Please be sure to select the correct rail for your gas length. This is the list of handguards we currently know will work with our system without any modifications, this list will be updated as more handguards are discovered to work with our system:

1. The Free Floating or Drop In rails available on our website

2. Samson Star-C (carbine only)

3. Samson Star-C- EX-P (carbine only)

4. Samson Star-M (mid only)

5. Samson Star-M- EX-P (mid only)

6. Samson Star-R (rifle only)

7. Samson Star-4 (pistol only)

8. Samson Star-4-DI (pistol only)

9. Samson Star-4-EX (pistol only)

10. Samson Star-DI (pistol only)

11. Samson Evolution Series 4 EX (pistol only)

12. Samson Evolution Series 7 (carbine only)

13. Samson Evolution Series 7 EX (carbine only)

14. Samson Evolution Series 9 (mid only)

15. Samson Evolution Series 9 EX (mid only)

16. Samson Evolution Series 12.37 (rifle only)

17. Daniel Defense Standard Length Omega Rails

18. Daniel Defense Standard Length Lite Rails

19. Daniel Defense Standard Length Omega X Rails

20. Daniel Defense 9.5 FSP Lite

21. Daniel Defense 12.5 FSPM Lite

22. Daniel Defense EZ Car 7.0

23. Ergo Grip AR Z Float

24. Ergo Grip AR Z Rail

25. Midwest Industries Gas Piston Two Piece Free Float Forearm

26. Arms #50 Bi-Level S.I.R. System

27. Magpul MOE handguards (most recent version cut to accept gas pistons)

28. Troy Industries Drop In Carbine (Mid length and Rifle length require removal of handguard tension screw and arm)

29. Troy Industries TRX Battlerail Extreme 9″ and 7.2″

30. PRI Gen III Delta Carbon Fiber Forearm

31. Newtown Firearms Modular Free Floating Carbine Rail

32. The modified M4 style handguards provided with our standard system

33. Odin Works KMod Forend (XLP/Micro – slight modification to barrel nut)

34. Odin Works Sport Forend (XLP/Micro – slight modification to barrel nut)

35. Yankee Hill SLR (XLP/Micro)

36. Troy Industries VTAC Alpha Rail (XLP/Micro)

37. Troy Industries Alpha rail (XLP/Micro-slight modification to rail to allow access to set screws, and special installation instructions.)

38. Troy Industries M-LOK Rail (XLP/Micro-slight modification to rail to allow access to set screws, and special installation instructions)

39. Troy Industries SOCC BattleRail (XLP/Micro-slight modification to rail to allow access to set screws, and special installation instructions)

40. Midwest industries SS/SSK/SSM. (XLP/Micro-barrel nut modification)

41. Diamondhead VRS-T (XLP/Micro-barrel nut modification)

42. Brothers & Arms USA 3RGS M-Lok Hand Guard (XLP/Micro – request piston barrel nut from B&A)

43. Brothers & Arms USA 3RGS Keymod Hand Guard (XLP/Micro – request piston barrel nut from B&A)

44. X-Products Viper Free Float Rail System (XLP/Micro)

45. Black Dawn Free-Float Handguards (XLP/Micro – contact on top of block, may require some slight modification) 

46. BCM (KMR, MCMR, QRF) (XLP/Micro-barrel nut modification)

47. Aero Precision Gen II Enhanced(XLP/Micro-barrel nut modification)

48. Aero Precision M4E1 Enhanced Upper Receiver (Requires modification to barrel nut collar) (Must be used with Gen II Enhanced, Cannot be used with the Quantum, or Atlas rails (XLP/Micro))

49. Midwest Industries SP Series Handguards (XLP/Micro-barrel nut modification)

Most handguards/rails on the market can be modified to fit. If you do not see the rail you want use in the list above or in the category below then it can be modified to fit.

Our Piston systems will fit on all of the mil-spec standard lengths: Carbine, Midlength, & Rifle. We do make Pistol length kits which will fit on all pistol length barrels. However, as Pistol length does not have a mil-spec standard length, some barrels may need to have the drive rod shortened to achieve proper gap. Without the proper gap, the firearm may not function or the drive rod could become damaged/bent. For any questions on shortening the drive rod or you need assistance to properly gap the system, please contact

 Any tubular free-floating handguard (or rail that uses these handguards for their base). Any handguard that covers or extends over the gas block or in front of the gas block will not work with our system. Any handguard that uses a barrel nut longer than a standard milspec barrel nut. These are examples that have been found to not work:

