Thought you guys might like the post I made on CGN. Feel free to make it a sticky for easy reference. Enjoy...In this post, I will try and share my experiences loading for the M305/M1A (refered to as M1A from now on) for maximum accuracy. This is a very unique firearm with its share of quirks and misunderstandings. I will cover the history and the roots of this platform, to understand where the designers were coming from. From there, we will go to testing your firearm, loading for maximum accuracy, and learning how to shoot. I will even throw in my secret technique for match prepping ANY brass. You may not agree with it all, but it all works and works well.
How well? Well, I have been getting sub MOA groups with my accurized box stock M1A from DARK International. Took a grand total of 40rds to get it dialed in. Will get some long range shooting when the weather warms up and will post results and groups.
This info refers to the box stock "accurized" M1A. They come straight from the box pretty loose and unless the rifle is accurized (bedding, unitizing and shimmed gas system, trigger tuning to remove all that creep, solid and rigid scopemount), you will be wasting your time loading. When the rifle is properly bedded/accurized, there will be no movement at all between action/gas system and stock even with very aggressive tugging. The Op rod will slide back and forth smoothly without any binding or rough spots. Grease the moving parts properly. The Op rod spring will not bind or snag - consider a Rooster33 op rod, helps with consistent lockup.
At the end, we are trying to make the M1A run like a bolt action without having to run the bolt. So let's begin with a brief history lesson.
The M14 is a decendent of the WWII workhorse, the Garand. By moving the gas system, adding a detachable mag, and a few other tweaks, the M14 was created to use the smaller but equally effective Winchester T65 round. The Winchester T65 later became standardized as the 7.62 NATO (called 7.62 from now on) and commercialized as the 308 Winchester. The M1A is decended from the M14 by modifying the trigger group for semi auto fire only.
The specs for the 7.62 have been changed slightly over the years but has standardized to the following: 147/150gr @ 2700 to 2750fps (M80); 168gr @ 2600 to 2650fps (M852); 175gr @2500 to 2550 fps (M118). When loading for the M1A, it is best to stay within these vel ranges as that is what the gas system was designed for. Any faster/higher pressure and the problems so commonly talked about occur, plus accuracy is usually horrid. Remember that although the 7.62 and the 308 are dimensionally identical, their performance and operating pressures are not. The 308 is loaded to higher pressures with slower powders. The 308 is loaded for the Sportsman with bolt action rifles, not semi or auto fire battle rifles!!
First Things First!!:
Before we get too carried away with tuning and loading, we have to ensure that the rifle is worth the time. This is a simple test I do with all rifles I work on to test its potential. The heart of any rifle and its ability to shoot is found in the dimensions of the chamber and how true it was cut with the bore. If the bore was cut eyed, there is nothing that can be done to make this rifle shoot.
Start with 5 FL sized new brass, a starting load (ie 40 to 42gr of H335), a suitable primer, and any 150 to 168gr bullet you got. Fire the ammo.
Now examine the brass. The necks should have soot but the neck and case body should be clean. If dirty, increase the powder and try again with new brass until only the neck is dirty. This is the min pressure needed to fully expand the case into the chamber and will be used to determine the bores characteristics and accuracy potential. The brass should be free of any dents, dings or scrathes, looking like it came out of a bolt action rifle.
Now that you have 3 to 5 brass that have been fireformed, measure the runout of the cases. Measure 1/4" from the extractor groove, middle of the case body, and just below the shoulder. You should see runout under 0.005", less is better. Now the critical part. Measure at two locations on the neck. Hopefully, runout will be 0.005" or less. If above these levels, then the barrel will probably only be a 1.5MOA shooter. If there is a visible wobble to the brass, the chamber is eyed and the barrel is hooped. There is very little that will make it a shooter (sub MOA).
If you do not have a runout guage, you can roll the brass over a mirror or flat steel/plastic surface and look for any wobble. Another simple test is to put the brass back in the chamber. It should go in without any problems and will go in even when the brass is rotated then reinserted. If the brass goes in one way but will not when rotated, the chamber is out of round. Could still shoot but loading for this chamber would be a pain with short case life.
Hopefully, your chamber is concentric. If so, try test number two. The second test measures the length of the throat and its relationship to the bullet. If the bullet leaves the case neck before fully engaging in the rifling, that rifle will also not shoot well.
Take one of those fired brass, neck or FL size it and seat a bullet just into the neck. Reinsert into chamber and hopefully it will not fully chamber. This indicates that your throat is short enough for good accuracy. If the bullet cannot touch the lands, then the chances of a shooter is reduced the further the bullet has to jump.
