Transfer port

[Remchester]

What sizes are everybody running?

[KevG]

for sub 12 ftlbs it should start at 4mm stepped down to 3mm were it enters the bore.on a mk2 type block it can start at 6mm to match the top port in action block.
KevG

[KCE]

I learn something new each day I log on here.
Regards Kev.

[Remchester]

I have a ttr 19' barrel that's smaller than 3mm I think it's around 2mm to 2.5mm is there any advantage to opening it up to 3mm? I have a mk2 that has an un known barrel on and that has about a 3.5 mm would that also be worth opening up to 4mm/4.5mm?

[KevG]

opening the port can improve shot count.but don't go larger than 3mm on sub 12 ftlb.

KevG

[Remchester]

Spot on kevg thanks! Is it a noticable difference in shots?

[KevG]

yes.how many you getting now. 19 inch barrel and 280cc bottle should give you around 200 shots in .177.its not just about barrel port though.some rapids have the filter valve fitted that can also loose shot count.
KevG

[Remchester]

Think I get around 150 from a .22 400cc early r7 gamo trigger charged at 180bar to about 110 set at about 11.7 ish I think? It's been a while since I did a shot count on that rifle in fact I haven't shot it since before lock down so months ago👎 so with the figure you give me theres something not set up right by the sound of it?

[KevG]

Think I get around 150 from a .22 400cc early r7 gamo trigger charged at 180bar to about 110 set at about 11.7 ish I think? It's been a while since I did a shot count on that rifle in fact I haven't shot it since before lock down so months ago👎 so with the figure you give me theres something not set up right by the sound of it?

sorry I thought you ment you had a ttr gun
sub 12 mk1 should give you 200 shots on a 16 inch barrel with 400cc bottle at 180 bar
KevG

[Remchester]

Think I get around 150 from a .22 400cc early r7 gamo trigger charged at 180bar to about 110 set at about 11.7 ish I think? It's been a while since I did a shot count on that rifle in fact I haven't shot it since before lock down so months ago👎 so with the figure you give me theres something not set up right by the sound of it?

sorry I thought you ment you had a ttr gun
sub 12 mk1 should give you 200 shots on a 16 inch barrel with 400cc bottle at 180 bar
KevG

No just a r7 with a ttr 19' barrel no reg kev so I should get at least 200 shots? I doubt the barrel would get me many extra so I'm getting some hammer bounce or a slow leak some where?

[KCE]

19 inch barrel is much better at high power.
You could get a pre chamber from kevg it may help with more shots.
Regards kev.

[Remchester]

19 inch barrel is much better at high power.
You could get a pre chamber from kevg it may help with more shots.
Regards kev.

I could do with a few bits off him I have 5 r7s at the moment that's are all about 80-90% of what they should be

[Dazgrif36]

I've got stype and my port was 2.5 mm which was to small which was choking the gun losing shot count so kevg opend it up to 3mm seems lot better now kevg  nos what hes doing with rapids hes sorted mine out now after few little problems

[etiam viviens]

Just looking through some off the transfer port topics and found this one.

Just wondering if someone tried a ring style multi hole transfer port on there FAC rifles.

With a semi-ring over 270 deg and a port at 90, 180, and 270 deg. Keeping the location dimple as 0 deg and the ring starting at 45 deg and ending at 315 deg.
2 O-ring for sealing the barrel in the action.

I googled this butt did not find any information.

[Squinty]

Just looking through some off the transfer port topics and found this one.

Just wondering if someone tried a ring style multi hole transfer port on there FAC rifles.

With a semi-ring over 270 deg and a port at 90, 180, and 270 deg. Keeping the location dimple as 0 deg and the ring starting at 45 deg and ending at 315 deg.
2 O-ring for sealing the barrel in the action.

I googled this butt did not find any information.

I can't see any advantage from making 1/2 to 2/3 of the air go the longer route.
You can have two different ports at 90 degrees..say a 4.5mm fastflow and a 6x4 for reg.

Even if you want to maximize airflow you're limited by the  6mm top port, I believe the RAW (perhaps big bore.30/357/9mm) has 7mm block porting.
But for what it's worth I've read (not 100% recollection) .22/.25 efficiency is improved by sleeving this to 6mm with little loss in output.

surface areas..
6mm= 28.2sq/mm less the o/d of the valve stem 5-7 sq/mm =21-23 sq/mm

6x4mm oval = 20.5
3x 3mm = 21
3x 4mm = 36 sq/mm