F Standard Projectiles Rules ?

[superx10]

After checking the rules it stated that .223 weight projectiles up tp 91 grains are allowed, which have substantial ballistic advantage over the .305 155.5 full boar, I was hoping some one could shed some light on why more shooters are not shooting the .223

F class projectiles.PNG

[Malcolm Hill]

superx10 The better BC of the heavier 223 projectiles is only an advantage if they are driven at the same speed as the 308. Quite a few people I know are driving the 308's at 3050 which is not achievable in a 223 with anything over 80 gns. If you could get 3050 with an 85.5 in a 223 then there might be an advantage. You are never going to see those speeds with a 90 grainer unless you throw the cases away after each shot. Sure plenty of heavy 224 projectiles have a better BC than the 155.5 fullbore but you just can't drive them at the same speed to compare apples to apples. Regards Malcolm.

[KHGS]

What Malcolm Hill says is correct IMO. There is a point of diminishing return with all cartridges re bullet weight and velocity. Heavy high BC bullets offer little or no advantage if enough velocity cannot be be generated to utilise the heavier high bc bullet. My two cents for what it's worth.
Keith H.

[superx10]

Hi Thanks for your opinions but have you got the math to prove it ie BC in regards to velocity say 80.5gr .224 going say at 2830 FPS....... 155.5gr going 3000 FPS?

[argh]

On paper it seems like an advantage, and I used to believe it too. BUT, after coaching a few 223s in teams matches at reasonable velocities, compared to 308 immediately before or after, including some guys that ran relatively low 308 velocities, it always shocked me how much more the 223 would get blown (same condition). At 600 and beyond it seemed that despite what was on paper and theory, the 223 seemed to get blown further. If you allow for this fine, but trying to think/read the wind in comparison to a 308 155 not.. It appeared like you had to allow more drift at longer ranges

[AlanF]

Hi Thanks for your opinions but have you got the math to prove it ie BC in regards to velocity say 80.5gr .224 going say at 2830 FPS....... 155.5gr going 3000 FPS?

Its only a matter of getting the BC figures of the projectiles you want to compare and entering them into one of the many available ballistics calculators. You need a calculator that gives wind deflection at say 10mph. This is the key comparison figure.

[superx10]

Thanks Alan, ill do the figures and post them.

[superx10]

Wind deflection 10 MPH

85.5 @2850

snip 85.5@2850.PNG

155.5@3010

snip155.5@3010.PNG

[AlanF]

Using the online Berger calculator I get less wind deflection for the .223 at anything over 300yd, and quite significant at the longs. This assumes that the respective muzzle velocities you suggest are equivalent in terms of how easy they are to achieve.

Berger .223 85.5gn LR Hybrid @ 2850fps

85.5_2850.PNG

Berger .30 155.5gn Fullbore @ 3010fps

155.5_3010.PNG

[superx10]

Sight Height may have an effect on the the results, its interesting, and Ill have a more detailed look. Can anyone chime in and confirm that 2850 FPS from a .223 shooting a 85.5 gr projectile ?
seems at the high end but reasonable.

[AlanF]

Sight height will only affect vertical trajectory, and we're looking at windage.

Regarding velocities, in this example you could reduce the .223 velocity by nearly 100fps and it would still be no worse than the .308 at 1000yds. So I think this 85.5gn projectile may be a boost for the .223 in TR and F-Std. However I assume it'll need a tight twist (Berger says minimum 1:8 then implies ideally 1:7), so for most current .223 shooters, not just a matter of getting the bullets.

[Redhawk]

The question here is not about absolute wind, which is hardly ever constant….. but rather the variability of the wind in terms of strength and direction….. I have yet to see a 223 with heavy projectiles hold it’s own against the 155.5’s at longs in Target Rifle or FStandard…… they just get blown out…. Same argument for the 6mm’s vs the 7mm’s at the longs in FOpen….. it’s the varability of the conditions that kills it……
No doubt that at the shorts, 300-500, they do well.

[Redhawk]

Forgot to add……. Many many 308’s are very easy to tune with 155’s, and they fly stable…… not so many 223’s have been tuned to the same level of accuracy at the longs, as the nodes are very very narrow….. and then time will tell if they are as stable in flight…… those fast twist barrels are a lot harder to tune

[AlanF]

From what I've seen of 6mm vs 7mm the 6mms seem to get more affected with vertical in switching conditions. Could be because of less stability or maybe just less weight?

[Redhawk]

Suspect it is a bit of both……. at Belmont it is very pronounced at a 1,000yds when the conditions are on with big switches…. Heavier stable bullets get heaps less vertical….