M14 rifles have unique reloading requirements, beginning with case selection and preparation.
A lot goes into transforming a rack-grade M14 into a High Power competition rifle, but just having the gunsmithing work done as it should be is no guarantee of performance. What goes into an M14—ammunition—largely determines how well the guns work across the course, and sometimes whether they work at all. The three main ammunition performance concerns for High Power competition are accuracy, consistency, and wind drift, and this article will address points intended to improve each. But even if you’re not a competitive shooter and are using an M14, you better keep reading if you ever intend to recycle ammunition for it. As far as handloading goes, this rifle has a host of other important concerns you need to know about.
The best factory ammunition available for a match-grade M14 is Lake City Match (LCM) M852. This is the “standard” most folks try to duplicate with handloads, and it also carries the components which have become the standard for handloads as well. Another LCM round is called M118. The big difference between M118 and M852 is the bullet. M852 uses a commercially produced 168-grain hollowpoint boattail bullet, and M118 uses the 173-grain full-metal-jacket Lake City boattail. The powder used in each is a 4895 selected for optimal pressure characteristics. There are differences in head stamps, and M852 cases are knurled above the head to indicate that they’re loaded with hollowpoint bullets and, therefore, are not authorized for combat use, but the cases are materially the same.
Given that the focus of this article is reloading, some of the other commercially-produced match .308 ammunition is of little interest because the cases they are manufactured with are not suitable for recycling.
A Case For The M14
For those of us who do not have reliable access to loaded LCM rounds or once-fired brass, it may help to know that there’s also no material difference between LCM and LC ball-issue brass. LCM brass has no primer crimp, and its neck and shoulder area are annealed. Duplicating either of these in GI-issue brass poses no problem, although the only really necessary step is eliminating the crimp, which is best done using an attachment for the LE Wilson case trimmer.
The reason LC is given as the case of choice for the M14 has nothing to do with its quality (which ain’t great), but has everything to do with its construction. LC cases are a hard brass alloy and are relatively thick all around. Also, they are especially dense about the case-head area. Most commercial cases are not engineered to perform duty as recycled stock in a brass eater like an M14. They may work okay for one or two firings, but any more is literally stretching it. Also, equivalent cases can be had, which is good news for those who have limited access to LCs. New IMIs work fine, as do those from the “white box” WW commercial mil-spec ammunition. They deliver equivalent capacity and lifespan compared with LCs.
One thing you absolutely, unequivocally must accept is short case life. A few things may shorten it, but nothing extends it. Never allow more than four firings on a case. This means that once-fired brass you picked up can be loaded just three times, and, yes, this goes for LC.
The reason: Upon powder ignition, the cartridge case expands against the chamber walls, sealing the chamber. Since the case body is wedged against the chamber and can’t swell any larger, the “ends” of the case move away, stretching the case body near the head back into the bolt and “blowing” the case shoulder forward. Pressure subsides, and the case contracts back close to where it started. The M14 has about the quickest operation of any autoloading rifle—so much so that the bolt can unlock before the case has fully retracted from its expanded dimensions. The net result is that some amount of additional expansion occurs in a case fired through an M14.
Suffice it to say that an M14 case has to be strong, especially in the case head area. Also suffice it to say that it’s got to be resized a little more in this same area. Some people think their M14 just has a “big chamber” when it’s really the operation of the gun that’s causing additional case swelling. Don’t be fooled into thinking that brass from your M14 fire formed to fit the chamber. It has “fire deformed.”
The Amazing Shrinking Cartridge Case
Insufficient case sizing is probably the most common and costly mistake made in loading for the M14. “Insufficient” is in both die design and operator discretion. Due to the additional case expansion mentioned, conventional full-length sizing dies may not do the trick. Some of that depends on the state of your rifle and the original whereabouts of the brass. If your rifle has a “match” chamber, which should be a little shorter and tighter than GI, and if your rifle first-fired the brass, then a standard full-length die may work fine. But if you’re working from once-fired brass that was purchased as such, a small-base sizing die might be better. A small-base die will not negatively affect ammunition performance in any M14 rifle and is a recommended purchase, match chamber or not.
I have seen some rifles that actually shot better groups after a switch to small base. If your rifle tends to shoot better with new ammunition than your handloads (assuming your recipe is right), it’s worth a try. There are some high-theory ideas as to why this might happen, but, again, it’s mentioned here to re-emphasize that small base sizing will not hurt accuracy.
A small-base die is one that’s cut to a smaller inside diameter (i.d.) near the case-head area. How much smaller than standard depends on the standard, and a good standard is one cut to SAAMI minimums for the .308 Winchester cartridge.
Functioning is very important in an M14; each round must enter the chamber freely. Any hitch in feeding or lock up, especially such as might be caused by a blown-out shoulder, is an invitation to an open-bolt detonation at the worst and inconsistent target accuracy at the least.
Use a cartridge headspace gage to set up the die! Don’t even think about sizing another M14 case until you get one. Chamber headspace is a fixed dimension, but case headspace changes. Since you’re going to be pushing, and maybe exceeding, the limits of the sizing capabilities of a die, you’re certainly also pushing the limits of cartridge headspace tolerance.
