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 Here's one for the tuners 
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OberWOCer

Joined: Mon Sep 28, 2015 1:34 pm
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Unread post Here's one for the tuners
This isn't about an HW but my little Gamo - but it applies to springers in general - hence this forum not other makes.

If you've seen my post - viewtopic.php?f=30&t=24866 - you'll know that I can't get this (Freimarked) gun over the low 5s, try as I might.

With all the wet weather we've had recently, I've spent virtually all the time in the workshop tinkering with springers (not least of which is my new love, the HW80 :luv: ). With this one it's a nightmare trying to get the fpe DOWN so the Gamo makes a refreshing change.

Here are some measurements:- Stroke 63mm - Bore 25mm - Swept volume 31cc - transfer port - Length 15mm Dia 3-2.7mm (tapers) - Static compression ratio 1:312 (discounting other lost volume). In theory I should get at least 7fpe from this if not 9 - can't see why I don't.

The cylinder plug on these is a removable plastic one and very cheap, so I didn't mind playing about with it. I cut the length down by about 1mm (couldn't take any more off or the oring would be free), this gave me three improvements. #1 - the stroke was increased by 1mm - #2 the length of the transfer port was decreased by 1mm - #3 a depression on the face was removed hence further reducing the lost volume.

These small but measurable alterations raised the static compression ratio to 1: 369, close to optimum (some say) and also improved the actual ratio by removing the dimple.

I fully expected some increase in fpe, even if only .1 or.2, but no, still stuck at 5.3 max.

Next time I'm at a loose end I will flush off the face of the piston seal to just proud of the button, this will slightly increase the stroke and actual static compression ratio - but I'm not expecting much.

This is DEFINITELY not an issue with seals, and I even considered whether the breech lifted too early thus creating a partial vacuum (it isn't).

I honestly don't know what to try next, but this is becoming a challenge - any ideas?

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Thu Jun 16, 2016 9:03 pm
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UnterWOCer

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Unread post Re: Here's one for the tuners
You don't mention anything about springs , try a bigger one with some preload.


Fri Jun 17, 2016 6:18 am
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OberWOCer

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Unread post Re: Here's one for the tuners
Thought about that last night over a couple of beers - as I said in my post - "and have concentrated on finding the lightest, softest spring that still gives me this power level and making it as smooth as possible." - maybe I got this spring perfect for how it was, will try some pre-load this morning.

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Fri Jun 17, 2016 7:14 am
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OberWOCer

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Unread post Re: Here's one for the tuners
I must be getting better at this tuning lark than I thought - 4mm of pre-pack gave me a 0.15 increase in fpe - hardly earth shattering, but it does show that I had the spring perfect at the time. Any more and there is no increase, so again perfect.

The spread has become quite stable as it's settled down (how about - 119.3, 119.1, 119.2, 119.2, 119.5 m/s - almost all being 391 fps) and one hole groups at 20m is now the norm.

This is still well shy of what I think I should get from this rifle - but it is a little gem - I can literally **** this rifle with my little finger.

I'm keeping this for a while, it's a joy to work on and a real challenge so any more suggestions would be greatly appreciated.

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Fri Jun 17, 2016 9:05 am
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OberWOCer

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Unread post Re: Here's one for the tuners
I was reading the "Bible" last night (Cardew & Cardew - Trigger to Target) when I noticed that the bit they did on transfer ports was done using a rifle with almost identical specifications to this one.
Their work was done in imperial, but after converting to metric, it indicated an optimum transfer port of 3.175mm diameter.

Set to today, drilled it out and re-assembled.
I only like to change one thing at a time, so the same spring and pre-pack was fitted - guess what? - no change, still 5.4fpe.
Took the pre-pack out - no change. (interesting because it raised the fpe when I fitted it before) :scratch:
Added a piston weight (28gram plus 3mm pre-pack) - went down.
Took that out and put a total of 8mm pre-pack - still 5.4fpe.

In utter frustration I fitted a spring from my Omega that I know makes it over 12fpe, the gun was HORRIBLE :yuk: , just evil :evil: - guess what - went down.
This is not the answer.

