I just went to the range today with my 581 series Mini-14 and two test batches of 8 lots each. These represent the sixth and seventh series of test loads to see if I can nail down the best load(s) for the gun. I'm also revisiting some earlier promising loads since I did a glass bedding and match trigger job.
The scope used is a Leupold VX-2, 2-7X mounted on Ruger factory rings. Of course, this scope is not sufficient power to obtain a critical hold, but is sufficient for comparative, relative analysis with all loads tested. Higher powered optics would have certainly provided improved results.
There is no question that the Mini-14 works with a very narrow group of powders, and is quite fussy. Those that worked extraordinarily well in my SR556 and other AR platforms didn't perform necessarily well in the Mini-14. My experienced guess is that the barrel is much more sensitive to vibration and barrel time. Having said that, I was convinced that something will pan out, and indeed, it did
. I was not prepared for some of the groups that resulted. As I discovered, this gun does have the capacity to shoot with the correct load, provided that the gun first has a good trigger and bedding job
. There is absolutely no point in seeking any accuracy loads without first addressing these issues.
See my article on this forum: Tuning up your Mini-14
I've been using only the Sierra 52 grain HPBT MatchKing during the powder analysis, only for the reason that if a good load cannot be developed with this bullet, chances are slim that any other will be much better. While some experts differ from my point of view, my experience has been to nail down a workable powder first with a match grade bullet, as the powder is the variable that overshadows all others. Once that is done, I shop for bullets that I like and fuss with seating depth. A charge that works for a match bullet will be very close to the correct load for others in its weight class. Throughout all testing, primers should not be changed, as this can influence results. It is always a good idea to do a fine tuning by trying other primers. The .223 and 5.56 NATO do not require magnum primers. Though I did not have access to them at the time of testing from my retailer, I generally have preferred Remington 7-1/2 primers over the last 45 years with .222 class cases, which is the preference with the technician at Sierra labs that I spoke with recently.
I will not list powder charges; only the powders. Listing charges is pointless, as each rifle is a rule unto itself, but I do believe that certain powders performed so well in my Mini-14 that they should repeat that performance with others.
I seated bullets out to 2.268, slightly off from full magazine length, to minimize bullet jump. As you will see, while this may have a positive effect on accuracy, it effectively increases chamber dimensions and may have reduced operating pressures enough to cause sluggish ejection, as I discuss below. Please note that the NATO chamber used in the Mini-14 has such a long throat as compared to the .223 Remington that it's impossible to come anywhere near the leade where pressures would jump.
Bullets were given a moderate crimp with a Lee Factory Crimp Die, as I would recommend for any semi-auto to prevent bullet movement. However, for the sake of uniformity throughout the test procedure, I single loaded each round to prevent bullet distortion on cycling that could skew accuracy results. The Lee FCD is like no other on the market, and I recommend it highly. It requires no canelure, and will emboss its own to your exact preferred seating depth. Unlike other crimp dies, it does not roll the mouth, but rather crimps just as a factory loaded round is, and provides uniform release. I have had the experience of trying to dislodge bullets thus seated with an inertia bullet puller, and they will not budge, so they certainly will stay put with vigorous actions. In my testing, crimping never caused negative accuracy issues, although it does add to the work hardening of the brass which is a factor in case life. Can't have it all!
All loads tested with Winchester cases and CCI 400 primers. REDUCE CHARGES AND BEGIN AGAIN IF YOU SUBSEQUENTLY INCREASE SEATING DEPTH TO STANDARD OAL of 2.250". As a rule, the extruded single base powders were far more uniform, with the single exception of Varget, which surprisingly did not work with this bullet and rifle with the loads tested. Any number of successive groups of different charge weights could be superimposed. Such was not the happy case with the double base ball propellants that threw groups to different impact points.
In order of performance, best to worst: (All tests fired at 100 yards.) Hodgdon H322
: This powder gave extremely fine performance with average 4-shot groups slightly over 1-1/2 inches. With three different charges, it yielded MOA! No other powder came close. Groups did not meander around point of aim either. My loads were derived from Sierra's manual, and the charge weights were markedly heavier than Hodgdon's but quite gentle on cases, with well rounded primers. I recommend starting with 24.0 grains, and work up by 2 tenths. I ended testing at 25.4 grains, with no apparent pressure signs. Extremely clean burning, moderate report, and cool. Hodgdon Benchmark
: This was also a very uniform performer across the spectrum, but groups averaged 1-3/4, with one turning in 1-1/4". Still very nice for a Mini-14. Again, predictable impact zones, similar to H322. Extremely clean burning, moderate report, and cool. Hodgdon H335
: This powder produced some high quality 1-1/2" groups bracketed with wide open ones. Very dirty with carbon fouling at gas block and distinct level of flash and report. BL-C2
: Similar performance to H335, but works best at full throttle; NATO level loads, with resulting 30 foot ejection. If accuracy is secondary to velocity, and you don't care about your cases for loading up an ammo can, I've found this is a terrific powder. Hodgdon Varget
: So far, I have only tested this powder at substantially maximum density loads, and it simply requires too much compression to conveniently load. With higher potential velocity being its only advantage over the previous extruded powders, I have eliminated it from testing, as it did not provide accuracy in this rifle with loads that justify its use. However, on heavier bullets such as the 63 grain Sierra Semi-Point in other casual testing, it did show some promise, and I will further that study for possible use on deer or coyote. In a pool last year here in New Hampshire, a local shop recorded a number of coyotes approaching and exceeding 50 pounds. That is some serious critter that calls for a good bullet especially in our wooded country where they might run off and not be found. W748
: I've got a pound, so I'll try more testing when I have occasion to, but so far, it has been a non-performer with the limited testing I've done. Typical of ball powders, it was quite dirty. Conclusion:
H322 is unquestionably the powder this
rifle prefers, and it performed so well that there is no reason to use any other, except perhaps Benchmark, if the latter delivers substantially better velocity for a particular use. I have yet to chronograph any loads tested, and do not know. Variations in charges up the entire ladder test with extruded powders resulted in virtually no change in bullet impact zone. Group size changes were slight and not prone to radical changes from load to load, as is the case with ball propellant I have tried with this gun. No wonder the old timers never bothered to weigh charges at benchrest matches! First shots with cool barrels repeatedly pinwheeled into my bull, literally bisecting the cross hairs (of course, for field use I will adjust midrange trajectory). I am confident that this powder will work well with many 55 grain bullets in this class. The only negative issue I have found at this time with either H322 and Benchmark powder is sluggish cycling of the operating rod, with cases being kicked forward by the returning bolt before they have time to clear the ejection port. With the forward scope mount in the way, cases got trapped on two occasions, completely crushing one. Cases that are clearing the gun are landing six to eight feet in front of the bench at 2 o'clock, which is very uncharacteristic for this rifle which typically hurls standard loads 20 feet to my right and NATO loads 30 feet over my shoulder. This, together with low report, mild recoil, and rounded primers combined suggest the load is not up to sufficient operating pressure. I may try incrementally deeper seating, and if that does not effect a solution, work up carefully to see if it improves without losing accuracy, and will do some chronograph analysis. I'm concerned that the reason these powders work so beautifully in the accuracy department is simply because barrel vibrations are kept to a minimum, and that, if given throttle, the barrel will resonate and ruin accuracy. Given the first shot accuracy of the load for varmint shooting, I do not consider this a problem, but with a scope that exacerbates clearance issues, this would not be a good choice where reliable cycling is paramount. But, for showing off at the range against other Mini-14s, H322 loads I tested sure do impress!