So... sometimes you have one of these siting in your parts bin, you'd like to install it, but your M305 receiver looks so... neutered... or is it half-finished? Hard to say.
But then you think... wait a minute. We have the technology. We have a knee mill, a 45 degree bevel carbide surface plane, a big honking vise and an orphan M305 receiver. We also have the LBR M14 receiver drawing... Hmm...
In case anyone is wondering about M305 receiver steel - this is a 50 thou cut to take the wall thickness from .165" down to .115". The steel stayed almost glass hard all the way through the cut, and after milling would still skate a file. It sqealed like a pig... even with cutting oil. But this is a big honkin knee mill and high-end carbide tooling. It bent to my will...
Of course, then you need to clean it up a little.
And you still want it to lok a little more GI, so of course you copy the GI M14 drawing to square the bottom of the rail ledge up to the receiver legs. In this case, a cobalt end mill was used and then final finishing with paper wrapped around a file. Also a very hard piece of receiver steel.
And there you have it. The receiver heel now lines up with the connector bar cutout in a GI fibreglass stock. No overhang necessitating the cutout to be filled with bedding material.
To be perfect, I'd also mill the op rod rail narrower, but the Norinco rail actually supports the op rod better. I still haven't decided if I'll mill it down yet or not.
The receiver heel is going to get laser engraved, and the narrower heel looks a lot more authentic with GI-like markings.
Before anyone asks - NO - I do not do this for people. It's too much work to be profitable. Not shown is all the file work on the back of the heel to re-establish the proper contour radius. But I still thought you guys might find this interesting or informative.
I suspect it's about 60 to 90 minutes of work to do one of these if the barrelled receiver is already stripped. This includes setup and recontouring the back of the heel.
I prefer to remove the barrel, it's easier to fix in the mill that way, but that adds another few minutes to the job.
Literally, for a skilled machinist, that's about $100 worth of labor - not many ppl would pay that for a cosmetic change. Add in a park job, and you can see how it adds up. Someone doing this for profit would also have to account for tool wear. I expect the end mills and inserts would wear out every 3 or 4 receivers given how hard the metal is on these.
So probably another $40 per job to cover tool wear.
You get the idea.
But then you think... wait a minute. We have the technology. We have a knee mill, a 45 degree bevel carbide surface plane, a big honking vise and an orphan M305 receiver. We also have the LBR M14 receiver drawing... Hmm...
In case anyone is wondering about M305 receiver steel - this is a 50 thou cut to take the wall thickness from .165" down to .115". The steel stayed almost glass hard all the way through the cut, and after milling would still skate a file. It sqealed like a pig... even with cutting oil. But this is a big honkin knee mill and high-end carbide tooling. It bent to my will...
Of course, then you need to clean it up a little.
And you still want it to lok a little more GI, so of course you copy the GI M14 drawing to square the bottom of the rail ledge up to the receiver legs. In this case, a cobalt end mill was used and then final finishing with paper wrapped around a file. Also a very hard piece of receiver steel.
And there you have it. The receiver heel now lines up with the connector bar cutout in a GI fibreglass stock. No overhang necessitating the cutout to be filled with bedding material.
To be perfect, I'd also mill the op rod rail narrower, but the Norinco rail actually supports the op rod better. I still haven't decided if I'll mill it down yet or not.
The receiver heel is going to get laser engraved, and the narrower heel looks a lot more authentic with GI-like markings.
Before anyone asks - NO - I do not do this for people. It's too much work to be profitable. Not shown is all the file work on the back of the heel to re-establish the proper contour radius. But I still thought you guys might find this interesting or informative.
I suspect it's about 60 to 90 minutes of work to do one of these if the barrelled receiver is already stripped. This includes setup and recontouring the back of the heel.
I prefer to remove the barrel, it's easier to fix in the mill that way, but that adds another few minutes to the job.
Literally, for a skilled machinist, that's about $100 worth of labor - not many ppl would pay that for a cosmetic change. Add in a park job, and you can see how it adds up. Someone doing this for profit would also have to account for tool wear. I expect the end mills and inserts would wear out every 3 or 4 receivers given how hard the metal is on these.
So probably another $40 per job to cover tool wear.
You get the idea.
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