Combat Proven Upper Receivers for the M16
 1 La Cueva Creek Road • Glorieta, New Mexico 87535 • 505-757-3303 • Fax 505-757-2322
  M16 Clinic "VIPER™" Series
Upper Receivers



Posted by “Ryno” on 04-AUG-05

Greetings to all of TFers. I am enjoying my summer here in Iraq, its lovely this time of year. For all of you PSD types I would like to inform you of a nice little toy that my team is now using. It is a 7 inch upper called the M16 VIPER. It is a fantastic tool for the trade. It gives you the punch of a .223 and is smaller than an MP-5. We have had zero problems with it in the field.

The guy that produces them, Greg Leaf, runs a shop called the M-16 clinic and the price is right.

This thing drives nails, it doesnt have the sustained velocity at long range of its longer counter-part, but makes up for it in so many other ways. We have had zero malfunctions even on full auto. In my opinion it is the pinacle weapon for HRO's. For all of you Golfers, remember the first time you used a titanium Driver on the tee after years of using you Dad's old woods.

If you have any questions PM me and I will fill you in.

30-Jan-05 Baghdad

Dear Greg,

I just wanted to express my utmost thanks to you.  I deal with many tactical companies and the customer service I received from M16 Clinic is outstanding.

My M-4 has had over 20 magazines through it on both auto and single and has not missed a beat since receiving your equipment.  My weapon receives a lot attention from other PSD teams and US Forces here in Iraq, with the inevitable questions about reliability.  I always tell people: “If you've got a question about M16s, then speak to Greg at the M16 Clinic; as "He’s the Man!"

All the very best for the future.

D. P.
PSD Team Leader

M16 Clinic Viper Series
Superb accuracy for
Counter Sniper and
Spotter / Oserver
M16 Clinic in the Field
  CONTACT M16 Clinic
Mon thru Fri, 8am - 4pm (MST)
Corporate Sponsor

Awarded on 02/03 to the


Awarded on 10/03 to the



Hey, great to hear from you again. I am in love with the M16 Viper and am kicking around buying another Viper for my other lower.

You build the best M16 I have ever fired.

For such a short barreled weapon its rate of fire is very user friendly.

Let me know if you could build another one for me and what kind of time frame?


K. S.
Coconut Grove P.D. SWAT
2004 NTOA Conference attendee of M16 Clinic's Lecture: "Advanced Armoring M16s". Orlando, Florida

16-Dec-04 (As posted on SWAT forums, National Tactical Officers Association )

For anybody incurring M16, M4, AR15 problems, this is for you.

Over the past couple of months, I experienced a myriad of problems with my rifle (16" LE).  I took it to an armorer, allegedly a master armorer, supposedly capable of fixing problems.  He replaced some gas rings, and a little spring or two more as a maintenance action, and said he couldn't find anything wrong with it. The rifle continued to fail.

I contacted Greg Leaf, owner of M16 Clinic, and sent him my upper, bolt, charging handle, buffer, four casing from malfunctions and the action spring.  When told of training I would soon be conducting, he cleared his bench to get my weapon done. In no time at all, Greg had identified FOUR major problems, done extensive test firing of the weapon, replaced needed parts, reset the headspace, and shipped the upper back to me with startlingly detailed reports on all of the work performed.

All of the broken/replaced parts came back in sealed plastic bags marked with what the problem had been, while the upper itself was painstakingly repacked to protect it during shipping. Greg also included a couple bits of swag for each student in my course.  I took the upper out this weekend and tried my best to make it jam from either heat, or sustained firing. It functioned perfectly.

So, if you have business in this realm, give it to Greg Leaf at M16 Clinic ( ). You won't be sorry.

Stay safe.

BCH @ D.O.E.

16-Dec-04 PITKIN County, Colorado

Hey, Greg,

I received the Viper-XRP and managed to get out to our range this week.

The weapon fires great and prints paper even greater!  I remounted my Holosite and zeroed it at 100 yards from the bench, then moved to off-hand shooting, shooting while moving, prone and kneeling. The weapon consistently shot sub-moa from the bench; less than 2 MOA standing and moving.

