HOW TO CHOOSE YOUR FIRST XCR
The XCR is offered in so many different calibers and configurations that it’s difficult for some to choose which XCR to buy first. This purpose of this post is to help you choose your first XCR.
The first thing to do is to choose which caliber and barrel length you want for your application. We don’t have ballistic data for the calibers and barrel lengths. However, you can find data on the web which is generally applicable. Next, choose the model that is suggested for the caliber and barrel length you want.
XCR-LIGHT (XCR-L)
The XCR-L is available in and convertible to the following calibers: 5.56, .300 BLK, 7.62×39, 6.8 SPC, 6.5 Grendel, .224 Valkyrie, 5.45×39, and 6mm ARC. It is available in 4 basic models based on the length of the upper receiver. These lengths from shortest to longest are: Micro, Mini, Standard, and Competition.
XCR-L Micro and Mini
The XCR-L Micro and Mini are our most compact XCR-L models. They both are designed to accept 7.5” barrels. Their overall length is the same (about 18.25” with the stock or arm brace folded). The only difference is the Micro has a shorter upper receiver which exposes the gas block; and the Mini has a longer upper which covers the gas block. The gas block on either can be adjusted with the tip of cartridge. Calibers that work well with the Micro and Mini are 5.56, .300 BLK, and 7.62×39. Note: If you want a longer barrel now or in the future, you are better off buying the Standard model. Also, unless you’re shooting subsonic .300 Blackout, the Micro and Mini are not recommended for use with a suppressor unless it’s a flow-through suppressor or one with very little back pressure.
XCR-L Standard
The XCR-L Standard is our most flexible configuration. We offer it in the following barrel lengths: 9.5, 11, 12, 14.7, 16, and 18.6 inches. It works with all the calibers we offer, but some barrel lengths may not work well with all calibers. For the 9.5 inch barrels or to shoot subsonic .300 BLK ammo, a shorter gas system is required that puts the gas block inside the Upper (Buried). For barrels longer than 9.5 inch, it is best to use a longer gas system which puts the gas block outside the Upper (Exposed). 
XCR-L Standard with 9.5″ Barrel
XCR-L Standard with 11″ Barrel
XCR-L Standard with 16″ Barrel
XCR-L Competition
The XCR-L Competition is similar to the Standard model except the upper receiver is longer and covers the gas block. Also, like the Standard model, it can fire all the calibers we offer. It uses the same barrels as the Standard, except the shortest barrel offered with it is 14.7 inches due to the longer length of the upper.
XCR-L Competition with 16″ Barrel
XCR-MEDIUM (XCR-M)
The XCR-M is available in and convertible to .308 (7.62 NATO), 6.5 Creedmoor, .243 WIN, and .260 REM. It is available in 4 basic models based on the length of the upper receiver. These lengths from shortest to longest are: Micro, Mini, Standard, and Competition.
XCR-M Micro and Mini
The XCR-M Micro and Mini are our most compact XCR-M models. They both are designed to accept 9.5 inch barrels. However, the gas block is exposed on the Micro and covered on the Mini because it has a longer upper. It is not recommended to use suppressors with 9.5 inch barrels or calibers other than .308. The Mini upper is more flexible because it can also accept 12,13, 14.7,16, and 18.6 inch barrels of all the calibers we offer. With these longer barrels it is recommended to use the longer gas systems which exposes the gas block.
XCR-M Standard
The XCR-M Standard can accept 14.7, 16, 18.6, and 20 inch barrels and shoot all the calibers we offer. The gas blocks for all these barrel lengths are outside the upper receiver (Exposed).
XCR-M Standard with 16″ Barrel
XCR-M Competition
The XCR-M Competition is similar to the Standard model except the upper receiver is longer and covers the gas block. Also, like the Standard model, it can fire all the calibers we offer. It uses the same barrels as the Standard, except the shortest barrel offered with it is 14.7 inches due to the longer length of the upper.
XCR-M Competition with 16″ Barrel
NFA
All NFA Rules Apply