Xcr caliber conversions and rate of twists

[Randomized]

I am currently buying an xcr-l with a 1:8 rate of twist. First of all what's the major difference between the 1:7 1:8 and 1:9 rate of twist? Second, what exactly is needed to swap calibers and shoot a .308 or 6.8spc? Obviously I know the barrel needs to get changed but what other parts are needed?

 

[Brianma65]

The lower the twist the heavier the bullet, you can use. A 308 barrel will not fit the XCR -L . It's called XCR-M model. Not to sure about 6.8. I was in the same situation a couple months ago , but because I was impatient , on waiting for a 1/8 barrel , I went with 1/9. I'm glad I did, I find the lighter bullets more accurate .

 

[knock-knock]

I am currently buying an xcr-l with a 1:8 rate of twist. First of all what's the major difference between the 1:7 1:8 and 1:9 rate of twist? Second, what exactly is needed to swap calibers and shoot a .308 or 6.8spc? Obviously I know the barrel needs to get changed but what other parts are needed?

Sidenote: 7.62x39 isn't .308

To convert to 7.62x39 or 6.8spc you need a new barrel and bolt (sans carrier)

 

[9x19p]

The difference between 1:7, 1:8, and 1:9, is up to 2 inches .
1:7 will stabilize any .224 projectile. A good example being a 90gr VLD. The problem is, you won't fit 90gr bullets (loaded) in an AR magazine.
1:8 will stabilize up to ~82gr, and can still be loaded in AR mags.
1:9 will stabilize up to ~70gr.

If you're shooting out to 600, a heavier bullet will give you an advantage. If you're shooting 100 yards, 55gr will do just fine.
I think your choice of 1:8 is a perfect "do all". You'll be able to shoot anything that fits in the mag.

Caliber swaps need barrel/bolt face/magazine/case buffer. 6.8 to x39, you only need a barrel iirc.