I came across this on the Ballistics Advantage website - "We define sub-MOA as a group size of 1 inch or under at 100 yards with a 3 shot magazine fed group, or 5 shot single-loaded group factory ammo."

Does single loading in a semi auto rifle make that much difference in accuracy?  As a newbie to trying to shoot tiny groups I've always just filled my magazine and not worried about it.  At my skill level it's not going to make much of a difference, if any but for a good shooter?  I know there's the potential for slightly damaging a bullet when the cartridge is being pulled from a magazine and pushed into the chamber, be it semi-auto or bolt action but does that happen often enough to always single load when shooting?

Chamber normally, then eject gently from the mag, then do the same with a single round feed and compare. Drag marks and dents can cause very minute differences but barley noticeable unless the nose is being deformed.  I always do 5 round tests, I never thought 3 was enough

From what I’ve understood it’s more about tolerances and harmonics. Sometimes but not all the time, semi autos have looser tolerances and larger harmonics that is inherent in the operation of being semi auto.

That said semi auto can load more forcibly than a bolt action and small nicks, or deforming the projectile can affect accuracy at longer distances. I think the practice of handloading each round in a semi auto is to take away any variable of that. Accuracy is about repeatability and taking out as many changing variables as you can will increase accuracy.

So no probably wouldn’t make a difference that you can see until you start pushing it to extended distances. Even then maybe only experienced shooters might notice as most shooters the very small inconsistencies of shooting techniques will be more noticeable.

The process of feeding a round from a magazine over the feed ramps, and into a chamber is very likely to increase the runout (alignment) of the bullet to the center line of the cartridge.  The further the bullet is out of alignment with the center line of the cartridge, and barrel, the more wobble the bullet is likely going to have.

Bench rest shooters go to great pains to keep the cartridge and everything else centered with the center line of the bore.   The reason many shooters turn the necks of their cartridges is so they can have more control of the runout of the bullet in relationship to the center of the bore.

It all depends on how much accuracy someone wants, or where they want to spend their time.  Spending 15 minutes making each cartridge isn't nearly as enjoyment to me as shooting is.  I'll put up with an eighth of an inch less accuracy in order to have more time shooting and less time at the reloading bench.

The quote from BA was for AR barrels.  If they say their sub-moa "guarantee" only applies to a 3 shot group from a magazine or 5 shot single loaded group it seems like they think it makes a big difference at 100 yards.  Once I can afford enough ammo for my Grendel I'll try both methods and see how much difference there is.

No, not in a properly set up rifle.  If it does, that's a great diagnostic for bad magazines.

There is a reason benchrest rifles don't have magazines and all rounds are single loaded.  Absolute concentricity is essential.  Manipulating a carefully benchrest prepped round through a magazine and through feed ramps upsets that.

On a semi-auto with a tight chambered (at least tight throat) match barrel, the same principles apply.

But, if mere 1 MOA is acceptable,  magazine feed will probably get you there.

My match loads are sub 1/2 MOA when single fed in my Lilja match .223 16" M4 type barrel.  They open up to about .8 MOA if mag fed.

Interesting. I'm not familiar with this "damage to the round" idea from mag feeding. I definitely acknowledge it can happen. But I wasn't aware of this practice. In my personal experience attempting to load with the charging handle and not allowing the buffer to fully dislodge the round from the mag causes the most common visible damage I've personally seen.

I'm very familiar with rounds being hand fed because OAL is loaded longer than mag length for engagement in the lands. But I don't believe this is possible in most AR barrels. And I'm familiar with hand feeding ARs to avoid rounds cooking in the chamber to maintain temperature consistency between shots.

Ammo quality is more important than anything, even barrel quality.

I own rack grade AR-15's that group under 1 moa when fed premium chow. They shoot like shit with FMJ's. 3 moa or worse.

52/53 grain match bullets shoot the tightest groups with my 1:7 twist barrels. I know it doesn't make sense, but the fact remains.

For longer range (out to 300 yards) I prefer 69 grain SMK's.

You need .003" of neck tension on any bullet being fed from a magazine to keep it from moving. A bolt rifle doesn't need this much neck tension because the operator can't come close to the violence a semi-auto rifle endures. Loaded one at a time directly into the chamber dramatically reduces the neck tension needed to keep the bullet in place.

The guys that win the xtc matches I shoot in (they're shooting "master" and "high master") certainly don't single-load for every stage and they manage to clean their target rather well, and often. They all shoot sub-moa with auto loaders.

Jon

There are only a few 10X acorn decals out there.

Last military rifle match i was at there was one person single loading a A1/A2 style rifle. Took a look at his ammo and they were loaded way over magazine length. Looked like he was treating them as if in a bolt gun. He used an empty mag then chambered each round on his turn. 300 yard offhand match for reference. I am new to this but had my gears turning.

For my MK12 my standard is a at MOA or less 5 round semi auto group at 100 yards. Usually I shoot in the .85-.95 range.

I just got my first non hunting bolt gun so I’ll have to see if I can do any better.

I’ve pulled plenty of rounds in the chamber that had minute marks on the projectile. Also, consider that you’re  leaving the round in a hot chamber for varying amounts of time, and the chamber is heating up over time. I’m positive these things do something to the precision of groups. How much I don’t know. It’d be interesting to see a large scale test conducted, and I have a feeling it’s what would be necessary to bring out the difference.

When I precision test I single load just because it’s one less variable to have to worry about. I also shoot foulers when changing ammo, wait until the rifle cools between groups, etc.

I know quite a few "high master" shooters and they do a LOT of shooting from the magazine. You'd run out of time in an XTC match if you single-loaded during rapid-fire stages.