Milling service to cut an M1D barrel?

[ssgross]

I don't bother making anything level. I put a straight rod through the rear sight holes, and a straight rod on the gas cylinder flat. Torque until they are dead parallel.

I did the exercise in another thread, but since the topic is at hand, I'll do it again. The spec for alignment is +/- 20 minutes. With the front sight height spec .728-.005 and sight radius is 29.5, this translates to a max +/- 0.0042 of the front sight - which even the best eyeball can't see, but which gives not more than .522 MOA downrange. This means that, with a set of 24 inch alignment rods, your eyeball needs to detect a ~.070 difference at the rod tips to be within spec. or double that for 48 inch rods. It is challenging to get a longer front rod to sit flat on the front sight base, so there is likely a source of considerable slop there depending on how patient you are. I used to use the rod method with 2ft rods until I was gifted a badger jig set. It took some time to get that front rod balanced perfectly, the jig takes hardly any setup time at all. So I went back and checked my work on half a dozen re-barreling jobs I had done, as well as ~half dozen rifles with original barrels, with the jig and a machinist level with 90 second graduations. I found that with rods I averaged about 12MOA with eyeballs - best was 8 worst was 18. Of the originals, the best was 5 and worst was 11 MOA. The originals were almost always over target (past true) and I was always under target.
With the jig and a good level, it is pretty easy to get <1MOA every time. While it will make some sleep better at night, given my first sentence if your eyeball can detect .070, you will be within half a click of true, or 1 click if you have the NM knob installed.

EDIT: When using rods - I found it helps immensely to put a sheet of plain white poster board behind your setup.

[1903Collector]

Well...OK, I think I can afford that! :-) Hope I dont have to order from Canada...Trump will be ****ed at me! :-P

[browningautorifle]

Trump will be ****ed at me!

What can he do, cut your hair and make you join the Army? Let us know how this goes...worst case I can box my angle meter up and mail it. Gift...doubt I'll do any more of them any way. One old guy to another...

[1903Collector]

Hey, Id go USAF as long as they let me fly again...and I just got my hair cut yesterday...military high and tight (like Harrison Ford in Enders Game...I even look a little like him...Im in better physical shape but absolutely no talent nor camera presence). My Dad di, could have been a movie star! My Dad and Grandfather were both USAF pilot war vets and retired as Lt. Col Ret., but I didnt make a career of it like them.
Seriously though, I VERY much appreciate your offer, but I will buy one here in Texas. :-)

[browningautorifle]

Id go USAF as long as they let me fly again

I was army, Infantry and am glad not to be on cold miserable days...snowy or freezing. I couldn't take it any more, wouldn't be able to stand it. Too broke down from doing it when I could...

[Sapper740]

I was army, Infantry and am glad not to be on cold miserable days...snowy or freezing. I couldn't take it any more, wouldn't be able to stand it. Too broke down from doing it when I could...

The unofficial motto for the Engineer's school at Chilliwack was "if it ain't rainin', we ain't trainin'!" Fortunately our training was never curtailed due to lack of rain.

[browningautorifle]

lack of rain.

No lack in the Lindsay Valley...or OPSEE training area. Or the heat of summer.

[Embalmer]

I know someone with a spare 3006 criterion m1d barrel. Pm sent

[1903Collector]

I am going with Jim's recommendation of a digital angle meter. I had already done the math and rejected the rod alignment process as having too many variables to control and then its still depends upon a human eyeball judgement, and human error is a factor of Murphy's Law that seems to always seek me out.

The specs and "rod" process variables you provided are greatly appreciated. Being a retired mech design engineer I live an breath math and specs! :-)

Ive still got more than a few 1903 projects to complete and then still need to fit the M1D block to my selected barrel before i am faced with barreling my receiver with that barrel, but Ive got two other M1 Garand receivers with "matching" barrels and I think Ill practice barreling M1 receivers with them first with an angle meter.

I still cant fathom why Garand chose not to employ alignment scribe lines. Ive discussed this briefly with Jim in the past and I have math and mechanical design and manufacturing process reasons why I completely disagree with Jim's position on the inaccuracy of alignment scribe lines on the '03 and M1 Carbine barrels and receivers. I think many people misunderstand the actual mechanics the so-called "crush" factor when barrel torque specs are met when properly aligned to a receiver. I also know that if the rear sight mount body is not perfectly installed and aligned with the barrel scribe mark then it may seem that aligning the '03 barrel using the RSMB seem line to align to the receiver scribe line is not always correct.

HOWEVER, my entire experience is limited to Military long arms and I have none with modern commercial rifles, especially those with barrels that are completely symmetrical and have no front sight features that require alignment to the receiver. In fact, I am assuming that there are even rifles with such barrels...such is my limited experience! Vintage surplus military rifles, well over 500 have gone thru my shop of nearly all kinds in the past 29 years...but modern commercial rifles, NONE! Im thinking there may be a difference there.

---------- Post added at 11:29 PM ---------- Previous post was at 11:25 PM ----------

Thanks, but Im USGI parts only! I value authenticity more than accuracy and remaining barrel life. Putting these old soldiers back in uniform is my thing even if I am building an M1D with a receiver that may never have been an M1D previously. Having said that, I am no certain I can pull this project off, but its always fun trying! :-)

[ssgross]

a digital angle meter

I might suggest you pay close attention to the tolerence of whatever tool you have or plan to get. Most of the cheap digital levels you find don't even advertise their tolerance, and when they do, it is likely the range of the sensor, NOT the whole system. Most of the budget tools (like Klein, for example) advertise +/- 0.1 degree within a degree of 0 or 90, and 0.2 in between. 20 minutes is .33 degrees. I saw a cheap one on amazon claiming 0.029 deg, so you might think you are ok? Not so fast, the bodies are all plastic, with a groove down the length for pipes. I doubt there is any uniformity along their small length even close to the reported tolerance of the sensor. Great for hanging pictures, setting a line laying bricks, etc., but I wouldn't set a barrel with one. I didn't look too hard, but I failed to find a budget friendly tool (< $100) that looked adequate in overall build. A Mitotoyu digital protractor in the tolerance range we are talking about will set you back $275 minimum - over double the cost of a good machinists' spirit level with similar tolerence. Refurbished ones can be had even cheaper on eBay.

Another thought, how do you plan on taking the reading? Across the top of the ears are not a very good reference point, so you will need a square block, or the badger ord. jig, to sit between the ears. I think the jig is ~$90 if you can find it. You can likely get by with a 1-2-3 block. All this in mind, I think the logical conclusion is the only acceptable "budget" method of properly timing an M1 barrel is to get a set of drill rods (assuming you don't have any tools yet).

Just saying.