The Cardews were getting about 6fpe out of theirs, I fully expected to able to get at least 7fpe out of this with careful tuning BUT I CAN'T - and haven't a clue why not. :bang:

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Mon Jun 27, 2016 7:49 pm
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OberWOCer

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Unread post Re: Here's one for the tuners
Think I might have a clue. :idea:

I said it myself- "In utter frustration I fitted a spring from my Omega that I know makes it over 12fpe, the gun was HORRIBLE :yuk: , just evil :evil: - guess what - went down."

How come I managed to fit an over-powered Webley Omega spring into a 7.5j Gamo - just by hand compression? (would normally need some sort of spring compressor), the spring CANNOT be behaving normally.

May be a dead end, but worth investigating - may have implications for anyone considering a short stroke conversion - including myself (HW80). :shock:

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Mon Jun 27, 2016 10:46 pm
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OberWOCer

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Unread post Re: Here's one for the tuners
This was the thought:- A spring is normally very close to solid when the rifle is cocked, I know the Webley one was, so when fitted to the Gamo with less pre-load and only 64mm of compression instead of about 90mm the spring would not be working at any where near it's optimum capacity. Maybe that's what's happening here I thought.

To check this out I cut a length of spring that would be solid at about 55mm and cut a length of Aluminium tube to set it to about 110mm when packed. (this was easily worked out, the space for a packed spring in this rifle is 200mm)
So now when fitted it had some pre- load and would be just short of solid when cocked, mimicking how a spring in any other rifle is.

The result - DEAD END - lower fpe and just awful. :cry:
I tried various amounts of pre-load but couldn't find a "sweet spot"

However I did have partial success playing about with another spring. It was a short, soft one that I had tried before (was second choice actually).
I cut a series of Aluminium spacers at 10mm,20,30 & 40mm and tried them with this spring. The results:-

No additional pre-load (compressed this with one finger) - Average 94.8 m/s - 311 fps - 3.44 fpe
10mm ....................................................................................... 110.7 ...... 363 ....... 4.69
20mm ....................................................................................... 120.1 ...... 394 ....... 5.52
30mm ....................................................................................... 119.6 ...... 392 ....... 5.48
40mm ....................................................................................... 115.3 ...... 378 ....... 5.09

Obviously somewhere about 20 or 30mm gives optimum for this spring, tried 15,25 & 35mm but 20mm came out best.

The very slight rise in fpe is not significant and the "feel" with this spring is not as nice so I've re-fitted the old one.

I now await my next idea - or any suggestions. :D

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Tue Jun 28, 2016 2:24 pm
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NeuWOCer

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Unread post Re: Here's one for the tuners
Hi h2bas, thanks for taking time to post your results. I was wondering if you had thought about (or already done) starting with the longest spring that will fit when compressed, then adjust various factors, ie, preload with various washers. Then cut maybe 1 coil off the spring, various preload again, etc, etc. Then repeat, 1 more coil off, etc. I realise that it will be monotonous and take a long time but somewhere there might just be the 'sweet spot' . Apologies if you've already thought or done this.


Tue Jun 28, 2016 8:25 pm
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OberWOCer

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Unread post Re: Here's one for the tuners
Thanks johnnybongo1512 for your input, all and any is welcome.

This was intended to be a very detailed post - but it "got lost" :x a-bit-of-a-moan-actually-t24933.html

I just haven't the heart to re-do it in full, so this is a quick summary.

I have tried various springs, weights and pre-load in this rifle and always find the sweet spot at around 5.4 fpe - any stronger spring results in piston slap and lower fpe. I can easily tell when I get piston slap - from how a pellet placed on the elevation dial behaves (e.g. when the rifle's at it's best it stays virtually in the same place, if it somersaults backwards it's piston slap)
The rifle has been massively short stroked(by 37mm, down from 100mm) by Gamo for the sub-7.5j market and it's looking like they got it just about right.
This doesn't explain though why I and the Cardews have had more out of very similar rifles ( Cardew's 25.4mm, 63.5mm, 32cc - Mine (now) 25, 64, 31.5)

I'm not giving up on this rifle - it's such a challenge and so responsive to small changes - I usually learn something from every rifle I tune, I have learned a lot from this one.
On the contrary, I've decided to make it a "keeper" - scope? - no contest, just has to be an ASI DE LUXE 4x32 Wide angle (ASI & Gamo were closely connected, ASI's guns were Gamos).
How old is it? - they stopped making the CF20 in 1993 and I've seen some with much higher serial numbers - so I'm going for 1980s.

