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Author Topic: Bsa's quality machining at it's finest  (Read 4278 times)

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Longbow Nick

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Bsa's quality machining at it's finest
« on: April 15, 2016, 02:08:26 PM »

Working on an on going project at the moment and it's a good job that I'm doing a barrel chop anyway. As when stripping the rifle down, I noticed straight away how off centre the transfer port had been machined. Surely the quality control at the bsa factory ain't like it used to be.



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arron yeates

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Re: Bsa's quality machining at it's finest
« Reply #1 on: April 15, 2016, 02:13:43 PM »

Could you no complain about this and get a new barrel?
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #2 on: April 15, 2016, 03:46:17 PM »

Doubt it. As the gun has been opened. They like to protect their chimp like engineering skills. From bitter experience I have learnt the guarantee is pointless as they will either break your gun again or return it in the same condition. Think of it as a collection of parts that can be made into a good gun  by xtx rancid or some other skilled person. Doubt that's the roughest part of the gun, just the worst bit you've found so far. Any one from bsa on  the site like to contest this?
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Longbow Nick

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Re: Bsa's quality machining at it's finest
« Reply #3 on: April 15, 2016, 08:16:07 PM »

Doubt it. As the gun has been opened. They like to protect their chimp like engineering skills. From bitter experience I have learnt the guarantee is pointless as they will either break your gun again or return it in the same condition. Think of it as a collection of parts that can be made into a good gun  by xtx rancid or some other skilled person. Doubt that's the roughest part of the gun, just the worst bit you've found so far. Any one from bsa on  the site like to contest this?

Think you have summed it all up in one there. Re: chimp like engineering skills. :hee20hee20hee:
Three or four years ago. I stripped my R10, as the FPS variation was all over the place. I was shocked to find out how unclean the internals were, which resembled the swarf contents of bsa's shop floor.

In the end I blueprinted the R10 myself along with a barrel and shroud chop and a few tweaks here and there.
End result was that I had a rifle that shot like clockwork with a FPS variation of under 5 FPS over a 50 string chrono.
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ultra stu

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Re: Bsa's quality machining at it's finest
« Reply #4 on: April 15, 2016, 09:42:34 PM »

I have to agree the machining Marks are poor but it looks central to me .?
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Longbow Nick

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Re: Bsa's quality machining at it's finest
« Reply #5 on: April 15, 2016, 10:22:19 PM »

I have to agree the machining Marks are poor but it looks central to me .?

Yes machine marks are of poor quality, the bore of the barrel is central.
The transfer port hasn't been drilled central to the barrel and is well off to one side. The drill bit shank is a snug fit in the transfer port, which shows how pissed bsa were when they drilled this.
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ultra stu

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Re: Bsa's quality machining at it's finest
« Reply #6 on: April 15, 2016, 10:33:42 PM »

Oh i see .
Yep it is pissed .
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Carpace1

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Re: Bsa's quality machining at it's finest
« Reply #7 on: April 15, 2016, 10:36:23 PM »

Its clearly shoddy work &way off centre!!i would insist on a replacement!!
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Longbow Nick

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Re: Bsa's quality machining at it's finest
« Reply #8 on: April 15, 2016, 10:47:20 PM »

Its clearly shoddy work &way off centre!!i would insist on a replacement!!

Might be a bit difficult that one, if bsa want the complete barrel back. I've already parted off this section of barrel and the rifle is a few years old and is secondhand to me.
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #9 on: April 15, 2016, 10:57:21 PM »

Not really knowing much engineering stuff but the hole looks roughly finished central or not rough surfaces and fast efficient air passage are not compatible basic physics even electricians can work that out.
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RANCiDTOM

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Re: Bsa's quality machining at it's finest
« Reply #10 on: April 15, 2016, 11:04:10 PM »

Actually smooth surfaces especially highly polished ones are worse for airflow than slightly rough ones, smooth surfaces cause "skin effect" which can reduce the effective diameter of a port. Physics is full of contradictions, so is engineering. Air flow, fluid dynamics and particularly "unsteady gas flow dynamics" are a science in themselves and things get really tricky when we try to push gas down holes at sonic or transonic speeds.
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Carpace1

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Re: Bsa's quality machining at it's finest
« Reply #11 on: April 15, 2016, 11:35:49 PM »

Turbulance springs to mind though with a rough surface.
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RANCiDTOM

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Re: Bsa's quality machining at it's finest
« Reply #12 on: April 15, 2016, 11:41:48 PM »

Turbulent flow is not necessarily a bad thing, it can flow more air through a port or tube than one which has smooth walls and a slow/immobile skin layer of gas. Having spent many decades tuning 2 stroke engines and building exhaust pipes for them I have a lot of experience getting volumes of gas to travel through ports and pressure waves to propogate along exhausts which cause gas to move at supersonic speeds when employed correctly.
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #13 on: April 15, 2016, 11:46:59 PM »

Is this like boundary layer stuff?
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Carpace1

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Re: Bsa's quality machining at it's finest
« Reply #14 on: April 15, 2016, 11:55:40 PM »

Appreciate your skills rt,it jst goes through my mind that a "rough"surface would slow the airflow down??...so if not what would be the ideal surface for a transfer port??
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ultra stu

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Re: Bsa's quality machining at it's finest
« Reply #15 on: April 16, 2016, 12:09:52 AM »

