Frequently Asked Questions

This post will help you understand the different XCR Options click here.

XCR stands for eXchangeable Caliber Rifle, eXtremely Cool Rifle, or eXtreme Combat Rifle.  You decide.

Robinson Armament’s mission was to create the perfect autoloading rifle for collectors, hunters, police, and military.  It is NOT an AR15 – It is better.   It is NOT an FN SCAR, SIG MCX, ACR, CZ, B&T, or H&K – It is better.

The XCR borrowed ideas from the best rifles and improved upon them.  The XCR’s action is similar to that of the AK47 which has great feeding, extraction, and ejection for reliability.  From the AR15 was borrowed the excellent straight in and out magazine change, exchangeable pistol grips, and aluminum upper and lower receivers for light weight.   To these we added a quick-change barrel system allowing caliber and length changes; and the best ergonomics meaning the operator can keep his eyes on the target while manipulating all controls with either the right or left hand.

The XCR-L has been in production since 2006.  The XCR-M has been in production since 2012.

The XCR-L is chambered for 5.56 (.223), .300 Blackout, 7.62×39, 6.8 SPC II, and 6.5 Grendel, 5.45×39, .224 Valkyrie, and we’re working on 6mm ARC. 

The XCR-M is chambered for 7.62 NATO (.308), .243 WIN, .260 REM, and 6.5 Creedmoor.

All our barrels whether marked .223 or 5.56 can shoot either .223 or 5.56 ammunition.  Our chambers are designed to handle either cartridge.

No, the XCR-M is designed to shoot cartridges based on the .308 cartridge which is longer and wider than the 5.56 cartridge.  It does not make sense to make the XCR-M shoot .556 because it has a larger frame to shoot the larger .308 ammunition.  It would be a large and heavy 5.56.

Yes, it will due to the excellent design of its operating system.

All the calibers the XCR-M is chambered for are based on the .308 cartridge and are roughly the same width and length.  Therefore, to convert from one caliber to another, only a barrel change is necessary which takes two minutes.

Most of the cartridges the XCR-L is chambered for have different sizes and shapes.  Therefore, more than just the barrel needs to be changed to convert from one caliber to another.   Please refer to the chart below to see what parts are needed.  We offer the parts needed in the form of Caliber Conversion Kits.   Some of these kits require more parts that other.  In any case, the conversion process is simple and takes less than 5 minutes.

 Conversion Caliber 
Existing Caliber5.56.300 Blk6.8  SPC 7.62×395.45×396.5 Gren.224 Valk
6.5  GrenCCCEEAD
.224 ValkCCFDDDA

Legend for Caliber Conversion Chart.  Parts Needed to Convert

A = Nothing
B = Barrel, Gas Tube, Operating Rod; or just the Barrel if your 5.56 barrel has a blackout length gas system.
C = Barrel, Bolt, Magazine
D = Barrel, Bolt, Firing Pin, Magazine
E = Barrel, Firing Pin, Magazine
F = Barrel

For 5.56(.223), we use a 1/2×28 thread.   For all other calibers we use a 5/8×24 thread.

The hole in the magazine well of the XCR-L is the same size as an AR15.   For 5.56 (.223) and .300 Blackout, a standard AR15/M16 magazine is used.   For calibers 7.62×39, 6.8 and 6.5 Grendel, special magazines in many capacities are made by companies such as CProducts Defense in Florida.

We use 7.62×39 magazines made by CProducts Defense.   Unlike some AR-15s, the XCR works perfectly with these mags.  We do not use AK47 mags because they have no bolt hold open feature.   

The XCR uses a gas operated piston to cycle the weapon.  This is only part of what makes it more reliable than the AR15.  Other features such as the design of the bolt, extractor, and ejector also make the XCR more reliable.

Both the XCR-L and XCR-M use a piston driven, heavy-duty, three-lug bolt with an extractor and ejector which are very similar to that of the AK47 which results in better feeding, extraction, and ejection than systems used by our competitors.

No.  We find no evidence that piston driven guns are less accurate than direct impingement ones.

