As is common knowledge, the military forces in the 20th century had a very bad habit of disbanding sniper units and training between the major conflicts and after WWII it was no different for the US Army. So while they had gone through the effort and cost during WWII to first field the stop gap M1903A4 sniper rifle, and then develop and field the M1C and M1D sniper rifles, once the war ended, those rifles were stockpiled and packed away.
The M1C/D rifles made an appearance briefly in the Korean conflict, but they were never widely used and after those hostilities came to a cease fire, the M1C/D rifles were again packed away. Then the Vietnam conflict broke out and the US found itself in a guerrilla style war with a huge demand for qualified snipers and sniper rifles. This time around, the M1D rifles that were still around were not only old and out dated, but their 30-06 chambering was no longer the standard and the M1 Garand rifles were no longer in service. The US Army dabbled with scoped M-16s with very little luck, so finally a serious effort was made to develop and adopt a proper sniper rifle.
The US Army began its search in the same year that the USMC did, 1966, but the US Army did not go the route of a bolt action sniper rifle like the Marines, instead, they were believers in the semi-automatic and they started with modifying the M14. The M14 itself was an adaption of the original M1 but chambered in 7.62x51mm NATO (308 Win) and fitted with a detachable box magazine (DBM). They first tried using the M84 scopes from the old M1D sniper rifles and mounting them on top of a M14 with a modified swing over mounting system. The rifles were tested with both M80 and M118 match ammo, but the results were not very positive. The 2.2x magnification of the M84 scope was deemed unsuitable, the accuracy of the rifle with M80 ball ammunition was also unsatisfactory, and the scope mount, a hinged unit, was ruled deficient. But the National Match version of the M14 with M118 match grade ammo proved adequate and worthy of further development. So they continued with the program.
Because of the pressing need for sniper rifles in Vietnam, the Army actually deployed a good number of standard M14s with M84 scopes mounted in various different ways. This was done until a suitable permanent replacement system could be developed for the Army sniper program.
In 1964 James Leatherwood came up with a clever design for a mounting system that would allow a scope to be automatically adjusted when the zoom ring was changed. This was done via a cam system that would physically tilt the scope forward as the zoom power was increased. When he was based at Ft. Benning Georgia in 1965 the concept was presented to the Limited Warfare Laboratory (LWL) and a project was started to design a system that would work on a sniper rifle. An all-aluminum system was subsequently designed and then tested in 1967. It was called the Adjustable Ranging Telescope (ART) and was combined with a Redfield Accu-range 3-9x40mm commercial scope. You will probably recognize that this is the same scope the USMC adopted for their M40s during the same time. It was considered the best scope on the civilian market at the time.
The US Army had the scopes made without the tombstone ranging mechanism inside the reticle and instead had the scopes installed with a reticle that had marks on the stadia that covered 30 inches at 300 meters on the vertical and 60 inches at 300 meters on the horizontal. Since the reticle was located on the 2nd focal plane and did not grow and shrink with the power setting, it could be used to provide range estimation from 300-900 meters. The sniper would just zoom in until the marks on the vertical crosshairs would cover 30 inches, typically the belt line to the top of the head, and then look at the marks on the power ring to determine the range. At the same time, the cam would actually already be raising, or lowering, the scope to automatically compensate for the range at that distance. The entire unit performed as a system for rapid and accurate target engagement. Zoom in, hold for wind, pull the trigger. The cams were made to match specific cartridges and there were three different cams that could be switched out, one each for the M118 Match, M80 Ball and M2 50 BMG ammo.
Of course, all of the fancy auto-ranging ability of the ART system would do no good if the rifle could not perform adequately as well. The LWL contacted the United States Army Marksmanship Training Unit (USAMTU) to have them put together an accurized M14 for use with the ART. The USAMTU is where all of the competitive shooters for the Army are stationed and they came up with an extensive list of modifications performed on a National Match M14 rifle that included the following:
- Disassembled down to the receiver
- Barrels were selected for straightness and uniformity
- Barrels were installed with minimum headspace on the chambers
- Area of contact for the rod guide was knurled to prevent the guide from rotating on the barrel
- Gas cylinder and band were screwed together as an assembly and internally polished to reduce carbon build-up
- Piston was polished
- Flash suppressor was reamed out to specifications shown to provide best accuracy with M118
- Barrel and flash suppressor were machined for a perfect alignment
- National Match stocks were treated in a vacuum sealed oven, baking at 300 degrees for an hour to remove all moisture from the wood, then the stocks were impregnated with epoxy and baked for an additional hour while held at 100 psi. Then the stock was placed in an oven to cure for 3 days. This was done to stiffen and eliminate any warpage or swelling due to weather changes.
