Hollow boat tail bullet?

300wmSlick

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I started to post this in the reloading area but figured it might belong here instead. Has any manufacturer ever made a boat tail (or any type of rifle bullet) with a hollow tail? Think of a slightly shallow bevel within the tail for the powder explosion from the cartridge to stay centered more behind the bullet as it is exiting the barrel instead of potentially pushing around the outside of the bullet as it is traveling down the barrel.
Has something like this ever been experimented with? Did it work? Or was it all just a waste of time?
 

DevilDocAZ

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David Tubb has a rebated boat tail that obturates in the barrel for more contact and better captured gasses from what I understand.

I shoot them & while I don't have the ability to test what's taking place in the barrel what comes out and hits downrange is impressive.

 

300wmSlick

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Not quite what I was thinking but I can see how it would work that way too. My thought in the original post was basically if you took a drill bit and drilled a small hole in the tail (vertically, heading towards the nose), only doing it precisely and centered in the bullet.
 

GBMaryland

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Awwww.... just use incendiary rounds and be done with it... a little Vitavuori N560 and some good ol US Army bullets... 🤪
 

GBMaryland

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Oh, for what it worth, i have seen concave bullets, as opposed to flat base... but never in any of the ELD type HPBT (OTM) rounds.
 

300wmSlick

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Mine thinking on it was that it would help maximize the explosion happening in the chamber and reach a higher velocity. I am guessing feasibility would be the deciding factor on whether or not someone would make it.
But then again I am the newbie at precision distance shooting....
 

biffj

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I don't think it would work like you're imagining. The pressure is equal inside and outside the boat tail so it won't necessarily prevent the gas "overrunning" the bullet. It will do that anyway whether drilled or not. On the other hand you might look into some of the Privi Partizan 8mm 125gr bullets for the 8mm Kurz. The 500 I got all had a very open boat tail. It makes my bullet feeder useless but keeps the weight forward. My guess is they did it because its easier to load boat tails but they needed to keep the weight down.

Frank
 

300wmSlick

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I don't think it would work like you're imagining. The pressure is equal inside and outside the boat tail so it won't necessarily prevent the gas "overrunning" the bullet. It will do that anyway whether drilled or not. On the other hand you might look into some of the Privi Partizan 8mm 125gr bullets for the 8mm Kurz. The 500 I got all had a very open boat tail. It makes my bullet feeder useless but keeps the weight forward. My guess is they did it because its easier to load boat tails but they needed to keep the weight down.

Frank
I know not much pressure overruns the bullet during it's travel, I was just wondering if it might help maximize it's potential is all.
This was just an idea I thought of while winding away the hours at work so I thought I would ask it here where others have more experience than I do.
Thanks for the comments and lessons, and I will check out those 8mm's.
-John
 

THEIS

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Hi,

The answer to your question is yes they have.

Base drilled projectiles are what they are called.
You can search the threads here on information and testing of them by @Jim Boatright .

Sincerely,
Theis
 

ShtrRdy

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I wonder if a depression in the base of the bullet would cause more turbulence and therefore more drag. Not good for high BC.
 

b6graham

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Hi,

The answer to your question is yes they have.

Base drilled projectiles are what they are called.
You can search the threads here on information and testing of them by @Jim Boatright .

Sincerely,
Theis
wouldnt this technically be more beneficial with a solid?m same outside profile but faster.

curious whether the BC loss because of weight would overcome the velocity gain? we cant be talking more than a few grains
 

Jim Boatright

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I am taking delivery this week of a new batch of 338-caliber monolithic copper bullets CNC turned by Dan Warner to my design. They will be base drilled using a 0.125-inch drill to 0.400-inch depth, just more than half way through under the rear driving band. The base drilling has only the 10.6-grain weight reduction penalty, but has three advantages: (1) Allowing a controlled elastic expansion to improve gas sealing at peak base pressure. (2) Improves mass distribution for increased gyroscopic stability. (3) Allows faster muzzle speed.

These ULD bullets will also feature a rounded, radiused base (R = 0.310-inch) on the boat-tail to minimize disturbance in the muzzle-blast zone. We have been seeing more aerodynamic jump (inaccuracy) than I want to see due to bullet yawing right out of the muzzle with flat-base bullets. In reversed aerodynamics the location of the stagnation point is unstable with flat-base bullets. We do not want to radius the rear corners of the BT for better stability in forward flight at transonic airspeeds.

I increased the OD of the rear driving bands for more elastic compression in the throat, also for better bullet obturation. Optimum obturation should reduce the muzzle velocity spreads to single digits for ELR shooting. Barrel friction and shot-start pressures are already very low with these monolithic copper bullets.

The base drilled bullets fly aerodynamically exactly like the undrilled solid version. Unburned powder does not pack into the drilled holes. The 246-grain 338 ULD bullet should have a BC7 of 0.433 in hyper-stable flight and should be fired at over 3000 fps from a 338 Lapua Magnum. I have been hoping to find some of the new VV N565 propellant for testing, but no luck yet. We are using Alliant RL-26 with good accuracy but not max MV. I have 6.6-inch twist Bartlein 5R barrel and 7.0-inch twist Schneider P5 barrel for testing these new copper bullets. I might rechamber them from 338 LM to 33XC later this summer.

The same Mark IIb bullet design is to be prototyped in 375 caliber next. It should weigh 335-gr and have a BC7 of 0.481. That bullet should do quite well at Ko2M and remain supersonic to well beyond the target at Whittington. These bullet designs are US patented.
 
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300wmSlick

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Well it's nice to learn that one of my thoughts I entertained myself with while killing time at work has some value to it.
Thank you very much @Jim Boatright for the knowledge and the insight on what you are/have been working on!
 

Wormydog1724

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I started to post this in the reloading area but figured it might belong here instead. Has any manufacturer ever made a boat tail (or any type of rifle bullet) with a hollow tail? Think of a slightly shallow bevel within the tail for the powder explosion from the cartridge to stay centered more behind the bullet as it is exiting the barrel instead of potentially pushing around the outside of the bullet as it is traveling down the barrel.
Has something like this ever been experimented with? Did it work? Or was it all just a waste of time?

I'm shooting Cavity Back Bullets 105gr MKZ in my 6.8 SPC for coyotes, hogs, and deer. It's a copper monolithic bullet and the cavity at the back (Cavity Back) provides for more powder in the case for higher velocities. It's also claimed that it increases accuracy by limiting the shockwave behind the bullet (who knows). Also the driving band design allegedly won't spike pressure so they're usually able to be loaded pretty hot unlike some other mono's. The softer copper they use allows for very low opening speeds (as low as 1600fps) which increases the projectiles effectiveness on game at further range, also the petals do not break off like some other monolithic bullets except at very high speeds. From what I've seen, this allows the projectile to dump as much energy as possible into the animal and then continue to punch through creating a massive wound cavity and a gigantic triangular exit hole, blood just literally pours out. I am pushing the 105gr MKZ with 29gr AA2200 and CCI450 primer in excess of 2750fps from a 16" Wilson Combat barrel and Form1 all titanium suppressor.

I am not employed by CBB nor do I have any stake in it, I simply have used one line of their projectiles for one caliber and they flat out perform.

edit* Robert DeBell is the CEO of CBB and he can answer way more technical questions. Find him on 68forums and Facebook or the CBB website.