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Hi Guys,
I was very excited to receive these bad-boys today.
They are "prefit's" (read minor fitting required) for the No1Mk111 standard profile, No1 Mk111 (Lithgow) heavy profile, No4 .303 and No4 7.62.
The .303 barrels have been custom made to a major bore diameter of .311, they are fully chambered, timed with some additional underturn, and they have the extractor cutout made.
There's no shortage either!
Now that's a pile of barrels!
Don't tease. How much, and can you export to UK?
I see that they have the little "adjustment collar" at the rear of the tenon. Very crafty.
Your next task, should you choose to accept it, is to build a few "body gauges" so that gun-plumbers are not trying to re-barrel "flogged-out" receiver bodies. You could "rent" them to "approved" workshops or something.
"Gauging" the bolt bodies is a bit simpler, just start with a granite plate and a good height gauge, neither of which are likely to be found in your corner gun shop.
I've done a little bit of barrel swapping (No1) and found the first stumbling block you can face is stretched threads in both the receivers and the pull off barrels. Some combinations just will not index without shims, and then, unless the receiver has very little wear, you can struggle to find a bolt head to get to spec.
Starting with new made barrels should about halve that problem, but I'm with Bruce in Oz WRT needing some way to check the receiver for stretch and locking lugs wear. If there is an inspection bolt or two among the members here, I wonder if a suitable gauge could be made from the measurements.
Am I reading too much into this?
BinO and Son are DEAD right..... There will be some who will ignore the bleedin obvious and rebarrel a totally worn out body. That'll be a body that wouldn't CHS with any size 3 bolthead on an inspectors calibrated bolt body originally. But breech up now with a new barrel adjusted to a 0 bolt head.
It's not body stretch that concerns me particularly for reasons I've mentioned before but the worn out/worn through locking lugs
One thing I did in working through the details of this project getting to the point where I was comfortable doing this first production was ensure that these barrels had to be set-up, not just "screwed in". The intention being that they had to be fitted by a gunsmith, with a lathe and a reamer. The lathe to adjust the timing as they have a very small amount of excessive underturn, and the reamer/lathe to adjust the final headspace.
There is no difference between how you set these up, and how you would set up a rebarrel from a blank, except in my product the vast bulk of the work if done in advance. In that sense it is a question for the gunsmith and the owner of the rifle to be rebarrelled as to whether a rifle is a viable rebarrel option. This is a decision made every time a rifle is rebarrelled by any gunsmith, not only when using semi-fitted blanks commonly referred to as "pre-fits", such as these.
It is a fact that not every individual action is perfectly safe, which is true of all makes and models, and that is something any shooter or gunsmith would be a fool to ignore.
...and there lies them problem. There was a process in service used to determine the remaining safe serviceable lifespan of a receiver. The gauging does not exist anymore other than in the hands of a couple of very fortunate collectors, not likely even known about by today's gubsmiths.
Just going off the top of my head but regarding the lack of gauges and as Son says probably a few in the hands of collectors, surely if a set of drawings can be had, (must be somewhere on the net or again a few fortunate collectors) then the only things required from the drawing are the datums and measurements to the locking lugs ?? with this information and armed with some sort of gauge then other factors can then be considered ?
So far as I recall, the body gauges were for the factory. When we rebarrelled at Field or Base workshop, then a No3 bolt head was NOT permitted. We also had a rack of new and gauged used but as-new barrels to select from for initial over/underturn. A No3 bolthead was not nor never an option at Field or Base workshop when rebarrelling. Only a No2 bolt head and if there was any doubt, then it was used with the Gauge Inspectors Bolt - a calibrated bolt kept by Robbie Robertson or Mr Saw (the Chinese Out-Inspector) in his oily gauge box. No CHS on a No2 head and the rifle was scrapped. Much more to it than that of course.
As a rule of thumb, this is what I'd be doing re new made barrels on used bodies. Examine body in minute detail. If you cannot CHS existing body/barrel on a No2 bolthead using the inspectors calibrated bolt then it indicates a worn body. And a new barrel ain't going to correct or cure a worn body so go no further. Would welcome further criticism - constructive or otherwise - as I'm just thinking on my feet here