The XCR does not use AR15 trigger parts.  If it did, the lower receiver would have to be .5 inches taller.  We designed the XCR to be sleeker with a superior fire control (trigger) system.  The XCR comes stock with a reliable two-stage trigger.  We can provide a straight rather than curved trigger upon request.

The trigger pull is about 3.5 lbs.

No, we do not.  Gunsmiths can make one using our parts.  Two-stage triggers are safer and are more durable.

Our lower receivers are made from 7075  T6 Aluminum.  The uppers are made from a proprietary aircraft aluminum.  It is not 6061; it is harder and stronger.

They are made 4150 steel and chrome plated.  We also make some barrels in 416 R stainless.

They are not.  There is no advantage to hammer forging.  Our barrels are all button rifled and chrome lined or stainless steel.

The choice of twist rate chosen often depends on the caliber, barrel length, and weight of projectile to be used.   The twist rates available for any caliber and barrel length are displayed on our XCR-L and XCR-M Builders.

We use 1/2×28 tpi for 5.56, 5.45.   We use 5/8×24 tpi for almost everything else. 

Always remove the barrel from the upper receiver before removing or installing a new muzzle device.  You will need a vise.   Inexpensive aluminum barrel vise jaws can be purchased on Ebay.   If you are installing a muzzle device for a suppressor, do not use a crush washer.  Use the flat shim(s) that came with the muzzle device for the suppressor.

We can pin and weld on a muzzle device such as a flash hider or muzzle brake (either ours our yours) for $95.00.   If you send your brake to us, it must have the proper thread to match your barrel and you must put your order number on the package.

The answer to this question is personal.   Heavy contour barrels are noticeably heavier.  The best way to answer this question for most customers depends on what the firearm is to be used for.  If you mostly go to the range and shoot targets from the bench, we would suggest a heavy contour barrel.  If you are going to carry the rifle around to plink and hunt, we would suggest the light barrel.  One of the great things about the XCR is that you can own both light and heavy barrels and swap them back and forth in minutes.

The adjustable gas system meters how much gas goes from the barrel to the piston which cycles the action.   A higher number allows more gas to cycle the action.   You should use the lowest setting that reliably cycles your action.  Each brand and type of ammo is different so you may need to change the gas setting when you change ammo.   Our new Omni Brass Deflector, usually allows one to set the gas on a lower setting than our earlier brass deflectors.  We strongly suggest you use the Omni Brass Deflector.

What kind of ammo are you going to use?   How good a shot are you?  You can expect 1 to 1.5 MOA or better using good ammo in our rifles produced in 2017 and beyond.  Some of our customers are reporting groups well under 1 MOA.   Older XCRs can be accurized for a fee.

For the XCR-L models  there are five different length upper receivers from shortest to longest – Micro, Mini, Standard, Mid and Competition.  For the XCR-M models, there are four different length upper receivers from shortest to longest Micro, Mini, Standard, and Competition.  These receivers have a 1913 Standard Picatinny Rail running down the entire length of the top.   We can machine the other three sides of the receiver with Keymod or M-LOK Rails.    

We offer two different gas systems for the XCR-L and XCR-M.  One is a Type 2 Gas System which uses a Type 2 Gas Block which is labeled GB 2 in the XCR-L and XCR-M Builders.   The other is a Type 3 Gas System which uses a Type 3 Gas Block which is labeled GB 3 in the Builders.

The Type 2 Gas System has a short piston contained in the Gas Block.  (It is similar to the gas system as found on the M14 Rifle which is a White Gas Cut off System.  Some call this a Short Stroke Piston.)   As the piston in the gas block moves, it cuts off additional gas.   Our Type 2 Gas System has the gas adjustment dial on the side where it’s easy to see and adjust.  There are six positions including off.  The Type 2 Gas System is arguably cleaner, but weighs more and has more parts.  It may also have some advantages when used with a suppressor.  The Type 2 Gas System is not available on our upper receivers that used buried gas systems.

