tr/f class comps

[triggersqueezer]

it would be nice to find out as the chaps at diggle advised a 308 for 600 and more that is why i'm looking.at present the benefits are not worth it to 600.with respect brillo i hope your wrong as i'll save a fortune.

[triggersqueezer]

exbal

308 win 175 grn 2600fps

600 drop =102.6

wind = 31.3

[dannywayoflife]

If you could get the 80grain Amax's going mike that would fly even better it has a g7bc of .231 measured by litz.

[triggersqueezer]

perhaps when my varget dries up i'll start to play again.i'm in talks with yoda as we speak.want him to teach me the force as reading mirage is not working well for me at the moment.

[Brillo]

As promised; .308 SMK 155 grn @ 2900 fps - drop: 83.66" Wind drift at 10 mph = 4.5 moa

 

.223 SMK 77 grn @ 3000 fps - drop: 85.58". Wind drift = 5.6 moa. (Are you pushing at that velocity, cos my .223 only likes 2800 for the 77 grainers?)

 

Not a lot in it regarding elevation but the wind drift is considerable. If the wind was constant it could be managed but if its gusty

[Laurie]

This isn't an easy subject as it's difficult to compare apples to apples.

 

If you want to shoot .223 Rem competitively beyond 200/300 yards, you're talking 80gn bullets with the possible exception of the 75gn AMax. Assuming custom built turnbolt rifles with 28-inch or longer barrels, we're talking 3,000 fps + with an 80, in fact ~3,100 fps. The rule of thumb is that an 80 in 223R should be in the same veocity ballpark as a 155 in .308W. Sounds a lot, but remember US High-Power Service Rifle shooters aim for 2,800 fps MV from their 20-inch barrel AR-15s with the 80gn Sierra single-loaded for the 600yd prone, deliberate stage of fire.

 

Getting these sorts of MVs requires suitable chamber throating for the longer / heavier bullets, the Wylde form at the least.

 

Right, having got similar MVs, it comes down to BC as external ballistics is simply and invariably the combination / interraction of MV and BC irrespective of calibre, bullet weight or whatever. Moreover in terms of outputs forget 'come-ups' - they're irrelevant to the prone target shooter whose disciplines involve known target distances. (Tactical / pest / sniper comp etc shooters are in a different situation as they may shoot at targets at unknown distances and a flat trajectory minimises the effects of range-finding errors.) There is only one issue that interests the prone target rifle shooter with come-ups - has the rifle / scope mounts / scope or iron sights got enough elevation adjustment to put the bullet on target at the maximum range being shot over?

 

So, let's look at BCs.

 

.308/155 range from G7 BCs (Litz) OF ~0.212 (Hornady AMax, Nosler CC, Old Sierra Palma #2155) to a best of 0.247 (Berger Hybrid). The widely used 155.5gn Berger LRBT is rated at an average BC of 0.237. .237 is a significant advance over .212 especially at long ranges. It reduces the 10mph wind drift at 1K from ~10-MOA to 8.75, a 12% reduction. It also does a great deal of good to the 1K terminal velocity - 1,337 fps v 1,182 fps. Both are still supersonic but 1,182 is well into the transonic speed zone. US Army field trials back in the days of the .30-06 as a match cartridge found keeping terminal velocities above 1,226 fps crucial for 30-cal BT FMJs. Drop below that figure and group dispersion increased markedly and wind changes had an exagerrated effect on the bullet, greater than the ballistics theories predicted.

 

0.224/80 BCs range from ~0.217 (Sierra MK) to ~0.234 (Hornady AMax, 80.5gn Berger LRBT Fullbore), marginally below those of the .30 155gnHybrid but very much on a par with the 155.5gn Berger if the best of the 22s is chosen. So, given similar MVs, there is no difference in their ballistics.

 

However, unless you're a TR shooter or some other regulation limits you to bullets weighing 'less than 156 / 81gn'), that's not the end of the story. You can have .30 bullets up to and including the 230gn Berger Hybrid and the 90gn Berger and JLK 0.224" VLDs. The 90gn Berger has an averaged G7 BC or 0.281, nearly identical to the company's 185gn LRBT 30-cal 'Juggernaut'. A good 185gn Juggernaut load in a long-barrel .308 F/TR rifle or similar will be somewhere within the 2,750 fps to 2,825 fps range. For .223R, the key MV is 2,850 fps which is generally where these rifles / barrels perform well, and over 2,900 fps is possible without wrecking the brass in a couple of firings. So 223/90 'beats' 308 / 185.

 

Go up to the .30 200gn Hybrid, the 210gn VLDs, and 215/230gn Hybrids in .308W, and there is no ballistic equivalent in .223R. Loaded up for bear, the 308 will now always beat the mouse gun cartridge at long ranges. But 308/210 produces a lot more recoil and torque and many people don't shoot well with these super-heavy bullets. barrel life can be severely reduced too using heavies and double-base powders like N550 and Re17 at full pressures.

