Thread: BSA ultra SE
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Old 25th March 2016, 09:54 PM
cloverleaf cloverleaf is offline
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Join Date: Sep 2014
Location: Oxfordshire
Posts: 117

Originally Posted by Edwardsi View Post
Hi all, just thought that I would report back on some testing.
Purchased a combro b- 625 chronograph and pushed some pellets through this afternoon.
Filled the Ultra to 220 bar according to the gauge on the bottle.

First ten shots between 706 and 721 fps.
Shots 11 to 50 between 730 and 753 averaging 744 fps.
By my calculations, this shows the Ultra pushing 10.33 foot pounds, which is a little under power I guess.

How does this sound, to me this seems fairly flat in terms of power curve and with 40 fairly consistent shots shoul get through a HFT session?

As Simon says they're often a little under from the factory. Also, I've seen a number of warranty returns for low output (some as low as 2-3ftlb!) that have been resolved by a replacement exhaust valve.

The valve seals on a tapered seat which can cause it to deform radially at the seat, forming a ridge around the circumference of the valve. The valve head (c. 6.5mm dia) runs inside a pretty close-fitting restrictor (c.7.0mm bore) so any increase in effective valve head diameter harms flow.

My own .177 SE was doing around 11.1ftlb with Exacts when new, after removing a small ridge from the edge of the seating face at the valve (IIRC it had pushed the diameter out to maybe 6.6mm) increased the output slightly to around 11.3ftlb.

If you do have yours apart to reg it, it might we worth inspecting and measuring the before proceeding.

Tbh I think the SE is ripe for regging - the Huma reg is a nice solution since it just fits in place of the "body adaptor" and you can pretty much complete the conversion with off-the-shelf BSA (R10) bits - replacement off-the-shelf ports and striker components can be dropped in making a totally reversible conversion.

Another nice thing is that the reg sits downstream of the gauge, so the gauge reads cylinder pressure.

Of course performance can be improved further with some work on the striker and possibly porting
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