The TDR - Take Down Rifle
Return to airguns
The idea was to build a compact gun that would break down and fit
into a brief case,
be accurate, consistent and close to the UK legal limit of 12 ft
lbs.
The gun was to be based on the Chinese QB79 - this is a standard example
Basic specification :- choked BSA barrel, longer bottom tube
to give a larger pre chamber, modified valve, regulator adjusted to
1200 PSI
(MTC Mamba Lite) Chinese Bi Pod , My
transfer port modification
The silencer fitted now has been printed from a 3d printer -
Designed and printed by Albert - Full
details of silencer here
This pic shows original stock - ok but a bit rough
A modified
AGS stock from ebay lots of work with the Dremal and drill but I
Think it
turned out OK. - New photo just after a DIY re blue.
Took a shot string at the club today, not a disaster but I think a
longer bottom tube will give a larger pre chamber which will help
with this
as the bottle pressure is dropping the regulator cannot keep
up - the reg is responding more slowly as the pressure
is dropping
a little more power would be nice as well - so will up the regulator
pressure.
The target is to get basically a flat line with little to no drop
off as the bottle pressure is dropping until the pressure has
dropped close to the regulated pressure. All guns tested using the Blue
Shot
Android application -
connected to the Combro Crono
30/09/13
Re visited today and fired a few more shots to get a feel of the
power curve - starting with a 2500 psi fill - (different scale )
I am convinced the drop off is due to the regulator not being able
to keep up as the main pressure is dropping off - the next step is a
larger pre chamber to test this.
Quite an even drop off really, still here are today's shots :-
31/12/13
Decided to revisit the regulator today, and thinking on decided to
up the output pressure, stripped down and adjusted to 1200 psi this
was done by adding some spare spring washers and some testing to get
the pressure setting as required, the idea is a short sharp puff of
air I think the higher pressure will improve the efficiency of the
gun.
Very much improved shot string - a couple of odd readings but these
were totally unsorted pellets so this may explain the odd high / low
readings
I continued shooting until the power dropped to sub 11 ft lbs - this
was on the 116th shot - very happy with this result considering 13
cu inch bottle 177 calibre and a very short barrel.
Very happy with the consistency / shot count now.
Fitted a neoprene (thin) cover over the bottle - the original was a
rolled up mouse mat and a bit to thick, this lifted my eye slightly
too high for perfect scope alignment, I bought a laptop slip
(Samsonite) for £2.99 seems a shame to cut it up, but it has made
the perfect cover for the bottle.
