Are smaller bore's inherently more accurate?
- Thread starter horsemen61
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Haven't read the rest of the thread, maybe it's been mentioned, but I'll offer two reasons why a smaller bore may seem, anecdotally, "more accurate" than larger bores...
1) smaller bores generally have more barrel material present... Take a .223 and a .308 barrel on any number of common bolt guns, they almost always have the same external barrel dimensions, but the .223 will have thicker walls than the .308. Added rigidity can only help accuracy.
2) smaller bores generally mean less recoil... .204, .22-250, .222, .223... all relatively low-recoil cartridges. And as we all know, a gun with little recoil can feel like a laser.
1) smaller bores generally have more barrel material present... Take a .223 and a .308 barrel on any number of common bolt guns, they almost always have the same external barrel dimensions, but the .223 will have thicker walls than the .308. Added rigidity can only help accuracy.
2) smaller bores generally mean less recoil... .204, .22-250, .222, .223... all relatively low-recoil cartridges. And as we all know, a gun with little recoil can feel like a laser.
Catpop
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Recoil is the #1 factor that makes small bore more accurate. 40 years ago I shot 300 Win Mag in competition and produced ragged holes at 100 yards, but I was younger and could handle it then. I can't now so now I have to be satisfied with 223 ragged holes.
Good luck, catpop
Good luck, catpop
My question is, and correct me if I'm wrong here, but how can you shoot a group of .127 inches with a bullet that's .222 inches in diameter? Even if you were shooting through the same exact hole it would have to be at least .222 inches in diameter.
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quartermaster
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Groups are measured center to center. If you measure the largest dimension outside to outside of the holes or elongated hole in a target and deduct the bullet diameter from that measurement, you will have geoup size. QM
ironworkerwill
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Right, if you had a .224 hole your group size would be .000".
That's exactly my thought using the exact same examples. I wanted to see if anyone else had posted the barrel id/od thought before I posted. Heavy barrel rifles are commonly used in bench rest competitions to dampen whippiness as bullets travel down the barrel. A .224 caliber barrel simply has more steel around it than a .308. Another thought is rifle twist...heavier/longer bullets require a faster twist and that can cause extremely high RPMs in a hundred or more yards. Bullets with thinner jackets such as varmint bullets have less center of mass variance than a heavily clad deer or elk bullet.
This is why major bullet manufacturers don't recommend their .30 caliber match bullets for hunting. No controlled expansion because the thin jackets essentially fragment.
Anyway...that's my opinion on two possible reasons.
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tark
Member
I'm not sure. The best group I ever fired was a one inch group at two hundred yards from a Ross Mk III military rifle. A .303. But the best group I ever saw fired, from the bench, with a hand held rifle was; a ten shot 3 1/2" group at 600 yards with an AR. Chambered in 204 Ruger!!! I don't know if small bores are more accurate, but they damn sure can be very accurate!
Elkins45
Member
I look at it like this: the larger the diameter of the projectile the less of a difference a .001 flaw represents. Controlling tolerances to .001 can be done on big bullets just as easily as small ones. As was posted before, think how accurate the main guns on a Missouri-class battleship were.
COLOSHOOTR
Member
If you really want to learn the science behind the why read the book Applied Ballistics by Bryan Litz. It will tell you everything you ever wanted to to know about exterior ballistics and then some. Light recoil is something that can help make a shooter more accurate bit if you take the shooter out of the equation then ballistic coefficient (B.C.) is king. A higher B.C. bullet is more efficient flying through the air and will be less effected by outside influences such as wind. Another article by Bryan covers bullet weight and scaling and cab be found online. It explains why the .30 call is overshadowed by the 6.5 since it requires a much heavier bullet 220 grain to match the 140 grain 6.5mm in regards to scaling.
Then you throw a wrench into things with B.C. as it can be different depending on velocity, conditions or bullet construction. Bullets out if the same box can have different B.C.'s.
Then you add the other variable that one particular rifle may just really like a specific bullet and the shooter performance is better with that combination and the science just gets tossed out the window.
Then you throw a wrench into things with B.C. as it can be different depending on velocity, conditions or bullet construction. Bullets out if the same box can have different B.C.'s.
Then you add the other variable that one particular rifle may just really like a specific bullet and the shooter performance is better with that combination and the science just gets tossed out the window.
COLOSHOOTR: You are right that a better BC bucks the wind better, very true. But a better BC does not make a more accurate bullet.
Consistency is the issue here.
This is the smallest group I have ever shot; it was done using extremely consistent ammo from a specific lot selected for speed, a great gun, and even better barrel, an experienced smith in benchrest to put it all together, and finally a decent trigger-nut:
As you might have guessed, the caliber in question above is 22lr, which has a terrible BC. But if you are willing to pay for match ammo and test and tune for it (the gun had a Harrell tuner) and try different lots for the best avg. velocity and lowest SD, then you too can shoot groups like this. The important thing is consistency from shot to shot. Consistency in:
All those have to stay the same shot to shot to shoot small groups.
The reason the top centerfire shooters are all of course hand-loaders, is that to achieve the kind of accuracy for a centerfire bench gun to shoot in the 0.1" group-size club, you simply have to control all those aspects of ammo prep yourself and do so better than a million dollar machine that makes match ammo. And people regularly do this. They play with seat tensions and depths and powder charges varied by 0.1 grains or even smaller. They weigh and sort their cases and deburr the flash holes. They only use match-grade bullets. They do not mix brands of primers, cases, powders, or bullets, but they experiment with all combinations of those to find the best.
