, to ease the flow a bit.... I leave the exhaust port and throat stock diameters, the transfer port the stock 0.140", and the barrel port the stock at 0.134", as it is already 76% of the bore.... Likewise, in a .177 I do not increase the valve volume.... The F-T-P is a must to minimize pumping, of course.... and longer barrels add velocity....
.22 cal is a totally different story, they benefit from opening up the ports, and even increasing the valve volume, if you are using high pump numbers.... but hogging out a .177 valve is a good way to lose instead of gain.... Stronger hammer springs only make the gun harder to cock, unless you are pumping 15 times or more, then you may need more spring to dump the valve completely....
Bob
«
Last Edit: March 24, 2017, 10:49:22 PM by rsterne
»
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
WyoMan
Sharp Shooter
Posts: 839
Real Name: Gary
Re: 1377 Transfer port options?
«
Reply #3 on:
March 24, 2017, 10:52:52 PM »
Leave it oem - it's .140" which is 79% of the bore diameter... right in the sweet spot.
Also, the barrel port is .140". Enlarging the TP sleeve without enlarging the barrel port won't help. But it doesn't need help with the port size anyway.
Larger caliber and / or co2 guns can benefit from ports larger than .140".
Here's another 'rule of thumb':
http://www.network54.com/Forum/275684/thread/1386883683/Noodling+about+transfer+ports+and+supersonic+flow-
hth...
Wyo
sorry for the echo, Bob... hit post instead of preview
«
Last Edit: March 24, 2017, 10:55:40 PM by WyoMan
»
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Wyoming
Wolfer
Expert
Posts: 1214
yes
Real Name: Mike
Re: 1377 Transfer port options?
«
Reply #4 on:
March 25, 2017, 12:13:34 AM »
Thanks for the advice. I have made the solid pin. Stuffed the piston to cut down on head space with washer behind piston cup and o ring between cup and piston. Have to stock transfer port in but seems to be leaking. I have heard when using the stock port that a small o ring between barrel and port helps sealed it a little better. Trying to make this gun shoot without steel breach. Already have a couple with the steel breech and all the hot rod stuff. I wanted a pretty stock gun to put in my hunting pack and the stock breech is quite a bit lighter. Thanks again for all the replies.
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Dos Palos CA.
Wolfer
Expert
Posts: 1214
yes
Real Name: Mike
Re: 1377 Transfer port options?
«
Reply #5 on:
March 25, 2017, 12:17:19 AM »
I forgot to mention that the only valve work that I did was rounding the valve throat to the transfer port. Wolfer
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Dos Palos CA.
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1377 Transfer port options?