When does BC Adavtage , become a disadvantage?

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GSells
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When does BC Adavtage , become a disadvantage?

#1 Postby GSells » Wed Aug 08, 2018 7:49 pm

Hi all , I’m trying hard to keep in the shadows of late on this forum ! However of late you may not tell lol! But I thought tonight, this is a valid and interesting subject, and maybe of benefit to the fraternity!?

So I’ll repeat my Question as in Andrew’s post is .

WHEN DOES BC ADAVATAGE , BECOME A DISADVANTAGE IN RECOIL AND BARREL WARE , COST OF POWDER AND TIME IN RETUNING NEW BARRELS WITH THE INCREASED FREQUENCY? 8)

bruce moulds
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Re: When does BC Adavtage , become a disadvantage?

#2 Postby bruce moulds » Wed Aug 08, 2018 9:52 pm

b.c does not have to affect recoil, barrel wear, cost of powder, or retuning barrels.
that is more to do with ammount of powder burned, except where higher b.c bullets, being heavier have more recoil.
one advantage of higher b.c. bullets is that you can run them a bit slower than low b.c. bullets for the same wind deflection, and so run lower pressures and possibly more barrel life.
there are 2 disadvantages of high b.c. bullets that come to mind.
no 1 is that the user of such bullets might tend not to focus on wind reading as much, in the subconscious belief that b.c. will overcome all evils.
this is one of the biggest things holding back fclass at the moment.
no 2 is precessation and nutation.
higher b.c. bullets are longer, and require faster twists, which gives greater precession and nutation for a longer distance as well.
while a bullets are precessing and nutating, particularly long ones, they are literally steering themselves all over tha place, and away from the true line of flight.
this steering also manifests itself in increased spindrift, as longer faster spinning bullets when they stop precessing and nutating go into a greater yaw of repose than shorter and slower spinning bullets.
bullet manufacturers ,led by berger, have been pushing this envelope of latter years, and soon they must punch a hole in the sky and go past a realistic limit.
it will be interesting to see where it ends up.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
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wsftr
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Re: When does BC Adavtage , become a disadvantage?

#3 Postby wsftr » Thu Aug 09, 2018 4:57 am

If you look at FTR there are some examples as to how a combination of recoil is most likely contributing to being a disadvantage.
Typically this is with 215s and up. Most settle on 185 and 200s as that is a practical limit where a measurable disadvantage (precision) is found.
Typically heavy for weight bullets come with a better BC but the recoil disadvantages are greatly nullified in an F-class setup. You find the PRS guys settling on 6s and 6.5s I believe this is due to a bunch of things one of which is recoil.
Bruce has listed some issues but I'm not fully convinced about them being measurable disadvantages for Fclass. Sure a short flat base bullet can be shot very accurately at short range relative to a long high BC bullet. But in F class the relative precision difference is minor enough that its not an issue. This is backed up as F class moves to heavier and higher BC bullets because they shoot higher scores with an acceptable level of precision.
Yes there is a possibility that bullet design will reach a limit where the relative BC gain is weighed up against the difficulty of maintaining or achieving a necessary precision level. I'm assuming then the thinking will go into recoil management setups allowing heavier projectiles to be selected with an acceptable level of precision.
I'm guessing when all of that hits a boundary we'll get some one asking for rule changes ;)

Tim N
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Re: When does BC Adavtage , become a disadvantage?

#4 Postby Tim N » Thu Aug 09, 2018 8:45 am

GSells wrote:Hi all , I’m trying hard to keep in the shadows of late on this forum ! However of late you may not tell lol! But I thought tonight, this is a valid and interesting subject, and maybe of benefit to the fraternity!?

So I’ll repeat my Question as in Andrew’s post is .

WHEN DOES BC ADAVATAGE , BECOME A DISADVANTAGE IN RECOIL AND BARREL WARE , COST OF POWDER AND TIME IN RETUNING NEW BARRELS WITH THE INCREASED FREQUENCY? 8)


Out of the above listed disadvantages I'd say recoil is the only one most would consider as the others will occur naturally if you want to be at the cutting edge in F class.
Meaning if a 300WSM with 300gn super dooper projies was way ahead of everything else we would all be shooting that if we could handle the recoil :x
Just an observation- the bullet manufacturers all go past the max/optimum BC(whatever that is) for each caliber producing projectiles that look the best on paper but for whatever reason not in practice.
Probably alot to be said for shooting 1 caliber and getting to know it really well.
We don't rise to the level of our expectations, we fall to the level of our training. Archilochos 680-645 BC

AlanF
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Location: Maffra, Vic

Re: When does BC Adavtage , become a disadvantage?

#5 Postby AlanF » Thu Aug 09, 2018 9:20 am

Tim N wrote:...Probably alot to be said for shooting 1 caliber and getting to know it really well.

Agreed. An example of that is the number of very experienced TR or F-Std shooters who have problems with over-compensation when they move to F-Open. The same can happen in reverse when an F-Open shooter brings out the old 308.

GSells
Posts: 358
Joined: Sun Aug 13, 2017 11:04 pm

Re: When does BC Adavtage , become a disadvantage?

#6 Postby GSells » Thu Aug 09, 2018 10:10 am

What about Berger 195’s , they haven’t in my opinion really made any inroads and smk’s 183’s have sort of worked for some but not for others !??

Tim N
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Location: Branxton NSW

Re: When does BC Adavtage , become a disadvantage?

#7 Postby Tim N » Thu Aug 09, 2018 11:02 am

GSells wrote:What about Berger 195’s , they haven’t in my opinion really made any inroads and smk’s 183’s have sort of worked for some but not for others !??


That's what I was getting at, I am however about to try the 6mm 115s that most have given up on :)
We don't rise to the level of our expectations, we fall to the level of our training. Archilochos 680-645 BC


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