With that in mind, I didn’t spend my range time with the LM8MRP measuring shot groups at 100 yards and scribbling down the results in a log. I spent it as most of you likely will, moving, shooting, manipulating, and reloading. I tried my best to run this rifle hard and put it through some of the same conditions it would likely experience in law enforcement or military training and deployment. I had two hopes: that the rifle would maintain accuracy and there would be no catastrophic failures or malfunction problems.
What did I get? Exactly what I wanted. Here's the breakdown:
For ammunition I chose a mix of four different loads I had on hand; two of them were SAAMI Specification .223 caliber cartridges and the other two were true Mil-Spec 5.56mm loads. I won't go too in depth about ammo, but there is a distinct difference between .223 caliber and 5.56mm cartridges, and most modern AR-15s like the LM8MRP are timed to run both. That is due to the fact that more and more of the law enforcement community is using both, and agencies don’t have the budgets necessary to recalibrate their weapons every time they change rounds. The .223 loads were Hornady TAP 55-grain Ballistic Tip and Federal TRU 55-grain BTHP. For the 5.56mm rounds, I chose M193 and M855; both military standard rounds. The M193 is a 55-grain FMJ and the M855 is a 62-grain steel core and tip.
All rounds performed without issue and the LM8MRP's cold hammer forged barrel with a 1:7 twist rate maintained consistently tight groups on human silhouette paper out to 100 yards. I even fired a few quick sequences of 15 to 20 rounds to heat up the barrel before returning to the prone position for accuracy work and saw no difference in my groups. I ran these distance drills at the beginning and end of my range session to see if fouling would affect the accuracy and it did not.
Moving down range, I increased my rate of fire and concentrated more on manipulations and speed vs. accuracy drills. I was pushing my limits as an operator while trying to maintain the best shot placement possible. This is where extra weight or poor ergonomics will show themselves and, as I said earlier, they did not. Firing several drills, most with magazine manipulations in between, the LM8MRP ran without any malfunctions. I even mixed all four different rounds into one magazine and fired them in rapid succession to see if the varied pressures or bullet weights would induce a timing issue, and the LM8MRP ate everything without a hiccup.