My 6BR in 300yd F-class. Which bullet?

[gunsandgunsmithing]

Even though the twist rate might not be optimal (‘over twisted’) would you consider a flat base bullet for 300yds that our BR colleagues use?

IME, there might well be extreme limitations to this, but I've spent some time testing this very thing, this year. Testing tells me it's hard to discern "over twist" but longer bullets that require faster twist are less accurate. Case in point. I've been testing a 6mm 10 twist. The most accurate bullets, by very little in that twist, are 68's. Trying various 90-95gr bullets, more "suitable" to that twist, it appears that accuracy follows bullet length more than weight or twist rate. ...fwiw. Shorter, lighter bullets have consistently shot best at short range...100-300. 80's appear to be a very good compromise of accuracy and bc in that twist. I strongly suspect that accuracy from the 6BR based cases, out to 600 at least, may be better with the 90-95 class bullets than the more common 105-108 bullets. If so, it may or may not need more testing, to optimze proper twist for the better performing bullets, ie. 90gr bullets in a 9.5-10 twist vs shooting them in a 8 twist. But again, my main point here is that I think it's hard to "over stabilize" a bullet, but with limitations to that statement.

 

[LRCampos]

Here in Brazil, almost all F-Class are done at 300 meters (about 330 yards) and in the last 10 or more years, all Brazilian champions have used the 6BR.
Most 6BR shooters use Sierra or Berger 105-107grains bullets, mostly because this is what is (more or less) available down here.
That being said, what counts most, from our experience, is the accuracy of the bullet... to a point. Once the weight (and the BC) gets from 90 grains and up, what win matches and championships here is accuracy. The difference in wind from 90 to 107grains is not that great that overcome accuracy.
The competition is so fierce that is not uncommon to get at the Finals (the Brazilian Championship is a tournament format with about 4 to 5 matches during the year plus the Finals in November/December), with about ten shooters tied at the top with 100% score in points. Now the Xs count is what decides the Championship. And the X on a 300 meters/yards F-Class target is less than 0,5 MOA... it is small, really small!!!!

To get to the accuracy and precision we need here to win a Championship, the rifle/ammo/shooter has to perform at 0,35 MOA consistently (at 100 meters/yards targets, where we test most of our loads).
Of course, the lighter 6mm bullets, like 68-80 grains, give up a lot on BC and any wind can throw you way out of the 10 ring... so it is a no go. At least for us.

So, in my opinion and experience, if you get that with 90grains and only 0,45 with 107 grains, I would keep with the 90 grains. And if you get that 0,35 MOA (at 100 yards/meters distance) with more than one bullet weight/brand, pick the one with the highest BC.

Just my 2 cents.

 

[gunsandgunsmithing]

Here in Brazil, almost all F-Class are done at 300 meters (about 330 yards) and in the last 10 or more years, all Brazilian champions have used the 6BR.
Most 6BR shooters use Sierra or Berger 105-107grains bullets, mostly because this is what is (more or less) available down here.
That being said, what counts most, from our experience, is the accuracy of the bullet... to a point. Once the weight (and the BC) gets from 90 grains and up, what win matches and championships here is accuracy. The difference in wind from 90 to 107grains is not that great that overcome accuracy.
The competition is so fierce that is not uncommon to get at the Finals (the Brazilian Championship is a tournament format with about 4 to 5 matches during the year plus the Finals in November/December), with about ten shooters tied at the top with 100% score in points. Now the Xs count is what decides the Championship. And the X on a 300 meters/yards F-Class target is less than 0,5 MOA... it is small, really small!!!!

To get to the accuracy and precision we need here to win a Championship, the rifle/ammo/shooter has to perform at 0,35 MOA consistently (at 100 meters/yards targets, where we test most of our loads).
Of course, the lighter 6mm bullets, like 68-80 grains, give up a lot on BC and any wind can throw you way out of the 10 ring... so it is a no go. At least for us.