If anyone has ANY ideas please let me know. :D

Image Image

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Wed Jun 29, 2016 12:47 pm
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NeuWOCer

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Unread post Re: Here's one for the tuners
I remember the ASI make....I bought one approx 35 years ago, an ASI Sniper. Cost £72. When showing it to my mate and shooting in his garden, his dad took an interest, had a few goes...then went out a few days later and bought my mate and his brother HW35's, .177 and .22, aand a Feinwerkbau for himself! All with Tasco scopes! A couple of years ago, my mate gave me both 35's, which had stood in the garage for years. Still in excellent condition. As it happens, I'm going out in a few minutes with the .22 to see if there's any big bunnies! As for your Gamo, if it's now 'sweet' and shoots good, then you've certainly achieved what you set out to do.


Wed Jun 29, 2016 7:03 pm
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OberWOCer

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Unread post Re: Here's one for the tuners
johnnybongo1512 wrote:
As for your Gamo, if it's now 'sweet' and shoots good, then you've certainly achieved what you set out to do.


In a way yes :D (notice I did go for the slightly lower fpe because it was "nicer") but it still intrigues me. :scratch:

Here's my latest line of thought.

I can't put a stronger spring into this rifle because it would result in "piston slap". Here's the theory behind this:-

When the trigger is released the spring goes forward compressing the air. If the breech were plugged (very easy to do on this rifle, just leave the breech plug up), the air would be compressed to the smallest volume this spring could manage (and peak pressure) and the piston would bounce back.
Increasing the power of the spring would result in lower and lower volumes (and higher and higher pressures) until you reached a point where all the air was compressed into the transfer port and piston slap would again occur. Any further increase is spring power can not reduce the volume or increase the pressure, it will just increase piston slap.

In practice the breech is open, presenting if nothing else the pellet skirt, if this pellet was fixed the increase in volume it offers means a weaker spring has to be fitted in order to avoid piston slap.
Again in practice the pellet will move presenting even more "lost volume" - so the spring would have to be reduced further.
The further the pellet moves the more the lost volume increases, meaning even less spring energy can be employed. (with me so far? :) )

In order to be able to put more energy into the system I think I have to reduce this "lost volume" somehow.
This (I think) can only be achieved by reducing the amount of pellet travel in the initial stages - how to do this?

One way would be to speed up the cycle (spring velocity) so the pellet has less time to move. (tried this with the near solid spring, couldn't get the power low enough)
An other is use a heavy pellet (greater mass therefore more inertia). (I'm using AA Field, about the heaviest (practical) pellet I can use)
The only other way I can think of is increasing the friction in the breech plug. (hence my next line of inquiry)

One thing I did notice was that the pellet fit was fairly loose in the breech plug (not slack but not as tight as it would be in the barrel) and also that it was plastic.
The friction (I concluded) would be much less for the initial movement of the pellet than if it were placed directly into the barrel. (this, when I thought about it is the only difference between this rifle and the Cardew's)
To increase this friction I first thought of tightening the hole (by sleeving it) but if too tight it would ruin the pellet's contact with the barrel or if even slightly out of line would cause it to "clip".

I then remembered that a brass sleeved version is available for the CF30 (interchangeable) so I'm going to order one (£10.50 posted, a trivial sum to satisfy my curiosity)
I'm hoping that - #1 friction of lead against brass is greater than lead against plastic (fairly certain it is) and - #2 the new, unworn aperture is somewhat tighter.

I'll let you know how it works out. :)

By the way, if anyone is thinking "Worrel Odour", please say so - I won't be offended.

All this and it's not time for a beer yet. :lol:

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Thu Jun 30, 2016 7:20 pm
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OberWOCer

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Unread post Re: Here's one for the tuners
The breech plug arrived this morning, so I chrono'd the rifle (av AAF 5.45, SD 4.7) and after de-burring the brass edges (seen too any breech seals "shaved" by sharp metal edges) I checked it was a correct fit and carried out a few experiments.

