PDA

View Full Version : HW77 .177 transfer port size



magnummike
28-11-2013, 02:13 PM
Hi chap's in 1993 I bought a 77k in .177 with a 25mm piston . Back then most people were fitting OX kits including me :eek: Anyway a year later I sold it to a mate :( and he has had it since then . The other week I managed to buy it back after 19 years :) and I stripped it . The ox was still in there so degreased etc and plan to fit a standard spring when I get 1 . But all them years ago I cant remember if i opened up the transfer port when I fitted the OX kit , just wondering if anyone knows the standard size so I can check it ATB Mike :)

brucegill
28-11-2013, 02:17 PM
I think it's 2.8mm or something like that. If yours is bigger than 3mm you opened it up :D

magnummike
28-11-2013, 02:25 PM
I think it's 2.8mm or something like that. If yours is bigger than 3mm you opened it up :D

Cheer's Bruce I'll get the caliper out , fingers crossed E'h

MattyBoy
28-11-2013, 02:37 PM
I run all my 77s and 97s with a 3.2mm TP

I have a special "Gold" drill bit just for that job.

3.6mm is still perfectly fine but if it's over 4.0mm then it's sleeve-down time.

JB swore by 4mm so it seems the TP diameter is variable but different sizes will obviously affect the shot cycle considerably.

I like 3.2mm myself :)

Matty

Phil Russell
28-11-2013, 03:34 PM
Could optimal tp size depend on the spring as well?
The mention of the 'Maximiser' reminded me of my own, new in about 1984, HW77k.
The Maximiser tuning kit was all the rage then and I bought one as all the adverts promised me it would transform the feel of the standard rifle. It was my first attempt at any form of tuning so I leapt at the chance. I sweated all morning to get it fitted. I remember the square section spring (Ox??) took a lot of preload and I did not have a compressor of any sort. But I did it ..... all fitted with the minimum of spilt blood.
What a transformation. From a pretty docile but bit twangy rifle I now had a rifle that bucked and jerked around in my grasp. I had no chrono so did not know what it was doing; but assumed it was still within spec. But I hated the firing cycle. Late afternoon I took it apart again and refitted the original spring. All became nice again ... the piston liner and 'debur' carried out as per Maximiser instructions had helped. No more twang and a good sweet firing cycle.
The rifle stayed like that for about 20 years when a chrono check showed power was declining so I put a new standard UK power spring in. A chrono check revealed power ott so spring reduction was needed. No problem.
I have never touched the transfer port.

Cheers, Phil:)

Bulsaye
28-11-2013, 04:15 PM
or .118" if you want the decimal size.

TonyL
28-11-2013, 08:12 PM
Could optimal tp size depend on the spring as well?
The mention of the 'Maximiser' reminded me of my own, new in about 1984, HW77k.
The Maximiser tuning kit was all the rage then and I bought one as all the adverts promised me it would transform the feel of the standard rifle. It was my first attempt at any form of tuning so I leapt at the chance. I sweated all morning to get it fitted. I remember the square section spring (Ox??) took a lot of preload and I did not have a compressor of any sort. But I did it ..... all fitted with the minimum of spilt blood.
What a transformation. From a pretty docile but bit twangy rifle I now had a rifle that bucked and jerked around in my grasp. I had no chrono so did not know what it was doing; but assumed it was still within spec. But I hated the firing cycle. Late afternoon I took it apart again and refitted the original spring. All became nice again ... the piston liner and 'debur' carried out as per Maximiser instructions had helped. No more twang and a good sweet firing cycle.
The rifle stayed like that for about 20 years when a chrono check showed power was declining so I put a new standard UK power spring in. A chrono check revealed power ott so spring reduction was needed. No problem.
I have never touched the transfer port.

Cheers, Phil:)

Hi Phil,
Nice little write up. I'm sure many fell for these kits/springs back then, resulting in harsh firing cycles, probably OTT power and maybe the square edges of the square section springs nibbling away at the precious internals. :eek: I just thank my lucky stars that I never fell for them....I stripped and serviced a few rifles belonging to friends, all containing Ox springs. At least two HW35s and a Mercury to two, and all became much nicer once fitted with nice, sensible, round springs.

