AR-15 Sub-Caliber Training

Those of us who live north of the Mason-Dixon Line experience long hard winters that are not conducive to outdoor shooting. While ice skating is not as common these days as it was back in my misspent youth, skiing, snowmobiling, and ice fishing are all popular. None of those activities require the fine motor skills of delivering an accurate shot, however, and that is difficult to do outdoors in sub-zero weather.

Those of us in the north found ways decades ago to shoot indoors during the winter. 22 LR conversion for the 1911 is a popular winter training tool. Below center: Author’s father liberated this .22 LR training rifle used by German troops in WWII. 22 LR conversion. Right, barrels for dedicated .22 LR uppers don’t use conventional .223 barrel extensions. Builders must machine the raised flange into their barrels so they are held captive in the receiver by the barrel nut. Some of us have ranges right in our basements.

For those whose architecture (or the missus) doesn’t support that, we have lots of gun clubs with indoor ranges, commonly at 50 feet with .22 LR. Some indoor ranges allow centerfire pistol shooting but it is not unusual for "hardball" (Full Metal Jacket) ammo to be discriminated against. Many indoor ranges run leagues, hosting local and postal matches. Other shooters view indoor shooting as an off-season opportunity to retain their skills until they can get back outdoors at longer distances.

They prefer their indoor firearm to resemble outdoor, long distance guns. Not long after the Colt .45 was adopted as our official service pistol in 1911 it became extremely popular in outdoor NRA bullseye shooting. Shooters wanted a similar pistol in .22 LR with the same trigger pull, sights, and ergonomics as the .45 and Colt gave it to them. Called the Ace, the .22 pistol went through various design changes over the years. The use of .22 LR military training rifles was widespread worldwide.

My father brought back a German .22 LR single shot training rifle that looks and feels like a 98 Mauser following WWII. Not long after Eugene Stoner worked out the design of the AR-15, Colt came out with a .22 LR conversion for it. All the owner had to do was replace the bolt carrier and magazine with the .22 LR units. Unfortunately, accuracy of these AR-15 conversions was never very good. First, bullets for the .22 LR are not quite as fat as bullets for the .223 Remington or 5.56mm.

Normal dimensions for .22 rimfire barrels has 0.2170" lands and 0.2220" grooves. Centerfire .22 caliber barrels commonly have 0.219" lands and 0.2240" grooves. While the Ace conversion units for the 1911 and other dedicated .22 LR trainers had barrels with the correct internal dimensions and shot fairly accurately, the conversion units for the AR retained the parent barrel and there is too much slop for rimfire bullets.

Second, the parent AR had a .223 chamber, an enormous discrepancy compared to .22 LR, requiring a .22 LR chamber be incorporated at the front of the conversion unit. Attached to the front of that was an integral .223 steel dummy casing. When the .22 LR round was fired bullets went through this dummy casing with no support, keeping things only roughly in line with the too-big center fire barrel for about two inches before crashing into the rifling. Third, twist rates are different.

Dedicated .22 LR barrels usually have twist rates of 1:16" while Stoner originally designed the AR with 1:14, which was changed to 1:12 for arctic weather stability (Russia was a big worry when the M16 was being developed) and again to 1:7 with the M16A2. Finally, these units are known for severe bore fouling. We stagnated with the Colt, M261, and Atchisson (manufactured by Ciener) rimfire kits and the poor accuracy that they were known for. In

22 LR conversions. Above center: M261 conversion less dummy chamber insert as used by the author and Compass Lake for dedicated .22 LR uppers. Also shown is a ten round magazine inserted in a standard AR magazine. CLE Bob Sled magazine locks the bolt back. the mid 1980s I approached Krieger Barrels about making a dedicated .22 LR barrel for the AR-15. They did and I still have it. It worked out very well and it wasn’t too long before I heard other shooters getting gunsmiths to make something similar.

When I took over the Armorer position for the Army Reserve in early 2000 I remembered what a great training tool my custom unit had been during cold Pennsylvania winters and I looked for some to issue to my shooters. Derrick Martin of Accuracy Speaks and the All Guard Team published The Complete Guide To AR-15 Accuracy in 2000 and he devoted a chapter to custom dedicated .22 LR conversions.