The bolt and bolt carrier are great. The weapon is very solid and lacks that rattle most stock AR or M series weapons have. Locking back on an empty magazine has a really solid feeling. Very little muzzle jump, and the sights come right back to center.

I am very satisfied with the Viper-XRP and recommend it to every one!  Thanks!


G. F. K.
Deputy, Pitkin County Sheriff’s Office Aspen, Colorado

30-Sep-04 Iraq


I just fired the Viper and it is fantastic in every way. The reduced recoil was noticeable from the first round.

I slapped my Acog on top, zeroed with no problems and hit a bottle cap at 40 meters.

It feeds smoother than anything I have fired. No double feed issues or failure to eject issues. Just a pleasure to fire.

I feel much more comfortable taking the VIPER out on the road than anything I have carried here in Iraq.

The chromed bolt carrier group cleans up easier; which is always nice. I fired 90 rounds on semi and four bursts on auto from a 30 round mag with no issues. I did notice the rate of fire is slower and smoother than my other 7.5 inch upper which fired so fast on auto it jammed constantly, not to mention being totally out of control.

The Viper is so well tuned and controllable, it is simply perfect!

It was a pleasure doing business with you.

I will send photos and video later.

Take care,

R. S.


I just fired 150 rds through the Viper you built for me and it functioned flawlessly.  The accuracy is outstanding and the workmanship top notch. Your customer service is the best in the Industry.  The jpeg photos you emailed sent during construction convinced me that you and your equipment are indeed as advertised.

Well done Sir.




FOB -----, Somewhere in the Sandbox


This is some Damn Hot Equipment!!!  You are the Samurai of M16s!

I cant take my hands off of the M16 VIPER and everyone that sees it is going crazy with a case of VIPER envy!  The build quality is the best I have ever seen and the whole weapon all together doesn’t have a single rattle which I have always sought after with a passion.

I got the goodies you sent and gave Mike his package and he said that it makes him feel good to think that there are people out there that pay attention to us and not just the conventional forces. He appreciates the gifts.  I told him that it was from a guy who is very in touch with SOF and how they operate and understands their hardships from a touch of training himself. He liked that too.  Anyways I can’t wait to send you VIPER pics showing history in the making with my M16 VIPER.

Peace Joe

Ps. The M16 VIPER is better then I could have ever imagined. It’s the stuff sci-fi and video games are made of.

May 24, 2004 City of Georgetown

Dear Greg,

I wanted to let you know how much we appreciate your correcting the problems we had with our M16s.  Soon after the barrels were shortened, we experienced a multitude of reliability issues.  Even prior to that, accuracy was only adequate. After only a few days at the M16 Clinic, our uppers came back home with a “new attitude”.

Your skills and dedication became apparent as soon as we got some range time.  We now shoot tighter groups, more so than ever before, and the cycling problems are gone!  Prior to sending them to you, these M16s were restricted to entry use only.  With the levels of accuracy you achieved, we now use them in additional roles of perimeter and sniper/observer positions.

Being a small department with an ever-shrinking budget, you saved our agency several thousand dollars we couldn’t afford to spend. We considered buying new equipment as replacements.  M16 Clinic’s work made the replacement issue unnecessary.  Our thanks to you for your outstanding work and quick turn-around time.

We recommend M16 Clinic and its services to agencies and Special Operations Teams in need of improved accuracy and total reliability.

Stay safe.


Sgt. Danny Watson
Special Operations Team
Police Department
City of Georgetown, South Carolina 



I just zeroed the custom, M16 VIPER you built for me.  I zeroed at 50 yards and shot it out to 150 yards.

At 50 yards the group was the size of a dime.
At 100 yards the group was the size of a nickel.
At 150 yards all three rounds were touching within a dime size group.


Sean Clark, The Steele Foundation, Presidential Security Training Team
Palais National, Port-au-Prince, Haiti
USMC Scout Sniper School & Advanced Scout Sniper Instructor School

January 02, 2004

I've had the pleasure of doing business with Mr. Leaf for several years.  His ideas for perfecting the M16 and taking it to places it has never been are inspirational, as is his workmanship.  His uppers are habit forming.  Peering under the hood of one of these transformed uppers is similarly stimulating. The work is flawless.  He and his Clinic represent the apex of research and development of M16/AR15 systems.