Assuming your rifle passes these two tests, have it accurized/bedded and let's begin loading. Otherwise, know that the rifle might shoot but not consistently in the MOA or smaller. Replacing the barrel with a well cut chamber is the only real solution.
308 Winchester - No Good:
First thing we have to get rid of is most of the reloading data. Simply because it is for the 308 Winchester, not the 7.62 NATO. Also, forget about factory or surplus ammo. Factory ammo is loaded to 308 specs and will really beat up your rifle. Surplus ammo will have casual accuracy at best (3MOA is good stuff). The only ammo worth considering is Vietnam era M852 and M118 sniper ammo. However, since this stuff is rare and probably has collectors value, why waste it.
To load for the M1A, you must balance the harmonics of the barrel AND the pressure curve/timing of the gas system. So that means only a few applicable powders, bullets, primers and brass.
Powders: The best powders for the 7.62 are in the med fast range and include H335, Benchmark, H4895 and BLC-(2). I am not familiar with other brands of powders from Accurate Arms, Reloader, Winchester and IMR so will exclude.
I have found H335 to be one of the best surplus powders to use but it is temp sensitive. That means that loads will have to be adjusted if ambient temp change by more the 5C. Hotter weather less powder, cooler more. BLC-2 also has the same problem. WCC 845 from Higginson Powders would make a great plinking powder. Cheap like rice and it burns pretty well. A bit fast for optimum results but may work ok in other rifles. All ball powders share one unfortunate trait, they are very dirty burning powders. I would clean more often then with the extruded powders. Maybe every 100rds or so.
The Extreme powders from Hodgdon, eliminate that temp sensitivity and as a bonus burn very cleanly and consistently. This makes the H4895 Extreme and Benchmark the powders to use when competing or hunting. I will soon be doing extensive testing with Benchmark as its performance in BR types cartridges has been impressive. H4895 Extreme is a great standby but I prefer the smaller grain size of Benchmark as it would meter easier. Any old lots of H or IMR 4895 may be temp sensitive so keep an eye on that. Either will work well with bullets from 150 to 168gr.
The 308 standby of Varget is NOT suitable for the M1A - too slow, too much gas pressure, too much gas volume. However, reduced loads might give great performance. I just don't see any point in reducing the vels more then I have to.
The loads with the above powders are not whimpy at all. The max pressures are certainly lower then the 308 but not by much. They just burn in a different manner more suited to the M1A gas systems. The damaged op rods and high receiver wear rate/stretching can usually be traced back to using heavy doses of slow powder ie bolt action load data. If doing a lot of shooting, a recoil buffer (Buffer Technologies) is cheap insurance and will soften recoil too.
Bullets: The best bullet weights range from 150 to 168gr. Personally, I like the 155gr Hornady Amax because of its very high BC and excellent accuracy. I have shot it out to 1300m (1450yds) and it stayed stable and accurate.
The 175gr MK is now very common in LR match shooting but unless you modify your M1A to accomodate the heavier bullet and load, the NATO performance is not all that great. At 1000yds, the 155gr Amax will outperform the 175gr MK. In fact, at such a low starting vel, the 175gr bullet may not stay supersonic.
Other excellent choices include the 150gr Hornady FMJ BT, and poly tipped hunting bullets like the 150gr Hornady SST and Nosler BT. The 155/168gr HP match bullets from Sierra or Nosler are also suitable but with their lower BC, they are just not as good when ranges extend beyond 600m.
Forget about any surplus or pulled bullets, even "match" ones. They are simply not capable of shooting consistently in the MOA range. Garbage in, Garbage out.
I moly coat my bullets and it works for me. Uncoated bullets work just fine and in the chrome lined barrel, fouling is light anyways. I don't wax my moly bullets as I am concerned about fouling issues with the wax. My hands get dirty but they shoot well so I don't mind.
Primers: The best primer I have used is the Fed 210M. It is not a soft primer and I have not had any problems with slam fires. Another great choice would be the CCI BR2. Match primers do make a difference when distances get long or when accurate shooting is what you are after. Unfortunately, my favorite non match primer, the Win LR, slam fired quite regularly and has been dropped. May work in other rifles.
Speaking of slam fires, there are a couple of solutions. Increase the primer seating depth to max SAAMI depth using a LYMAN pocket uniformer, use a "tougher" primer like the Fed 210M, or play with the firing pin return spring. Oops, it doesn't have one - any enterprising machinists out there want to come up with one?
