Depending upon the buffer your MK10 has in it, you can use a different buffer with those loads. CMMG suggests for the Carbine Buffer that comes in the box with the gun, it should be used with ammunition that has a power factor of less than 190. The Buffer that is shipped in the gun, is an H3 Buffer, to be used with ammo with a power factor of more than 190. CMMG has a 3rd buffer you can order, that works with ammo with a power factor of more than 230. Power factor is found by multiplying your bullet weight x muzzle velocity and then dividing it by 1000. In your case, 180X1235=222.300 divided by 1000 = a power factor of 222.3. Also, CMMG states if your ejection pattern is consistently at 1 to 2 o'clock, a heavier buffer is recommended. If the bolt fails to consistently lock open after the last round, a lighter buffer is recommended.
CMMG has generous chamber dimensions and some report brass bulging with the standard and lighter buffer, but not with the heavier buffer with hotter loads, due to the heavier buffer keeping the Roller breech locking system closed longer. Variables exist that due to the load used, you need to experiment with what works for your gun and load.
As stated previously though by sqlbullet, one failure out of 20 is not definitive enough for a conclusion as to why.
Keep shooting.