You must set back the shoulder of cases intended for use in an M14 because just as the case head is subjected to additional expansion, so too is the case shoulder. Take your manufacturer-supplied sizing die set-up instructions and throw them away. It takes a lot more precision than threading the die down to touch the shellholder. One-piece drop in cartridge headspace gages provide a machined step which indicates excessive or insufficient headspace by sighting along the case head of a cartridge inserted into the gage. These gages are normally based on SAAMI extremes and provide a visual go- or don’t-go evaluation, but not much precision. If you’re setting it up to size M14 cases, thread in the die until the case head nears the bottom level on the step rather than the normally suggested top line.
A better gage provides a decimal measurement. I like the Stoney Point headspace gage because it’s not influenced by case body size or something like a dinged extractor groove. Measuring a fresh fired case in a drop-in gage can be misleading because the depth the case will drop into the gage may be impeded by a hangup elsewhere, which may be misread as a massively blown shoulder. This is a minor point since it may not affect a reading off a sized case, but be aware of it. The Stoney Point gage also points out a problem with a backed out primer, which may also indicate a headspace problem. Punch out a primer without sizing the case and check again.
As for how much to set back the shoulder, you need to know where the case started both before and after firing. Most new rounds show minimum dimensions, and most chambers allow a little more than that. I think you’ll be safe to add 0.002 inch to what you read from a new case and go with that. You may be able to get away with less set back, but not crowding this dimension adds a safety and reliability margin this rifle needs. Given its effect on brass in other areas, and given that you’re not sizing these cases very many times, overworking the brass is a small worry.
To make sizing easier, especially through a small-base die, make sure they’re clean. It probably doesn’t matter how you get them clean, but be aware that whatever gets inside a case also gets inside the barrel. Suffice to say that any abrasive residue, such as from tumbling media additives, should be removed.
Take extra care in cleaning the insides and outsides of case necks, and there is nothing wrong with using a small amount of lubricant (as long as it’s the right lubricant) to ease the neck. The right lubricant is Imperial Sizing Die Wax, and it’s what to use for the case body, too. Rub the wax on with the fingers and you nearly eliminate the possibility of applying too much or not enough of the substance.
To Die For
Now that we’ve talked about base and shoulder sizing, what’s left is to discuss the relationship between them.
Do not attempt to get more sizing down on the lower portion of the case by simply threading the die further and further in. Some people have even gone so far as to suggest grinding from the bottom of a full-length die to get more sizing, but without offering the first caution of checking for headspace violation. Good Lord. Dies are not self adjusting: more sizing down low means more up top, which can mean over-compression of the shoulder. Now, it may be necessary to grind a die base (rare, but I have seen it) to get enough shoulder compression, but the point is to have a way to know what you’re getting, and that, again, is the purpose of the headspace gage.
If you can’t get all the sizing you need near the head without overcompressing the shoulder, try a small base die for a .358 Winchester, a necked-out brother to the .308. Remove its expander ball and thread down this die as far as you want; it will allow for all the sizing possible but without touching the shoulder of a .308. You will then, of course, have to follow up with a .308 Winchester die to treat the neck and shoulder. It may be possible to use a neck-only die for this provided it has shoulder bump capability.
The zoot capri setup is to have a die modified to provide tunable sizing fore and aft. In this operation, the neck and shoulder area of a sizing die are milled away and in their place is a shoulder/neck sizing bushing that comes from one of the various benchrest die makers, like LE Wilson.
This allows adjustment of the die from both ends and also eliminates the need for an expander ball, but more about that next.
Pains In The Neck
The thicker neck walls of LC and equivalent brass are sized too much by standard dies. The case neck i.d., assuming the expander ball is used, will work out about the same for thin or thick walls, but the amount of compression and expansion the necks went through to get there makes a big difference downrange.
Consider a military case with an 0.015-inch neck wall against a commercial case with an 0.013 inch wall. Size the two through the same die, and it’s obvious which gets the most elastic workout. Let’s say the die sizes each neck to an outside diameter (o.d.) of 0.330 inch. That means the military case i.d. is reduced to 0.300 inch and the commercial i.d. to 0.304 inch. Running a 0.3065-inch expander ball back through the tightened necks opens up the first 0.0065 inch and the second 0.0025 inch. They both end up with about the same i.d., but the military brass really went through the ringer.
To ease up the amount of swaging, have a good machinist open up the neck on your sizing die. If this dimension is really tuned in, and if you’re willing to always use brass with the same specs, there is then no need for the expander, eliminating this sore spot in conventional sizing die design (the expander grabs the neck). In the above example, the die could be opened up, say, 0.004 inch and used with either case type, provided the expander was left in place, and could be opened up 0.006 inch and devoted to LCM with no expander installed. But even with the expander in place, it will exercise less negative influence on the case neck. The expander may be necessary, though, if your rifle tends to ding case necks.
It’s wise to lightly chuck the expander in a drill and break any sharp edges using a fine stone, followed by fine grit emery. This will help smooth its operation. Be careful polishing the major diameter, though, unless size reduction is what you want. Also, tighten down the decapping rod when the expander is inside a case neck on the return press stroke; this will help center the expander, especially if you set up this trick with a case with uniform neck-wall thickness.