 

At 600 yards, these issues are still there, but are FAR LESS important than at 1,000. Certain things apply at all distances - primarily consistency and precision. A really tight grouping combination that is easy to handload and shoot, and holds its elevation really well will nearly always beat a heavy recoiling, larger grouping combination in typical conditions at 200-600 yards.

 

So ........ that leaves two factors - recoil and consistency. .223 even with 90s is a delight to shoot such is the low recoil (quarter that of a typical 308 Win combination). In an 8kg F/TR rifle, it's like shooting a rimfire as the reticle stays on the aiming mark and you can 'follow the shot through'. Fancy wide-foot bipods are far less important with the mouse gun.

 

BUT ... getting 223R to shoot really well and consistently, achieving the aforementioned MVs etc is MUCH harder work than with .308. Full case preparation is crucial, bullet batching, weighing powder charges to very small tolerances, the bullet being well matched to the barrel's internal dimensions and chamber form all assume a much greater importance. Then 223R displays irritating habits - like needing 4 or 5 shots to 'settle down' when starting with a clean barrel when shooting 90s, suddenly 'going off', or producing excessive pressures etc, etc. Many people cannot get heavy-bullet 223R to perform well, few people suffer that in .308 if starting with a good rifle and handloading components. Take powder charges - 0.1gn weight change = 10 fps change in MV with the 223 and 80s or 90s. My research shows that even careful use of beam scales usually sees most charges within a 0.2gn range, but the odd example increasing that to nearly 0.3gn. 0.3gn variuation = 30 fps MV range ven before other factors like neck tension add more.

 

Then ... there are only a handful of good 80gn 224s and now that Berger has dropped its 90gn LRBT, only two suitable 90s, both VLDs which many people don't like. There are scores of good 308s in a huge range of weights, makes and designs. ~20 powders work well in 308 match loads, maybe 4 or 5 in .223/80 and even fewer in 223/90.

 

That's why only one person has regularly used 223 in the GB F-Class league series of matches, and so far as I know ever at all in 800-1,100yd matches (me) ... and I now shoot 308 as it makes life a lot, lot simpler. The 223R is a great little cartridge and if you're going to restrict yourself to 600 yards matches is well worth looking at with 80gn bullets. (Not the 77s - they're all relatively low BC designs meant to be used at 2.26" coal in magazine fed semi-auto AR operation in US SR matches.) Nevertheless, it's a lot easier to go with the herd even in club matches, and certainly very advisable for the tyro, and stick to .308 Win.

[gbal]

I'll post the exact stats tomorrow (I'm using my laptop which doesn't have the Sierra Ballistics software on) but if you go by muzzle energy (ME) alone a 75 grain bullet with a MV of 3000 fps has a max muzzle energy of 2032 joules whereas a 155 grainer with a MV of 2800 has a ME of 3660 J.

This tells you that bullet drop and the wind effect of the .308 is less than the .223. From memory, at 600 yds with a 10 mph wind, the .308 is 4mins less than the 223.

I can only add that when its been my turn in the butts the 223 loses out to the 308 in windy conditions.

I'm sure that Laurie and Vince will bear and this.

Download Strelok to your smart phone and you'll see the ballistics favour the .308 after 200 yards.

Muzzle energy isn't the statistic that helps with drift and drop-have a look at the very high energies for African calibers-big,but very large drop too-for other reasons,including bullet shape etc etc.Energy isn't a good guide to other ballistic facts-esp drop.

I think you will find those you mention know will agree that 308 beats 223 most of the time,and 223 needs extreme parameters esp bullet weight to compete at all esp at long range..

[gbal]

I'll post the exact stats tomorrow (I'm using my laptop which doesn't have the Sierra Ballistics software on) but if you go by muzzle energy (ME) alone a 75 grain bullet with a MV of 3000 fps has a max muzzle energy of 2032 joules whereas a 155 grainer with a MV of 2800 has a ME of 3660 J.

This tells you that bullet drop and the wind effect of the .308 is less than the .223. From memory, at 600 yds with a 10 mph wind, the .308 is 4mins less than the 223.

I can only add that when its been my turn in the butts the 223 loses out to the 308 in windy conditions.

I'm sure that Laurie and Vince will bear and this.

Download Strelok to your smart phone and you'll see the ballistics favour the .308 after 200 yards.

Muzzle energy isn't the statistic that helps with drift and drop-have a look at the very high energies for African calibers-big,but very large drop too-for other reasons,including bullet shape etc etc.Energy isn't a good guide to other ballistic facts-esp drop.

