BSA Standard Pattern struggling to make good power

[jirushi]

Hi,

A friend recently bought a BSA Standard Pattern.
The gun turned out not to have a piston seal
Wouter bought a new leather piston seal from Knibbs.
It didn't fit first. Without reducing the diameter, he squeezed it in really tight and turned the piston around in de cylinder with a drill.
It now fits.
The tap doesn't appear to leak.
But... power is low; 5.9 ft/lbs with 15.89 gr JSB 5.52 mm
I advised to try H&N 5.55 mm; power is even lower with this pellet.
The gun has a new spring, also from Knibbs, apparently for BSA Standard.

Please may I ask some questions on Wouter's behalf:

1. what is "normal" power for these? I thought they should do legal limit quite easily?

2. my feeling says that the piston seal isn't right. Probably too tight, even though the leather will have compressed by now.
Do these piston seals need sanding down? And is neatsfoot oil really the best oil to use? Any good alternatives?

3. any recommendations for the best spring to use?

4. any recommendations for the best pellets to use?

Many thanks, Louis

[DCL_dave]

Hi Louis,

Sorry can't help with most of you questions...but, if a leather cup seal is too tight to begin with it becomes a brake under pressure/load, effectively robbing the gun of power. If you have no other way you can size the seal by mounting it on a bolt with washers and a nut and spinning it in a drill whilst sanding it down to a uniform sliding fit in the cylinder, don't rush it though, take a little off at a time and test for a nice easy sliding fit, once it is sized correctly, then oil it with neatsfoot and fit to piston.

HTH,
Dave

[jirushi]

Hi Louis,

Sorry can't help with most of you questions...but, if a leather cup seal is too tight to begin with it becomes a brake under pressure/load, effectively robbing the gun of power. If you have no other way you can size the seal by mounting it on a bolt with washers and a nut and spinning it in a drill whilst sanding it down to a uniform sliding fit in the cylinder, don't rush it though, take a little off at a time and test for a nice easy sliding fit, once it is sized correctly, then oil it with neatsfoot and fit to piston.

HTH,
Dave

Thank you Dave, much appreciated.
I have passed on your advice to my friend; he will reduce the diameter of the piston seal this afternoon, carefully, and he can't wait to see the results.
He doesn't have neatsfoot oil, but I see that it is for sale at horse shops here in Holland.

Does someone know: is the benefit of neatsfoot oil that it diesels less, or not at all?
Compared with for instance Ballistol.

Cheers, Louis

[Josie & John]

Hi Louis,

I have found that most washers, springs and parts from Knibbs do require fitting. Protek replacements are usually closer fitting and I have used Meteor Mk 6 or cut down Airsporter springs in the past.

Kind regards,

John

[jirushi]

Hi Louis,

I have found that most washers, springs and parts from Knibbs do require fitting. Protek replacements are usually closer fitting and I have used Meteor Mk 6 or cut down Airsporter springs in the past.

Kind regards,

John

Thank you John, that's good to know!
Cheers, Louis

[Jerry Cornelius]

Hi Louis,

I have found that most washers, springs and parts from Knibbs do require fitting. Protek replacements are usually closer fitting and I have used Meteor Mk 6 or cut down Airsporter springs in the past.

Kind regards,

John

Likewise. In fact with knibbs parts I am usually reminded of the definition of traditional British craftsmanship, “ the ability to make two parts that don’t fit, fit”.

(Everyone else just makes parts that fit in the first place)

[jirushi]

Likewise. In fact with knibbs parts I am usually reminded of the definition of traditional British craftsmanship, “ the ability to make two parts that don’t fit, fit”.

(Everyone else just makes parts that fit in the first place)

I shall remember that! The ability to make two parts that don't fit, fit.

I was trying very hard not to write this, but here it is: I stopped buying from Mr Knibbs Esquire a while ago, due to continuous problems with their parts. It almost always cost me time and money to make them fit LOL. Indeed, better products from Protek.