I know some have posted on here that some of the square section springs, such as the ones HW fitted to the 97 as standard for a while, were actually fine, as they didn't exhibit those nasty, sharp edges.

And, yes, big time. Any tune, on any gun, will be down to balance. So a certain TP size will suit a certain set-up better than another. There will be cases, however, where the standard size is too small or large for any ideal set-up, I bet. And, as Matty Boy says, yes, by the sounds of it, with the 77 you can go right out to 4mm, depending on personal preference. A TP this wide would be a bad move on many guns with longer TPs, due to more lost volume, certainly at our power level.

brucegill
29-11-2013, 09:49 AM
I run all my 77s and 97s with a 3.2mm TP

I have a special "Gold" drill bit just for that job.

3.6mm is still perfectly fine but if it's over 4.0mm then it's sleeve-down time.

JB swore by 4mm so it seems the TP diameter is variable but different sizes will obviously affect the shot cycle considerably.

I like 3.2mm myself :)

Matty

Hi Matty

Do you just drill yours out, or do you ream them as well?

Cheers for the info
Bruce

greenwayjames
29-11-2013, 10:33 AM
When asked JB said he used to use a 5/32" drill on FWBs, HW77s etc but advised against doing it unless the rest of the conversion that he did was carried out. He used a 5mm drill for HW80s:eek:

bigtoe01
29-11-2013, 10:52 AM
4mm is perfectly safe on a 77, work out the static compression ratio and you will see why. A Diana 52 has a 6mm long TP with seal length and in unrestricted mode has 4mm dia TP...no different.

peak power comes under 4mm but not by much, i often see gains over over 1fpe going from 3 to the sweet spot ;) with the same spring and preload, this then allows the spring to be backed off etc.

If using an O ring head the TP needs to be a tad smaller than on a synthetic seal, this is to raise the compression, O ring heads are more efficient and make power easier, so a smaller TP can be used and you get the same results.

brucegill
29-11-2013, 02:22 PM
If you open up the TP on a 77 from standard to 3.5 (for augments sake), would it require less preload or more to get the same power levels?

Thanks
B

bigtoe01
29-11-2013, 02:39 PM
Bruce, peak power is not produced with a TP of 3mm, that means a TP of 3mm is not efficient. As you increase the TP dia the power grows till eventually it peaks and for a small further increase in TP dia you can tune the distance from the breech face the piston stops before slamming into the breech face...so you can tune the bounce point.

Peak power is around 3.9mm, 4mm gets the piston a little closer to the breech face (and lets not forget piston weight plays a part also)

So if you increase efficiency you can use a weaker spring...however this may not be ideal but often does result in less felt recoil.

On an O ring piston you need to go smaller with TP dia as the pistons fly faster and generally the O ring is more efficient with less lost volume, so peak efficiency may be 3.5mm...i fell in the trap of expecting an o ring head to work like a synthetic seal ...they don't.

So quick answer is it should require less preload.

I tested 3 to 4.2mm in .1mm steps and settled on 3.9, i know Wonky likes 3.9 also, JB likes 5/32 which is just a nats over 3.9, T20 uses 4mm, BTDT runs 4mm on his 77k....the list is long for rifles that all run very close to the same transfer port dia...now ask yourself why ;)

MattyBoy
29-11-2013, 02:44 PM
In answer to Bruce, I just drill them then polish them with Autosol on a boot lace :) .

In answer to Tony, in that case I'll be taking my ports out from 3.2mm to 3.8mm immediately :D

Matty

brucegill
29-11-2013, 02:47 PM
Bruce, peak power is not produced with a TP of 3mm, that means a TP of 3mm is not efficient. As you increase the TP dia the power grows till eventually it peaks and for a small further increase in TP dia you can tune the distance from the breech face the piston stops before slamming into the breech face...so you can tune the bounce point.

Peak power is around 3.9mm, 4mm gets the piston a little closer to the breech face (and lets not forget piston weight plays a part also)

So if you increase efficiency you can use a weaker spring...however this may not be ideal but often does result in less felt recoil.

