Marine Corps Gazette

Accuracy at Night
By the numbers

by 1stLt Robert Casper

t’s long been assumed that the laser Ibore sight (LBS) system offers Marines an accurate baseline from which to start a battle zero (BZO) for their small arms. This statement is largely true. LBS will get the shooter on paper to begin his BZO so that fewer adjustments are needed. However, due to ammunition and range constraints, many companies (Infantry Officer Course included) shoot ranges without a live fire confirmation of that zero. A night BZO on a PEQ–15/16 variant is particularly time-consuming. The average Marine will shoot 20 rounds over 25 minutes to obtain a night BZO. However, this step must not be skipped. LBS is no substitute for live fire and will significantly limit the shooter’s accuracy at ranges as short as 100 meters (m). Furthermore, commanders may want to consider a 200m PEQ– 15 BZO if they are operating in an urban environment with closer engagement distances.

The LBS system is advertised as a way to increase your accuracy when starting your zero. It was never advertised as a replacement to live fire zeroing. Compare that with many companies’ practice of skipping the live fire confirmation step altogether. This article details why LBS is inherently inaccurate.

A minute of angle (MOA) is defined as 1.0472 inches at 100 yards. For all practical purposes, the measurement is simplified to 1 inch at 100 yards. The idea behind the measurement is that given a perfectly stable platform, the same point of aim, and three or five rounds fired through the weapon at 100 yards, the group of impacts can have a circle drawn around them. This circle’s diameter, or MOA, represents the accuracy of that weapon. M16A4s have, on average, four MOA. That is to

>1stLt Casper is the CO, Company G, 2d Bn, 5th Mar. The battalion returned from deployment as the Battalion Landing Team, 15th MEU, during which time the battalion conducted bilateral training in Kuwait, Jordan, and Hawaii.

say, at 100 yards three rounds will impact as a group within a diameter of 4 inches. To find the accuracy at each dis-

The LBS system is
advertised as a way
to increase your accu-
racy. . . .

tance past 100 yards, simply multiply the distance in hundreds of yards by the MOA at 100 yards. For example,

at 300 yards this same M16A4 will fire a group roughly 12 inches in diameter.

The LBS maintains eight MOA. That is a significant amount of error on top of the inherent rifle error. If the shooter only LBSs his PEQ– 15, he will have a weapon that maintains 12 MOA at 100 yards. His rounds will impact within a 12-inch diameter circle at 100 yards away assuming all else is perfect. Now add on the natural bullet rise of 4. 5 inches at 100m of a 300m zero. It is entirely possible then that a perfect shooter could impact 16. 5 inches high at a range as short as 100m. This error is only magnified at longer distances. At 300 yards, the weapon will maintain 36 MOA. Clearly, hitting within a 3-foot diameter at as short a range as 300 yards is unacceptable. This is why LBS is merely a starting point and not the final product. A live fire confirmation will reduce that LBS’ eight MOA to only an additional one-half MOA with the infrared laser. The end result will be rounds that will hit within a 14-inch