When I finally got a purchase budget I was able to follow up with Derrick and had him to build some .22s on the Atchisson unit with the same barrel contour as our competition rifles, float tube, and quarter minute sights. Ergonomically, they were identical to our centerfires and fit any AR lower. The guys really liked them and are still in service on the USAR Team. The Guard mobilized Derrick to the Gulf and had Compass Lake Engineering build units in his absence.

Accuracy Speaks and Compass Lake used Douglas blanks for the conversions. Eventually I got enough of the conversions in service with other blanks and determined Krieger and Lilja (in that order) delivered more accuracy. If you are planning to buy a blank for one of these projects remember that .22 barrels have no barrel extension on the back like a regular .223 and that raised flange is necessary for attachment to the upper receiver via the barrel nut.

Lacking this extension on the .22 LR the builder must incorporate a raised flange integral with the rest of the machining from a blank. To accommodate the fatter dimension of the flange you need to buy a blank no less than 1 1/4" outside diameter to allow for machining. I would get it about 24" long to finish at 20". Compass Lake offers their dedicated .22 LR uppers in either A2 upper receivers and 20" Service Rifle length or on a flat top Match Rifle configuration with a 24" barrel.

If you buy a dedicated .22 LR upper from either Accuracy Speaks or Compass Lake they will weigh and balance just like the real deal and that is critical for valid cross training. I build my dedicated .22 LR AR-15 uppers like Accuracy Speaks or Compass Lake with three major exceptions. First, I use a premium Krieger barrel.

Other custom builders will also give you a premium blank upon request (and sometimes along back order period waiting on the barrel factory to fill orders.) Second, I use only the DPMS Lo-Pro heavy walled upper receivers and include a carry handle with quarter minute match sights, double pinned at extra cost. The Lo- Pro has much thicker the walls than a standard flat top. About the last inch of any barrel mounted in an upper receiver is enclosed inside the receiver itself.

About the front third of that enclosed part is inside the threads for the barrel nut and the thickness of that section of receiver is set to match the nut. The rear two-thirds is enclosed by the receiver walls themselves. The theory is thicker receiver walls provide better and more rigid support for that back barrel section resulting in more uniform (and perhaps dampened) barrel harmonics.

You might not think that a little pipsqueak .22 LR would generate all that much barrel whip to profit from the thicker walls of the DPMS receiver but since I switched from standard upper receivers to the thicker Lo-Pro I have noticed .22 LR group shrinkage on the machine rest. I am also switching to this receiver for centerfire match rifle uppers and groups are also running a little tighter. I want to

get a little more data on the effectiveness of the thick walls on accuracy before passing final judgment but so far I am optimistic! The Lo-Pro receiver fits standard AR-15 lowers but I don’t know if thicker receivers are legal in NRA or CMP Service Rifles as they do constitute an external modification. Thick walled receivers are legal elsewhere and I use them for match rifles.

Like the Lo-Pro, Sun Devil (sundevilmfg.com) thick upper receivers fit standard ARs and are cosmetically better, especially on Sun Devil’s lower. One additional advantage of a Sun Devil matched set is the tensioning screw in the lower receiver that acts like a Accu-Wedge on steroids to tighten upper to lower fit. Glen Zediker praised these receivers in his newest The Competitive AR15: The Ultimate Technical Guide.

The third different thing I do is properly stabilize the back of the barrel in the upper receiver using a combination of shim stock and Loctite The aiming black is too large and the scoring rings are not properly scaled for difficulty. Use National Match Air Rifle 200 yard reduced targets (right) instead. Below center: 200 yard targets scaled to be shot indoors. Top to bottom, 25 yard, 50 feet, 33 feet. On bottom is the Crosman MAR177. Above center: Can you identify the imposter in this photo?

Top and bottom are .223 centerfires, center is a dedicated .22 LR. The match rifle and dedicated .22s are built on DPMS Lo-Pro receivers. 45 ACP upper and magazine shown with Figure 14 "Hun’s Head" targets. Green 290, removing slop that results in about a 1/3 reduction in average group size in all AR-type rifles. I have found that most Stoner accuracy enhancing techniques work across the board. See "The Relationship Of Barrel Extension Diameter To Accuracy In The AR-15" in the March and April 2013 issues.