So, in my opinion and experience, if you get that with 90grains and only 0,45 with 107 grains, I would keep with the 90 grains. And if you get that 0,35 MOA (at 100 yards/meters distance) with more than one bullet weight/brand, pick the one with the highest BC.

Just my 2 cents.

Agreed. I think we might be assuming some things, like higher bc is always better. My testing shows the accuracy improvement at 100-300 yards is of more value than the bc of the heavier bullets. Conditions will of course play a role, especially 600-1000 yards, but I think the lighter, faster bullets deserve more testing out to 600. It's been done, so maybe re-visiting is a better word, as accuracy improvements have been made over the last several years that might invalidate some of the older tests along these same lines. The good thing is that ideal twist seems to be over valued, meaning that I wouldn't hesitate at all to test 90-95 class bullets in existing 7.5-8 twist bbls. My testing so far shows little or no effect on accuracy potential when we're talking say an 8 twist when optimum calculated twist is say a 10. An "over stabilized" bullet corrects itself sooner and effectively has better bc characteristics vs a minimally stabilized bullet. Spinning a bullet only fast enough to be stable assumes imperfections in the bullet that are of more detriment than is the bc advantage of a more stable bullet. Simply put, bullets are better than they were several years ago. I hope to test some of this next season a bit, shooting a few 600 yard matches using a 10 twist with the 90-95 class bullets, and just see how it goes. I feel like there will be days that they are better and days where the 105 class bullets still have an edge, in heavier conditions. But out to 300ish yards, I feel very good with what I've seen so far with this 10 twist and 80-95gr bullets. It shoots competitively, even at 100, so it's not leaving much, if anything, on the table accuracy wise. The biggest factor is me, so this is a good excuse for me to shoot more and get back to shooting better.

 

[gcabrera]

Agree 100%
Around here (Cincinnati area) I have been ‘promoting’ the 90gr/10 twist combo quite a bit.
From my experience, the 90 grainers strike the best balance between accuracy and wind resistance from let’s say 200-400 yards, no wind flags.
Over wind flags, they would still be the ones to beat from 300-400 yards, and remain competitive at 200 yards (but this is now 6PPC/30BR habitat).
At 100 yards nothing touches a 30BR for score / 6PPC for group, with or without flags.

For a couple of years now I have been shooting our 600 yards benchrest matches (groundhog targets), with wind flags. A bit of an stretch for the 90 grains, but knowing that our range is kind of protected, I gave it a shot literally.
And it has not disappointed.

This is I think my best target so far, one shot a bit high, the other 9’s well grouped.

It is by no means the best bullet at this distance, but under mild conditions it can work.

 

[gunsandgunsmithing]

Agree 100%
Around here (Cincinnati area) I have been ‘promoting’ the 90gr/10 twist combo quite a bit.
From my experience, the 90 grainers strike the best balance between accuracy and wind resistance from let’s say 200-400 yards, no wind flags.
Over wind flags, they would still be the ones to beat from 300-400 yards, and remain competitive at 200 yards (but this is now 6PPC/30BR habitat).
At 100 yards nothing touches a 30BR for score / 6PPC for group, with or without flags.

For a couple of years now I have been shooting our 600 yards benchrest matches (groundhog targets), with wind flags. A bit of an stretch for the 90 grains, but knowing that our range is kind of protected, I gave it a shot literally.
And it has not disappointed.

This is I think my best target so far, one shot a bit high, the other 9’s well grouped.

It is by no means the best bullet at this distance, but under mild conditions it can work.

View attachment 1480406

Thank you George! That's what I'm after, as much as anything...is where is that point of diminishing return, both at short and long..err, 600 ish yard range. Thanks for your feedback. I'm a little familiar with the format you guys shoot up there and I know you test a lot of different stuff. Thanks again!

I am curious after looking at the target you posted. What do you believe kept it from being better? I'm sure you're aware of group shapes and wind. Meaning, there is a clear up and to the right diagonal shape to that group. Of course it can be your hold so I can't assume anything but with or without flags, there's no wind condition that will do that from a rh twist bbl. Just curious if you have any thoughts in regard to that.

