Mark I lower blueprints?

[Grizzlypeg]

Does anyone have a blueprint or specs for the overall length of a Mark I lower? I need a accurate measuring point for determining how long it should be when sectioned back together.

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Brit plumber]

I've not got a blue print but I can measure mine if you want. How many sections is cut into?

[Grizzlypeg]

It's cut into two pieces. The cut is at the rear very close to the butt stock, just forward of the pin. It might be a cut only the width of a torch wide, or the two pieces might not even belong together. I'd hate to cause it not to line up with some other point if its slightly too long or short.

[stencollector]

99% chance that your two pieces did not belong together. The original source of your parts kit had all the pieces mixed. That is why sometimes you can have them overlapping, and sometimes you wil be missing an inch of material.

Easiest way to do it is to position the back portion of the lower square and flush with the back of the upper receiver. Then place the front half of the lower to a position where the change lever hole falls right underneath the S marking.
Use the upper receiver as a jig initially and weld the bottom and a portion of the sides. Remove the lower and finish the welding. Dress the area, especially the rails which slide into the upper. You will need to dress the internal area as well if you are going to fit the gun with a piston group, as it will jam up on any excessively raised portion.

There will be some distortion, so the lower will likely have to be heated up again in the area of the welds and bent in order to fit into the upper.

All that said, I usually wait until the upper is done first. That way, you can use the forward portion of the lower as a jig to hold the two parts of the upper in place during welding. The forward portion of the lower has to be slid in further than it would normally sit.

I have done more than a few of these parts kits into dewats with very good success. Let your parts cool after welding rather than quenching them, otherwise you will mess with the metallurgy and it will not accept the bluing in the areas you have repaired.

[Peter Laidler]

I realise that it's not strictly relevant to this thread but as Armourers, we never really understood why the butt slide assembly was serially numbered to the gun. They all fitted each other pretty well, from the very first to the last - variations excepted of course, but they still fitted. Talking of which, we had a programme running in the machine shop at Aldershot main workshops of converting plentiful surplus Mk2 butt slides to Mk3 spec (machining the height of the side walls down).

The only REAL sensible reason for numbering a butt slide that any Armourer came up with was that for overhead fire (OHF) from tripods, the tripod mounting holes were gauged and certified so as to prevent any slop but generally speaking, the calibrated/certified OHF guns were marked with 'OHF' on the butt in white paint in any case!

[tankhunter]

]I realise that it's not strictly relevant to this thread but as Armourers, we never really understood why the butt slide assembly was serially numbered to the gun[/B]. They all fitted each other pretty well, from the very first to the last - variations excepted of course, but they still fitted. Talking of which, we had a programme running in the machine shop at Aldershot main workshops of converting plentiful surplus Mk2 butt slides to Mk3 spec (machining the height of the side walls down).

The only REAL sensible reason for numbering a butt slide that any Armourer came up with was that for overhead fire (OHF) from tripods, the tripod mounting holes were gauged and certified so as to prevent any slop but generally speaking, the calibrated/certified OHF guns were marked with 'OHF' on the butt in white paint in any case!

Peter, You know what it's like at Workshops. There are a HUGE amount of Civvies employed at these establishments. All this extra & really unnessacary numbering, kept the engraving shop in gainfull empolyment!
ANY extra work was appriciated, as when it came to finacial review time. All the paperwork 'Traffic' & registers of work completed. Justified thier existance & argument for keeping the shop on when budget cuts came along. You couldnt blame them really I suppose, Most were Guys with mortages & families to support! Just my own observations & expirience when at 27 Command Wksps!

[Peter Laidler]

VERY true Tankie........ but when the cuts DID come, they struck with a vengeance. These huge places are a shadow of their former selves. Mind you, it takes you back to the days of OHF with Brens/L4's doesn't it! I 'transferred' the old Taylor Hobson engraving machine from 27 Command.......

[tankhunter]

VERY true Tankie........ but when the cuts DID come, they struck with a vengeance. These huge places are a shadow of their former selves. Mind you, it takes you back to the days of OHF with Brens/L4's doesn't it! I 'transferred' the old Taylor Hobson engraving machine from 27 Command.......

Peter, The more I hear these days about cuts in the .M.O.D & the consequent pressure imposed upon our Service Personell. The more it sadens me, gone are the 'Halcyon Days' of our Era unfortunately! It's ALL about bean counters & 'Streamlining' of procedures & reduction of this & that Etc. You are a Lucky Begger getting that engraving Machine! I am scouring Ebay constantly for a dencently priced Gravograph version!
Still, its interesting to see some long entrenched customs havent died out. Saving Pennies, & Wasting Thousands!................LOL!

[Grizzlypeg]

The idea of lining up the selector switch with the markings on the upper receiver seems like a good one. When I do so, there is a gap of up to 3/8" on the sides of the lower receiver pieces. I see photo's of a dewatt that was welded back together and he probably just closed the gap, because the hole for the selector switch doesn't come close to middle marking. Probably doesn't matter on a welded up dewatt, but I'll fill the gap and make it proper.

[stencollector]

3/8 of an inch is pretty reasonable. You should be able to fill that in with gas weld, and then reshape it. At that location of the gun, a rotary file on an air tool or even in a drill press will work well. You only need a sanding disc on an angle grinder for the bottom.

Do the weld with the lower slid into the upper, and the back of the lower angled slightly downwards. When you remove the lower, and then weld up the rails portion, the back tends to shift forward and then not fit into the upper. You will likely have to heat the lower red to shape it to fit back in, but sometimes they slip right back in.

Good luck.