So what makes the quality difference in ammunition?

[45dotACP]

Shooting some 9mm a little while ago I took two different types of ammunition, both the same weight. One was Speer Lawman, the other was Aguila, both 115 grain. The difference in group size was considerable...dummy behind the trigger notwithstanding, the Speer ammo would put bullets within 3-4 inches 25 yards (some of my best efforts) while the Aguila was visibly less accurate...again I am not an excellent shooter but between 4-6 inches (even with my best efforts). This was with two separate pistols, a G34 with a Wilson barrel, and a Commander frame 1911 in 9mm with a hard fit barrel. I also ran some federal 124 grain HST and it was considerably more accurate.

I understand some guns just like certain ammo better, but I've usually taken this to mean specific bullet weights.

I suspect the performance difference has more to do with the greater quality control that Federal and Speer exercise over their lines. What would that manifest as however? More consistent powder charges? Seating depths? Better crimp? Or perhaps the velocity of the Lawman (which is a hotter round) is more suited for a 115 grain round, while the lower velocity of the Aguila ammunition is less stable?

[hufnagel]

Your thoughts in your last paragraph are in the right ball park.

The aspect of ammo "tuning" to a specific firearm, while not as dramatic with pistols as it can be with long range rifles, does have an effect. Quality control of ammo production to required performance specs however plays a larger role in how a round performs. If you want to see some dramatics examples, go grab some boxes of some low end crap and see how awful it is.

As for your self-depreciating comment... I'm of the opinion that most of the members of this forum are sufficiently skilled enough in at least the basics to perform at a level where ammo selection *will* have a noticeable impact on their perceived performance; OP is included in that. (3-4 inch groups at 25 yards, IMHO is pretty darn good, for a non professional face shooter.)

[peterb]

Consistency is a huge part of it. Consistent bullet weight and dimensions and shot-to-shot velocity are some of the major factors, but all the variables add up. Serious target shooters who reload may worry about details like casing wall thickness variations, and will measure every case and round and weigh every bullet and powder charge.

[1slow]

As was said consistency:
Case internal volume, length, wall thickness, external dimensions, primer pocket dimensions and flash hole size,
Crimp tightness, hardness of brass case,
Bullet dimensions, weight, base consistency ( affects how it exits barrel),
Bullet seating depth, hardness ( affects how it takes rifling and has an effect on pressure).

I'm sure I overlooked a few factors.

Incidentally, bench rest powder measures are reputed to throw charges that give more consistent velocity than weighed charges. I am not sure I understand this claim unless the actual volume of the powder has more effect than minute weight variations on velocity.

Functional rough overall consistency can be tested by shooting ammo through a chronograph to check for consistent velocity.

[LtDave]

Every gun is different, but I've also noticed that 9mm pistols are all over the place as to what they shoot best.

I've had good luck with Aguila 9mm ball and their .22LR offerings. In my experience, the Aguila Super Extra HV .22 LR is very close to CCI Mini Mags in performance. It used to be a real bargain, but prices have risen to near CCI levels. Shot this group yesterday with Aguila 124 grain 9mm ball at 15 yards with an iron sighted Walther PPS M2:



Here's the first 5 rounds fired out of a Walther PPS M2 RMSc with red dot sight:



I guess the Walthers like Aguila.