Cases: By far the best commercial case are those from Winchester. After all, they did design this round. Many service rifle shooter use this brass and it is consistent and durable. Fed Gold Medal brass is next up. Heavier and thicker then Win, it holds less powder so back off loads with this brass. Very nice stuff. Surplus NATO brass follows. For those, concerned that surplus brass doesn't shoot, all I can say is my smallest group ever fired was with surplus NATO brass. I will discuss latert how to get the most from your brass.
I wouldn't bother with "match" brass like Norma or Lapua because these are at least double the cost, usually softer and may not last as long. We are not shooting a BR rifle where a few thou matter.
Brass Prep: Now that we have our new cases, what do we do with the? I start by deburring the flash holes using a tool from RCBS. The brass is then loaded with the starting load you found in the testing stage and fireformed. Examine the brass. There should not be any scratches, dents, shiny spots on the surface. Primers should be well rounded, not flattened.
Try putting the brass back into the chamber. It should fit smoothly and easily - perfect. Now comes the most controversial part...Sizing.
Sizing Your Fireformed Brass:
A lot of misinformation is out there about sizing fired brass and is the single largest cause of problems with head separation and short case life. This is the same problem faced by those who load for the belted magnum cartridges, and the solution is the same for both. But first let's define a few terms so that we are all talking about the same thing.
Headspace is a measure of the difference in distance from a datum line on the shoulder of a bottleneck cartridge to the rear face of the cartridge and the bolt face. Basically, what we are concerned about is the gap between the back of a fully chambered cartridge and the bolt face. Less is better as long as it does not interfere with chambering. Why do we want this? Because during the firing process, the firing pin drives the case forward till it can't go further anymore. The pin then compresses the primer igniting the load. Under pressure the case expands to fill the gap (headspace) and stretches.
Why Full Length Sizing is Not Always Best:
If you were to now FL size the brass andmove the shoulder back to min.dimensions, the next time you fire, the case will stretch again. This causes enormous strain on the web or head of the case and will eventually lead to case separations and other nastiness.
There are two solutions: reduce the headspace so that FL sizing will work. Problem is that FL sizing dies can introduce a fair amount of runout in the brass which is not good for accuracy. Also, you must get the die and chamber dimensions to be within a few thou. That is also not easy and will require a lot of parts swapping or custom dies. Both are very expensive.
The second is to work with the fireformed brass and the chamber/headspace you now have.
When you work with fireformed cases, we are working with cases that has essentially zero headspace. This reduces case stretching and the chance of head separation. It also is in perfect alignment with the bore (remember the runout we were measuring at the start). The ensures a straight start for all those expensive bullets.
All rifles have varying amount of headspace and differing chamber dimensions, even BR match rifles. So when sizing, we want to minimize any change in case dimension which can affect case life or accuracy. The best part is that the actual chamber dimension no longer matter. We are forming brass to fit whatever the chamber dimensions are, even something that would swallow a no-go guage. The cases you form are a custom fit to that chamber alone. Don't bother using someone elses ammo and certainly never share ammo. Just think of it as having a custom chambered match rifle.
So how do we size the case and maintain all that wonderful alignment and fit? We neck size. "But the cases won't chamber" BUNK. You just proved it when you pushed the fireformed case easily back into the chamber. "But the cases will grow too big and jam later" BUNK. At the reduced pressures of the 7.62 loads, good quality brass will survive many firing before there are any fit issues. I am using brass that has over 8 high pressure 308 firings BEFORE going into my M1A. This brass has been shot another 5 times with no chambering issues at all. I can use light finger pressure to chamber the fired brass. Awesome.
Today, there are only two types of dies that are worth using: the Lee Collet Neck sizing die and a bushing die from Redding or Hornady. Forget about the common neck sizing dies from all companies. You run a very good risk of making runout because of the expander ball and decapping rod. Sometimes the rod/ball are straight, most of the time they are not.
My favorite die is the Lee Collet neck die. It works great, affordable, and sized cases have virtually no runout. Once you use this die and see what it can do for your loads, you will switch over everything you shoot!!.
Trimming and Final Prep: Now that all the brass is neck sized and deprimed, I run them through a trimmer just to square up the necks. Not a big deal but I like square necks...looks more accurate. The neck is then inside and outside deburred and chamfered.