Generally speaking what works for this the best is a short, fat case necked down to a smaller caliber bullet (0.2) that has a good, but not necessarily great BC, but is made extremely consistently. Hence 6mmPPC and 6mmBR holding a lot of records.
Consistency is the issue here.
This is the smallest group I have ever shot; it was done using extremely consistent ammo from a specific lot selected for speed, a great gun, and even better barrel, an experienced smith in benchrest to put it all together, and finally a decent trigger-nut:
As you might have guessed, the caliber in question above is 22lr, which has a terrible BC. But if you are willing to pay for match ammo and test and tune for it (the gun had a Harrell tuner) and try different lots for the best avg. velocity and lowest SD, then you too can shoot groups like this. The important thing is consistency from shot to shot. Consistency in:
- POA (clear target, high power scope)
- ignition (priming or primer brand, FP strike, case prep)
- burn (powder type, barrel length)
- velocity (powder charge, barrel length)
- exit (barrel whip, smooth trigger pull, free recoil)
- flight (projectile shape and density)
- external conditions (generally impossible to control for)
All those have to stay the same shot to shot to shoot small groups.
The reason the top centerfire shooters are all of course hand-loaders, is that to achieve the kind of accuracy for a centerfire bench gun to shoot in the 0.1" group-size club, you simply have to control all those aspects of ammo prep yourself and do so better than a million dollar machine that makes match ammo. And people regularly do this. They play with seat tensions and depths and powder charges varied by 0.1 grains or even smaller. They weigh and sort their cases and deburr the flash holes. They only use match-grade bullets. They do not mix brands of primers, cases, powders, or bullets, but they experiment with all combinations of those to find the best.
Generally speaking what works for this the best is a short, fat case necked down to a smaller caliber bullet (0.2) that has a good, but not necessarily great BC, but is made extremely consistently. Hence 6mmPPC and 6mmBR holding a lot of records.
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COLOSHOOTR
Member
tuj,
That's exactly why my last sentence about throwing the science out the window holds true as well. There is way more to accuracy than external ballistics alone. My reply was very basic as I did not want to get to lengthy with my reply as the subject itself is very complicated with a huge number of variables. Consistency is absolutely a huge factor with accuracy and the highest BC bullet of all time will not change that. Still some rifles seem to buck all the science and just defy logic for whatever reason.
Take that same .22LR out to 500 yards and I guarantee that even with hand selected components it will be outdone by any decent. 6.5 Creedmoor rifle using factory match ammo as B.C. will once again be king as the distance increases. Then we can throw another wrench into the mix and have someone shoot a .308 using more consistent ammo, while shooting a lower BC bullet, and now that rifle may out shoot the 6.5 CM (tossing all other factors such as wind aside) due to the consistency.
With shooting it is never an absolute but all other things being equal heavier with higher B.C. is your best bet for accuracy but even then you will eventually run out of case capacity (as well as limitations on the rifle and shooter) and you won't be able to sling the bullets fast enough to actually achieve the high BC numbers. At that point you are now you are losing out on accuracy when bullets get too long and heavy. Then we can add the shooter to the mix and I may be able to shoot one ragged hole with my rifle while you you won't be able to get a good group at all as it fits me better. Then you could shoot a group like that with yours then hand it to me and I could have a horrible group with it. Clear as mud really does define the science of accuracy with firearms!
BTW nice group!
That's exactly why my last sentence about throwing the science out the window holds true as well. There is way more to accuracy than external ballistics alone. My reply was very basic as I did not want to get to lengthy with my reply as the subject itself is very complicated with a huge number of variables. Consistency is absolutely a huge factor with accuracy and the highest BC bullet of all time will not change that. Still some rifles seem to buck all the science and just defy logic for whatever reason.
Take that same .22LR out to 500 yards and I guarantee that even with hand selected components it will be outdone by any decent. 6.5 Creedmoor rifle using factory match ammo as B.C. will once again be king as the distance increases. Then we can throw another wrench into the mix and have someone shoot a .308 using more consistent ammo, while shooting a lower BC bullet, and now that rifle may out shoot the 6.5 CM (tossing all other factors such as wind aside) due to the consistency.
With shooting it is never an absolute but all other things being equal heavier with higher B.C. is your best bet for accuracy but even then you will eventually run out of case capacity (as well as limitations on the rifle and shooter) and you won't be able to sling the bullets fast enough to actually achieve the high BC numbers. At that point you are now you are losing out on accuracy when bullets get too long and heavy. Then we can add the shooter to the mix and I may be able to shoot one ragged hole with my rifle while you you won't be able to get a good group at all as it fits me better. Then you could shoot a group like that with yours then hand it to me and I could have a horrible group with it. Clear as mud really does define the science of accuracy with firearms!
BTW nice group!
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ironworkerwill
Member
Lapua RBT with other BTHP bullets
Flat based Sierra
Corbin design RBTCorbin basically says that flat based bullets are very accurate. Mostly because they disperse gasses 90degrees from the bore.
Boat tails act like an airfoil focusing gasses, which are much faster than the projectile, in front of the bullet. This might destabilize the bullet.
The RBT design acts as a hybrid of the BT and FB bullets. It has increased BC over FB bullets and has a rebated area to keep gasses from being focused out front.
Corbinhttp://corbins.com/rbt.htm
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