 

[gcabrera]

Not sure about the vertical in the group, most likely at near the gun’s limit plus my lack of table manners, and some (though minimal) updrafts.
I would not read much on the windage, as I was favoring right to protect the left edge of the target, my goal was to shoot center or center/right due to the predominant R to L wind.

 

[gunsandgunsmithing]

Not sure about the vertical in the group, most likely at near the gun’s limit plus my lack of table manners, and some (though minimal) updrafts.
I would not read much on the windage, as I was favoring right to protect the left edge of the target, my goal was to shoot center or center/right due to the predominant R to L wind.

Thank you! It's hard to read group shape when shooting for score too. No telling where the shooter is holding, so hard to tell much with that being the case. Even being relatively small, I'd lean toward it being a little out of tune but like I said, hard to know

 

[fatelvis]

If you look solely at the BC of the 90 gr weight class 6mm bullets, you're talking about wind deflection comparable to a .223 Rem F-TR rifle with 75-80 gr bullets (30" barrel). So of course you can shoot the 90s at 300 yd. But will you win using those? That totally depends on the wind conditions, the skill of your opponents, and the bullets/loads they will be using. In all likelihood, you will be giving up a fair bit of windage to some of the other F-Open shooters. If the 90s load with outstanding precison in your setup, it might compensate for a small disadvantage in wind deflection, but probably not for a large difference.

FWIW - I've won a number of club matches shooting Berger's 80.5 Fullbore bullets from a .223 Rem F-TR setup at about 2860 fps. The ballistics of that load are probably not too different than what you might get from a 6BR with a 26" barrel using Berger's 6mm 90 gr Target BT. Then again, I wasn't competing against F-Open shooters. That would have made a BIG difference, and not in my favor.

This is the post that is making me bring a box of 90s to the matches (which shoot very well with H4895) AND a box of 107s also, in case it’s gusty or windy. Thanks Ned!

 

[fatelvis]

I'll let you know soon!

I have been getting better accuracy at 300 with the Berger 90s over H4895.

 

[Ned Ludd]

This is the post that is making me bring a box of 90s to the matches (which shoot very well with H4895) AND a box of 107s also, in case it’s gusty or windy. Thanks Ned!

I hope one or both work well for you! Let us know how things end up. I don't know how your matches are, but the 300 yd matches I use to participate in were very competitive. Dropping more than a point or two in F-TR usually meant you weren't going to win, and high X-counts were the norm. As expected, the F-Open scores were even better. We usually had enough wind that dropping a few to several points wasn't at all difficult if you lost focus. Hence the reason I favor higher BC bullet choices as long as the precision is comparable. Best of luck!

 

[Cory porter]

108g Berger at 300 in an 8 twist 6br
300 yard varmint match

 

[gcabrera]

View attachment 1481820

108g Berger at 300 in an 8 twist 6br
300 yard varmint match

Nice shooting, Corey!
Nothing wrong with the 8 twist

 

[wildcatter]

26" 1-8 krieger on a Savage Axis, in a laminated BR stock with 3" forearm.

It will shoot under .250 moa. Without stomping on my brass. 34.5 grains of H4350 @ 3050 fps, my Dasher Beater. 95 grain Bib. Pic yer primer!

 

[JFrank]

103gr Vapor trails out of a 1-8 twist shoot pretty well at 300 yards.

 

[wildcatter]

Same gun runs well with Varget, and the same bullet. Another dasher beater near identicle coefficient as the 105's and 108's, @ 3006 fps av. and single digit ES. What I like about the standard 6BR, easy to load for and not picky.

 

[foxguy]

I have been getting better accuracy at 300 with the Berger 90s over H4895.

Care to share the Powder Charge weight you are using with the H4895. I just purchased some 90 Gr Bergers t try in my 6MM BR Savage F Class rifle.