284 versus 6SLR (243AI) comparative ballistics F-class options

J

Jefferson

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Cartridge Bullet Vel FPS 300yd Drop/Drift 600yd Drop/Drift 1000yd Drop/Drift
7mm WSM 180gr Berger VLD 3000 9.75" | 3.83" 63.81" | 16.13" 235.19" | 49.31"
7mm SAUM 180gr Berger VLD 2970 10.02" | 3.87" 65.38" | 16.38" 240.81" | 50.10"
.284 Win 180gr Berger VLD 2830 11.31" | 4.10" 73.27" | 17.69" 269.88" | 54.26"
7mm-08 168gr Berger VLD 2670 13.32" | 4.67" 85.03" | 20.39" 317.97" | 64.04"
.308 Win 175 Sierra MK 2690 13.84" | 6.24" 91.58" | 27.64" 365.74" | 89.24"
6.5-284 142 Sierra MK 2950 10.42" | 4.48" 69.25" | 19.52" 263.08" | 61.02"
.243 Win 115 DTAC 3120 8.97" | 4.24" 60.82" | 18.25" 232.3" | 57.0"


in a 10 mph wind at 1000 the 6slr has 218 drop and 54 inches of drift with a 115 DTAC or berger so how come more guys are not using it for f-class,


Jeff
 
6mm 115gr bullets have proven to be difficult to tune well.

Bore life is horridly short.

Bullets of equal BC - the heavier will win in the real world.

No different then 223/90 and 308/185. On paper, the 223/90 is better but in the real world at 1000yds, not even close.

Jerry
 
I had a TRG22 re-barreled with a 7.5 twist Bartlein and chambered in 6mm SLR. Still in the process of finalizing a load but am very close. My best load so far runs 105gr. Scenar's at 3270fps from a 28.5" barrel. 115gr Bergers showed some good results as well but there is little BC advantage when compared to some of the sleeker 105-107gr. bullets and they run about 100-125fps slower.

Could care less about trying to maximize barrel life. If I can get 2000 through it before its cooked I'm happy.
 
Because drift is way more important than drop. The first four F-O combinations you list all shoot inside the 6 SLR / 115 DTAC by as much as 8.5" at 1000 yds.

That's equivalent to one and a half scoring rings worth of wind you give up by using the 6SLR.

In reality, it's actually an even larger gap. My 7-300 WSM runs the berger 180 hybrids at 3050 fps so the difference is above 9" of drift.
 
You may find the 6mm more comfy to shoot and it should do very nicely at mid range. Long range too on days that aren't too bumpy

But at 900m/1000yds, you can't drive a light, low BC bullet fast enough to be competitive with the larger slugs in bumpy air.

Unfortunately, inertia still matters and rarely calculated in ballistic drop programs
Jerry
 
Mystic Precision said:
Unfortunately, inertia still matters and rarely calculated in ballistic drop programs
Click to expand...
Disagree.

The "BC" parameter rolls up all relevant ballistic parameters into a single number. The effects of the mass of the bullet (and therefore its inertia) is already included in the BC (as are the cross-sectional area and the degree of "sleekness").

Two bullets with the same BC, fired at the same speed, will perform identically as the go downrange:
- their speed will bleed off at the same rate
- they will be pushed left/right by the wind the same amount
- they will be pushed up/down by the wind the same amount

There are plenty of fine points and subtleties to what a BC is and is not, and what the limitations of its applicability are etc, but, but they don't apply to the topic at hand. Provided you have two "apples-to-apples" BCs, which is to say the BCs are from the same source and used the same methodology to measure (for this I *really* like using Litz's data), you will not see heavier bullets being blown around more by the wind than a lighter bullet of the same BC and same MV.
 
I wished the to be true but it isn't.

Spent 2.5yrs working with the 223/90 in hopes of using this "physics" to let me shoot without recoil pain vs the 308/heavies. At Raton and every other range I have shot out to 1000yds, the smaller bullet was simply punished more for small wind reading mistakes or in bumpy air.

I am not saying the 308 shooters beside me didn't get moved around but when they got bumped into a high 10, mine was a higher 9. Same direction.

Comparing starting winds and wind useage, my adjustments mimicked the 308/185 over several shooters. We both made the same conclusions about the left and right BUT it was the bumps up and down and gusts that hurt me much more.