- Stock liner was removed to provide 1/8” of bedding compound in the recoil areas
- Barreled actions were glass bedded in a two stage process to provide centering, and then pre-loading of the front part of the stock to dampen barrel vibrations.
- Triggers adjusted to 4.5 – 4.75 lbs
- Hand guard was cleared of the stock and anchored to the band
- Gas cylinder lock was indexed to be finger tight at the six o’clock position
- A new operating spring guide was installed
- Cams, corners, and bearing surfaces throughout the mechanism were modified to provide smoother operation and uniform return of all moving parts
- Rifles were then tested for accuracy and the ART mounted and zeroed
As you might imagine, these rifles were very accurate. They performed tests where they were getting 10 round groups at 900 meters that measured under 10”. The rifle was designated the XM21 The Army then sent 10 of these original XM21’s to Vietnam in 1967 for evaluation. There were several weaknesses found, but overall they were satisfied with the system as a whole. At the same time some M16s were being tested as sniping systems as well, but the smaller 5.56 cartridge could not match the long range capability of the XM21. The Army also considered bolt action rifles but elected to go with a semi-auto because it provided the ability to perform rapid follow up shots, rapidly engage multiple targets, allowed the sniper to better defend themselves and the M14 already was setup for night vision capability. They did recognize that the one major disadvantage was the flying brass that was ejected and could be a target identifier, but this was considered to be acceptable when compared to the advantages.
At about this same time the 9th infantry division requested help from the USAMTU in setting up a sniping program so in 1968 the AMTU sent over 10 instructors and then later sent over the first XM21 rifles for use with the 9th ID. Also, in early 1969 the AMTU sent over a batch of Sionics M14 suppressors for test and evaluation at the 9th ID sniper school with great success.
Finally in February of 1969 the XM21 was fully funded by the US Army and larger production began and the XM21’s were deployed in large numbers, about 50 per week being built to the exacting specs already mentioned. Officially the name remained the XM21 up until 1972 when the Army officially adopted it as the sniping standard and it became the M21. There were over 1300 XM21s used during the Vietnam conflict and while there were some failures, the rifles held up extremely well and served with distinction and great effect out to 900 meters. After Vietnam, the sniping program in the US Army went dormant, again, until some interest was rekindled in 1976. The M21 was tested against the M40A1, M82, AR10, and some others and the M21 more than held its own and the Army elected to hold on to it as is. Once the official Sniper program was adopted by the Army in 1988, the M21 was replaced by a new bolt action sniper rifle known as the M24. There are still some M21’s in Army vaults around the country, but none are in wide spread use by the US Army today. Though the M21 still lives on having spawned some very successful offspring such as the XM25 and EBR.
As you can see from the comments below, the M21 holds a dear spot in many U.S. Army snipers hearts (me included), and rightfully so.
i like to buy this one, good to have this one at home..
Agreed. I would love a real M21
I had a Norinco , yes Norinco m14 and set it up with the Art scope and trigger job and a custom stock. It shot great with that scope once you set the cam timing with the cartridge. It did shoot M o a oh. And bedding
[…] M25 is similar to the M21 in many regards, it is a National Match M14 glass bedded in a McMillan fiberglass stock, uses a […]
Very informative site and well done as far as accuracy of info o the XM21/M21 platforms. I used an M21 in VN with the 173rd Airborne Brigade in the Central Highlands. I am rebuilding it as close as possible using an accurized M1A with a original AR TEL scope. I have an incomplete AR TEL mount, I have the lower but it is missing the Base and rings with spring. If any of you have any info on where I might be able to find the missing parts, or may be selling a complete mount, I would very much appreciate your feed back! Tough to find items…. Rene'”Dutch” Macare’
Thanks, glad you found it useful. I would love to get an ART setup as well at some point. Loved the M21 system. Something unique.
Contact High Lux Optics
tell them Pat from Camp Valor sent you
Thanks Pat – Yes I did contact them and became a friend of Corbett Leatherwood whose father designed the ART scope I used in Nam. I finally found a good example of the original ART-1 and aslo ownan original(working) model of the Starlight scope I used. It was just a phenominal sniper platform for its’ time, and I believe that it helped save many friendlies lives.