Dedicated .22 Training You can certainly train rapid fire strings with these .22’s indoors but there are disadvantages. First, most rapid fire strings call for a rapid reload and most .22s don’t lock back on the last shot. While it is simple enough to reach up and work the charging handle to chamber around following a reload, doing so might program "bad code" in the shooter’s mind.

Derrick Martin suggests charging an extra round in the first magazine and practicing a "hot" reload with a chambered round with a press of the bolt catch, just as with the centerfire rifle. Jeff Cooper noted, "A man will push himself harder to win a little gold medal than he will train to save his own life." What we practice stays with us when under stress, even if that stress is "just" trying to win a little gold medal.

Second, there is a lot less recoil with the .22 LR than with the .223 and training rimfire rapids requires less recoil recovery, which may give the sensation of taking too long shooting the centerfire gun. Many shooters will overcompensate, shooting too fast and scoring lower because of the panic of thinking they are running out of time causes them

Using a standard A2 sight adjustment tool, the gunsmith can install sights with narrower posts. Below the MAR177 is a ten round circular magazine and weighted facsimile that helps give the balance and ergonomics of a real service rifle. not to dress up shots well enough. Finally, while there is a reduced standing and sitting target for 50 foot shooting, I can’t find a reduced 300 prone rapid fire target. Dedicated rimfires really shine training standing.

You can get a Bob Sled magazine from Compass Lake for single feeding slow fire and it will hold the bolt back like normal. Ray-Vin has free targets for printing on their website scaled for 50 feet and 25 yards. Rimfire has longer barrel time since most standard velocity is only 1,085 feet per second compared to .223 77 grain bullets at 2,770 fps. Shooting good standing scores with the rimfire requires more followthrough and will greatly improve scores with the centerfire.

Not long after the Reserve Team began using dedicated .22 uppers some of our members were getting good outdoor training with them at 100 yards using MR-31 (scaled 600 yard) targets With a 1 3/4" ten ring, it’s no small marksmanship task to center a group there with the short AR-15 iron sight radius. This also provides wind doping practice for full distance. In terms of quarter minute clicks, compensating for wind and mirage at 100 yards with the .22 closely mirrors 80 grain centerfire bullets at 600 yards.

Using the specs of standard velocity Eley .22 ammo (1,085 fps, 40 grains, ballistic coefficient 0.145) the handloads.com ballistic calculator confirmed we were pretty close to being right. The .22 at 100 yards drifted a little less than the 80 grain at 600 yards measured in minutes of angle. If a shooter did a good enough job Lower right shows approximate pellet impact when windage parts of the rear sight stick. The 10, 9, and 8 rings are all black in this target.

The three targets across the top were fired with different lots of Vogel pellets. The first two on the left were fired with standard .177 (4.50 mm) pellets and top right is a Vogel 4.495 mm pellet. Second row left is Final Match pellets, center is with Champion’s Choice (flier at 5 o’clock is from a slightly marked pellet) and at the right is RWS. The two bottom targets on the left were fired with Crosman’s Premier Super Match.

This was fired with one MAR177 and I several others tested with nearly identical results. Bottom right marks approximate point of impact when the sight sticks clear to the left. Nickel is a reference for size. of programming his brain with the .22 at 100 yards, in the same conditions he would tend to under dope at the 600 yards just a bit. When we started to convert to the 90 grain bullet I ran the numbers a second time and the comparison with a .22 LR at 100 yards is nearly identical. This is a big deal!

Availability of 100 yard ranges is greater than 600. Even if you do have a 600 yard range available, you’ll need pit service as trying to train without instant target feedback is nearly worthless. You can train by yourself at 100 yards and see the impacts in your spotting scope without a pit pig. If you have a .22 and haven’t tried this I strongly urge you to do so ASAP. You may have been overlooking a valuable training aid.

Other Options I mentioned that one of the down sides to the .22 LR uppers was lack of recoil. Olympic Arms makes centerfire pistol uppers such as 9mm and .45 ACP. The 9mm obviously has more recoil than the .22 but the .45 ACP is nearly identical to the real deal. These are basically submachine gun uppers and accuracy is like the original .22 conversions with the fake .223 casings on the end. Like all Stoner rifles, they improve with properly stabilizing the back of the barrel in the upper receiver.

