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#11945199 - 04/02/17 APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS"  
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RickBin Offline
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Hi Guys:

I would like to thank John Barsness (Mule Deer) for his latest exclusive Campfire article, FLAT-BASE AND BOATTAIL RIFLE BULLETS , which is now on the Home Page (click link above).

Please use this space to ask John questions about the article. I hope you enjoy it.

Thanks again, John!

rb


Rick Bin
24hourcampfire.com
CMG 300 BP

#11958564 - 04/08/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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bobnob17 Offline
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Nice article John.

I've never bought the line that BTs lose their core / jacket more than FB bullets. While I've not documented recoveries of bullets like you, my casual observations echo your notes.

I also think for rough and ready handloaders like me, boat tail bullets tend to be easier to seat straight in the case because they start into the case mouth so easily. Whether due to this factor or not, I tend to see better accuracy with my BT handloads, all other things being equal.

Not sure that last bit holds water, but I'm going with it until proven wrong!

#11961029 - 04/09/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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GuyM Offline
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Enjoyed the heck out of the article John, thanks for actually keeping track of all those shots!

Last year I had four "big game" hunts on the schedule: black bear, antelope, mule deer and elk. I chose to use the same rifle and load for all four hunts; a .30-06 Rem 700 CDL with the 165 gr Nosler Ballistic Tip loaded to about 2900 fps.

People questioned me about my choice of the 165 gr Nosler Ballistic Tip for the bear and elk, but it worked out great on all four animals. I shot the bear while he was quartering away. The bullet went in the rib cage, and only the core exited through his off side chest/shoulder area. We found the expanded jacket hung up in his hide. Very quick kill, and he traveled only a few feet after being hit.

Also recovered one bullet from the mule deer, which was shot facing me. It retained much of the core, nicely expanded. The pronghorn of course didn't retain the bullet, and the bullet that took the elk was never located, though it went through the on-side shoulder causing tremendous damage in the chest cavity, then punched a hole in the off-side shoulder blade as well. All from a little 'ol Ballistic Tip.

Sometimes things are not as they seem. I had good reason to believe that "my" Ballistic Tips were plenty tough enough for the tasks. And accurate? Yes indeed... It pays to learn about the bullets we're going to use, for varminting, or for hunting larger animals.

Regards, Guy

#11968549 - 04/12/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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2525 Offline
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Quote
One indisputable effect of boattailed bullets is an increase in throat erosion, due to hot powder gas slipping by the tapered tail. This has been documented numerous times in military research...

I must admit I don't visualize this one. Is it a matter of the shorter shank exposing the throat sooner, or does the shorter shank permit more blow by early on, or does the boat tail deflect the early blow by more vigorously onto the throat, or ...

How strong is the effect, say in terms of % reduction in number of rounds fired before accuracy is affected?

(Thanks for the article.)

#11969148 - 04/12/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: 2525]  
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Mule Deer Online content
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Lead-cored bullets tend to "obturate" (expand slightly) when booted in the rear by powder gas. The rear ends of flat-based bullets obturate quicker, due to more area exposed to the hot gas than the smaller flat area at the end of boattails.

Boattails tend to funnel some powder gas into the rifling, due to the angle on their sides, while flat-based bullets tend to have sealed the bore by the time their rear end passes the start of the rifling.

Or at least those are the conclusions of the research I found.


John

"Gunwriters, as you know, aren't as informed as their readers are and if it wasn't for the readers, there would be no need for writers..."--Shrapnel, May 2015
Alpha

#11976627 - 04/16/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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nifty-two-fifty Offline
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Excellent article, John. Thanks for sharing your experience with us.



Bobnob17,

I check a majority of my loaded rounds on a Sinclair Concentricity Gauge. I don't find that the boattail bullets necessarily seat any straighter than flat base bullets. They are just easier to handle getting started into the case mouth.

The factor that seems to make the most difference in how straight the bullets seat is how well the bullet seating stem fits the front end of the bullet.

Some of my older seating dies do not work well with sharp-pointed plastic-tipped bullets like the Barnes TTSX. I had a rough time yesterday seating 140 gr TTSX bullets in 7x57 cases with an older Forster Bonanza seating die. Many bullets were loaded out of round as much as .010", and I needed to use the Tru-Angle tool on almost very round to correct them to acceptable straightness (for me, .003" or less).

Redding offers an optional VLD style seating stem for their seating dies, to better handle the sharper-nosed bullets.

I am glad you are getting good accuracy with your boattail bullets. And as John noted in the article, the boattails do achieve less wind drift than the flat-base bullets.



Nifty-250

"If you don't know where you're going, you may wind up somewhere else".
Yogi Berra
#11979992 - 04/18/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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lastround Offline
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Thanks for the article, JB,
I knew there was a reason those Sierra Pro Hunters shot so well, just wasn't sure why.