C. L.

Dec. 28, 2003


You are the M16 KING when it comes to M16 Knowledge. I would send anyone of my customers to you in a heart beat, and am sold American when it comes to the M16 Clinic.

Yours truly,

James Cook, C.E.O.
Palm Bay, FL

Aug. 10, 2003 Town of Jackson Police Department, Tactical Team

Thank you very much for the quality job you did on our two M16 uppers.  The Tactical Match went great with NO jams!  We will recommend M16 CLINIC to everyone else in the tactical community.

Greg Pranzo, Asst. Team Leader,
Jackson Hole Tactical Team
Jackson Hole, Wyoming

07-JUN-03 Presidential Palace, Port-Au-Prince, Haiti

Made it to the range.....25 cent piece shot groups at 25 meters!  She be zeroed!!

The M16 VIPER does all you said, and more..... They work just fine.

Damn good job, many thanks........I already have a warm and fuzzy feeling with my M16 VIPER.

Warmest Regards,

Lee E. Sharon, Presidential Protection Unit,
Palis National
Port-Au-Prince, Haiti


100 East Second St.
Monroe, Michigan

Our Department purchased four Bushmaster M-4s for our Special Response Team. We sent these rifles back to Bushmaster to have 11.5 inch barrels installed. We had continuous double-feed problems with each one. I began to search for an answer and was told to contact you at the M16 Clinic. After a couple of conversations, I shipped all four uppers to the M16 Clinic. You said it would be a one-week turn-around for the work on all four of the uppers.

To my surprise, we had all four uppers (the “Four Horsemen”) back in about four days. We were amazed at the difference in our weapons on the very first day at the range. They all performed EXACTLY as you said they would; we had no malfunctions. We have since been all over our County and State pushing rounds through our “Leaf” modified Bushmasters.

At last count amongst the Four Horsemen we have fired approximately sixteen thousand (16,000) rounds total, or about four thousand (4,000) per weapon. We have used every kind of .223 ammo that we could get our hands on, and WE HAVE NOT EXPERIENCED ANY MALFUNCTIONS OF ANY KIND.

Our training occurs no matter what the weather or the environment. Greg, you are a man of your word. Your expertise with the repairs of our weapons is evident. There is no doubt that the work and concern you put into our weapons have made me and the other operators that carry the “Four Horsemen” more confident, more accurate, and more efficient.

We are very grateful to you. When we bring more .223s to our Team, they will spend a week at the M16 Clinic first. Take good care of yourself.


Sgt. Frank Atkinson

November 12, 2002


Thanks for the great service! It runs GREAT & is very controllable. If we have any future problems I will send you more jobs.

Eric W.
Deputy, United States Marshals Service
Dept. of Justice, District of Oregon

Oct. 10, 2002 City of Long Beach Department of Police

Thanks for the two pigtails. They were won as prizes at the 2002 WORLD 3 GUN CHAMPIONSHIP in Las Vegas, Nevada. Thanks for the generous gift and your support of the shooting sport.  To receive a prize that can be used by our SWAT Team is appreciated.

Officer Bob Correia / SWAT
Long Beach Police Department, Long Beach, Ca 90808.


Went to the range yesterday!  After TWO YEARS of fighting this little monster and spending a small fortune, we have lift-off. I wish I knew about you 2 years ago, I could have saved a great deal of money and a ton of frustration. The gun fired flawlessly!  I fired an entire C-Mag (100 rounds) without a jam or mishap.  That is really impressive considering that the gun has never fired more than 5 rounds with a problem.

Thank you for all of your help, I am impressed!


Bob Rieger

August 21, 2002

It kicks ass, 'Nuff said......
You rock dude, and I will be using your services again in the future.



