Is making a delrin transfer port a bad idea?

[clarky]

Hopefully here is a pic of the port in question,

....well if you want to go with the advice of a materials eng ...you could go with exactly the same material.
If its not a bearing, which must always be a different, or harder material, going with same materials brings with it the same rates of exspansion/contraction...regardless of what conditions its being subjected to....thus if its a drive fit ....it will stay a drive fit...
So i would drive in a turned lump of solid brass and then simply drill the hole to the size you want.
It might even look like it was meant if you polished it front and back face....as if made from one piece.
Alternatively ill machine you one from solid one piece if wanted.

[rovercoupe]

Thats a really good idea, i might see whats in the bits box and see if i can find a bit of brass and turn it down.

Thanks guys I might knock up a few delrin ones of differing size holes and see what happens and then once I know the size go all out in brass!

[robs5230]

Hopefully here is a pic of the port in question,

Unless my eyes are deceiving me or the other end of that tp has reduced diameter, that port is way wider than 2mm bore

[clarky]

Unless my eyes are deceiving me or the other end of that tp has reduced diameter, that port is way wider than 2mm bore

looks at least 4mm to me ...

[riku]

looks at least 4mm to me ...

Looks very much like a 5mm TP from BSA Hornet.

[Benelli B76]

I would make the part out of metal myself. Brass, mild steel and aluminum are much easier to machine accurately as plastics tend to soften due to the heat produced by machining and a lot of plastics are too elastic and holes drilled in them are smaller than the drill.

Looking at the tiny application I would agree. I don't see the point of using Delrin, which is an option to use when there is a lot of hard work involved and in this case there isn't. Quick job and piece of cake to knock out in brass.

Baz

[robs5230]

Hopefully here is a pic of the port in question,

Someone mentioned that it looks like a BSA transfer port. If you can give me the dimensions I have a spare BSA one here. You stated it was a stalker rifle. Were these not based on BSA ?

[greenwayjames]

I have a rifle with a transfer port thats too big and making it inconsistent so need to knock up another so would one in delrin work or would it just implode with the pressure? Its only a small port about 8mm width by 10mm high with a 2mm hole

Or should i just order some brass bar!

Stalker used BSA and Daystate rifles as a base for many of his products but Bowket also produced handmade actions for some of the range. Leopard, Lynx, Bobcat, big bore Pumas etc. The 50 ft/lbs version of the Leopard was popular in Japan apparently Most were FAC versions he told me so it might be wise to contact him as he would know the best dimensions for a transfer port suitable for your Stalker. Have a look on the Facebook JB Fanpage for piccies of some.

[Bjacobs571]

.
So i would drive in a turned lump of solid brass and then simply drill the hole to the size you want.

Why not drill the hole when the part is still in the lathe as the hole would be in the middle, concentric all the way down and won't fill the gun with swalf.

[NickG]

Okay, slightly off at a tangent, as it's not a springer that the OP is referring to, but, Barry, as Phil says above, Jim's been playing with acetal transfer ports on TXs. All good. And that silly high temperature is only generated for a miniscule amount of time meaning no ill effects with the synthetic TP.

Don't wish to be anti Jim as he does some fantastic work, i spotted a problem with his trans port as part of the stroke shortening plug he is testing. once cocked the breech lock up will be non existent as the barrel would push the plug rearwards when the cocking lever is returned , leaving just the o rings to take the pressure , on the TX the trans port creates the cavity for the o rings to work once it contacts the barrel. Jim is only using this set up to test with so not a problem .
I tried delrin for o ring piston heads and after time it broke up, cant say if this was due to temperature or the impact.

[TonyL]

That hadn't crossed my mind, Nick.

So, as you say, Jim's in the trialling stages at the moment. Once the final dimensions have been decided, maybe the insert could be secured by a pin or grub screw going in from the OD of the comp tube, providing the integrity required and also the ability to remove / substitute at a later date?

[BTDT]

That hadn't crossed my mind, Nick.

So, as you say, Jim's in the trialling stages at the moment. Once the final dimensions have been decided, maybe the insert could be secured by a pin or grub screw going in from the OD of the comp tube, providing the integrity required and also the ability to remove / substitute at a later date?

Not necessary, Tony; the o rings in fact bear against a shelf in the steel of the end plug, and lockup is unaffected.

My concern now is not whether the Acetal transfer port can withstand the elevated air temperature of the shot cycle, but the elevated air temperature of 10,000 shot cycles.

[junglie]

I just filled a port just like that with solder & drilled the required size hole in, easy & if you start small you can bore it larger if need be . plumbers solder using flux works best on brass btw.

[TonyL]

Not necessary, Tony; the o rings in fact bear against a shelf in the steel of the end plug, and lockup is unaffected.

My concern now is not whether the Acetal transfer port can withstand the elevated air temperature of the shot cycle, but the elevated air temperature of 10,000 shot cycles.

I just knew that you wouldn't have overlooked anything, Jim.

10,000 shots, eh? Someone's going to be a very busy boy!. But, as you've said before, these things need testing thoroughly over an extended period and proves your responsible and methodical approach.

[rovercoupe]

I just filled a port just like that with solder & drilled the required size hole in, easy & if you start small you can bore it larger if need be . plumbers solder using flux works best on brass btw.

Ohh might give that a go and save the delrin for the spring guide!