I think you will find those you mention will agree that 308 beats 223 most of the time,and 223 needs extreme parameters esp bullet weight to compete at all esp at long range..308 is the clubman's safe option.

gbal

[triggersqueezer]

thanks laurie, i think i followed most of that.i'm happy with my 223 very happy .using 75 amax i wonder if its even worth trying the 80s or concentrating on wind reading skills for the difference?i know it could be the difference between a win or lose but until you get to such a standard as to be at the top consistently. I'm happy for the next year or two learning to read that wind with the 223.

 

i was under the impression that the 308 was a big advantage but unless your prepared to push your loads to max and eat through barrels again at my level it simply does not make a big enough difference.even if the 308 out to 600 is better its marginal.i'm only getting 2707 fps but my vertical spread at 600 on sunday was about 5" and i wager a large part of that was me and the wind.the wind on the other hand was a nightmare.out of 18 shots 14 printed on a 12.5" target and it was bad wind calls that cost.the mirage was flowing to 2 oclock (the flags had dropped showing no wind behind the target) so i held off one milldot as had been working before and the bullet impacted where i aimed missing the paper target.so reading that migage is a skill i do not posses.i understand the theory but i'm not seeing it correctly.

 

as you can see more miss than hits.

 

in short laurie would you say the extra cost per round and a whole new rifle purchase would be worth it if only learning out to 600 max?

as you say the 223 is such a sweet round to shoot and if i can spend the time learning how that wind affects the 223 i hope results will improve greatly.

[Laurie]

Mike,

 

I'd say stick with your 223 at this stage. If you want to experiment give the 80.5gn Berger BT Fullbore bullet a try. It works very well in some people's rifles and is a tolerant design in terms of jump. MV, powder etc. Expensive though compared to Hornadys! When you think you've outgrown the rifle / cartridge that's the time to start thinking about a new or secondhand custom 308W F/TR rifle and whether you want to shoot light (155), mid-weight (185-190) or heavy bullets etc.

 

My maximum corrected wind change between shots during that match was 1.25 MOA and that was exceptional caused by a fishtailing switch from three-quarters left (actual) to half-minute right (actual) and then back again (twice over 4 shots). Everything else was quarter to three-quarters-MOA or at the very most a full 'minute' change. A full mil-dot aim-off is 3.48-MOA, so you were aiming off 22 inches and likely far, far more than the wind changes required.

[Brillo]

Muzzle energy isn't the statistic that helps with drift and drop-have a look at the very high energies for African calibers-big,but very large drop too-for other reasons,including bullet shape etc etc.Energy isn't a good guide to other ballistic facts-esp drop.

I think you will find those you mention will agree that 308 beats 223 most of the time,and 223 needs extreme parameters esp bullet weight to compete at all esp at long range..308 is the clubman's safe option.

gbal

I disagree on that point. Muzzle energy and therefore kinetic energy has a big effect on any projectile. Although the plot of a graph of flight over distance will be shallower for a low weight projectile up to a given distance the greater the mass of a projectile ensures the high projectile continues when the lower mass projectiles fails. Calculus proves this and this is why a lot of shooters elect to shoot (for example) a 190 grain bullet over a 155 grainer at longer ranges.

Bullet drop is only a one consideration and the main thing I've learnt recently is the effect of wind.

The kinetic energy of a high mass projectile is bound to beat one of low mass. This is intuitive but can also be demonstrated mathematically. Ballistics is new to my science and statistics background but I'm finding it fascinating. So much so that it is in danger of distracting me from actual shooting.

With the right programme or time enough to work it out on paper, a shooter should be able to predict true bullet drop and wind deflection (assuming correct wind speed calculation). I am amazed and in admiration of those who do it in their head and from experience.

[triggersqueezer]

Mike,

 

I'd say stick with your 223 at this stage. If you want to experiment give the 80.5gn Berger BT Fullbore bullet a try. It works very well in some people's rifles and is a tolerant design in terms of jump. MV, powder etc. Expensive though compared to Hornadys! When you think you've outgrown the rifle / cartridge that's the time to start thinking about a new or secondhand custom 308W F/TR rifle and whether you want to shoot light (155), mid-weight (185-190) or heavy bullets etc.

 

My maximum corrected wind change between shots during that match was 1.25 MOA and that was exceptional caused by a fishtailing switch from three-quarters left (actual) to half-minute right (actual) and then back again (twice over 4 shots). Everything else was quarter to three-quarters-MOA or at the very most a full 'minute' change. A full mil-dot aim-off is 3.48-MOA, so you were aiming off 22 inches and likely far, far more than the wind changes required.

that egg shoot target was one i had printed to practice on ,the mill dot was yesterday at kingsbury at 600 and was working well when the flags were being watched but not so well when i was trying to guess the wind using mirage.20" is only a 6 mph wind that was correct for most shots its just the wind seemed to drop but i read the mirage wrong.