[Jerry Cornelius]

I shall remember that! The ability to make two parts that don't fit, fit.

I was trying very hard not to write this, but here it is: I stopped buying from Mr Knibbs Esquire a while ago, due to continuous problems with their parts. It almost always cost me time and money to make them fit LOL. Indeed, better products from Protek.

I don’t think I have ever had anything from them that didn’t need something doing to it

In fairness, after the application of the traditional British craftsmanship, I have always been able to use their parts. On occasion i have found myself thinking it would have been just as easy to make it myself though.

[jirushi]

Traditional British craftsmanship; I must practice!
However, a lot can be done with some diamond files, a small hammer, and a sixpack of Leffe!

Some news from Wouter:
after reducing the size of the leather piston seal, as kindly recommended above, velocity went up from 440 to 490 ft/s.
Not bad. Not good enough though, imo. Also, Wouter now describes the gun as twangy.
I recommended to drink a 500 ml Bavaria beer (absolute cowpiss, but it comes in a steel can) and use that for a piston sleeve. Perhaps not the most durable solution, but it worked in my Meteor.

Could his spring be too long/strong? Is there something like an oversprung gun giving less power than when a shorter, correct spring is fitted?

Also, he hasn't used neatsfoot oil yet. Perhaps that will up power; yes, it must make the leather softer, and thereby increase its sealing capacity.
I think

[Garvin]

Traditional British craftsmanship; I must practice!
However, a lot can be done with some diamond files, a small hammer, and a sixpack of Leffe!

Some news from Wouter:
after reducing the size of the leather piston seal, as kindly recommended above, velocity went up from 440 to 490 ft/s.
Not bad. Not good enough though, imo. Also, Wouter now describes the gun as twangy.
I recommended to drink a 500 ml Bavaria beer (absolute cowpiss, but it comes in a steel can) and use that for a piston sleeve. Perhaps not the most durable solution, but it worked in my Meteor.

Could his spring be too long/strong? Is there something like an oversprung gun giving less power than when a shorter, correct spring is fitted?

Also, he hasn't used neatsfoot oil yet. Perhaps that will up power; yes, it must make the leather softer, and thereby increase its sealing capacity.
I think

I think it was Ed who once said that the seal size was the right when the piston would drop slowly in the cylinder under its own weight (and the force of gravity) and stop when you put a finger over the transfer port (ie closed the BSA's loading tap). When the compressed spring is released, obviously the piston seal opens up parachute-style to form an air seal...

[junglie]

Thank you Dave, much appreciated.
I have passed on your advice to my friend; he will reduce the diameter of the piston seal this afternoon, carefully, and he can't wait to see the results.
He doesn't have neatsfoot oil, but I see that it is for sale at horse shops here in Holland.

Does someone know: is the benefit of neatsfoot oil that it diesels less, or not at all?
Compared with for instance Ballistol.

Cheers, Louis

hempseed oil works very well i found & very nice on salads too. As for the knibbs seal if it's anything like the rock hard grey/greenish "leather"seal i got from chambers he'd be better off making his own from an old leather belt as i was.......theres a post on here on how to do it & form them into a cup shape with a jubliee clip.

[edbear2]

Looking at the simplified pivot on the cocking arm, this is a late gun which will have the extended skirt patent piston, I have found these top out in the high 10's compared to the earlier 45 guns which can go full power, the later guns have a smaller swept volume as per this photo as the latch rod is slightly longer (45 inch sporting is second from bottom).

https://www.flickr.com/photos/312284...-6vbwPf-5DJfux

Pellet wise, you could try superdomes out of the modern ones or Hobbies even, they do tend to like "shorter" pellets I have found, obviously Wasps and Webleys are getting hard to find now, FTT's in 5.54 worked well in one of mine, another did not like them, so a case of experimenting.