A shark has a "  rough"  surface to its body .this is to trap water in the indentations and allows the shark to slip through the water faster .swimmers have suits the same .
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RANCiDTOM

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Re: Bsa's quality machining at it's finest
« Reply #16 on: April 16, 2016, 12:15:05 AM »

Golf balls!
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #17 on: April 16, 2016, 12:28:33 AM »

Would smooth be worse than the op,s picture?  No need to swear Tom.
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RANCiDTOM

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Re: Bsa's quality machining at it's finest
« Reply #18 on: April 16, 2016, 12:40:06 AM »

For best results (from my experience) in small holes 3-10mm diam a 320-400 grit finish is pretty much the optimum for gas flow. Any smoother and the skin or boundary layer will actually be thick enough to reduce the effective diam of the tube.
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arron yeates

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Re: Bsa's quality machining at it's finest
« Reply #19 on: April 16, 2016, 08:38:20 AM »

Very interesting topic this.
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #20 on: April 16, 2016, 10:15:30 AM »

RT I'm assuming this is mostly about efficiency?  Using less air for a given power/speed. What's the difference between a good one and the one pictured  10%?  3%?  I appreciate it probably gives you a headache to think down to my level ;-).
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Longbow Nick

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Re: Bsa's quality machining at it's finest
« Reply #21 on: April 16, 2016, 10:38:55 AM »

Am with RT on this one.  How many people back in there boy racer days actually did more harm then good on polishing and porting there own cylinder heads and gained nothing out of it.
Like as with inlet manifolds or cylinder heads, a good clean up of all casting flash and irregularities with a fairly textured finished with say 60-100 grit paper seems to do the job. Rough texturing port surfaces with a rough carbide burr will be enough to see HP gains alone. Polish them smooth and you will lose that gained HP.

Now back on subject, you reckon bsa will own upto there chimp like engineering skill. :hee20hee20hee:
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #22 on: April 16, 2016, 11:02:44 AM »

No chance.
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RANCiDTOM

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Re: Bsa's quality machining at it's finest
« Reply #23 on: April 16, 2016, 02:03:09 PM »

BSA can't even be bothered to use a new tool tip (hence the torn and scraped finish on the end of the barrel). Would they admit to bad QC? Have they ever?
As regards what to expect from correct surface finish in tubes and ports that flow gas if we had a really rough drilled transfer port that was drilled with a blunt drill producing a scored and "barreled" hole it won't flow gas as efficiently as a smooth finish (drilled with a sharp drill run at correct speed and feed) parallel hole. If the hole is reamed and has a surface finish approx equivalent to 400 grit emery finish we will get even better flow, but finer polishing such as lapping to 600 grit or finer (many people assume the word "polish" must mean a mirror finish so they get the "T Cut" out which gives approx 8000 grit finish) will cause the skin effect or boundary layer to become significant. One method of preventing this is to taper the hole, slightly reducing the diam over the length of a transfer port will make it flow much better even if the inish is rougher than 320 grit.
It's very hard to say in percentages what the efficiency difference may be but in some guns when we are trying to get them to push a pellet at 950+fps they just won't do it with smooth and mirror polished ports, simply roughening and tapering correctly can bring a gun MV from 850 up to 950 fps. It can mean that big a difference.
In an engine if you can speed up gas pressure wave propogation you can make them produce perhaps 20-30% more BHP on the dyno if you optimise the fueling, valve and ignition timing to make use of the faster pressure wave propogation. In an engine the gas flow is initiated or stopped and can even be reversed by a pressure wave, knowing how the pressure waves can be reflected, inverted or magnified can make these huge differences. Much the same can be said with the flow of air in a PCP and also through the transfer port of a spring gun. As we can easily demonstrate simply by making different diam, finish and taper on transfer ports for PCP's we have a bit more difficulty with a spring gun but the spring gun also has to deal with the fact that the transfer port gas flow is at massively higher temp than in a PCP, springers will heat the air in the cylinder as it is compressed, if the transfer port is correctly designed and sized gas temp will be at a few hundred degrees above ambient rather than in a PCP where we find the temp of the expanding air will actually be below ambient temp. This makes a huge difference in the speed of pressure wave propogation which can help or hinder exhaust valve closing which is the main cause of inefficient air use in a PCP.
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bishopp1

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Re: Bsa's quality machining at it's finest
« Reply #24 on: April 16, 2016, 03:53:35 PM »

Devils in the details as usual thanks
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SparkUK

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Re: Bsa's quality machining at it's finest
« Reply #25 on: July 27, 2016, 12:32:31 AM »

That really is miles off, did it line up though? ie was everything else symathetically crooked?
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johnbaz

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Re: Bsa's quality machining at it's finest
« Reply #26 on: August 01, 2016, 08:35:56 PM »

Is the OP's rifle an old Brit Beesa or a Spanish one??


John..
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Re: Bsa's quality machining at it's finest
« Reply #27 on: August 01, 2016, 09:51:21 PM »

Is the OP's rifle an old Brit Beesa or a Spanish one??


John..

They don't make BSA PCPs in Spain.
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johnbaz

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Re: Bsa's quality machining at it's finest
« Reply #28 on: August 01, 2016, 11:34:06 PM »

They don't make BSA PCPs in Spain.
Doh!!

I wasn't thinking straight! I thought he meant a loading tap!!  :57:

Thought he was talking about a springer!!  :wink:


John  :sign0087:
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