Milling service to cut an M1D barrel?

[MAC702]

Lines aren't needed. They would only lead you astray thinking you were correct when you weren't.

Agreed. I'm no gunsmith, just an armorer level knowledge, but I've done lots of Garand barrels, including at the CMP's Garand building class. A couple of alignment rods for the rear sight flat and front sight flat (temp fit the gas cylinder) make it an easy task. Have the correct barrel or action vise, and correct action or barrel wrench.

[browningautorifle]

Have the correct barrel or action vise, and correct action or barrel wrench.

I had to make a barrel vise and an action vise that I could come on to and I use an angle meter on the front sight flat and rear sight flat. That works for both M1 and M14. This scope mounting block will have been put on with a jig for locating and then machine drilled and pinned. Not done by eye or guess.

[1903Collector]

From an design engineer and manufacturing point of view, no, the scribed lines should be absolutely correct, being scribed within a calibrated jig (or so would have been my spec if I had been the design engineer). I have also barreled nearly 100 M1 Carbines, over 200 '03s and 1 (one) M1917 and the results were always dead on.

HOWEVER, to my surprise I am currently working on an M1 Carbine and the scribe lines DO NOT line up! This is a first for me. The early WIN barrel is NOS from James River and the receiver is WIN is an early SN, but in not so good condition. I suspect the barrel, but there is something else going on with this barreled receiver. It may be an optical illusion, but the centerline of the barrel does not seem to align perfectly with the center of the receiver when looking down the length from the back of the receiver. It is as if the center of the threads of the barrel is not concentric with the bore, or the thread of the receiver is not aligned with the center of the receiver. Ive never seen such a thing before. Yet, when fully assembled, the carbine seems to function properly with rounds feeding and ejecting from the barrel without any problem. Even though the receiver is in poor cosmetic condition, I begin to suspect that the barrel is the problem...and I paid A LOT for that barrel!

[MAC702]

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.

[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]

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.

[browningautorifle]

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.

That's right.

[ssgross]

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 suppose I'll chime in on this one too. I have no preference for or against the design of witness marks, or lack thereof. But as to why they were not used on the Garand...I think perhaps it had to do with the controlling of stacking tolerances between the concerned reference points and the impacts on production effeciency. As evidence, I reference a scathing review of Springfield Armory practices during 1903 production in Fred Colvin's autobiography "60 Years of Men and Machines". Colvin was asked by the secretary of war ~1916 to review manufacturing processes at Springfield Armory. His negative report, basically calling out the whole operation as bass backwards and antiquated, caused quite a scandal. Colvin thought his review was for the Secretary's eyes only, but some biased Generals got their hands on it first.
So, I think the real reason for no witness marks on the garand can be as simple as the elimination of an unnecessary production step. We often overlook the fact that there were far more considerations in design and practice than just the rifle itself.

[1903Collector]

SSGross is correct that there are additional process steps, and even a special fixture for cutting the "draw line" on the receiver and barrel on the 1903 Springfield. The "draw lines', as named in the process route follower, are created in a separate manufacturing process step and has its own precision fixture. As a result, the locations of these lines are, for lack of a better term, dead nuts accurate with the possible exception of the human factor of securing the work piece in the respective fixture. This and the following can be verified relevant sections in the works provided by Brophy and by Herbert (both are ponderous to read, but include both engineering drawings and sketches of jigs and fixtures as well as the original process route follower work instructions.

Upon review, I was amazed at how many individual process steps were required and at the large number of custom precision jigs and fixtures were necessary. Of course, this was long before the days of CNC machining and 5 axis machines. I can understand why Fred Colvin's review of the manufacturing processes at Springfield Armory resulted in a negative report, but I challenge that he actually stated that the whole operation was "bass backwards and antiquated". However, it is indeed complicated and the process routing is quite astounding.

This may indeed explain the decision not to utilize alignment "draw lines" on the M1 Garand, but I have trouble accepting that. In any case, it would have been possible to include "draw lines" and they would have been very effective. I can only conclude tht either it was an unintentional omission, or related to reduce and simplify process steps, operations and fixtures, or that there was some other reason yet to be learned.

Actually, part design, manufacturing processes, jigs and fixtures and inspection fixtures and methodology is my professional expertise (2 years in the oil industry BOP and tools and fixture design, 2 years EVA equipment design for NASA STS 11 & 13 missions at JSC, 13 years bio-medical automatic blood blood analyzer design, 4 years cell phone, and finally 4 years aerospace). After careful review and many cups of coffee I can point out that Brophy and Herbert have some part, jig and fixture dwgs as well as a process route follower for every step in the manufacture if the '03 receiver and barrel that helps to address, at least in part, this topic. However, I was disappointed that there were still a few details not provided. I spent the last week pouring over these to capture the design intent, manufacturing process and the implications of assembly methodology. The possible, if not potential errors inherit in the manufacture and process steps as well as the possible resulting variation due to these possible human factor errors.

What I write below is not absolute, and it desperately needs peer review to identify corrections or improve the clarity of the text. The following statements accepts as being read that the cutting tools are not worn, the cuts are all made to spec, and the precision jigs and fixtures are verified to the dimensional and assemble specs for them. This is not an unreasonable starting point since the tools are under strict maintenance control and the jigs and fixtures are crafted and rigorously inspected to meet all specs with no deviation at all from the dimensions (i.e., jigs and fixtures are made exactly to nominal with no tolerance allowed from the dimensional and geometric spec). This is as true today as it was then in the manufacturing industry, in fact, it is essential. Variations in manufactured part dimensions and geometry is nearly always due to:
1) improper fixturing or movement of the work piece (related to errors in seating and affixing the work piece to the jog or fixture) at the particular process step;
2) machine operator error, and
3) flaws in the work stock

However, the issue of barrel and receiver alignment is not tolerance stack up in the sense suggested. The specific dimensioning of the interfacing parts offer the absolute minimum in tolerance stack up, and after reviewing the tolerances of the mating features of the receiver and barrel the worst case is extremely tight (this worst case scenario is statistically unlikely, since actual max stack up in a typical population of parts is distributed within +/- 3 sigma) and within seconds of an angle in the position of the start of thread of both the receiver and barrel. The biggest variation (within spec) is due to the dimensional clearances and tolerances of the internal and external threads, but this variation only results in differences in the torque necessary to align the "draw lines" of the barrel and receiver. Due to the precise orientation and location of the start of the first threads of both parts, the final alignment and torque is solely dependent upon alignment to the "draw lines" when the shoulders of the barrel and receiver are in contact. Headspace adjustment or results are related to solely to these features.

Note: when the shoulders of the barrel and receiver are in initial contact the draw lines do not align. When they are aligned by applying torque the shoulders do not "crush" or deform. The mechanics in action is the increased binding of the mating sheer surfaces of the threads (which have small dimensional variation thread to thread and what is happening is the taking up the small slack due to nominal internal and external thread clearance as well as closing the equally small tolerance stack up of the location of the mating sheer areas of the threads. Wear of the mating thread sheer surfaces can at times allow over rotation of the barrel to achieve the required torque. The addition of shims serves to take up the additional slack and does not result in any change to the headspace as long as the draw lines are aligned. Note: alignment of the draw lines not only sets the headspace, but also sets the alignment of the position of the barrel features relative to the bolt lugs. (We all know that a barrel that is rotated too little or too much often prevents the bolt from seating and the bolt wont come even close to closing.)