Doug
#11986589 - 04/20/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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Etoh Offline
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Great article

most metals flow on compression, and any small elements (slices) will have a later moment of interia than slices close to the nose. Whether this is a "sealing" process is open to debate

because

the surface area of truncated cone is larger than the surface area of a circle having the same diameter. If nothing more than its a 3 dimensional surface rather than 2.

Im not going to say that the base of a boat tail bullet sees more pressure than a flat base because I know what kind of names I will be called.


If you have an opinion, it's on a bell curve--somewhere
#11987840 - 04/21/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: Etoh]  
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Mule Deer Online content
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A boattail's base obviously "sees" more pressure than a flat-base, because there's more area to the base behind the full-diameter bearing surface of the bullet, and PSI is pressure per square inch.

But with a boattail much of the pressure is applied to the side of the truncated cone, not directly forward on the flat base. This difference is larger in high-BC boattails with very small flat bases and more elongated truncated cones.

Or at least that's the way I'd read it. Whether or not that's correct, the military studies documented quicker throat erosion with boattail bullets, after firing hundreds of thousands of rounds, and attributed it to gas blow-by.


John

"Gunwriters, as you know, aren't as informed as their readers are and if it wasn't for the readers, there would be no need for writers..."--Shrapnel, May 2015
#11989621 - 04/22/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: nifty-two-fifty]  
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bobnob17 Offline
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Originally Posted by nifty-two-fifty
Excellent article, John. Thanks for sharing your experience with us.



Bobnob17,

I check a majority of my loaded rounds on a Sinclair Concentricity Gauge. I don't find that the boattail bullets necessarily seat any straighter than flat base bullets. They are just easier to handle getting started into the case mouth.

The factor that seems to make the most difference in how straight the bullets seat is how well the bullet seating stem fits the front end of the bullet.

Some of my older seating dies do not work well with sharp-pointed plastic-tipped bullets like the Barnes TTSX. I had a rough time yesterday seating 140 gr TTSX bullets in 7x57 cases with an older Forster Bonanza seating die. Many bullets were loaded out of round as much as .010", and I needed to use the Tru-Angle tool on almost very round to correct them to acceptable straightness (for me, .003" or less).

Redding offers an optional VLD style seating stem for their seating dies, to better handle the sharper-nosed bullets.

I am glad you are getting good accuracy with your boattail bullets. And as John noted in the article, the boattails do achieve less wind drift than the flat-base bullets.



Makes sense as well.

For my big game rifles I work hard to achieve consistent MOA accuracy for three shot groups. Hardly the most exacting standards.

For my long range rifles I work towards 0.75 MOA and I do find those VLDs tricky to seat at times.

You've given me something to think about...

Bravo

#12055102 - 05/26/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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ColoWyoMan Offline
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A BT base may "see" more pressure, but I've always understood FB bullets develop more chamber pressure because of the base obturation. One can increase charges with BT because less obturation tends toward lower chamber pressures, however increased charges may not be possible due to BT length extending into the case volume. The same powder charge behind a FB and BT will typically result in higher velocities with the FB, true or is there more to the story?


J & S Stuff & Smithing
FFL in Western CO
#12055343 - 05/26/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: ColoWyoMan]  
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Mule Deer Online content
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Mule Deer  Online Content
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There's a little more to the story: Flat-base bullets of the same make as boattails also have more bearing surface against the bore, increasing pressures slightly, often increasing velocities as well. Which just illustrates, once again, that pressure on a bullet works in various ways, so simply calculating the PSI against the base area isn't the entire influence of pressure on velocity.


John

"Gunwriters, as you know, aren't as informed as their readers are and if it wasn't for the readers, there would be no need for writers..."--Shrapnel, May 2015
#12056067 - 05/26/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: Mule Deer]  
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bigwhoop Offline
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So can we conclude, MD, that any slight increase in flat-base bullet psi will not exceed any book "redline"? Or was that even taken into account when testing was done? The exception being mono-metal and high BC designs.

Also if pressure is applied more to the side of the truncated cone, does that result in accelerated barrel wear?


The best remedy for "fake news" and pro sports is your clicker.
#12174452 - 07/29/17 Re: APRIL - Ask John Barsness Questions About "FLAT-BASE AND BOATTAIL RIFLE BULLETS" [Re: RickBin]  
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LDHunter Offline
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John,

That was a thorough and very informative article full of the kind of well backed up technical information we've come to expect from you.

I would like a clarification though. I suspect I already know the answer.

You mention that hollow point bullets don't fare as well over longer distances as tipped bullets but the obvious fact is that so many target bullets don't have tips. I assume that by "hollow points" that you don't mean the typical Berger or Sierra target bullets (the ones I'm most familiar with) but rather a true hollow point meant for violent expansion in varmints?

Clarification please.

Thanks,
$bob$


Many who have freedom have no idea where they got it....

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