Cartridge Inherent Accuracy Question

[socalbeachbum]

I know benchrest shooters certainly stick to particular cartridges for their inherent accuracy.

I am curious as to the 'inherent accuracy' properties of the cartridges available for the AR-15 platform:

.204 Ruger
.223 Rem
5.56 mm
6.5 Grendel
6.8 SPC
6mm x45
.30 AR Remington
.300 Whisper
.300 Blackout
and others

I know that the case capacity, geometry, bullet form + weight lend to repeatable burn rates, etc. etc, but I'm asking, are there any standouts?

Or should I just work with match grade .223 ammo and barrels? I'm in the market for a barrel, so it's time to consider caliber before I go further. Range for me and my tired old eyes is 100 and 200 yds. Once in a while 500 yds when I get the chance.

 

[243winxb]

http://www.brownells.com/rifle-parts/barrel-parts/rifle-barrels/ar-15-match-grade-dcm-barrel-prod54578.aspx Most cartridges will do well with good equipment.

 

[taliv]

I believe you could make any cartridge "accurate" but some are easier than others due to having a wider range of powders available in the sweet spot, or a 30* shoulder, small primer pockets, and better available brass.

ARs are "accurate" rifles but there's a reason you don't see them in benchrest competitions. I wonder if you could tell a difference between any of them in an AR.

a good approach to narrowing it down would be to ask which cartridges in your list have Lapua and Norma brass for sale.

 

[Tirod]

At 100-200 yards, it's going to be a small incremental step.

First, most benchrest competitors handload. So they can optimize the characteristics. They use $400 and up barrels, too.

The load one round at a time by hand to keep the bullet from being knocked off axis from chambering the round with a bolt carrier that just crams them in, and they don't have to crimp to keep the bullet from getting set back, too.

They start their selection of cartridges by which bullets are available with the highest ballistic coefficient, and it takes shooting at 600-800 yards to actually get those to show their superiority.

From the choices listed, any one could do quite will at the ranges specified. For the cost, stick to 5.56 as the components reloading will be less expensive. Cheaper ammo well made means more shooting, which increases accuracy. At the point you find skill isn't limiting the group size, then you start working up loads.

Then reloading equipment, measuring cases for identical capacity, bullet selection, measuring concentricity of the case, mouth, and loaded bullet all start playing. It will be a game of making ammo much more precisely than store bought rounds assembling in working equipment that chuck out 1,000's of rounds an hour, and where one batch is different than the next.

 

[1948CJ2A]

I believe you could make any cartridge "accurate" but some are easier than others due to having a wider range of powders available in the sweet spot, or a 30* shoulder, small primer pockets, and better available brass.

ARs are "accurate" rifles but there's a reason you don't see them in benchrest competitions. I wonder if you could tell a difference between any of them in an AR.

a good approach to narrowing it down would be to ask which cartridges in your list have Lapua and Norma brass for sale.

I agree with this. The largest factors of accuracy are:

• The rifle itself
• The shooter
• The other components and accessories
• Firearm maintenance and cleaning

Generally speaking, all things being equal, one cartridge doesn't hold enough advantage over another to justify better accuracy for the average shooter/hunter.

Now that said, professional shooters will give you their gospel on why they use said cartridges for competition shooting. But for the common man like myself, it really doesn't matter.

 

[itsa pain]

I agree with this. The largest factors of accuracy are:

• The rifle itself
• The shooter
• The other components and accessories
• Firearm maintenance and cleaning

Generally speaking, all things being equal, one cartridge doesn't hold enough advantage over another to justify better accuracy for the average shooter/hunter.

Now that said, professional shooters will give you their gospel on why they use said cartridges for competition shooting. But for the common man like myself, it really doesn't matter.