Everything I needed:- digital kitchen scales, slide calipers, a pen (dual purpose), a bottle top, AA Field and Superdomes and a copy of the "Bible" just in case.

Image Image

First - inside diameter - Old 5.69mm - New 5.45mm, then to establish the force required to push the pellet through.
I put the loaded breech plugs over the bottle top resting on the (zeroed) kitchen scales and slowly pushed down on the pellet with the pen, noting (as best as I could) the number of grammes displayed.

The results:- Old - AAF - 112, 114, 143 / SD - 927, 902, 964........... New AAF - 982, 947, 822 / SD - 2739, 2782, 2932
This is a MASSIVE difference - this just HAS to effect the way the rifle shoots.

So new plug fitted and chrono' mounted (a right pain, I have to take the fore-sight block off and mount it upside down - making sure I don't forget to hold the under-lever in place).

Image

As expected, the fpe went down - after all I've introduced more friction into the system without increasing the spring energy.
AA Field - very consistent 4.9 fpe .............. Superdome - not so consistent 3.6 fpe

Then added 10mm of pre-load - I'm giving the full strings (in m/s) this time because they are VERY interesting.
AA Field - 121.4,123.2, 123.0, 119.8, 124.1, 117.4, 119.6, 119.3 - the highest one was 5.9fpe - the rifle then settled down to is previous level of about 5.5fpe.
Superdome - 118.0, 118.2, 115.7, 114.7, 117.3, 113.9 - the highest being 4.8fpe - it settled down around 4.6fpe.

Then 20mm of pre-load:-
AA Field - 127.0, 122.2, then settled at about 120.5 (5.56), but the high one was 6.2fpe.
Superdome - 135.2, 127.8, 128.0, 120.5, settling at about 5.05fpe but the high one was 6.3fpe.

I probably won't post any more results for a day or so - I've got to go through the tedious bit of tuning to a spring that suits it best - but it does look like I'm on to something. (notice, among other things how the Superdomes are catching up)

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Sat Jul 02, 2016 1:50 pm
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Unread post Re: Here's one for the tuners
This didn't take as long as I thought, so here's a summary.

Used pre-load on the existing spring until I could tell it was coil-bound (absolutely, the trigger would just set but the breech didn't quite lift all the way up - needed another 1mm of cocking). During this process the pellets showed an increasing tendency to fall into two groups - a "high" group and a "low" group, both as regards POI and velocity.
By the time I had reached maximum pre-load they were either high (about 6.2fpe) or low (about 5.5fpe) forming two distinct groupings.

It was during this stage that I remembered an old one from when home chronos were quite rare - it takes just over 6fpe to make a hole in an AA Field pellet tin - I have two states, each one side or the other of this so it saved a lot of chrono'ing, it would make a hole or it wouldn't.

Image

There was no indication of piston slap as yet so I changed to a more powerful one. I tried the one that came with it (a square section "OX" type), but it was far too powerful and would not group at all. (The rifle only gave 2.6fpe with this when I got it)
So I tried the "Omega" spring again - the difference was unbelievable - no sign of piston slap, felt quite nice and when shooting a pellet would stay on the turret cap as though glued in place AND every one was in the high state.
Obviously I have raised the capability of this rifle to produce quite high peak pressure.

Grouping was good, not quite as good as before (has since much improved), about 3/4" at 20m.
Chrono'ing gave:- 126.1, 127.3, 126.7, 126.1, 127.4 - av 126.7 +/- <0.5%, (415.7fps) - 6.15fpe.

In effect I now have two rifles - one easy to **** and 5.5fpe (just swap spring and add 10mm to compensate for the tighter breech), the other a bit more like a "proper" rifle at about 6.2fpe - in both states it is very accurate and I suppose is the junior equivalent of the HW57.
With this in mind I will probably designate the Meteor Mk6 as "kiddies corner", it will be company for it and the equivalent of an FAC HW80. :lol:

I have actually spent more on pellets than I paid for the rifle - but after all that's why I bought it in the first place - to play about with. :D

Not quite finished with it yet, but only just to tidy up the rough edges.

It's funny in a way - if anyone had suggested that I needed to INCREASE the friction in a rifle to INCREASE the fpe - well I don't know what I would have thought. :roll:

Nearly forgot - What about the Superdomes?