Given the carbine length, ergonomics are like the M4. For military combat matches, we had rapid engagement phases such as head targets at 25 yards and I just

The empty case of the excellent Erie Railbender is just there for sizing purposes as alcohol and firearms don’t mix. Above center: Checking windage tracking on an MAR177 using the Ray-Vin gauge. happen to have a 25 yard range in my basement. The Olympic Arms .45 ACP was just the ticket for me. There are other .22 uppers and whole guns appearing (and sometimes disappearing) rapidly. Some resemble AR-15s, others not so much. Brownells sometimes has examples.

A lot of these have 16" barrels and if you are shooting a carbine they make some sense. If you shoot a regular 20" barrel normally, however, I would not recommend a carbine as the ergonomics would suffer just too much. Crosman MAR177 The Crosman Modular Adaptive Rifle is a pre-charged pneumatic (PCP) AR-15 upper. Over the years other outfits tried making AR-15 air rifle but none of them filled the bill. Overly light triggers, poor ergonomic matches with the real rifle, sights not the same, you name it.

Not to mention high prices! I did a real double take when I handled the Crosman units. I feels and looks like the real deal, is a flat top, and has an AR-type carry handle fixed to the back. The overall length and weight were very similar to a 20" AR. Shooters reported stellar reviews. One of the things I like most is using your actual lower, giving an identical trigger pull. I have been a federally licensed firearms dealer for over 40 years and I contacted Crosman about getting set up as a dealer for the MAR177.

The 2013 retail price on the MAR177 was $600 and I am able to sell them for half the cost of a .22 upper, making them affordable. In fairness, the .22s offer more options, such as rapid fire and simulated long range practice. Other than the MAR177 upper itself, you’ll need properly scaled targets. This includes the bull (aiming black) giving the same apparent size as full distance. Despite how the math may work out, this can be a bit subjective between shooters.

The scoring rings also need to be scaled to the distance and capability of the gun so the shooter gets reliable feedback. If the accuracy of the gun and the scoring rings are in balance a shooter should fire about the same score with a sub-caliber device. I would not attempt to fire an MAR177 on standard AR-5 ten meter air rifle targets because they are designed for expensive target rifles with entirely different sights, light triggers, and different ergonomics.

There are different 33 foot NMAR (National Match Air Rifle) targets specifically for the MAR177 through the Civilian Marksmanship Program (thecmp.org) made by Kruger (krugerus-targets.com) and sold by MK Tactical (mktactical.com, Targets include scaled 200 and 600 yard versions for standing and prone, respectively. These can also be used at 33 feet with .22s as well and the MAR177 can be shot on 50 foot and 25 yard versions as well. You’ll also need away to fill the air reservoir.

Crosman sells a device that looks like a bicycle pump, retailing for $156.25. Crosman reps warned this takes a lot of work and they’re not kidding. If you want to avoid the exercise session involved with the hand pump, Crosman markets a scuba tank and adapter for about $400. When trying to decide if I wanted to stock these, I Googled "Scuba Shops or Dive Shops" and a number of them within a two hour drive.

My county is 97% forested with only one stop light and I have never seen a scuba diver since I moved here about 33 years ago, so I think most of you would locate even more scuba shops around you. Regarding air, the manual says you get about 120 shots per fill. There is a little gauge on the gun itself for air pressure. There is a bottom suggested limit and Crosman says going below that risks lodging a pellet in the bore. There is also atop gauge not to be exceeded for safety.

Stay between those two red lines and your 120 shots provides a fair amount of standing practice. If you plan on shooting less there is

Above center: Remove the elevation wheel and drill a second rear hole exactly matching the existing front hole. Trim a standard US spring to the same length as the existing front spring. no advantage to filling the gun to the top limit of 3,000 psi. I fired test groups over my Oehler chronograph at full and almost empty pressure and detected no accuracy difference, no change in vertical point of impact, and no velocity degradation with a uniform spread.

The factory says you can get about 600 fps and mine clocked 539 fps. I don’t consider that a problem at all. My extreme velocity spread between the fastest and slowest pellet was only 11 fps. I don’t know of a single service rifle competitor on the circuit that wouldn’t kill to have his 600 yard ammo that consistent in velocity! The factory recommends storing the MAR177 with no air in the reservoir and instructions cover how to bleed it out.

