BSA Improved Model

[jirushi]

Ah, Louis

When I suggested using the spring out of a tape measure I meant the clock Spring inside the case which you can't normally see.
The clock Spring is just blued steel and wouldn't need cleaning, but no matter using the actual tape should do the job.



All the best Mick

Ah I see! Yes that would save some work.
I will make a few of these rear sight springs. It's actually fun to do.
Cheers

[edbear2]

Ah I see! Yes that would save some work.
I will make a few of these rear sight springs. It's actually fun to do.
Cheers

Hiya,

Have a look for a punch kit (the link is to a cheap knock off copy of a Roper Whitney but still OK for light work) but I have no idea what is available where you are, but they pop up used at various places.

A handy thing to have for all sorts of jobs, and it will make the spring job easier if you are doing a batch.

Just make one carefully out of say 1mm or so steel as a pattern, then you can start on the thin ones by punching the hole, inserting a dowel as a guide, the using the pattern to scribe round.

Then all your batch will be more accurate in relation to each other

https://www.zoro.co.uk/shop/hand-too...0aAjk1EALw_wcB

ATB, ED

[jirushi]

Hiya,

Have a look for a punch kit (the link is to a cheap knock off copy of a Roper Whitney but still OK for light work) but I have no idea what is available where you are, but they pop up used at various places.

A handy thing to have for all sorts of jobs, and it will make the spring job easier if you are doing a batch.

Just make one carefully out of say 1mm or so steel as a pattern, then you can start on the thin ones by punching the hole, inserting a dowel as a guide, the using the pattern to scribe round.

Then all your batch will be more accurate in relation to each other

https://www.zoro.co.uk/shop/hand-too...0aAjk1EALw_wcB

ATB, ED

Hi Ed,
That is a great tip. Looks like a very useful tool.
Cheers, Louis

[edbear2]

No Problem Louis,

It's also S.O.P. to make little helpers in a factory or even home workshop when you are manufacturing more than one item, it depends on the person and item of course, but any factory fabrication especially workshop will have a shelf of little jigs and fixtures knocked up to do short run jobs.

It's a balance between the time to make the fixture and the time saved obviously which is the decision of the person on who's bench the job lands on, this is down to experience of course.

Often these will only be used the once and will be recycled for other jobs in the future as provide a good "start" rather than making from scratch.

Of course toolmakers and toolrooms will do stuff for industry, but any skilled person in engineering is capable of rattling up something to make their life easier on the spot.

A "jig" could be little more than a piece of metal with a couple of holes in to allow rapid positioning of centres for holes, or in your case would be the bit of drill shank or dowel and the thicker "master" spring pattern.

Sometimes even just something to hold an item saves time, like when polishing small parts etc.

ATB, ED

[jirushi]

Thank you Ed once again for your good advice.
I haven't done a batch of rear sight springs yet, but just finished two, which I am using as a pair.
The tape measure metal is too thin and does not have enough spring power otherwise.
But with two layers, it works well (although it won't win any beauty contests!).

[jirushi]

A Dutch friend who bought some parts from the Frank Korn (RIP) estate, sent me a flat section spring.
It turns out to be original BSA.
That's my spring problem sorted; I only had one well fitting flat section spring, now a pair, and they are counterwound.
We'll have to see what the power is with these two springs.

[jirushi]

What I find the most difficult part of this Improved Model repair, is the leather washer.
The one that was in the gun (perhaps original), is damaged and does not seal well.

I bought a new 28 mm leather seal (see photo above), but it is much too "deep" and it has a hard red disc with a small diameter, which doesn't look right to me.
Then I bought another new 28 mm leather seal from Protek, see photo below.
This one looks better (nice and shallow), but it didn't come with a leather buffer or dished washer.

Does anyone have tips on how to DIY, for the leather buffer or dished washer?
Is it right that the top of the piston seal (the rim) should protrude from the screw head in the center?
I guess the screw head would crash onto the end of the compression chamber otherwise?

Protek seal


I cut this leather buffer out of another seal. I think it is "suboptimal". The washer is not dished, and the diameter of the leather buffer is probably too small.

[edbear2]

[QUOTE=jirushi;8186261]Thank you Ed once again for your good advice.
I haven't done a batch of rear sight springs yet, but just finished two, which I am using as a pair.
The tape measure metal is too thin and does not have enough spring power otherwise.
But with two layers, it works well (although it won't win any beauty contests!).

Hi,

The original springs had the ends folded down as shown, can't see if your's does;



ATB, ED

[jirushi]

[QUOTE=edbear2;8186276]

Thank you Ed once again for your good advice.
I haven't done a batch of rear sight springs yet, but just finished two, which I am using as a pair.
The tape measure metal is too thin and does not have enough spring power otherwise.
But with two layers, it works well (although it won't win any beauty contests!).

Hi,

The original springs had the ends folded down as shown, can't see if your's does;



ATB, ED

Cheers Ed.
Mine don't have the ends folded down, but due to the round shape of the tape measure metal, and its springiness, it works well (when I use a pair).

[jirushi]

Yesterday I finished the Improved Model... for now.
I am using a shallow piston seal from Protek.
As a leather buffer, I am using the cut out bottom of another leather 28 mm seal.
And the original (?) brass dished washer and screw.

The leather seal seems to work well. It isn't too tight in the cylinder, but when moving the piston up and down with a finger on the barrel, it creates good vacuum / air pressure.

Springs wise, I tried a few combinations, but settled on what was in the gun when I bought it: a counterwound set of a flat section spring, and a normal round section spring that has a smaller outer diameter. The flat section spring is at the rear (on the spring guide), and the slimmer one is in the piston. I have put one steel washer in the piston. And a bit more grease on the springs than the thin smear of moly that I normally use. This time I actually used grease from a Vortek kit. Don't know why, but it's thicker than moly and I thought it would work better. I think it helps against vibrations and twang, because the gun is now nice and quiet, and has a pleasant shooting behaviour.

Chrony results: nice and consistent, but velocity is lower than I had expected.
650 ft/s with 7.0 gr RWS.
My Light Pattern does 620 ft/s, but is a bit harsher.
Overall, I prefer the Light: the length, balance and stock suit me better.

[jirushi]

Any firsthand chrony results with a .177" similar length prewar BSA?
The 6.6 ft/lbs I'm getting now feels a bit tame, but perhaps I should leave it this way and simply enjoy, as it will probably be a good 20 meter gun.

[coristan]

My Improved Model D, serial No.18170 does around 7ftlbs...never had it in bits though......

[jirushi]

My Improved Model D, serial No.18170 does around 7ftlbs...never had it in bits though......

Thank you coristan.
That is a bit more than mine, but quite similar.

I thought that these were capable of higher power, but probably that's with .22's?