1. YHM rails – use a tubular handguard as a base

2. GG&G free-floating rails – use a tubular handguard as a base

3. Vltor VIS – modular upper/rail that can not be modified

4. Daniel Defense FSP (Except the 9.5 FSP Lite)

5. LaRue Rails – uses oversized barrel nut

6. MI Two Piece Forearm Extended Carbine Length – continues in front of the gas block

7. MI One Piece Forearm T Series – uses oversized barrel nut

8. Troy Industries 10′ MRF-MX – extends over a low profile gas block

9. UTG Pro Slim line – too small

10. PSA Freefloat rail(barrel nut too long)(would need to have driverod turned down)

11. Fortis Switch(unmodifiable barrel nut assy)

12. PWS rail

13. Seekins Rails (barrel nut)

14. Phase 5 WSI LPSN15

15. Phase 5 WSI LPSN15-MLOK

16. Phase 5 WSI LPSN7.5

17. Phase 5 WSI LPSN7.5-MLOK

 Our system will work with any barrel that has a shoulder diameter (where the gas block sits) of .750″. It also requires a shoulder length of 2′ toward the front of the barrel.

The picatinny style gas block sits at the same height as the upper receiver. We developed it this way so the average user can use his or her choice of flip up iron sights.

Our Picatinny gas block is set up with 3 different gas setting that are easily adjusted by pressing down the detent pin and rotating the gas plug either clockwise or counter-clockwise. The 12 o’clock position is the full or open position and should be used with normal fire. The 1 o’clock position is the low or suppressed position and is best used with a suppressor on the firearm. The last 3 o’clock position is the off position and allows your AR to fire without cycling the action. Our Micro Adjustable Blocks have 5 gas settings (100%/74%/53%/32%/11%) for fine tuning or for suppressor use.

Our system comes in 4 lengths: pistol, carbine, midlength, and rifle. The most common listed measurements for these are: pistol ‘ 4’, carbine ‘ 7’, midlength ‘ 9’, and rifle ‘ 12’. These measurements can be found by measuring the distance between the front of the upper receiver and the shoulder where the gas block sits. These measurements are not exact but are rounded to the nearest inch for ease of terminology and for quad rail compatibility.

You can get a more accurate measurement by measuring the barrel extension in the upper receiver and the back of the gas block, where the shoulder starts on the barrel.

While installing the system remove the bushing and spring from the drive rod and slightly loosen the gas block screws. Remove the upper receiver and place the bolt carrier (with our carrier key installed) into the upper pushing it completely into battery. While holding the back of the bolt carrier into battery place the drive rod and gas plug into the gas block and turning it to the 12 o’clock position. The drive rod should not touch the carrier key when this takes place. If it does gentle tap the gas block forward on the barrel with a rubber or plastic hammer until the drive rod is no longer touching the carrier key. Once you have the drive rod and plug installed you should see a gap between the drive rod sleeve and the gas block wide enough to fit two business cards in. If you do not have a business card available measure the gap and make sure it is between .015′ and .025′. Once this is accomplished tighten the gas block down.

All of our systems comes with a lifetime warranty provided you have not modified any of our parts or used them for anything other than their intended usage.

In order to install our system you will need to remove the flash suppressor/muzzle brake from the front of your firearm. If your state requires this to be welded on or permanently attached you will need to find a reputable gunsmith or armorist that is capable of removing the flash suppressor/muzzle brake and legally reattaching it.

Yes it can, however, it has to be a stateside address.

Not at this time, we are processing the paperwork required and will update the website when we are capable of doing so.

 Adams Arms does produce complete uppers and lowers. For a list of the current configurations visit the products section of our website.

No, the Adam’s Arms retro-fit system and uppers are considered an AR accessory and can be shipped directly to the customer. However, any complete rifles or lowers MUST be shipped to an FFL.

We designed our system to be installed by you, the end user, and can easily be installed by anyone with some basic mechanical skills and a good working knowledge of an AR15. You can also call here and talk to one of our representatives directly if you have a question during installation. If you do not feel confident in the installation of our system you can take it to a competent local gunsmith or armorist. They should be able to follow the instructions and install the system for you. If they have any questions they can call us here directly and we will help them over the phone with the installations.

We rely on our reputation in this industry and do everything we can to make sure our customers are happy. Should you need our help call us or email us directly with a phone number, best time to call, and a brief description of what you are experiencing, and we’ll contact you in a timely manner to make sure you are taken care of.

Currently our system will function with the 5.45×39, the 5.56/.223, the 6.5 Grendel, and the 6.8 SPC without any special modifications needed. We offer a 300BLK specific kit as well. We are in the testing stages right now with the .308/7.62 NATO and will update our website when we have a system that will work to our standards.

Carrier tilt is a symptom of a problem not the actual problem. The actual problem is sloppy or loose tolerances in the receiver. Our one-piece carrier combined with our bolt spring eliminates carrier tilt in even the sloppiest of receivers. For those who have normal mil/industry spec AR’s, the design of our system does not have an issue with carrier tilt. The fact is piston systems on the market vary from manufacturer to manufacturer we believe that ours has several design features that benefit over the competition in the market.