The Type 3 Gas system has only one long piston attached to the operating rod.  It goes directly into the Gas Block (Type 3).  It has eight positions including off.   There is no separate piston in the gas block.  It has fewer parts and is smaller and lighter.   It can also fit inside our upper receivers where a buried gas system is needed such as in the Mini Buried, Standard Buried, and Competition upper receivers.  You can see these different upper receiver selections in our Builders.

If you are unsure which gas block to choose for the XCR-L, choose the Type 3 (GB 3).

The only difference between the exposed and buried gas blocks is that the exposed gas block is outside the upper receiver and the buried is inside.  The gas block is always buried when the upper receiver is longer than the gas system.  For more information, watch this video

Yes.  There is a dial on the gas block that is visible through the oval ports on the upper receiver.  It is very simple to adjust the gas dial with the tip of a cartridge.

n ATF Form 4 is used when you are buying a Short Barrel Rifle (SBR) from a local FFL Dealer or individual.   In addition to personal information, the ATF Form 4 requires you to supply passport sized photos and fingerprints so the government can do a background check on you.   You will also have to pay a $200 one-time tax.  It can take several months to a year for your ATF Form 4 to be approved before you can take possession of you SBR.

An ATF Form 1 is used when you want to put together or manufacture a Short Barrel Rifle yourself.  It requires the same personal information, photos, fingerprints, and one-time $200 tax as the ATF Form 4.   It also takes several months to a year for the ATF Form 1 to be approved before you can take possession of the SBR.  Some prefer the ATF Form 1 because they can buy and take immediate possession of a rifle after a standard firearm background check and use the rifle while they wait for their ATF Form 1 to be approved.  Once it’s approved, they can install a barrel under 16” in length and possess their SBR.   Alternatively, they could buy a pistol and take immediate possession of a pistol after a standard background check and use the pistol while they wait for the ATF Form 1 to be approved.   Once it’s approved, they could install a stock on their pistol and possess their SBR.

Note:  Once you have an SBR, you cannot take it to another State without approval of the NFA Branch of the BATFE.


Our products are built to order so you may not find what you want at a local dealer.  It’s best to order firearms directly from us using the Builders on our website  However, firearms and firearm receivers must be sent to a local Federal Firearms Licensed (FFL) dealer who can perform the required background check and transfer.   You will have to send us a copy of your FFL dealer’s license.  


Please note that payment is NOT required at the time of order.   Once you place an order online, we will review it and send you an invoice.  Once you have approved the invoice, we require a $500 non-refundable deposit.   The balance of the payment is required approximately 5 days before we ship the completed rifle.   You can pay by check which is mailed, emailed ([email protected]), or faxed (801-355-0401).   You may also pay by credit or debit card for a fee of 3%.

The XCRs can be shot thousands of rounds reliably without in cleaning.  However, it is good practice to clean a firearm each time it is shot if only to examine the firearm to make sure it’s all in working order for the next time it is to be used.

The answer to this question is Yes.  One can hold the XCR by either hand and and manipulate all controls while keeping his eyes on the sights and target.   If one supports the XCR with the left hand, he can reach under the firearm with his right hand and easily cycle it.  (This is exactly how experienced right-handed operators cycle AK47s.)   Those who are left handed often ask whey we don’t have a charging handle on both sides of the XCR?   The answer is that the only place to put it would be near the top rail which makes it difficult to operate with optics and other accessories on the top rail.   We placed it well below the top rail in accordance with the wishes of seasoned SF operators who also wanted it non-reciprocating which it is.  Left handed shooters love the XCR because it’s easy to operate and it ejects the spent cases forward.

Under the National Firearms Act (NFA), a Short barrel rifle (SBR) is defined as,

“a rifle having a barrel or barrels of less than 16 inches in length; or a weapon made from a rifle if such weapon as modified has an overall length of less than 26 inches or a barrel or barrels of less than 16 inches in length.”

It is illegal to possess an SBR that is not first legally registered to you with the NFA Branch of the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF).

