The NRA has released the results of its .308″ GGG ammunition testing – and it appears to be very consistent ammo indeed, according to the test results.
The table below, which is currently posted outside the NRA offices, shows the results of the testing of this year’s GGG batches along with results from the same tests carried out with batches of RWS/RUAG .308″ match ammo from previous years. Each test consisted of a 10-shot string.
Very good, now what does all this mean?
Not being a mathematician, or a statistics geek, or indeed someone who can do more than add up the score from a 2+15 without needing pen and paper, UK Shooting News’ author doesn’t fully follow all of the various derivations, but knows that V is the vertical (y-axis) and H is the horizontal (x-axis). RMS is Root Mean Square, which – we’re reliably told – in this case is simply the square root of x squared + y squared, or if you like the length of the hypotenuse, the long side of the right-angle triangle formed by x and y.
In UKSN-friendly terms, RMS means the diameter of the circle enclosing the group. Phew.
Note that “mean of RMS” is the median of the four test samples and V-bull proportion is calculated from that median figure.
The “V-bull proportion” in the table is the length of the diameter of the circle enclosing the group relative to the effective diameter of the V-bull. This, I’m told, is an extreme spread measure rather than a proportional one like CEP (Circular Error Probable, the diameter that encloses 50% of the projectiles fired).
The lower the value in the “proportion of V-bull” column, the tighter the expected group, basically.
What’s hot and what’s not
RWS 60PG appears to be the best (most consistent in terms of where it hit on the target) batch of ammunition out of all of those listed here, with a V-bull proportion just a smidge larger than half the V.
Looking at the GGG results, of this year’s batches 100-2015 produced the most consistent result, which equated to a V-bull proportional group of 0.59. The median velocity SD for 100-2015 is 13fps, which is very good – though batch 080-2015 has a median velocity SD of 8, which is pretty phenomenal.
GGG 090-2015 was the statistically worst result, with a V-bull proportional group of a whole three quarters of the V bull. This, UKSN suggests, is not going to worry anyone because it’s still well within the V.
There was a difference between average velocities when comparing NRA test barrels 6 and 7. However, even though the rounds were slower out of barrel 7, the velocity variation was, on the whole, no larger than that of barrel 6.
GGG is consistent ammunition no matter what you fire it out of. UKSN also refers you to Robert Oxford’s physical analysis of GGG, where he pulled the bullet and measured everything measurable.
What this means for the real world
If you’re shooting the NRA GGG and you aren’t hitting the V-bull, it’s almost definitely your fault (or your rifle’s) and not the ammo. The V-bull proportion measure, being an extreme spread measure, takes fliers into account – and in the test groups at least, there were very, very few fliers.
However, the test groups were only 10-shot strings. UKSN’s gut instinct is that fliers make up far less than 10% of a given sample of ammunition.