Home Forums Hunting & Shooting Ask The Gunwriters Flat Base vs. Boat Tail - is one more accurate?

Read something interesting lately about flat base bullets being more accurate at short (~400 yds) ranges than boat tail bullets. It had to do with the bullet exiting the muzzle and the flat base having a better chance of pressure being equal around the bullet where the boat tail is still in the barrel when the gas escapes around the boat tail giving the chance to upset the bullet. Any experience with this?

I think the standard answer is that boat tail bullets take longer to stabilize (>200yds), but have better ballistic coefficient. Flat base stabilize quickly (<100yds), but not as good ballistic coefficient.

answer: Flat base are generally more accurate at sub 300yd. Boatails are generally more accurate at greater than 400yd

...YMMV

Mule deer has done his usual thorough study, as have I on a less spectacular scale. He will hopefully comment but my experience is that "It all depends." The .30 cal Sierra FB 150 gr bullet is as as good (accurate and deadly)as any I have ever fired out to 400 yards but the Sierra HPBT will reach a little further and opens up better at longer range.

Terry

The one that is more accurate.

Some rifles simply do not like BT's. Those that do, shoot them more accurately than flat bases so Steelie is correct.

I have found several Weatherby chamberings shoot more accurately with flat based bullets remembering that all Weatherby's do not have freebore.
John

Generally flat base bullets shoot a little better though its not a solid rule. I had an /06 that shot the sierra 180 gr flat base into about 6" at 100 yds while it shot the Nosler 180 gr ballistic tip under and inch.

The same Sierra 180 that I tried in my /06 would shoot 1/2" groups out of a 300 win mag.

Shod

This.

centershot,

Yes, "short range" benchrest shooters have found flat-base bullets are more accurate, the reason they're almost universally used in typical benchrest matches. But the difference isn't enough to show up in most hunting rifles, which have far looser internal chamber and barrel dimensions than benchrest rifles. (This is also probably why some hunting rifles won't shooting boattailed bullets very well.)

However, at longer ranges accuracy depends as much on a bullet's wind resistance as a rifle's ability to shoot tiny groups at 100 or 200 yards. This is why long-range shooters universally use boattails: Everything else being equal, they resist wind-drift more than flat-base bullets.

In the last few years boattails have started to show a presence in the winners circle in Short Range Benchrest. Which is most accurate, either can be, its a combination of a lot of factors, bullet shape being only one that determines which is most accurate in a particular firearm.

I usually find boat tails more accurate.

I guessed its because my sloppy handloading isn't shown up as much with boat tails because they allow me to seat bullets straighter.

But I really dunno.

My most accurate bullet is a flat base, but there are boat tails very close to it, and some flat based bullets are worse than many boat tails. I wouldn't make a bullet decision based on that feature, just not enough of a discriminator in my experience.

prm,

Of course, some flat-based bullets are inaccurate, whether because they're poorly balanced or whatever. But that wasn't the question.

The theory behind flat-based bullets being somewhat more accurate is the square base of the bullet leaves a correctly-made crown more "cleanly" than a tapered boattail. This is why some bullets have very short, steep boattails, or "rebated" boattails, with a sharp, steep angle between the shank of the bullet and the boattail itself. Neither a short, steep boattail or a rebated boattail increases ballistic coefficient as much as a very long, gently angled boattail, but they still increase BC somewhat over a flat-based bullet of the same weight, diameter and ogive shape.

Whether any bullets shoots better in one particular rifle also depends on throat and crown conformation, and probably actual bore diameter as well. Boattail bullets don't seal the bore as well as flat-based bullets (there are also some other factors that go into this, such as jacket thickness and core hardness), and that's also a factor in whether a particular rifle "likes" a certain bullet.

Certainly base-shape also affects how straight bullets are seated in the case neck. Probably the overall trend favors boattails, but I have seen it work both ways in certain cartridges, probably due to other factors, such as the seating stem of the die, whether or not the seating die has a short cylindrical section to keep bullets straight, and even how the case mouth was chamfered.

But in general, yes, flat bases allow bullets to leave the muzzle more consistently than boattails. Whether or not this results in overall finer accuracy at different ranges in any particular rifle is dependent on a host of other factors, and whether or not any individual rifle shoots boattails more accurately than flat-bases doesn't prove much one way or the other about the intrinsic accuracy of a certain design.

I agree with you. I am only relaying that the theory, in my very limited experience, does not bring results that are worth differentiating a bullet choice for my application of hunting and a hunting rifle. But those flat base .338 160 TTSXs sure do fly well!!

I agree with you too!

I was told once by a very respected custom benchrest bullet maker that boat tails are more difficult to get consistently concentric edges of the boat tail shoulder than flat base bullets with their 90 degree base and a pressure ring.

Gee, it would seem that the one that is more accurate is the bullet type that is more accurate.

Weird..

This may have been true at one time but not any more. The king of the benchrest shooters Tony Boyer has been shooting Hottenstein bullets for quite some time, Lowell Hottenstein only makes boat tails.

At the last benchrest match I attended in May about 30% of the shooters were using boat tails, In my experience some barrels like flat base some barrels like boat tails.

Interesting. I couldn't find any photos of the Hottenstein bullets. How much of a boattail do they have?

Thanks, that explains a lot.

That's not much of a "boat tail". I personally have seen better accuracy from flat based bullets, unless I'm shooting past 400 yards. After that, the boat tail bullets buck the wind better. This attributes to better accuracy at longer range..

My best short range BR rifles preferred boattails although the boat tail was relatively short. I liked that one could make boattails without the pressure ring at the base which was always present on the flat-based bullets. Not many custom makers make boat tails suitable for short range BR and I suspect that is as large a factor in the prevalence of the FB bullets in the BR venues as anything else. GD

Could be.

It could also be that the few who do make the boattails so short there's really not much difference between them and a flat-base.

Not much difference but enough to make a difference in loading and sizing. I don't really think boat tails are necessarily more accurate; they just shot better in my rifles. I am unable to pronounce one design better than the other because I don't really KNOW. Others have no trouble in making such a pronouncement. Could be that they do know. GD

I am just parroting the competitive shooters on the usenet before the www 20 years ago:
flat base out to 200 y
boat tail beyond 200 y

I kill most big game between 400 and 500 yards, so I use boat tail bullets.

Part of the reason is I can't hit anything beyond 500 y and I can do very well on the targets at 400 yards, so I stalk until it is a sure thing.

I did some asking around elsewhere about barrel attributes, specifically crown and leade angles.

After having a target crown get dinged and looking into getting it recrowned, a gunsmith friend recommended a piloted reamer that imparts a 45 degree chamfer into the muzzle. The depth is such that the chamfer extends slightly wider than the grooves. I had it done, and the rifle shoots respectably, as well as having shot both flat and boat tail base bullets about equally well. I don't really understand this stuff well enough to understand what this alteration has accomplished, but I'm fairly certain the crown is less likely to get dinged.

When I asked what the relationship was between ogive and leade angle, I got a surprising answer from a barrel maker/gunsmith. His response was that the leade angle slowly changes over time to conform more effectively with the bullet's ogive, wearing it in as it were, and suggested that this was a particularly good reason to pick a bullet and stick with it as long as possible.

Greg

Hmm, I suppose this is why we handload and try different loads in our rifle's to see what works. Just a guess.