I fired over 2,000 rounds (1,100 without cleaning) with NO malfunctions!  The Bench Package conversion makes my 10” Bushmaster work like I never thought it would.  Special recoil springs, modified buffers, different bolts -- I tried them all. Nothing makes it work the way your piggie does. The recoil is lighter and slower.

Chuck Landrum
East Point, Georgia

April 19, 2002 Rock Hill Police Department, Rock Hill, South Carolina

I have used M16 CLINIC's services and products for over a year now.  Greg and I met over the telephone as a result of my search for a solution to a problem I was experiencing with short recoil, failure to feed and failure to eject on a 6.50 inch barrel Entry Upper. From our first conversation, I knew Greg speaks from experience. The man clearly understood the problems L.E.O.s were facing and what all it took to make a short barrel .223 system function reliably.

M16 Cinic’s basic Shop Package is great!  The attention to detail in hand fitting and tuning of uppers is unbelievable. My Entry weapon now functions reliably with all the empty cases ejected into a neat pile. An additional benefit I found is the reduced cyclic rate in Full Auto. It allows single shot squeezes in Full Auto.

In closing, I have found Greg Leaf to be a man of his word who has consistently gone above and beyond in his business dealings. This is uncommon today.

Ken Fields,
Detective, Rock Hill Police Department, SWAT
Rock Hill, South Carolina


I own a retail firearms operation here in Baton Rouge & we place a very high importance on customer satisfaction. Our new goal will to be to strive for the level of excellence you have afforded me!! This is "hands down", the best customer service that I have ever received (and worth every penny!!).

The following reasons are why I will refer people to you and M16 Clinic in the future:
1) Honesty
2) Extremely knowledgeable & informative
3) Very friendly
4) Excellent packing & quick shipping
5) Very fast turn-around time
6) Keeps customer updated on status
7) Top notch warranty
8) M16 PIGTAIL WORKS!!!!!!!!

I certainly hope to do business again in the future!!

Best regards,

Marshall Morgan
Precision Firearms & Indoor Range Baton Rouge, Louisiana


My customers are very pleased with your product.  So many have called to let me know that the “Pigtail” is terrific.  I will continue to send everyone purchasing Pistols & Barrels to you.


Oct. 06, 2001

I have been fighting with the 7.5" upper on my M16A1 for a while now and could never get it to function reliably.  Finally I gave up and sent it off to a pro, Greg Leaf at M16CLINIC.  He diagnosed several problems with my upper: one was the barrel. He recommended and installed a new barrel.  Greg is a pleasure to deal with, answers all E-mails quickly and only took a couple days to do my install.

I got out today and shot the upper, well it works!  It rips through magazines like a raped ape!  Well I love the Pigtail, and from my experience I really don't know how you can get a pistol upper to run full auto without one.

Portland, P.D.

MACVSOG Oct. 06, 2001 TX, USA

Well, you have found the secret to getting pistol uppers to function. I will not put a pistol upper together for anyone unless I use a Pigtail. With the Pigtail the rate of fire is slower and there is no slamming of the bolt carrier into the back of the buffer tube.

Greg Leaf has really developed a great product that allows us the reliability and controllability that we need out of these little shorties.

All of the Class III's that I know that have dealt with him have had nothing but praise for both him and his product.

Charles Tatum
Alamo Professional Arms


Dear Mr. Leaf,

I recently installed one of your M16Pigtails in a friend’s 10" barrel M-16. This 10" upper never worked properly, like so many of them, from the time that he purchased it. The owner, extremely frustrated, had gotten to the point where he didn't know what to do.  We installed the pigtail, a simple operation even we could do, and gave it a try.  Much to our amazement not only did the upper suddenly work, but it ran flawlessly!!  Rate of fire is now lower and controllability is excellent.

Thanks for a fine product that actually works!


David M. Fortier

 All sales final  •  LIFETIME GUARANTEE ON ALL UPPERS built by M16 Clinic  •  M16 Clinic does not sell firearms
Sales are limited to active duty military, active duty law enforcement, and civilians deployed overseas as State Department Contractors

M16 VIPER™, Patent Pending  •  Copyright 2005, Greg Leaf images and/or text may not be reproduced without prior authorization from Greg Leaf