My tests show you don’t have to bust a gut filling the thing clear full for an average practice session. Put as much air in as needed and have complete confidence in the air rifle’s accuracy and uniformity of velocity. You’ll also need pellets. I did an accuracy test using several of the uppers and a variety of pellets not long after I received my stocking shipment from Crosman, shooting ten round groups at 33 feet from a machine rest. Group sizes ran 1/4-1/2".

Putting the accuracy in perspective, those groups in MOA would be between a little over 2 MOA and about 4.5 MOA. The groups are tight but none of us would accept a four minute gun for real distance shooting, however, accuracy is relative. Since the scoring rings of the targets are properly scaled, shooters are getting about the same scores with the MAR177 at 33 feet as their centerfire Service Rifle at 200 yards.

I don’t claim to be air rifle smart by any stretch and my initial machine rest testing was the first time I ever fired an air rifle. Scott Pilkington, one of America’s authorities on air rifles and designer of the MAR177, told me that air rifles are very "lot specific" in their pellet preference. .22’s also have a reputation for being lot specific in accuracy performance and I see that on my machine rest when testing dedicated .22 LR AR-15 uppers. A note on pellets.

When I was loading the little circular magazine to shoot a group with Champion’s Choice pellets I noticed a slight mark on the little hollow base of one pellet. It also resisted going into the magazine a little. That pellet ended up being a flier. With the exception of RWS that is packed individually, other pellets are bulk dumped into a tin container, so there is an opportunity for them to get boogered and that is most likely what happened with that bad pellet I identified.

Being new to pellet shooting, I wanted to try it and it resulted in a flier. The lesson to anyone shooting these things is that obvious deformities in the pellets will likely result in degraded performance and one should cull such pellets. In hundreds of rounds of testing it was the only blemish and the only flier I shot so your odds of getting good pellets are very high.

In summing up the accuracy testing, I found all of the MAR177s tested would clean the reduced standing target at 33 feet with most any quality pellet. Perhaps part of the reason for the accuracy of the MAR177 is the Lothar Walther barrel which enjoy a good reputation among air rifle accuracy enthusiasts. As a military armorer for over a decade I tried to test every custom barrel on the market, including Walther. I don’t have an axe to grind with any barrel maker.

Every one of them I have experience with was anxious to please and went out of their way, including Walther. I personally know a shooter who set national records with Walther barrels and some swear by them. To me, that simply means one good shooter got one good barrel. My accuracy testing with a batch of Walthers caused me to drop them from consideration for use in Service Rifles. They may be fine for air rifles, however.

Glen Zediker in The Competitive AR15 is even less reserved in his comments on both Walther and Wilson. A USAR shooter won the President’s Match at Camp Perry one year with a Wilson barrel and that was one good shooter with one good barrel. Like Mr. Zediker, I dropped Wilson barrels fairly early after testing. I’ll expand on my bar-

rel test results in a later article that will have every barrel maker in the United States except for two taking out contracts on me! We had a similar incident about a decade ago when an AR company with four initials in their name came out with a dedicated .22 LR upper. Their price was well below custom ones from Accuracy Speaks and Compass Lake and government purchasing regulations will take the low bidder.

I got stuck with these uppers that averaged of 3.9 MOA with multiple lots of high quality matchgrade ammunition. The barrels used were made by a low-bid barrel maker that normally produces black powder barrels. Their black powder barrels don’t have a bad reputation but the .22 bores were rough as a cob and shot terrible. After a bunch of work I was able to cut the group sizes to about 2/3 of what they were when they came in my shop.

That still made them well over double the group sizes of the quality Accuracy Speaks and Compass lake uppers. I have learned that cutting cost corners in this business frequently results in accuracy degradation. To make matters worse, the upper had two extractors and the one on the right side had a bad habit of going into orbit of its own volition with very modest round counts, often under 100. That really ticked me off, so I contacted the company and complained.

In spite of run arounds and unfulfilled promises, I never got any replacement extractors and they soon withdrew the uppers from the market. They stayed in their fox holes all this time but have recently reintroduced a dedicated .22 upper. If they are anything like the previous offering, let the buyer beware! Last, but not least, you will need a bullet trap appropriate to the distance, target, rate of fire, and caliber of firearm you are shooting.

