SMK QB78 Servicing

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The SMK QB78 is generally in very good condition. But it was a second hand rifle and I did not know it’s history. So as a matter of course I replacied all the seals and o rings.

In fact I upgraded it with tuning parts from T R Robb, This rifle didn’t need re-bluing or the stock worked on excessively There are a couple of indents rather than scratches in the stock, but being a Chinese gun I can live with these.

The parts have arrived but as can be seen I have not even opened them yet. I have various other priorities at the moment , but I will get round to it in due course. I have also bought a second tuning kit for the TH78 which has yet to be fitted. I was pretty disappointed with the TH78 out of the box performance wise So I will give that rifle the same treatment that the QB78 has had. Probably including plating it.,

There is a special tool needed for stripping it down (bottom picture), Which has been used many timesย  so has been a worthwhile investment.

The adapter so that I can use the larger CO2 cartridge, or even air directly from the pump, a dowdy seal and quick fill adapter (top right). Don’t need the dowdy seal, but it comes with the fast fill valve.

Using air it is limited to 960ils which is quite low and apparently does not give that many shots,(around 20) but this is OKl for testing and at that pressure it does not take many pumps to fill it either.

Other than that I also have a new end cap (top Left) and a new safety follower (top, second from left.) Added to that I also have the tuning kit (Top second from right. )All arrived on 12/12/2016.

The old end cap is brass plated in an attempt to match with the contrasting parts of the Rifle, This was no easier or harder than the plating on the Falcon though, It is made of steel, but it is knurled and has been damaged in the past presumably with a pair of pliers, or a mole wrench .I plated a base coat with Replica Chrome and then Brass plated on top of it. It will do for now I may have better results gold plating the stainless steel replacements though.

 

The end caps, stock nut and the Quick fill and adapter have all been gold plated. Some of the other parts I have given a thin plate of nickel to prevent them from going rusty. I didl however polish them before greasing them and fitting them to the gun.

No tuning is ever going to be cheap, it cost about ยฃ50 for the tuning kit

I had a good excuse to rework the rear of my stand as this it just a bit to far back for the QB78 which actually rests on the front of the cylinder rather then the stock. The modifications were more extensive that I thought they would be, but it is now done.

I fitted an adaptor to the rifle which allows it to be used as a PCP or use the large Gas canisters. I used air to test it and it seems to be holding its charge. Though it is limited to 950 lbs. I was suspicious of the adaptor as it seemed to use a fibre washer instead of an o ring, but it seems to work OK.

The safety catch broke due to crap manufacture. To get a new one would require I get a completely new trigger mechanism. I am watching a second hand trigger assembly on ebay, but failing that I will improvise my own safety catch. Trying to repair the old catch I bent it and it now no longer fits in the gun.

I do not think

a I could straighten it out sufficiently to use it again.

b. Even if I could straighten it out sufficiently to fit back in the rifle, the handle is not to be trusted

This was the mk II version of the new safety catch I made which worked well and is what the final version was based on.The lever was a bit to long on this version, but at that point I had already decided I was going to make it out of Brass, so did not bother to trim it down,

I made a new safety catch which works well is smooth should not fall apart and I think it looks better than the original. his was the Mk III version though I made 2 previous catches out of mild steel. but they were very different designs and they all worked well. Helped I think by the modified safety follower made by T R Robb as the shape is better and smother. I have since though shortened the lever, but it can be flicked off easily with the trigger finger.