How big should a transfer port be...?

[Shed tuner]

Whilst browsing the Bay of Fleas, I stumbled accross item# 124345568761

Check out that whopper of a TP in the last pic... no wonder he's selling for spares, that must have destroyed itself pretty quickly !

[DedIdick]

I would say have it the same diameter as your pellet!

[bighit]

could it have been bored out to fit a sleeve so the TP could be adjusted ?

it is way to big but the above may be a reason why .

[BTDT]

I would say have it the same diameter as your pellet!

Only if the objective is to lower muzzle energy and harshen the recoil cycle.

[piggy589]

I remember a dealer handing me a nice looking Mercury.
Smirking, he asked me for a tenner.
The barrel said .177 and the transfer port accepted a three sixteenth bit just fine.....

[Benelli B76]

I would say 3.6mm works well on quite a few rifles, and I think 4 mm would be max in certain cases. At least you can back track on a mistake by bushing an oversize bore as in the hebay pic.

Baz

[greenwayjames]

Cant see the item but my old .22" HW80 with JB FAC conversion had a transfer port of 5mm. That combined with other modifications shunned by todays experts gave a very soft shooting, accurate and consistent 850 fps with Eley Wasps. I only moved it to get into fac pcps at the time. Wish I hadnt

[maximus]

Cant see the item but my old .22" HW80 with JB FAC conversion had a transfer port of 5mm. That combined with other modifications shunned by todays experts gave a very soft shooting, accurate and consistent 850 fps with Eley Wasps. I only moved it to get into fac pcps at the time. Wish I hadnt

There's always more than one way to skin a cat. Diana 34's have a longish 4mm port and shoot nice. Getting the spring right in any set up makes huge differences.

[Hsing-ee]

Whilst browsing the Bay of Fleas, I stumbled accross item# 124345568761

Check out that whopper of a TP in the last pic... no wonder he's selling for spares, that must have destroyed itself pretty quickly !

Thing is that all the sheeple believe what you 'experts' say, most true airgun Doctors I know totally disagree with the Archant propagandists and JSR BBS elite home tuners like you and T20... It's not rocket science to see that the bigger the transfer port the better as the air has less work to do squeezing through a hole to power the pellet. In fact there was a rifle, the Hardacre Stoat, which had no transfer port at all and held the piston back at the end of travel by a special interruptor gear.. it was so powerful that after testing by the HOme Office SAS (Special Army Soldiers) a patent was refused, Hardacre paid off and the designs destroyed. Just think about it, a bazooka has no transfer port and they were used to kill King Tiggers in WWII.

Mock all you want but eventually the truth will come out.... I bet that bloke gets barred from e Bay and a visit from the Special Branch.

[DedIdick]

Thing is that all the sheeple believe what you 'experts' say, most true airgun Doctors I know totally disagree with the Archant propagandists and JSR BBS elite home tuners like you and T20... It's not rocket science to see that the bigger the transfer port the better as the air has less work to do squeezing through a hole to power the pellet. . Just think about it, a bazooka has no transfer port and they were used to kill King Tiggers in WWII.

Mock all you want but eventually the truth will come out.... I bet that bloke gets barred from e Bay and a visit from the Special Branch.

This Tigger?

https://i.pinimg.com/originals/f8/e7...d3329f708e.jpg

Aye, but the Bazooka was a rocket propelled grenade, not an "Airgun"; at least the PIAT was a "Springer"!

[Rich]

Surely what one is looking for is a high compression ratio, as it's adiabatic compression this leads to very high instantaneous pressures due to the heat not having time to dissipate.

The volume of the transfer port adds to the dead space above the piston, and a large volume TP means a lower compression ratio, potentially lower power, having to put in a bigger spring etc.

What in my view are far more important are the entry and to some extent the exit conditions of the TP. There is abundant evidence to show that a sharp edge is a very bad thing. Ideally the TP wouldn't be a parallel bore either.

[bighit]

Cant see the item but my old .22" HW80 with JB FAC conversion had a transfer port of 5mm. That combined with other modifications shunned by todays experts gave a very soft shooting, accurate and consistent 850 fps with Eley Wasps. I only moved it to get into fac pcps at the time. Wish I hadnt

Here is a pic .

[IMG][/IMG]

[greenwayjames]

Here is a pic .

[IMG][/IMG]

Thanks. Its not very clear but it does look a bit weird with the halo from a breech washer? surrounding it. Perhaps a mini black hole from outer space. Has gross digit been on the acid again

[Josie & John]

Only if the objective is to lower muzzle energy and harshen the recoil cycle.

That's a very interesting article you have written on this topic in October's Airgun World Jim.

Must admit I'm a loyal fan of leather washers. I have bought and stripped vintage airguns that are decades old and congealed grease and oil have preserved the ancient leather washers. I only replace them if they crumble and some of my prewar BSAs still have their original leather washers in place. OK so performance may not be as high as it could be but cocking stroke and shot cycle are smooth enough to obtain accurate performance at realistic open sight distances. Plus, they're original to the guns, so if they still function - in situ they'll stay

Kind regards,

John

[Hsing-ee]

Aye, but the Bazooka was a rocket propelled grenade, not an "Airgun"; at least the PIAT was a "Springer"!

Exactly my point, the PIAT doesn't even bother with half the compression cylinder, allowing free circulation of air. They're called AIR guns, the clue is in the name, why restrict it?