If you are experiencing slam fires, now would be the time to lower the primer pocket to max SAAMI depth. I like the Lyman pocket uniformer tool. Just takes a few seconds per case.
Neck turning is next and is really optional. With a chamber with such generous neck dimensions, it really doesn't matter. However, since we are going for "match" prepped brass, if you got the tools, what the heck. At best, remove no more then 60% of the circumferance. Leaving necks too thin will allow them to split prematurely.
If noticing neck splits, annealing the necks might help. But if you turned them down thin, toss them.
Prime the brass and WEIGH the powder charges. I have found the M1A to have a very narrow sweet spot. Work up the loads in ½ gr increments. Groups will shrink and expand within a half to one grain change of powder. Once a good load is found, a powder dispenser can be used to speed up reloading. Just be sure that charges are within +/- 1 tenth of the target load.
If using a ball powder, loads will have to be adjusted up or down depending on temp and humidity changes. That is why I will only shoot Hodgdon Extreme powders when the shots matter as in competition or hunting.
Cartridge OAL is easy. Seat the bullets to the longest length that will fit in the mag. The throats are long enough that a "hard" seated cartridge so not happen. That was checked in test #2. As to seating dies, just about any die is fine. The runout caused in loading usually happens in the sizing stage. Very little problems are caused in the seating stage but check just to be sure.
The ammo should be as close to zero runout as possible. Ammo with more then 0.005" of runout is not going to shoot consistently MOA or under. This applies to all ammo.
Shooting the M1A/M305:
In order to get the best accuracy, we need to shoot off a solid bench with good front and rear rests. A rolled up blanket on the hood of a truck is not going to work. A concrete or heavy wood bench, a pedestal front rest with rabbit ears bag, and a rear bag with rabbit ears will help with consistency.
Sorry, but I don't consider a bipod a good rest for developing a load. They wiggle and bounce too much. They make for a great field rest but not for load development.
When shooting strive for consistency and repeatability, not speed. The hold, eye position, breathing, trigger control, follow through are all part of good groups. If unsure, go get some help from a BR type shooter.
Because the M1A does bounce around during recoil, I have found that holding under the receiver with the left hand helps smooth things out. Just use even and consistent pressure. Also, I rest the rifle as far forward as possible to reduce the amount of jumping. I set the front rest so that the front swivel touches the rear of the bag. This helps being consistent when setting up for the next shot.
Mount a solid and secure scope base and use a good quality scope. My eyes just won't see accurate enough for MOA type groups using open sights. With a scope, I want to be able to define at least 1/8" at 100yds, preferably less. Buy the best scope you can afford.
The groups will quite large, then shrink, then grow again. Good groups/loads tend to be where the velocities match the NATO specs. That is why shooting over a chronograph will speed things up greatly. Because the loads are at NATO vel and pressures, the cases should not show any dings or dents. Feeding and extraction should also not have any problems.
Reshoot the loads that show promise then move out further. If this is to be a Long Range shooter, then shoot and test at long range. 100yds groups tell you exactly that...100yd performance. They do not represent what will happen at longer ranges no matter what the math suggests.
I have found many loads that shot in one big hole at 100yds that wouldn't stay on the paper at 500yds because of stringing. Shoot at the furthest range expected and tweak the loads to match that performance. It may not be the smallest 100yd group load!!!
How to Match Tune Your Brass:
Here is my way to get match performance from any brass. I use this technique to sort once fired, surplus brass, and mystery gunshow stuff. Always sort by headstamp.
Fireform and prep the brass as described earlier. Load with your accurate load. Then test fire. As long as conditions are calm and good technique used, any shot that is a flyer is suspect. I mark that brass. Usually firing again will cause a flyer again. Toss the brass.
The brass remaining will shoot consistently into the same group, NO FLYERS!!! This is truly match brass. Forget about weighing and other such nonsense. Only small consistent groups will tell that the brass is up to the task.
Sort, through firing, enough brass to meet shooting needs. It is more time consuming but performance is guaranteed and we all could use the extra trigger time. The competitive shooter will know that each cartridge is as close to identical as humanly possible. Gotta be worth a point to two.
Well, that touches the surface of precision loading for the M1A/M305. I hope that this information will prove useful and that more of these wonderful rifles will start shooting to their potential. Even with paying for the accurizing and tuning done (which I can offer), we are able to own a great shooter for about ½ the cost of a Springfield.
If there is interest, I will post more thoughts on other topics including optics, rifles and reloading for 1000m shooting, stock bedding, and shooting techniques.