Ammo Matters Update

Testing Every Ammunition Lot is Important

You may remember a few weeks ago that I wrote a very positive review of American Armaments Company 77 grain Sierra Match King 5.56 NATO ammunition. That is PSA’s (Palmetto State Armory) house brand.

I was so impressed with it that I decided to switch from Federal 77 grain to AAC 77 grain for shooting at long range. I had different results in a chronograph session that I did on Friday (15 September 23) at the Sawmill. This ammunition is from a different lot (batch).

In the table below you see the results from the chronograph session on Friday. This session was with my primary rifle so use the right two columns in the bottom table for comparison. As you can see, the variance for this session (expressed in spread and standard deviation) is 17.2 and the spread is 60. That’s a difference (from the first session) that matters. I used the same rifle (primary rifle in the bottom table) as the first session.

Commercial ammunition, even from the same manufacturer, can vary quite a bit. If precision is important to you, then test every lot (batch) that you buy.

One last note: the boxes that I bought in this second lot are marked as having a velocity of 2,700 feet per second. I measured the velocity as considerably faster than that. In my ballistic calculator the “holdover” difference between measured (2,860 fps) and stated (2,700 fps) is two inches at 300 yards and five inches at 400 yards. Does that matter? Depending on the shot that you are trying to make, it can matter.

Below are the results from the chronograph session from 2 August 23.