Well I would say the 308 Win case and all its variants are the most accurate rounds ever produced. Overall they are even better then bench rest rounds which require a chemist and a scientist to assemble rounds that barely nudge past the 308 class

 

[socalbeachbum]

thank you, all good info. I do handload, but the match grade .223 ammo available seems good enough to match my equipment and abilities. I'm borrowing my son's 24" .223 barrel right now and with a cheap scope and cheap bipod, am making one ragged hole at 100 yds. if I do my part.

I enjoy experimenting though. Might try playing with .300 Blackout

 

[Nom de Forum]

I believe you could make any cartridge "accurate" but some are easier than others due to having a wider range of powders available in the sweet spot, or a 30* shoulder, small primer pockets, and better available brass.

ARs are "accurate" rifles but there's a reason you don't see them in benchrest competitions. I wonder if you could tell a difference between any of them in an AR.

a good approach to narrowing it down would be to ask which cartridges in your list have Lapua and Norma brass for sale.

Perhaps a listing of reasons why ARs are not used in benchrest competitions would be beneficial. Off the top of my head (I am not a benchrest shooter) I would think some of the biggest reasons would be too slow of lock time, inferior uniformity of bolt lug lock-up, and inferior receiver rigidity. I think these may also be why it would be difficult to tell the difference between properly developed cartridges in an AR.

 

[Swampman]

Originally posted by: socalbeachbum
I enjoy experimenting though. Might try playing with .300 Blackout

My understanding is that one of the biggest differences between the Whisper and Blackout is that the Blackout was designed with a thicker neck so that it could be easily formed by simply cutting .223/5.56 cases to length and resizing. The .300 Whisper was originally formed from .221 Fireball, so the outside neck diameter is a good bit smaller. Making Whisper cases from .223's involves reaming or turning the necks in order to fit the chamber.

The tighter neck of the Whisper should (theoretically) provide better accuracy.
Whether or not there'd be any real difference, I have no idea.

I don't own either a Whisper or Blackout, so my (extremely) limited knowledge comes pretty much from what I've read or heard from others, l may well be off base on this whole thing.

 

[TBH]

Sounds to me like you need to purchase two AR barrels from Lilja! A .223 & a 6.5 Grendel! I have both calibers, and both can be very accurate. My Grendel has a CSS barrel. I have a love hate relation with it. What I have found is when I clean the barrel, my groups open up to 1- 1 1/4 moa. After 100- 150 rounds it tightens up to 1/4- 3/4 moa.:banghead:
Thinking its time for me to get a Lilja.
Both shoot well out past 500 yds.

 

[Jim Watson]

A .223 Rem chamber AND GOOD AMMO.
I assume you will buy or load "match grade" ammunition and not expect great things out of Walmart imitation army surplus or real Slobbovian surplus.

If I wanted to stretch the range - and .223 does quite well for the NM shooters at 600 yds - I would try the 6.5 Grendel.

 

[Longhorn 76]

I spend a lot of time on the brass I use for bench rest. A handful will outlast my barrel. There is no way I will subject them to the indignities of a semi auto.

 

[burrhead]

Not on your list but 22 and 6mm PPCs will fit the AR platform. Pretty accurate.

 

[redneck2]

I suspect I'd lean towards the 6x45 simply because of the number of 6mm match bullets, though it would be difficult to argue with anything in 6.5. There was a guy on another forum I frequent that had one that would easily shoot .3's. Highest quality build all around

As noted, I'd be looking at super quality barrel to build around. Kreiger's, PAC-nor, etc. I have an AR in .358 WSSM that shoots .4's. Has a Shilen Ultra-Match

 

[R H Clark]

You need to think in terms of bullets first. Then think in terms of a good way to deliver them. This includes cartridge, brass, barrels, chambers, mag length, triggers, and sights, but it's always about bullets first.

 

[Swampman]

Originally posted by:R H Clark
You need to think in terms of bullets first. Then think in terms of a good way to deliver them. This includes cartridge, brass, barrels, chambers, mag length, triggers, and sights, but it's always about bullets first.

Uhhhh... OK.
But since the OP has already stated that this is for an AR-15, maybe we could move some of those "secondary" considerations like mag length and cartridge up in the line just a LITTLE bit?