On an O ring piston you need to go smaller with TP dia as the pistons fly faster and generally the O ring is more efficient with less lost volume, so peak efficiency may be 3.5mm...i fell in the trap of expecting an o ring head to work like a synthetic seal ...they don't.

So quick answer is it should require less preload.

I tested 3 to 4.2mm in .1mm steps and settled on 3.9, i know Wonky likes 3.9 also, JB likes 5/32 which is just a nats over 3.9, T20 uses 4mm, BTDT runs 4mm on his 77k....the list is long for rifles that all run very close to the same transfer port dia...now ask yourself why ;)

Many thanks Tony! Better find some nice drill bits :D


In answer to Bruce, I just drill them then polish them with Autosol on a boot lace :) .

In answer to Tony, in that case I'll be taking my ports out from 3.2mm to 3.8mm immediately :D

Matty

Thanks Matty!

Appreciate the info guys :cool:

bigtoe01
29-11-2013, 03:26 PM
remember however, if the gun you have is nice already, why alter it?

If you must experiment drill the TP to 4.2mm and tap to m5, get some 6mm long m5 grubscrews and have them drilled from 3 to 4mm in .1mm steps, use a little blue loctite to hold them in and seal the threads, you can now play with TP dia and see what works for you ;)

A little heat and an allen key gets them out, run the tap back in to clean the threads and screw a new one in to resume testing.

greenwayjames
29-11-2013, 05:18 PM
"I tested 3 to 4.2mm in .1mm steps and settled on 3.9, i know Wonky likes 3.9 also, JB likes 5/32 which is just a nats over 3.9, T20 uses 4mm, BTDT runs 4mm on his 77k....the list is long for rifles that all run very close to the same transfer port dia...now ask yourself why"

The list of many longtime professional "tuners" who kept to the original or even sleeved transfer ports is even longer..... now ask yourself why? from first hand experience I include in that list Cardew, Mike Wade of Power without Powder fame, Venom, Worcestershire Black Powder Supplies, Kestock and many more. They must have done a half decent job to stay in business as long as they did with many repeat customers.

The best piece of advice is.
"If you must experiment drill the TP to 4.2mm and tap to m5, get some 6mm long m5 grubscrews and have them drilled from 3 to 4mm in .1mm steps, use a little blue loctite to hold them in and seal the threads, you can now play with TP dia and see what works for you

A little heat and an allen key gets them out, run the tap back in to clean the threads and screw a new one in to resume testing"

T 20
29-11-2013, 05:43 PM
The list of many longtime professional "tuners" who kept to the original or even sleeved transfer ports is even longer..... now ask yourself why? from first hand experience I include in that list Cardew, Mike Wade of Power without Powder fame, Venom, Worcestershire Black Powder Supplies, Kestock and many more. They must have done a half decent job to stay in business as long as they did with many repeat customers.



I thought Mike Wade just supplied his "Viper" tuning kits and didn't actually tune guns for anybody ? :confused:

If you look at Mike Wade's order form that came with Power Without Powder, he recommends drilling the transfer port out on the 77 for both his Max power and FT Viper tuning kits. ;)




All the best Mick

greenwayjames
29-11-2013, 06:38 PM
My mistake:(. I was thinking of his recommendations for the HW80 tune. He did tune some himself for a chosen few in addition to selling his 80 springs. He also made a regulated high power PCP for his own use I was lead to believe. Ahead of its time.

T 20
29-11-2013, 06:41 PM
My mistake:(. I was thinking of his recommendations for the HW80 tune.

He recommended drilling the HW80 transfer ports out as well. :)





All the best Mick

T 20
30-11-2013, 10:01 AM
And come to think of it Cardew wasn't a professional tuner either.

Though he did do a few experiments where he opened transfer ports up. :)




All the best Mick

greenwayjames
30-11-2013, 11:32 AM
He recommended drilling the HW80 transfer ports out as well. :)





All the best Mick

Did he really. I no longer have a copy so I will take your word for it. Cardew used to tune quite a few rifles for shooters in addition to repairing/restoring antique pneumatics, Giffards etc. He charged for the work he did. Cant agree with you about ports having read his books.

The main point of my first post was to agree with the advice that whatever you do should be "undo-able"if it doesn't work out:)

T 20
30-11-2013, 12:35 PM
Did he really?

