Home Forums Hunting & Shooting Ask The Gunwriters Consistency of factory ammo?

I once measured a box of Winchester Supreme 7WSM 160 Accubonds just out of curiosity using a Sinclair comparator.

From ogive to base there was an extreme spread of .022

Eye opening to say the least.

I took that box of loaded factory ammo and broke it down into lots that only varied by .002 (had some left over that didn't fit in to any group, so i put them in their own lot)

I shot each lot at 100 and the further I got away from the lands, the more the groups opened up.

IIRC, the longer lots stayed MOA or better, towards the end, I was getting 1.5" groups.

Plenty good enough for hunting purposes, but you wouldn't want to use it if you were at the range making bets with your buddies.

Granted this was only 1 box, but I would think that a $58.00 box of ammo would have been a little more consistent than that.

Made me wonder about the consistency of charge weights as well...

Anyone else ever measured factory stuff? If so, what did you find?

Might make a good article, but may hurt some ammo makers feelers too.

What I've found even more important on factory ammo is bullet concentricity--or at least I did before owning a TruTool bullet straightener.

Have also found that sometimes small seating depth variations don't make any difference in accuracy, I would assume due to throating dimensions in a particular rifle.

Mass-produced ammo is just that, so will vary, though some varies less. Have even measured "match" centerfire ammo where a pretty high percentage of the bullets had more than .005" runout.

I don't use all that much factory ammo, but do use some. If it shoots accurately I don't worry about variations. A good example is Nosler's 55-grain Varmageddon .223 ammo. I have a good supply, and so far it's shot really well in several rifles.

But if factory ammo doesn't shoot well, I get suspicious and start measuring bullet run-out. If that's OK then I'll measure seating depth.

Before I had the TruTool I just sorted factory ammo. The stuff with the worst runout was used for preliminary sighting-in or offhand practice. But I once sorted three boxes of Hornady Light Magnum 7x57 ammo into three batches: bad, OK and best. The bad stuff (over .005" bullet runout) averaged 1-1/2" for 3-shot groups at 100 yards in a very accurate custom rifle. The OK ammo averaged around an inch. The good ammo averaged 1/2 to 3/4".

I chronoed some Fed. premium 150 BT 30-06 last year and was stunned to see 4fps deviation across 6 shots. They were also 80fps faster than advertised and 50fps faster than my warm handloads.

I've tested a bunch of Hornady SST Superformance with .001-.002 runout too. I can't top that with virgin brass.

Factory ammo still can't tune seating depth to my rifles but sometimes it doesn't matter.

In a well developed load that's not a big deal unless you're shooting way out there.

I recently installed a new scope base on an accurate 308 of mine. After putting the scope back on I boresighted on a large bullseye at 100 yards. I fired three quick shots to settle things in, then dialed for center. A bit more carefully done five shot group landed on center, and the outside measurement of the bullet hole smudges is 0.52". The load used thrown charges of IMR4064, a crunchy metering stick powder for those readers who don't know.

This same rifle also shoots extremely well with thrown charges of IMR3031, another long stick powder.

Because of the way errors combine, a shooter needs to get a lot of ducks in a row before extremely precise weighed charges make a provable difference. If Ol' Betsy won't go five in an inch, more than likely it isn't because of a couple of tenth grains of powder.

I use more thrown charge of late because many of the powders I use, like IMR782 can be had in the SSC version which meters great. And H4350, one of my favorites, has pretty small "grains" too. Same goes for the Reloader stuff too. Just no good reason to weigh every charge with these powders, it's real close to being a total waste of time.

JB, Good point about run-out. Didn't have a way to measure it. Need to get me a Sinclair concentricity gauge for my loads or better yet, the Tru Tool so I can fix 'em.

I assumed on new factory brass that's been sized and is using the same seater, the runout on factory loadings would be at least be consistent, whether it be bad or good.

What you found proves this was an incorrect assumption.

Mathman, the variance in base to ogive just made me wonder about everything else. Wish I could have measured the runout like JB did.

what I wonder is how consistent is ammo of the same type through the years? I have 5 boxes of 308 win 150 grain WW powerpoints I bought off a guy who had them in his safe, some of them are IIRC priced at $15 a box with a sticker some at $21 etc so they were bought "over time".

I chronied the same factory ammo above and was getting 3095+.

Box said 3050 fps assumed it was from a 24" bbl. Mine was 23".

I have cronographed some decades old Remington 150gr 300 savage they average 2641fps in the 90;s it was 2641fps, in the 2000 era it was 2641fps. Pretty dang consistent out of my 24" model 99.