I love the accuracy and high ballistic coefficient of the Hornady 800 grain, .510" AMAX too, but it's gonna be a little difficult to shoehorn 'em into an AR-15 and have room for enough powder to get 'em moving much faster than rock throwing speed.

In any event, there are good target bullets available in pretty much all the calibers mentioned by the OP (I'm not entirely sure about the .204), so it's not like he's ignoring the fact that he's going to need quality projectiles. He even stated that "the match grade .223 ammo available seems good enough to match my equipment and abilities."

Anyone with any knowledge of shooting knows that good bullets are important.

There are a lot of superbly accurate 6.5mm bullets.
I've never seen a 6.5 Carcano in the winners circle at ANY target shooting competition.

Think about it.

 

[R H Clark]

The question was about "inherent accuracy", which makes it first about bullets and bullet design.

 

[jerkface11]

The only thing that would make one cartridge more accurate than another is the availability of good brass.

 

[benzy2]

Inherent accuracy is a bit of a myth, at least in the way it gets tossed around.

What you need to do is list the goal and then find the bullet and case that provides the best solution for that goal. There is not a perfect "inherently accurate" round that shoots best for every situation. Guys shooting 100 yard bench rest will use a different round than guys shooting 600 yard bench rest which will use a different round than guys shooting 1000 yard F-class, etc, etc.

There are many accurate rounds. What typically is seen is that there are very good 6mm bullets made, often flat base and light-medium weight that do best in the 100-300 yard range. In the 300-600 range, you've moved into the heavier/longer 6mm options or even 6.5mm or .30 caliber. As range lengthens, you see a stretch in bullet length. For a while the trend was to go with bigger calibers as well, though many have found total match scores to be better (even if a given few shots aren't) with a lighter recoiling option in a smaller diameter rather than going to the faster .30 caliber chamberings. The larger diameter rounds may at that distance hold a technical advantage, but the wear and fatigue they cause many shooters make them harder to score well.

Then you need to look at the game you're play as well. If you play worst edge for score, you want the smallest bullet diameter you can get. If a .22 and a .30 both shoot equally well, the .22 will score better. On the reverse, if you are playing a game with best edge, the larger diameter bullet will score better. If you are playing simply for smallest CTC group, bullet diameter on it's own won't play into results. There are also situations where you may also want a round that doubles as a hunting or defensive round, in which case effect down range means as much as absolute accuracy. This would be where guys (using long action bolt rifles) opt for a .300 win mag over a hot 6.5mm option using similar BC bullets. And don't forget about guys shooting unknown distance games where guessing at distance (and bullet drop) are required. In those games, a flat shooting bullet that has a longer point blank range will be more important than the absolute most accurate load.

In the end, you have to narrow down the specific situation you want the round to do best. If you can't give a single specific goal, just stick with something common and have fun. If I were to guess, I'd say something in the 6.5 AR/Turbo would technically be towards the tops of the list for short to medium distance CTC competition, though at 100 yards a well built 6mm is probably going to be easier on the shooter to shoot through a match/competition. It's all a guess though as there is no way to measure which round is inherently more accurate. You can simply follow trends and results for different competitions and make a guess based on them.

 

[taliv]

pointless bickering deleted...

Perhaps a listing of reasons why ARs are not used in benchrest competitions would be beneficial. Off the top of my head (I am not a benchrest shooter) I would think some of the biggest reasons would be too slow of lock time, inferior uniformity of bolt lug lock-up, and inferior receiver rigidity. I think these may also be why it would be difficult to tell the difference between properly developed cartridges in an AR.

heh maybe. i think your list is a pretty good start. i would add to it that while the AR ergonomics are awesome for practical shooting and traditional positional shooting, they absolutely stink for a bench. the pistol grip and magazine stick down too far and make the gun sit up too high. if you look at benchrest guns they are short and fat for a reason, not narrow and tall like the AR.