Mel if you are interested in the history in detail of Sniping in Viet Nam, check out a book called “The Long-Range War” by Peter R. Senich. You will enjoy the content I think.
E-co 3/187th 101st A/B . Served from July 1970 til July 1971. It was boasted that from July of 1970 to and through July of 1971, our company consisting of recon snipers mortar and radar had more confirmed kills than any like company in our Battalion
I am proud to say I was one of the 10 man instructor teams sent to Vietnam to train the incountry soldiers. I was attached to the 23rd Inf Div for supply and logistics. The weapon was actually very good for a production although our gunsmith did make a few improvements. Thanks for the posting of this article.
Thank you for your invaluable service
Well done article. I’ll never forget the M-21. I was trained on it in August of 1986 at Ft. Campbell, KY and then used the same rifle in Sniper competitions and won the Division Match but stopped there because I ETSed. Mr. Joe White was highly respected as our instructor (Mr. Bosworth as well) and we always went back to Range Control to visit with him. I think he retired from Civil Service in the late 90’s but Mr. White was an Infantry Sniper in Vietnam with over 50 confirmed but he never once discussed it, we found out through back channels. And yes, I have my civilian version of the M-21 made out of a forged receiver and use a Leatherwood ART scope. I’m honored to be among you.
I have a Federal Ordnance M-14 that Joe White rebuilt to M-21 specs for me except for steam drying and coating the stock with epoxy. He did everything else, even changing out my standard barrel and replaced it with a NM barrel. He went to church with my wife until his death. They were/are LDS and I am Southern Baptist, so I got to know him through my wife. I still have the rifle although I never had an ART or ART II scope on it. It has a second ATN X-Sight 4K Pro scope and is my “designated deer rifle”.
101 Sniper grad. 5 Dec 1981. Mr White, the real deal
I actually own an XM-21 that was given to me by a friend that was a Recon Marine in the 80s & 90s. I would love to know what the value of it is. I cannot find anywhere online that talks about what one would be worth today.
The first question that would need to be answered is whether it is a real XM-21, which would have to be handled by a class 3 NFA rules since it has the full auto selector switch. But if it is a documented M21 with a real ART-I scope on it, then the value would be VERY high as these were not available outside of the military. Do you have any pictures or info you can send me (via email)? I would be happy to help determine.
I served in the US Army Infantry from 99-05. I depolyed to Iraq in 04 and had never seen or handled an M14 in my life. However, I was and E-5 team leader w/o a team leader slot available. After shooting expert at Doha’s South range, My Plt. Sgt handed me the M14 and said that I was going to be the platoons designated marksman. I spent two weeks with the battalion scout snipers and learned everything I needed to know about the rifle and basic sniping techniques. I fell in love with that Springfeild and found it to be more than capable out to 600m. I played the DM role for the first three months in country before I got a team. I loved that rifle so much that the first thing I bought when my tour was done was a Fulton Armory M-21 Scout with all the NM modifications. When I do my part, that rifle shoot 1.5-2.0 groups. Fine shooter!
I used an XM-21 sniper rifle for my last 7 months in Viet Nam with the 173D Airborne Brigade. I loved that rifle. If it had been a girl, I would have married it and brought it back home with me. I used it a number of times.
I used it one time to take out an enemy sniper that decided shortly after I had moved to a new unit to snipe us. He got the bad end of the sniper duel because I used one round from my sniper rifle to put an end to his bad act.
Another time, I used my sniper rifle to drop a feral hog while we were on a patrol in some foothills in the Crescent Valley. That pig fed a number of Sky Soldiers and local troops and their families.
The XM-21 sniper rifle, for the time period, was top-of-the-line! We couldn’t have asked for a better rifle to meet our shooting needs.
First AATW!!! Carl were you trained in country? If so what school was that? We may have been at the same school during the same time period. Also were you a regular that was pulled from the brigade or were you a LRRP or Ranger?
Cheers – Rene “Dutch” A/3/503
XM-21 is a very good weapon from what I’m reading and would like 2 buy one
Purchasing a real one will be extremely difficult as they were never sold on the civilian market, primarily because they were capable of full automatic fire. But you can buy a nice Springfield Armory M1A rifle (Super Match, National Match) and build a nice clone easy enough.