Why Flat Base Boolits are Better at Close Ranges

[GregLaROCHE]

Here is photographic proof that flat base boolits are better under 200 yards, than boat tails. I have often heard this and it was backed up by the fact, that the best bench rest shooters use flat based. Here is why.
I never understood why Lee made their 230 grain mold designed for 300 blackouts boat tailed. Was it just to make it look cool?

https://youtu.be/ZDUL_1vrABI

[Rapier]

When working with a new 30 cal revolver cartridge to shoot 30 cal spitzer rifle bullets, I tried and tried to get BT SPs to shoot in testing at 50 meters. Finally called Sierra's technical department and talked to an engineer. "You do nderstand that the BT pulls a vacum on the boat tail and the bullet stabilizes between 75 and 100 yards, right" Well I had heard that. "The Flat base stabilizes out of the muzzle. So out to 200 the flat base is a better choice." Right from Sierra.
I have seen those 200 grain plus, 300 BO subsonic factory rounds with BTs, that is just for cool, sure can not use or add one thing to a subsonic round. I use the 230 grain cast flat base PCed at around 1,000 fps in my 16" AR, shoots 1/2" inch with H-110.

[414gates]

I never understood why Lee made their 230 grain mold designed for 300 blackouts boat tailed. Was it just to make it look cool?

Maybe it has a better BC for the low velocity out a 300B. It needs all the help it can get.

[stubshaft]

The Lee 230 was designed well BEFORE the 300 BO was even thought of. It was designed for the 300 Whisper.

[reddog81]

The video shows a 115 grain and 155 grain bullet. I would assume different amounts of powder were used and possibly different powders. Seems like you'd want to use the same bullet weight and same powder if comparing flat base vs boat tail. That said, the Lee 230 grain blackout bullet is a complete turd in my book.

[racepres]

The Lee 230 was designed well BEFORE the 300 BO was even thought of. It was designed for the 300 Whisper.

Huh???? I thought the BO was just the Whisper...renamed??

[megasupermagnum]

Huh???? I thought the BO was just the Whisper...renamed??

It more or less is. I'm not sure why Lee chose to go with a boat tail cast bullet, but they did. If I had to guess it was due to the idea of longer range shooting with subsonic ammo. If you are going to shoot a subsonic bullet, may as well make it super aerodynamic, hence the 230gr very long, slender, and boat tailed bullet. It might not have panned out that great for accuracy, but that's my guess as to the thinking.

[Hick]

The only BTs I have are jacketed-- and that's why I save them for situations when I want to shoot at velocities above cast and at ranges at least 400 yards.

[megasupermagnum]

Here is photographic proof that flat base boolits are better under 200 yards, than boat tails. I have often heard this and it was backed up by the fact, that the best bench rest shooters use flat based. Here is why.
I never understood why Lee made their 230 grain mold designed for 300 blackouts boat tailed. Was it just to make it look cool?

https://youtu.be/ZDUL_1vrABI

It's an interesting video for sure, but I'm not convinced that is the only reason. I don't like that they used two WAY different bullets. There could also be differences in balance, design, and aerodynamic characteristics that are factors. It has always been my view that there are two types of rifle accuracy, absolute, and practical. Absolute accuracy being the group size you are getting under ideal conditions, pure mechanical accuracy. Practical accuracy being the groups you are getting with environmental factors. I don't think it's so much that boat tails stabilize at longer ranges, it's that their improved aerodynamics allow them to group better by being less effected by pretty much every factor besides gravity. That's more of a long range shooters game though. Even at 300 yards absolute accuracy is still practical accuracy.

[charlie b]

The BT is there for reduced drag at supersonic velocities. 200yd and below it doesn't add anything and can detract. One reason is the forward blast as shown in the video. The other is the need for absolute accuracy of the BT since it creates a jet at the crown. This amplifies any irregularities at that point.

So, a flat base need only be flat and true at one point. The BT must be truly concentric along the entire length of the BT.

FWIW, Lapua also made a rebated BT to try to mitigate the muzzle blast issue. They are still favored by some.

[M-Tecs]

In the past the 300 yard and under benchrest shooters had a strong preference for flat based bullets. As bullet tolerances have gotten tighter that is changing.

The video IMHO is junk since it compares a 115 grain FB to a 155 grain BT. Also if the powders are different the makes the comparison even more junk. Makes you wonder why they didn't use the same bullet weights and powders unless it didn't give them the results they wanted.

On my match rifles I do initial load development at 100 yards or 100 meters depending on which range I use. Normally I expect to see 1/4" to 1/2" MOA with 3/8" being the norm for five shot groups. On new barrels I do ten shoot groups to check for barrel walking. I have not seen any change between FB and BT in groups.

The Bart’s Custom Bullets – 6mm 65gr BR Ultimate Boattail have a very strong short yardage following.

https://www.bulletcentral.com/product/barts-custom-bullets-6mm-65gr-br-ultimate-boattail-qty-500/

When all is said and done there is only one metrics to judge this issue. That is at the target.

[GregLaROCHE]

I was wondering too why they didn’t use more similar bullets.