If you are just shooting a .177 caliber pellet rifle at 33 feet, your requirements may be met with something you might find at a Walmart. I have a 15"x15" Detroit Bullet Trap for use with the Olympic Arms .45 ACP in my basement. I practiced on Figure 14 targets, firing four shots in three seconds from at 25 yards from "Standing Alert Position" (stock in the shoulder and muzzle down at 45 degrees.) Obviously this takes a bigger and stronger bullet trap than a pellet rifle.

MAR177 Sights The front sight post is about 0.072", give or take a couple of thousandths, standard A2 sight width and popular with current military and older shooters. The threads in sight base are compatible with replacement posts. The rear sight has an aperture of about 0.046" and is one of the more common sight options. There is no hood but under consistent lighting I am not sure it needs one. Older shooters like the 0.046 and some go on up to 0.052".

To me, shooting indoors under artificial lighting never gave the clear sight pictures I get outdoors and I think the fat rear aperture might help clear that up. The elevation is supposed to be quarter minute (about 1/32" at 33 feet) and windage is half minute. Shooters normally find differing adjustments confusing but 1/16" windage movement seems plenty fine at 33 feet. The last step I perform before any custom gun leaves my shop is gauging the sights.

When I was the armorer for the Army Reserve I likely spent nearly as much time tinkering with sights as replacing barrels. The fine 1/4×1/4 threads wear out fast and the slightest speck of dirt can cause havoc. I checked sight tracking on the MAR177. It says on the box "Made in the USA with some foreign components." I can sure guess what one of the "foreign components" might be and from what country it might hail from! On the very first one tested the elevation wheel didn’t want to budge at all.

It was jammed up and it didn’t take but a quick visual inspection to find the cause. The elevation wheel was jacked at a terrible angle, way high in the front where the spring loaded detent pushed up on the underside. I got my feeler gauges out to measure the severe tilt. I disassembled and measured the diameter of the threaded stem (the part fitting under the sight base) and compared that to the corresponding bore hole in the carry handle. It was way too fat, permitting the stem to sit crooked.

At that point I was tempted to substitute a quality sight base with a standard diameter stem. I dug one out and it wouldn’t fit. Now the hole wasn’t big enough for the standard American part. It would (Continued on page 22)

have been easy enough to ream the hole but I would add the expense of the new sight base. I figured the problem could also be fixed by adding another spring and detent under the rear of the elevation wheel to even out the front and rear pressures. Remove the elevation wheel and set your drill press to stop at the same depth as the existing front hole so the spring pressures become equal, then install a second spring and detent in the new rear hole to match the front set.

When I put anew American coil spring in there I found that the front Chinese spring was a couple of coils shorter. Absolutely nothing to spec in this rear sight! I cut coils off the American spring so it was of equal length, reassembled everything, and the elevation wheel sat level the way it should and the sight moved more normally. Fortunately, my inspections indicate there aren’t many sights with these elevation problems.

In the future I’ll ship offenders back to the factory and let them replace the whole carry handle. Shipping carry handles back with this next problem probably won’t work because every one I’ve inspected had this problem! There is an enormous gap between the right edge of the sight base and the left side of the windage knob. When shooters make windage adjustments they often press in to the left on that knob when doing so, forcing the windage screw left.

The coil spring buried in the windage knob is supposed to exert enough pressure to correct this. Sometimes on the MAR177 and some ARs the screw sticks, yielding point of impact to the left, and then creeps gradually back with each shot, stringing shots horizontally along the way. The fix works for ARs as well. Get 250×375 shim washers in assorted sizes from 0.001" and 0.002" (for fine tuning) and some 0.016" and 0.020" sizes.

No two sights seem to want the same number of shims, with some needing four thicker shims and others requiring only a few. Your feeler gauges on that gap between the sight base and windage knob will help get a ball park idea. It’s faster if you leave the actual sight off while rough fitting. If you get too many shims stacked up you’ll have difficulty driving the roll pin back through the windage knob and the sight will run hard for the customer.

If you fail to use enough you’ll still end up with some unwanted left windage. A little practice and you’ll get it just right. I like to finish off with another tracking check with the gauges any time I tinker with a sight just for insurance. I am performing this windage correction on all MAR177 sights. The sights are the only weakness that I have found on this otherwise very well designed unit. AG