As for the oil I use air tool oil and shoot the first shots slowly to allow the excess to disperse and avoid dieseling, that's my preference, others have their own personal opinion, I just grew up with mineral oils and if used sparingly they are fine for me anyhow.

Piston sizing and max power with leather seals will occur after 500-1000 shots of running in, you can speed this up by sanding the dry piston a bit as mentioned so it is a light sliding fit.

Leather seals take some patience, we have all become accustomed to modern synthectic ones that are pretty much at perfect performance if sized correctly

ATB, Ed

[jirushi]

hempseed oil works very well i found & very nice on salads too. As for the knibbs seal if it's anything like the rock hard grey/greenish "leather"seal i got from chambers he'd be better off making his own from an old leather belt as i was.......theres a post on here on how to do it & form them into a cup shape with a jubliee clip.

Thank you junglie, that's a good tip! I remember tasting hempseed oil in a salad; very nice. The Knibbs seal looks like "normal" leather. Learning how to make these myself, would be great. Another thing to add to the list!

[jirushi]

Looking at the simplified pivot on the cocking arm, this is a late gun which will have the extended skirt patent piston, I have found these top out in the high 10's campared to the earlier 45 guns which can go full power, the later guns have a smaller swept volume as per this photo as the latch rod is slightly longer (45 inch sporting is second from bottom).

https://www.flickr.com/photos/312284...-6vbwPf-5DJfux

Pellet wise, you could try superdomes out of the modern ones or Hobbies even, they do tend to like "shorter" pellets I have found, obviously Wasps and Webleys are getting hard to find now, FTT's in 5.54 worked well in one of mine, another did not like them, so a case of experimenting.

As for the oil I use air tool oil and shoot the first shots slowly to allow the excess to disperse and avoid dieseling, that's my preference, others have their own personal opinion, I just grew up with mineral oils and if used sparingly they are fine for me anyhow.

Piston sizing and max power with leather seals will occur after 500-1000 shots of running in, you can speed this up by sanding the dry piston a bit as mentioned so it is a light sliding fit.

Leather seals take some patience, we have all become accustomed to modern synthectic ones that are pretty much at perfect performance if sized correctly

ATB, Ed

Thank you Ed for your very informative reply.
That is very interesting.
Wouter will do lots of shooting and he might see power go up. He has tried a few different springs, which all gave approximately the same power. But one of the springs was smoother than the others, so that's in the gun now.
Have a nice weekend, Louis

[edbear2]

Thank you Ed for your very informative reply.
That is very interesting.
Wouter will do lots of shooting and he might see power go up. He has tried a few different springs, which all gave approximately the same power. But one of the springs was smoother than the others, so that's in the gun now.
Have a nice weekend, Louis

Have you checked for leaks at the tap too? Cock rifle, open tap, hold cocking lever open to rear as if cocking again.

Take a good hold of the cocking lever as if you are de-cocking........pull trigger with free hand and feel what happens, a really good seal will mean the cocking arm will stay way back and hardly move even if you let go, and you can very carefully and slowly open the tap and the cocking lever will slowly return forward when a loading tap is in perfect condition.

Sometimes you will get a gun where you can wait several mins as the cocking lever slowly inches forward, I had a Webley MK3 like this recently!

This is rare though, but you do want some sign of resistance or a slight whistle and slowing on the piston going forward to show the tap is not leaking badly.

It maybe worth taking off the tap cover plate (the tap should open and close with a pronounced resistance or slight click if the small spring and plunger are in good order)........and checking the spring and plunger, you can carefully stretch the springs a bit if needed.


Clean everything and grease the tap taper, and the tap cover plate track lightly, and make sure the plate screws are snug too.


The tap should open and especially close with a pronounced resistance / soft "click" as they did when new, I am lucky to have had / have a couple of very little used guns, and they all have this feature (obviously all Improved or Standard types with the spring plunger system).

Video of what a good one should look / sound like here;

https://www.flickr.com/photos/312284...posted-public/

Every little helps.

ATB, Ed