The modified die mentioned earlier, which accepts interchangeable neck/shoulder sizing bushings, can easily be tuned since the bushings are available in different sizes.
I replace the shellholder spring clip on the press ram with an O-ring. This allows for better centering of the shellholder and allows it to sit flat in its groove. Determine the size you need (it varies press to press) and head to the hardware store.
And keep your sizing die clean!
Now that the brass has been sized, there are two case-preparation steps to consider. One is usually mandatory and the other is optional.
Due partially to the M14’s treatment of brass and largely to the sizing method recommended, it’s normal to see a good deal of case growth, which means trimming is in order. By the way, a fired case will be (or should be) shorter; the growth measured after case sizing resulted from the sizing.
I like the LE Wilson trimmer because it’s simple, fast, and precise. The Wilson, unlike most others, doesn’t use a pilot cutter on an unsupported case. The case is instead held inside a sleeve which sits atop a rail. This arrangement, combined with the machining precision the trimmer is produced with, gives the most consistent and truest cut possible from a bench-mounted tool. Purchase a sleeve sized for new cases to better accommodate small-base sized brass.
As for what your trim-to length should be, most chambers will accommodate brass that’s a little longer than the SAAMI minimum of 2.000 inch, but how much is variable. I say either check it with a gage or stick with the minimum. Sinclair makes a gage that will show chamber length if you care to know.
I don’t know what the accuracy ramifications of safely inconsistent case lengths are because I always trim my cases, but it’s a relatively painless assurance using a Wilson trimmer. The square cut guaranteed by the Wilson trimmer does have a positive influence on bullet seating. The bullet will contact the mouth flush and, therefore, start straight.
Make sure the case mouths are deburred inside and out with the tool of your choice, and the neck is done.
The final case-prep step we’ll consider in this article purports to improve ignition quality. That is inside deburring, done, of course, with an inside deburring tool. It’s been my experience that it can pay off. These tools remove a burr from inside the case that surrounds the flash hole. The flash hole is punched rather than drilled, and that’s the source of the burr. Some of these can be over 1/16 inch high and do nothing positive for the consistency of the spark that jumps into the case. This is one of those things that may not noticeably shrink group size but may reel in a flyer.
There are a few of these tools available, but, again, the Sinclair is the best. It’s depth adjustable and cannot cut too deeply even if the shooter doesn’t use this feature.
Good, Better, Best
We’ll now back way up and get to one of the first things you might actually do after you’re set up. Let’s say you have acquired a pile of brass. Do you load it up straight away or pick at it for a while? Your choice depends a lot on your beliefs, and on the time you have or are willing to spend and on where you got the brass.
“Case segregation” is a buzz term of the bench-loving shooter, but it’s hard to say what it will do for you. There is some merit to eliminating bad cases from your match batch, but you better not set your standards too high if you’re working with LC. High Power shooters need quantities of very good ammunition, not a handful of perfect rounds. It’s been my experience that tool quality and set up and component choices best accommodate that need.
Very carefully inspect any once-fired purchases, and never buy resized brass. I use a drop-in gage and intuition. I can’t describe my standards because it’s subjective. I can tell if brass has been thrashed, and you’ll be able to as well after you’ve handled enough cases. Beyond such visual inspection, note extra effort in sizing and look for excessive case length after sizing. Again, it’s subjective based on what you read from examining your own first-fired rounds.
If you wish to segregate cases for quality, I think it’s good to do so by neck-wall thickness, or, more correctly, by finding evidence after the fact that inconsistent wall thicknesses exist. I do this with a concentricity gage, also known as a spinner. I use this when first sorting a batch of sized cases and then again on loaded rounds. Now, I am aware that the only truly accurate way to sort by wall thickness is using an inside micrometer or something like a Sinclair Neck Wall Thickness Gage, but wobbly case necks are usually indicative of the same condition, and it’s a whole lot faster and easier to use the spinner.
By the way, skip the rotation if you’re sizing without an expander. Since the neck i.d. wasn’t touched, they’ll all roll flat; spin after bullet seating to see the truer nature of the necks, and keep the better cases sorted for future firings.
Other factors, like chamber quality, can result in case malformations which might misdirect evidence of thickness inconsistencies, but I still think that selecting those which run out the least is a good assurance that the neck is better centered, and that gives me more confidence.
Weighing cases has always sounded suspiciously simple as a sole means of segregation because weight variances give no clue to the source of inconsistency. Combined with other hands on measurement criteria, weight segregation is probably a viable criteria, but it is tedious. Also look for defects like off-center flash holes and always, always for structural problems.
However you segregate cases, set your criteria based on your experience—that is, don’t try to measure variables you know nothing about. If you don’t have or can’t get the necessary tools and expertise, spend your time doing something else. Also, there’s a rule of thumb I believe is worth considering: I think you’re kidding yourself if you’re trashcanning more than 10 percent of the LC cases that pass safety. You’ll be using a lot of time and effort and money eliminating perfectly good High Power cases.