Yes he did --- in both editions of Power Without Powder (there were two different editions) Mike recommended opening the HW80 transfer port out.




Cant agree with you about ports having read his books.

As good as Trigger to Muzzle is and how revolutionary it was when first released in 1976 you need to bare in mind that a lot has changed in 37 years.

In 1976 calculators were in their infancy --- 1977 being the first year they were deemed good enough to use them in O level exams. ;)

Decent cheep chronographs were unheard of.

Digital scales were unheard of.

And all Weihrauchs had Leather seals fitted back then.


You would need to have followed Gerald Cardews later works in Airgun World to have read his transfer port and stroke experiments.

Most home tuners on here have equipment which Gerald Cardew could only have dreamed about in 1976.





The main point of my first post was to agree with the advice that whatever you do should be "undo-able"if it doesn't work out:)

Amen to that









All the best Mick

TonyL
30-11-2013, 07:22 PM
Yes he did --- in both editions of Power Without Powder (there were two different editions) Mike recommended opening the HW80 transfer port out.

As good as Trigger to Muzzle is and how revolutionary it was when first released in 1976 you need to bare in mind that a lot has changed in 37 years.

In 1976 calculators were in their infancy --- 1977 being the first year they were deemed good enough to use them in O level exams. ;)

Decent cheep chronographs were unheard of.

Digital scales were unheard of.

And all Weihrauchs had Leather seals fitted back then.


You would need to have followed Gerald Cardews later works in Airgun World to have read his transfer port and stroke experiments.

Most home tuners on here have equipment which Gerald Cardew could only have dreamed about in 1976.
All the best Mick

Yep, Mr Wade certainly advocated opening the TP up.

And, YES, as above re The Airgun from Trigger to Target.....Revolutonary and eye-opening in its day. I have read and re-read it many times in the past. And we can all be grateful for Mr Cardew's work and insight.
But times move and technology has moved with it, especially with the advent of the synthetic seal.

Jim Tyler and Dr Mike have dis-proved some of the Cardew work. For example, the reliance of the springer on a controlled burn in order to make power.

Not having a go at the book or theories. As I say, we can all be grateful for this insight. With every generation of new tuner, we now have a wealth of previous work and information to tap into to. Many of the basics are in place for the modern tuner to just tweak and, step by step, make small, incremental improvements. So we all owe much to Mr Cardew, Mr Bowkett, Messrs Hancock and Popes, Jim Maccari, Ken Turner etc. And, in AGW and right here on the BBS, the many expert tuners such as your good self, Mick, Bigtoe, Wonky Donky and many, many more.......:)

But the ones who I'd also loved to have really met are those earlier pioneers. The guys that came up with the original theories and ideas. How did they work out or guess at the bore and stroke dimensions, for example? I assume that, firstly, it was down to handling/size/weight to arrive at an aesthetically pleasing layout that was portable, dictating the outer cylinder diameter, thus the internal. Then lengthen the stroke to up the power.

I remember in one of John Milewski's excellent little write ups of an early 1900s rifle (can't remember the make/model right now), where the maker fitted an aluminium piston in the target version to reduce recoil.

Without digging books out, someone remind me of which was the earliest springer. Was it the Quackenbush design? And, I know they were a little later (post WW1?), but those Lincoln Jeffries rifles were beautiful, no?

brucegill
30-11-2013, 07:58 PM
Trying to get another set to play with.

These grub screw.... Do you need to do anything else to the grub screw, other than drill them?

Cheers
B

Snooper601
30-11-2013, 08:11 PM
Just make sure the gurb screw length is the same as the port length to save making any extra lost volume.

Cheers

John

bigtoe01
30-11-2013, 08:16 PM
drill them from the back so the Allen key still works to get them in and out and make sure each one is sized to exact length to finish flush with each face both inner and outer.

brucegill
30-11-2013, 08:17 PM
Just make sure the gurb screw length is the same as the port length to save making any extra lost volume.

Cheers

John

Thanks John

I was worried about the actual Allen key hole, would this not cause problems?