Yes, my 223/90 have little to no vertical and shoot great accuracy.

Same can be seen in Open where the smaller cals simply bleed more points vs the big heavy bullets at 1000yds. All of the BC's vs muzzle velocities are very close. The larger heavier bullets do not get bumped as much by localised winds or gusts.

This season with my 308 and heavies, my shots were "smoother". Of course, there were ups and downs and missed winds but it was truer to the conditions presented and made more sense.

There are other shooters around the world who have also tried to exploit the 90gr BC/muzzle velocity vs the 308 and have all given up.

On a stable day, even if windy, no problem. On a bumpy day, the lighter bullet WILL get moved around more.

Jerry
 
I would like you guys to argue this BC thing some more!!! I have always wanted to ASSUME that good BC #'s would indicate as Daniel says, all variable's, but I do know some old timers that say heavy wins out because of some unwritten enertia or somthin!! I have Litz's book but have not read it enough to determine if he talks about this phenom. My only experience is with 6mm 105's, 6.5mm 140's, and 7mm 180's. With these 3 calibers, 6br, 260rem, 284win, it appeared to me that they were all pretty true to their BC's. I have had occasion to shoot beside 223's and 308's, the 308's appeared to be ballistically challenged however the 223's at times reminded me of shotgun pattern :>). Could there be something else going on? other than lack of weight???
 
shockman, dial back the clock a few years at the Farky. You had a 260Rem, me a 260 improved, new shooter my back up 6.5 Mystic.

All launching 140gr VLDs around 2900fps

On Sat, the winds were horrid, bumpy, twitchy, gusty... good Kamloops wind. We placed 1 and 2 with the new shooter 4th for the day.

Sunday is a way calmer day, trigger pull for some. The 6BR's dominate pushing me lower for the day (unsure about your placing). New shooter does really well.

We end with 6.5s 1st, 2nd, 3rd for the 2 day agg. Despite scoring so well on Sunday, the losses on Sat didn't allow the 6BR's to catch up.

Scotland a few years back. The Brits/Scotts dominate with 7mm. The US team plays catch all match with their 6.5's. Maybe a fluke event but this single match helps drive F Open to larger cals.

I believe it was Ballard who dominated NRA 1000yds F OPen for a few years with the "new" 284 over a sea of 6.5's.

Shiraz and others in the US continue to put 30cals on the podium at big matches.

Take a 6.5/140, 7/180, 30/220, and 338/300. Push them at equal ballistics and see what happens in bumpy air at 1000yds and beyond. As they say, been there done that, burnt up the barrels.

For anyone who doubts the effects of inertia, shoot rifles of varying bullet weights and see for yourself.

The best current example is the 223 vs 308. Run the numbers and you will find the 223 is better then many 308 combos ON PAPER. Ask those that shoot these combos and see how they feel in the real world.

I have no interest in shooting a 308/heavy if I could be competitive with my 223/90. Why would anyone?

Ballistics program can only calculate steady state situations and constant variables (there is an oxymoron). At mid range (600m), the ballistics really work well for the most part and light/fast can keep up with heavy/slow. But extend that to 1000yds and the difference is obvious.

Just shoot the stuff on a breezy day and see for yourself.

In BC, we have some of the BEST 6mm shooters and wind readers in the World. Ask them their thoughts between their 6 BR/Dashers and 6.5/284's and 30cals. Some have done superbly at 900m with a 6BR but they all seem to want to compete with 7's now.

Inertia helps you with the conditions you do not see along the bullet path. Liking hitting a gust of wind on the highway - usually, the smaller vehicle gets buffeted more.

Jerry

PS Given that you are one of those BEST shooters, what do you think?

Feel like putting a 130gr VLD or 123gr into your 260R and see what happends?
 
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Mystic Precision said:
6mm 115gr bullets have proven to be difficult to tune well.

Bore life is horridly short.
Click to expand...

Not my experience. The 115 DTACs in my Crusader have probably been the easiest combo to tune that I have ever fired. I've run several barrels to over 2000 rounds without ever adjusting seating depth. This group was fired on an old barrel after minimum development with 117 Matrix VLDs.



