Boattail....not always the best!

[BuzzBoss915]

Re: Boattail....not always the best!

I have been told that an optimum RPM for benchrest accuracy is in the range of 185,000 and it's a simple formula based on twist rate times velocity. Personally, I am not that much a devotee, but I have always wondered at the tendency of some people to equate a fast twist with "better". Maybe more suitable for driving a VLD heavy for caliber bullet at longer range? If so, there goes your versatility. I guess a short barrel needs a faster twist to stabilize a heavy bullet, but some of this stuff, you really have to know the reasons for your specifications. I do not like boat tail bullets, as a general rule. They may be more sophisticated, possess a higher ballistic coefficient, etc. but I'm not a believer. Yet, I listened to someone else and bought a 243Ackley 30" barrel with a 8.5" twist. I'm still chewing on that one. BB

 

[boltgunluvr]

Re: Boattail....not always the best!

I must say the 243AI cartridge just looks cool. You used one key word that is always in my vocabulary...."Versatility."

 

[cascade tactical]

Re: Boattail....not always the best!

ArmchairElite:

Brian Litz in his book on pg. 284 states:

"Some of the .30 caliber (Sierra) Match Kings including the 168 and 180 grain bullets have (approx) 12 degree boat tails which is much steeper than the optimal 7 degree angle for reducing base drag. It is commonly believed that the excessively steep boattail on the 168 grain Match King is responsible for the dynamic instability problems it displays at long range".

YOu are in concurrence with the notion that boattails are more difficult to manufacture correctly. The concentricity of the boattail must be perfect; otherwise it will detract from overall performance and accuracy.

 

[Helmet]

Re: Boattail....not always the best!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cascade tactical</div><div class="ubbcode-body">ArmchairElite:

Brian Litz in his book on pg. 284 states:

"Some of the .30 caliber (Sierra) Match Kings including the 168 and 180 grain bullets have (approx) 12 degree boat tails which is much steeper than the optimal 7 degree angle for reducing base drag. It is commonly believed that the excessively steep boattail on the 168 grain Match King is responsible for the dynamic instability problems it displays at long range".

YOu are in concurrence with the notion that boattails are more difficult to manufacture correctly. The concentricity of the boattail must be perfect; otherwise it will detract from overall performance and accuracy. </div></div>Thanks for pointing that out. Brian Litz has so much good information in Applied Ballistics that It's easy for me to miss something. What I should have said (just to be safe) was that Brian Litz did not single out any bullets on the pages I was referencing. I find it fun to browse through the bullets he has tested to see which ones have proper angles which influence me on what bullets I'm going to put my energy into.
I'm switching from 308 to 7mm because I know that I would need at least a 208gr bullet in a 300Win mag to match the combination of speed and BC that I can get out of a modest 7mm. While looking though 7mm bullets I can't help but be impressed by the 177gr Cauterucio VLD. Check it out on page 462. The numbers on this bullet seem impossibly good, but it has a 9 degree boat tail. I think that what the ideal boat tail angle is exactly can be very dependent on the design of the rest of the bullet. I still have a lot to learn so I wouldn't dare state this as a fact, but maybe most bullets just can't utilize a 9 degree BT the way the Cauterucio does. The Berger 90gr VLD in .224 (page 324)is one of these bullets that obviously can with a 9.3 degree boat tail. It's form factor is also very impressive. In any case a 12 degree angle for a boat tail is way too much. Some Amax bullets are terrific. The 7mm 162 Amax and the 308 diameter 208 Amax have very good boat tails, while the common 168 and 178 grain Amax bullets are way too steep.

 

[boltgunluvr]

Re: Boattail....not always the best!

Thank you....a person that actually gets it. Seems as if too few get it. Forget techno junk, bc, speed, etc. Its about the end result....accuracy. We're on the same wave length.

 

[Helmet]

Re: Boattail....not always the best!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: boltgunluvr</div><div class="ubbcode-body">Thank you....a person that actually gets it. Seems as if too few get it. Forget techno junk, bc, speed, etc. Its about the end result....accuracy. We're on the same wave length. </div></div>I can only speak for myself, but for me it's all about the enjoyment. For right or wrong I seem to find the most enjoyment in the PURSUIT of accuracy, which for me personally includes much of that stuff. One of the great things about this hobby that we all enjoy so much is that their are so many different ways to attempt to improve accuracy. Different people approach things from different perspectives, and I think that makes it so much more interesting. Many of the really old guys at my rifle club will never even own a computer. They tell me that flat based bullets are the most accurate because this is what their experience has taught them over their 65+ years of shooting. Who am I to disagree with them or tell them that my calculator says their wrong ? Maybe over the next 40 years of shooting I will decide that they were right all along and they didn't need anything but lots of trigger time to figure it out. I do enjoy the numbers part of this hobby though. And like most things you enjoy, you'll probably keep doing it

.

 

[BuzzBoss915]

Re: Boattail....not always the best!

I'm usually careful about blanket statements. Therefore, I "prefer" flat base bullets, and believe some rifles do not shoot boat tail bullets as accurately as flat base bullets. Have I tested every rifle and every bullet? No. Is there some empirical evidence that I have a 50% chance of being right? I think so?

I don't have the time, nor the inclination to test every bullet made, so in my limited experience, I am comfortable with my beliefs and the knowledge that there are a few old farts in Commifornia that share my opinion. BB

 

[George63]

Re: Boattail....not always the best!

IMO in the sliding scale of compromises FB advantages over BT would almost always be under 300 yds

 

[BuzzBoss915]

Re: Boattail....not always the best!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I was the first to use FB bullets in 1K comp. A 187 Gr. BIB They were and still are the most accurate bullet I have ever shot at that distance. I never had any issues the base mushrooming. I pushed them over 3150 FPS and know guys who approached 3300 FPS. They ran into issues with bullets coming apart from heat and high RPM's.
</div></div>

Did you happen to read this little gem on page one?
BB

 

[Helmet]

Re: Boattail....not always the best!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BuzzBoss915</div><div class="ubbcode-body"> I don't have the time, nor the inclination to test every bullet made, so in my limited experience, I am comfortable with my beliefs and the knowledge that there are a few old farts in Commifornia that share my opinion. BB </div></div>LOL...It's more than just a few that agree with you. It's most of them and they have been shooting almost every day since before I was born. That has to be worth something.
I don't always follow their advice, but I respect it none the less. They have acquired a great deal of knowledge over the years . I have alot of things I still want to try. FB bullets are one of them.