Cheers
B

Snooper601
01-12-2013, 06:53 AM
As Tony says above, make them flush at both ends.
The slight lost volume due to the Allen recess is only slight and is like putting a pellet with a deeper skirt in the barrel, probably less than the 0.1mm size difference in the drilled holes, though it may be a bigger difference on a short transfer port.

Cheers

John

greenwayjames
01-12-2013, 08:00 AM
There was a very early 20th century, pre first world war, trade magazine called Arms and Explosives? I read an article in an edition which detailed in several pages experiments carried out by BSA using the Lincoln Jeffries patent underlever rifles they were making at the time. They experimented with light and heavy pistons eventually settling on the heavy for best overall performance in their production air rifles.

"an early 1900s rifle (can't remember the make/model right now), where the maker fitted an aluminium piston in the target version to reduce recoil."

bigtoe01
01-12-2013, 08:08 AM
the difference now is in an age of sharing, before 99% was all kept secret, so even though 99% has been done before it really is all new as before most was never released.

Ask Jb if he will share all his secrets....report back to us what he says ;)

the gun trade is very secretive.....

greenwayjames
01-12-2013, 09:10 AM
"the gun trade is very secretive...."

Read my previous post again.



There was a very early 20th century, pre first world war, trade magazine called Arms and Explosives? I read an article in an edition which detailed in several pages experiments carried out by BSA using the Lincoln Jeffries patent underlever rifles they were making at the time. They experimented with light and heavy pistons eventually settling on the heavy for best overall performance in their production air rifles

That doesn't sound very secretive to me:confused:
As well as I can remember JB gave details in Airgun World of what he did in his air rifle conversions including information about piston heads, weights transfer port sizes, barrel locks, adjustable hinge bolts etc. Is there anything specific you want me to ask him tomorrow? Why don't you ring him and seek his advice yourself? It would save me the cost of a phone c:Dall

brucegill
01-12-2013, 09:33 AM
drill them from the back so the Allen key still works to get them in and out and make sure each one is sized to exact length to finish flush with each face both inner and outer.

Thanks Tony. I didn't see your post yesterday for some reason.

ATB
Bruce

bigtoe01
01-12-2013, 01:00 PM
"the gun trade is very secretive...."

Read my previous post again.



There was a very early 20th century, pre first world war, trade magazine called Arms and Explosives? I read an article in an edition which detailed in several pages experiments carried out by BSA using the Lincoln Jeffries patent underlever rifles they were making at the time. They experimented with light and heavy pistons eventually settling on the heavy for best overall performance in their production air rifles

That doesn't sound very secretive to me:confused:
As well as I can remember JB gave details in Airgun World of what he did in his air rifle conversions including information about piston heads, weights transfer port sizes, barrel locks, adjustable hinge bolts etc. Is there anything specific you want me to ask him tomorrow? Why don't you ring him and seek his advice yourself? It would save me the cost of a phone c:Dallyou think jb would talk to me lol.....dream on man...in fact I would not dream of asking him as I prefer to make my own notes.

you seem quite hostile with me, I think it best we do not comment on each others posts going forward, we do not want to upset the admin now.

I respect your opinion, please respect I have my own too, if I offer advice its up to the in decidual if they choose to except it or not.

thank you

greenwayjames
01-12-2013, 01:42 PM
Everyone is entitled to their opinions and the right to state them providing it does not cause offence. I respect that. When a puzzling comment is made it deserves a response. Hopefully that response expands on the matter. That is called a discussion. That's how we find things out. :)

bigtoe01
01-12-2013, 03:21 PM
just do your own testing and make your own decissions....thats the best way...and what i do.

until you test it yourself how can you be 100% sure....i dont take anthing for granted until i have tested i it.

It would be nice to see you do some testing on a springer, with stroke, transfer port and piston weight all covered freely publushed on the forum :-)

T 20
02-12-2013, 06:28 PM
With every generation of new tuner, we now have a wealth of previous work and information to tap into to. Many of the basics are in place for the modern tuner to just tweak and, step by step, make small, incremental improvements. So we all owe much to Mr Cardew, Mr Bowkett, Messrs Hancock and Popes, Jim Maccari, Ken Turner etc. And, in AGW and right here on the BBS, the many expert tuners such as your good self, Mick, Bigtoe, Wonky Donky and many, many more.......:)




Wow there Tony :eek:

I don't profess to be an expert tuner, and never have done --- I'm at best a well established bodge artist. ;) :D




All the best Mick

Hsing-ee
02-12-2013, 06:35 PM
Wow there Tony :eek:

I don't profess to be an expert tuner, and never have done --- I'm at best a well established bodge artist. ;) :D




All the best Mick

Anyone who can get 12 ft/lbs out of a B2 without sticking a .22 Short cartridge in it has to have some skill.