A 6 SLR is not going to keep up with a big 7mm driving the 180 hybrids though. The Crusader comes close, but its a bigger case (6mmAI).
 
shockman said:
I would like you guys to argue this BC thing some more!!! I have always wanted to ASSUME that good BC #'s would indicate as Daniel says, all variable's, but I do know some old timers that say heavy wins out because of some unwritten enertia or somthin!! I have Litz's book but have not read it enough to determine if he talks about this phenom. My only experience is with 6mm 105's, 6.5mm 140's, and 7mm 180's. With these 3 calibers, 6br, 260rem, 284win, it appeared to me that they were all pretty true to their BC's. I have had occasion to shoot beside 223's and 308's, the 308's appeared to be ballistically challenged however the 223's at times reminded me of shotgun pattern :>). Could there be something else going on? other than lack of weight???
Click to expand...


THis is probably the best explanation as to why the theoretical advantage of the 223 does not translate in the real world...

http://riflemansjournal.########.ca/2012/03/cartridges-223-for-palma-competition.html
 
I think some people should read that article a few times, it explains an inherent problem with a particular cartridge and set of circumstances and does not mention the heavier bullet defying its BC
 
Mystic Precision said:
shockman, dial back the clock a few years at the Farky. You had a 260Rem, me a 260 improved, new shooter my back up 6.5 Mystic.

All launching 140gr VLDs around 2900fps

On Sat, the winds were horrid, bumpy, twitchy, gusty... good Kamloops wind. We placed 1 and 2 with the new shooter 4th for the day.

Sunday is a way calmer day, trigger pull for some. The 6BR's dominate pushing me lower for the day (unsure about your placing). New shooter does really well.

We end with 6.5s 1st, 2nd, 3rd for the 2 day agg. Despite scoring so well on Sunday, the losses on Sat didn't allow the 6BR's to catch up.

Scotland a few years back. The Brits/Scotts dominate with 7mm. The US team plays catch all match with their 6.5's. Maybe a fluke event but this single match helps drive F Open to larger cals.

I believe it was Ballard who dominated NRA 1000yds F OPen for a few years with the "new" 284 over a sea of 6.5's.

Shiraz and others in the US continue to put 30cals on the podium at big matches.

Take a 6.5/140, 7/180, 30/220, and 338/300. Push them at equal ballistics and see what happens in bumpy air at 1000yds and beyond. As they say, been there done that, burnt up the barrels.

For anyone who doubts the effects of inertia, shoot rifles of varying bullet weights and see for yourself.

The best current example is the 223 vs 308. Run the numbers and you will find the 223 is better then many 308 combos ON PAPER. Ask those that shoot these combos and see how they feel in the real world.

I have no interest in shooting a 308/heavy if I could be competitive with my 223/90. Why would anyone?

Ballistics program can only calculate steady state situations and constant variables (there is an oxymoron). At mid range (600m), the ballistics really work well for the most part and light/fast can keep up with heavy/slow. But extend that to 1000yds and the difference is obvious.

Just shoot the stuff on a breezy day and see for yourself.

In BC, we have some of the BEST 6mm shooters and wind readers in the World. Ask them their thoughts between their 6 BR/Dashers and 6.5/284's and 30cals. Some have done superbly at 900m with a 6BR but they all seem to want to compete with 7's now.

Inertia helps you with the conditions you do not see along the bullet path. Liking hitting a gust of wind on the highway - usually, the smaller vehicle gets buffeted more.

Jerry

PS Given that you are one of those BEST shooters, what do you think?

Feel like putting a 130gr VLD or 123gr into your 260R and see what happends?
Click to expand...

I would not go to a 130 or 123 as they have lower BC's !! All the examples you give above show that the higher BC bullets win out! I just want to have someone explain to me how a heavier bullet performs BETTER than its BC??? I see we have "one mans opinion" on how the 308/223 battle goes, and it makes sense to me? Good article! I still have some old-timers around me that think the big 30 cal bullets will trump the 7mm 180! I say if you run the velocities and BC's the math will tell, however you need a heavier than 210gr (bergers) to beat the 7mm 180, SO now what case do you need to equal its velocity??? Now I can see a whole nother set of problems with that much recoil :>))) I doubt very much that you will see those bullets knock the 7mm off it's pedestal
 
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Great discussion guys. It's nice to see a group of experienced shooters sharing their opinions and experience but remaining civil. Makes for a good read when there is no bickering going on. I've recently sold my 6.5x284 and now I need to decide what to replace it with. Something in 7mm is the path I'll take. Just not sure what cartridge.
 
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