Latest chrono'ing - AA Field 127.5, 126.5, 127.8, 126.3, 127.3 - av 127.1 - 6.19fpe ......... Superdome - 133.2, 136.8, 137.7, 135.4, 136.2 - av 135.9 - 6.4fpe.

So yes they did catch up - well sort of - the superdomes do have slightly more energy at the muzzle, but by the time they reach 5m the AAF are the same, after that AAF are "streets" ahead in this respect (at 30m AAF still have 4.6fpe, S/D only 3.6fpe) - so no, I won't be changing pellet.

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Sun Jul 03, 2016 4:09 pm
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Unread post Re: Here's one for the tuners
I thought I'd finished with this one (for a while at least), but a bit of an oddity has just cropped up.

I have a BSA Meteor Mk6, a very early one but also made by Gamo, only this was made in Birmingham.
Just for something to tinker with I decide to strip it down and fettle a little, the power was down at about 8.5fpe and it smoked a bit.
Soon realized that I was on very familiar territory, I knew the trigger was the same as this Gamo and some other bits - BUT THE PISTONS !!!

Image

On the left Meteor - on the right This Gamo. The only difference is that the Gamo has been lightly machined and I have recently polished it.

I checked the rest of the tube over - Stroke, The Same - Spring housing, The Same - Transfer port, virtually the same (Meteor 3mm, Gamo now 3.175mm (I altered it)) - Port length, virtually the same.

The power plant on these two rifles is in effect ...........THE SAME ............. :shock: :scratch:

So I swapped a few things around.
Pistons - virtually no change in either rifle.
Gamo spring (6.3fpe) into Meteor - Massive drop in power (< 4fpe and heavy smoke), felt awful.
Meteor spring (8.5fpe) into Gamo - Dropped to 5.7fpe, no smoke, felt smooth.

I really do not have any idea at all what is happening here. :scratch: :scratch: :scratch: - BUT I'M GOING TO TRY TO FIND OUT !!!

Has ANYONE got ANY ideas ???????? - I think it must be something to do with the pop-up breech (or the BARREL ? - could it be heavily choked?) - BUT WHAT ??????

_________________
Air Arms TX200 mk3 .22 Zenit-BelOMO 3-9x40 ffp / Vector Optics 10-40x56 sf tt ffp
Weihrauch HW35E 1979 .177/.22 (both barrels) Optima 4x32 wa tt / Tasco 628T 3-9x40 tt / Open sights / Weihrauch Mikro-Präzisions Diopter
Weihrauch HW80 mk 1 .243 (Harper) Simmons WTC11 1.5-5x20 wa
Weihrauch HW80 mk 1 .22 Kassnar 3-9x56 wa ao tt
Weihrauch HW80 mk 2 .177 Kassnar 3-9x40 wa ao tt / ATN MK390
Weihrauch HW77 mk 1 .22 Optima 3-9x40 wa tt / Tasco World Class 6-18x40 ao tt
Weihrauch HW77k mk2 .22 Optima 3-9x40 wa tt / Tasco TR 6-24x40 ao tt
Webley Omega Carbine .22 Tasco AG 2-7x32 wa oa tt
Webley Stingray Express LE .22 Simmons WTC13 3.5-10x40 wa
Webley Longbow (Turkish) .22 Simmons WTC13 3.5-10x40 wa
BSA Mercury mk3 .22 Tasco AG 1.75-5x40 wa oa
BSA Meteor mk1 .22 Tasco 663 A 4x32
BSA Meteor mk5 .22 Tasco 629 AG 3-9x32
Webley Tempest (Brum) .177/.22 (both barrels) Original Mod'5 1.5x15 / open sights


Last edited by has2baspringer on Sat Jul 23, 2016 8:25 pm, edited 1 time in total.



Fri Jul 22, 2016 8:12 pm
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Location: Laval, Quebec, Canada
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Unread post Re: Here's one for the tuners
Hi. This might be silly but...is the transfer port well align with the barrel (pellet).

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Jacques13
Quebec, Canada................and proud member of the YCHJCYA2PDTHFH Club


Sat Jul 23, 2016 1:29 pm
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