Robinson Armament Co. does.  We make many them in many different lengths, configurations, and calibers.   They all work extremely well.  We sell components so that you can build your own.   You must follow all NFA Rules

Update 12-29-23 Because of a decision by the 5th Circuit Court of Appeals, we can now sell Pistols with Arm Braces. That may change. If it does and you have one of our Pistols with an Arm Brace, you will have to remove the Arm Brace, make your pistol into a rifle with a 16″ barrel, or register you firearm as an SBR.

Yes, we asked this question of the ATF.  In short, they stated that you can possess a pistol and a kit containing a rifle stock and barrel 16” or longer.  However, you cannot put the stock on the pistol unless the 16” barrel has been installed first.   If you install the stock with the pistol barrel (which is shorter than 16”) on the firearm, you have made and Short Barrel Rifle that is not registered which is federal offense with severe penalties.

With such a kit, you can still File an ATF Form 1 and register your firearm as a Short Barrel Rifle.  After receiving your approved ATF Form 1, you could then use the barrel less than 16” with the rifle stock.  All NFA Rules Apply

In addition to the Black, Flat Dark Earth (FDE), and Olive Drab  Green (ODG) shown on our builders, we offer almost all Cerakote, GunKote, and Gun Candy colors.   Cerakote colors are $100 extra.  Gun Candy Colors are $300 extra.  Other custom paintwork quoted upon request.

We offer M-LOK or Keymod rail systems on all our upper receivers.   We have discontinued making uppers with 1913 Standard (Picatinny) Rails on the sides and bottom of our uppers.

Whether you have an Keymod or M-LOK rail system on your XCR, you can remove your barrel without removing the accessories, but you must use screws of the proper length.   Many of the screws that come with your Keymod or M-LOK accessories have screws that are longer than needed.  By simply using shorter screws, you can solve the problem.  If you cannot find shorter screws, send your accessories to us and we’ll shorten the screws for you.

When ordering online, if you don’t see the option or color you want, you can put what you want in the comments.   We will get back to you with availability and pricing.

We have a complete satisfaction guarantee.   If you order from us, and you are dissatisfied with our rifle for any reason, you may return it within 15 days of purchase for a full refund of the purchase price excluding shipping.  We will deduct for any damage that is done to the product.  So go a head and order with confidence.  We are sure you will find it to be the best product of its kind.

No.  We’ve tried to do our best to explain things in as simply and accurately as possible.  However, laws changed from time to time and differ from state to state and from city to city. You should consult the ATF, your local firearms dealer, and a lawyer for legal advice.

We can upgrade any XCR to the current specs.   If you want to see the changes that have been made to the XCR over the years, go here.   We have stopped making replacement parts for some earlier versions so it’s wise to upgrade.  The upgrades make the XCR smoother, more reliable, and more accurate.  They also make your old XCR compatible with the newer caliber conversion kits.  You can upgrade you rifle by emailing [email protected] for pricing and instructions on returning your XCR to us.  

If you live in the US, you can return a firearm to us for repair or upgrades without going through an FFL Dealer.   You’ll want to make sure you package it so it won’t be damaged.  Make sure to get a tracking number.  You are responsible for loss during shipment so you may want to insure it.  It’s best not to have anything on the package that would indicate it’s a firearm.   For more information contact [email protected]  Our shipping address is:

ZDF Import/Export, LLC
925 W 100 N Ste A
North Salt Lake, UT 84054

All XCRs have an adjustable gas system which make them ideal for use wtih a suppressor. However, there are some configurations where the barrel is too short for use with a suppressor resulting in too much powder being burnt in the suppressor. This can damage the suppressor, the firearm, and may hurt the shooter. The following XCR configurations should not be used with a suppressor:

An XCR-L with a 7.5″ barrel shooting any caliber other than subsonic .300 Blackout.

An XCR-M with a 9.5″ barrel shooting any caliber.

Most of our other XCR-L and XCR-M configurations work very well with suppressors. However, we recommend suppressors with no or little back pressure. If a suppressor has a lot of back pressure, the chamber will foul quickly and the shooter will get lots of gases in his face.




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