The bolt spring goes behind the bolt in the bolt carrier and minimizes cam pin wear. Be sure to remove the gas rings from the back of the bolt before installing the bolt spring.

We researched the advantages and disadvantages of a pinned sight and decided that screws on the gas block had more advantages to what we were trying to accomplish. The greatest of these advantages being the systems design is to be installed by the average user without having to permanently modifying the firearm. The screws are more than adequate to hold the gas block in place, and we do not have issues with its security.

Some manufacturers drill out the hole in the upper receiver a few thousands of an inch too big and the receiver bushing doesn’t have the necessary tension needed to hold it into place. An easy remedy for this issue is to cover the outside of the receiver bushing with the red Locktite provided in the system. It will need approximately 36 hours to properly dry before shooting. Since this particular bushing is only a guide and has no load bearing properties, the Locktite will hold and the bushing will not be knocked loose.

Our parts and product are developed to work with each other and are not developed to be used with other manufacturers systems. If you have another manufacturers piston driven AR you may find our products helpful, however, because they are not being used for their intended use the warranty and return policy will be void.

While the time will vary due to the abilities of the installer and type of AR you own, the average customer installs our system in approximately 20 to 30 minutes.

The Adams Arms Retro-Fit Piston System keeps the hot burning gases from entering the receiver. This means the normal time and energy exerted on cleaning your AR15/M16 will be drastically reduced. To clean our system, simply wipe off the parts with a dry, clean towel.

The areas of the system that see the most dirt is the front of the gas block and the back of the plug and drive rod sleeve. These parts may require some scrubbing with a nylon cleaning brush or old toothbrush and some cleaning solvent.

To access the drive rod for cleaning, simply press the detent button and turn the gas plug knob to the 9 o’clock position. Then remove the drive rod and gas plug. Wipe the outside off with a dry, clean towel and spot clean with your choice of solvent and a nylon brush as needed.

If you find an area that has a heavy build up of carbon which will not come off with solvent, use a knife, pick, or some type of scraping tool to remove the heavy spots. Due to our meloniting process the parts are virtually scratch proof and shouldn’t show any wear.

Once cleaned, replace system and continue shooting. Oiling the piston system is not necessary; however, if you choose to do so, apply only a thin coat over the moving parts.

Our uppers that are chambered 5.56 can shoot 5.56x45mm NATO and .223 Remington. For our uppers chambered 5.45X39 you can only use 5.45 ammunition. Our Small Frame .308 is designed to use .308 ammunition but not 7.62×51.
At Adams Arms, we do our best to ensure that your desired item gets to you in a timely manner. However, sometimes certain items are subject to a backorder due to unforeseen demand or circumstances. If this occurs, your payment reserves a place in the queue for that item, which then will ship in the order that the items were purchased as soon as it becomes available once again.
If the item you desire is on backorder, the most efficient way to ensure your prompt receipt of that item is to place the order while it is in backordered status so that it will ship as soon as the product is back in stock.
PLEASE NOTE: the “ship-by” date beside any and all items will change daily as it is designed as if you placed your order today. That date does not apply to backordered items if you have placed a prior order and is only an estimated time frame (subject to vary).

We do not price match with any other dealer, distributor, or online retailer as we do not want to compete with our distributors. We also do not price match if an item goes on sale or special AFTER your initial purchase. If you make a purchase on our website and the item(s) are discounted any time after your purchase, we will not issue a refund, credit, or any free items.

If you are not completely satisfied with your new product, you can request a RMA (Return Merchandise Authorization) Form from Adams Arms within 30 days from the shipping date of your order. We do not accept a return if a RMA is not requested from us within 30 days from the original date of the shipment.
Adams Arms contact information for returns:
YOU MUST get a RMA from Adams Arms prior to returning the merchandise and receiving a refund. Include your original invoice (from Adams Arms) with your return letter explaining the reason for your return. Ship via UPS, FedEx, or US Mail; Insured and Return Receipt Requested. Credit will be issued for the item, minus full shipping charges and a 15% restocking fee.
ALL original materials must be included in your return. The cost of any materials NOT included will be deducted from the refund.

To ensure proper packaging and delivery of the correct items, we are unable to combine multiple orders or offer discounts on shipping

To purchase a rifle, you must be 18 years or older. To purchase a pistol, rifle lower, or a stripped receiver you must be 21 years or older. Please consult your local law enforcement regarding any other restrictions. If a purchase is made and your FFL dealer is unable to transfer the firearm, you are responsible for the return shipping costs and the 15% restocking fee.

Our system was designed around mil-spec buffer tubes. Using a commercial buffer tube may cause cycling issues due to the extended length of the buffer tube.

In-stock items can take up to 10 business days to ship.

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