T 20
02-12-2013, 06:56 PM
Anyone who can get 12 ft/lbs out of a B2 without sticking a .22 Short cartridge in it has to have some skill.

Hi Alistair

The big thing I found out with that exercise was that you could increase the power output of certain guns by reducing the transfer port diameter. :)

The other classic example of this is the Webley Hawk MK2 --- sleeve the transfer port down and watch the power go up and the recoil come down.

U.K.Neil, kindly gave me a Webley MK3 at the Boinger Bash --- this is next on the list for a reduced transfer port. :cool:





All the best Mick

Hsing-ee
02-12-2013, 06:59 PM
Hi Alistair

The big thing I found out with that exercise was that you could increase the power output of certain guns by reducing the transfer port diameter. :)

The other classic example of this is the Webley Hawk MK2 --- sleeve the transfer port down and watch the power go up and the recoil come down.

U.K.Neil gave me a Webley MK3 at the Boinger Bash --- this is next on the list for a reduced transfer port. :cool:





All the best Mick


Exactly. In the 80s I remember the legions of tuners boring the TPs out and sticking in massive springs and polishing the bejesus out of everything to little practical effect ... even Webley up-gunning the Hawk to give the Vulcan with a stronger spring, 'advanced' piston washer 'system' and bogger swept volume ... when all they needed to do was sleeve the TP down. The difference between you and them is you did your thinking with your brain, Mr Mick!

T 20
02-12-2013, 07:12 PM
Exactly. In the 80s I remember the legions of tuners boring the TPs out and sticking in massive springs and polishing the bejesus out of everything to little practical effect ... even Webley up-gunning the Hawk to give the Vulcan with a stronger spring, 'advanced' piston washer 'system' and bogger swept volume ... when all they needed to do was sleeve the TP down. The difference between you and them is you did your thinking with your brain, Mr Mick!

I think Webley may have cottoned on at that time Alistair. :)

The transfer port on the Hawk was 4mm diameter X 16mm long

The transfer port on the Vulcan was 2.5mm X 19mm long





Al the best Mick

TonyL
02-12-2013, 07:32 PM
Hi Alistair

The big thing I found out with that exercise was that you could increase the power output of certain guns by reducing the transfer port diameter. :)

The other classic example of this is the Webley Hawk MK2 --- sleeve the transfer port down and watch the power go up and the recoil come down.

All the best Mick

There are many reasons why I have never attempted going down the road of "wholesale" and "structural" changes:-

What you've stated up above is something that's always been at the back of my mind.

Lack of bottle is one of the big reasons. My guns are all special to me and I'd hate to think I'd ruined it by going too far......Obtaining some near-to-worthless wrecks would certainly help in this regard!
I'm also hampered by a chronic lack of time and don't have the workshop facilities. If I had the time, bottle and gear, and could obtain enough basketcases, I'd LOVE to be able to delve a little deeper than my usual de-burr, polish, replace seals and fit guides etc.

So, to date, I've been happy with just making what's there just a little nicer.

Yes, I'd love to be able to play with sleeving down the bore and altering stroke etc. And, yes, I realise that, with the right gear, if you go to far with the TP diameter, this can be rectified.

But, sticking to the standard dimensions will do me for now, but I'll always feel very grateful and indebted to peeps like you, Mick. And Bigtoe and Wonky. There are more out there, too. Intrepid tuners who are happy to share their knowledge with us.

Cheers guys!:)

TonyL
02-12-2013, 08:20 PM
Anyone who can get 12 ft/lbs out of a B2 without sticking a .22 Short cartridge in it has to have some skill.


And the HW35/LGV hybrid, eh, Mick?

Yep, what a bodge that was! :D;):D