[Green Frog]

Just my dos centavos… back in the Golden Age of Single Shot Rifles, when cast lead bullets were the standard for all shooters, flat based bullets were the order of the day. Shooters were advised that flat bases with sharp, square edges were needed for maximum accuracy at the popular range for target shooting in those days… 200 yards.. With a lot of practical experimentation, that was their conclusion, and I don’t feel qualified to argue with them.

Froggie

[charlie b]

The video merely shows the difference in effects at the muzzle between FB and BT. I don't know why they used different weights bullet, or even different mfg, but, the difference is still valid.

The conclusion they drew can be argued. I am another who does load development with BT bullets at 200yd and sometimes 100yd.

[MostlyLeverGuns]

Too many unknowns, what powder was used for each bullet, what primer, what was the actual result on target at 100, 200, 300, 400 yards. Other considerations, finning - bullet metal displaced and causing turbulence at bullet base; do flat base bullets seat straighter than boattails - how the bullet fits the seating punch is critical. Way too many variables beyond flat base versus boattail versus rebated boattail versus seating... Not much proven by the picture regarding affect (effect?) of the bullet base on accuracy, velocity. I've seen little difference in accuracy between boattails and flatbase at 100, 200 yards as long as seated carefully to be straight.

[scattershot]

The Lee 230 was designed well BEFORE the 300 BO was even thought of. It was designed for the 300 Whisper.


300 B is a copy of the Whisper. I hope J D Jones is getting royalties.

[Tonto]

Video interesting, would have been a better experiment with two same weight bullets, same powder and charge and a number of runs plus an actual target accuracy element.

[megasupermagnum]

300 B is a copy of the Whisper. I hope J D Jones is getting royalties.

He is not. That was his choice to keep it proprietary and never submit it to SAMMI. He owns the name, not the cartridge.

[dtknowles]

There is a lot here to unpack.

First the muzzle blast effect is real but not the only negative issue with BT bullets.

As range to target gets longer BT bullets have an advantage because at longer ranges BC is king. High BC flattens the trajectory and reduces wind drift.

Making BT bullets as flawless as flat base bullets is hard. Short range benchrest shooters don't care so much about BC and tiny flaws in bullets matter more to them. They care so little for BC they choose bullets that are light for caliber and choose small calibers.

Cast BT bullets are even more prone to have flaws. Sizing bullets without a nice flat base to hold it concentric in the sizing die is going to produce some bullets than are crooked. You will be able to see that the witness marks from the sizer and not perpendicular to the long axis. You can see this on flat based bullets that don't have a step between the bore riding section and the ojive section. It is not as big an issue when it is on the front of the bullet but when it is at the base you make the muzzle blast issue much worse.

Tim

[Bent Ramrod]

It’s my understanding that boat tail bullets only come into their own at or beyond the range where the bullet breaks the sound barrier and becomes subsonic again—400 yards or so, with jacketed bullets at the typical loading intensities. The cavitation off the base is mitigated by the design, as is the disturbance of the line of the bullet’s flight.

Cast boolits, in typical loadings, spend much less time at supersonic velocities (if any at all), and any advantage they might have at ranges past the drop back to subsonic velocities would likely be negated by the enhanced directing of the “young gas” upon firing around the base and past the shank by the conical shape as the boolit slips through the leade into the barrel. More opportunity (by design) for base erosion, and even leading of the barrel. Neither condition conducive to accuracy.

I found a boat tail spitzer mould for .38 caliber rifles made by Andela Machine Co. that so far doesn’t shoot as well as the typical flat-based, flat-nose designs in my .38-55. I wouldn’t expect it to do any better at longer ranges in a “hot loading” in a .375 H&H either, but I’ve never had the success with any >2000ft/sec CB loads that others allege.

[GregLaROCHE]

If nothing else, boat tails are easier to seat in cases.

[elmacgyver0]

I was wondering too why they didn’t use more similar bullets.

Perhaps they did, but didn't get the results they were looking for.

[GregLaROCHE]

Perhaps they did, but didn't get the results they were looking for.

That’s quite possible. People doing research are always playing around different factors, to get the results they are looking for. That’s been proven over the years, especially in the drug industry.

[barnetmill]

300 B is a copy of the Whisper. I hope J D Jones is getting royalties.

the whisper was loaded with super-long pointed bullets that I believe may of had a boat tail. Some 300 blackout people may have copied boat tails from the whisper.
The whisper in 300 caliber was not a bench rest round so much and more originally was meant to kill people with the bullet technology of the day. A very long bullet will likely tumble in flesh. The longer the bullet, the worst the wound track should be when it tumbles. There were not a lot of subsonic bullets that would expand well in those years.
What I am not seeing is just how much the gas vortex thingy impacts. No information on pressure and velocity factors either. I also wonder if upping the diameter a bit of the BT bullet would help with the gas leakage.
Essentially more information is needed and the accuracy that a bench rest shooter is seeking vs what most of us are dealing with is not that significant to me.
You will not likely find any discussion of bullet tumbling by people writing about these rounds and so I am making an assumption it happens.
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