Boat tail vs Flat base and and twist

B

bronkorob

Member
Whats everyone's take on the relationship between boat tail/flat base bullets and barrel twist rate? Is one inherently better/more accurate than the other when it comes to shooting a slower twist? I see a lot of old info that says flat bases are better on slower twist, but its old, and curious if anyone has seen anything in their real life experiences that drives them one way or the other.

The old info seems to have to do with tolerances and mfg processes. Seems like modern bullet mfg could have addressed most of this.

I get the boat tail allows for different shapes that help with BC and carry longer distances more accurate, but lets talk 400 yards and under.

I have a 22-250AI with 1:12 barrel that shoots 55gr Sierra blitzkings pretty well. Looking to experiment with lighter bullets, and in the 40-50ish grain category, and there's a lot of options for both boat tails and FBs, even within the same manufacturer for the same category of varmint bullet.
 
Greenhill formula = Flat base bullets
Miller formula = Boat tails bullets

1:12 in the .22 bore will stabilize up to a 60gr, depending on it's length and applying the correct configuration if boat tail use the Miller formula, if Flat base use the green hill formula. Now that we have STABILITY out of the way. Stability does not always equal accuracy, but accuracy demand stability. So yes for the 40's they will work for stability, HOWEVER with the 22-250 AI you might find you need to dial down the speed so centrifugal force doesn't rip that bullet apart. and it can do it to a a 55gr as well DEPENDING on jacket and core construction. Varmint bullets usually have a thinner jacket than say the FMJ or match or hunting bullets. That thinner jacket can fail at the speed and literally vaporize into a cloud of grey smoke down range.. now apply actual truth to this it's not as common as the internet actually has one to believe. It's pretty simple just develop your load and if you observe it just back the velocity off a bit and just have fun and enjoy life. Just find the one that your rig likes and again have fun.

bronkorob said:
I get the boat tail allows for different shapes that help with BC and carry longer distances more accurate, but lets talk 400 yards and under.
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400 yards and under I've always found that Flat base bullets will out perform even the sexist high B.C. boat tail in the accuracy department. Now will there be outliers sure, there always are. But at that short of a range the High BC isn't helping you as much as you think. It's when your beyond 600 that the high B.C. come into it's own and does so with a vengeance. Which one is better depends on your application. In under the 400 yard mark I actually prefer the FB.
YMMV as well as preference.
 
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bronkorob said:
I see a lot of old info that says flat bases are better on slower twist, but its old,
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Just because it's old doesn't mean it's wrong or irrelevant. Honestly it depends on your goals, say the Varmint or what ever your shooting at is just a bit beyond 400 yards "on Paper" the Boat tail should perform better. But then reality steps in and kicks you in the groin.

Now I pretty much prefer the slower twist rates, many don't that is fine.

Picked up a nice 6mm Creedmoor barrel , fast twist, long freaking throat. Every PRS and internet keyboard commando's dream. BUT I want to shoot PD's and gophers... which I lean toward the shorter lighter bullets, because I can literally drive a 68gr bullet to 3980 fps with 6.5 Staball powder.

In order to keep the jacket happy and everything I'll shoot the Barnes 68gr FB Match Burners deadly accurate (side bar is that the Barnes doesn't mind a big jump so that was great). When I sub the Barnes Varmantor bullet ... well let's say the bullet doesn't make it there even at slower speeds. And yes I wound up giving them to a buddy as he had a slower twist 6mm and they work great for him. I literally could NOT slow down the bullet slow enough to get the bullet into Barnes RPM envelope with that twist and cartridge combo.
If you actually call the ballisticians be that Mike at Sierra or at Barnes and discuss the RPM threshold for a certain bullet with then you will dummy it down and just give you either in fps or rpm based on your twist. Or your favorite bullet manufacturer they can actually break it down for you. Mike at Sierra happens to be a Varmint hunter so here is that

Why I'm bring this up is not to change your topic or side rail it .. It's simply one can wind up with a combination that yields these results..
IN your case I don't suspect you will find it to be exactly so... but... could happen.
 
Sgt_Mike said:
400 yards and under I've always found that Flat base bullets will out perform even the sexist high B.C. boat tail in the accuracy department. Now will there be outliers sure, there always are. But at that short of a range the High BC isn't helping you as much as you think. It's when your beyond 600 that the high B.C. come into it's own and does so with a vengeance. Which one is better depends on your application. In under the 400 yard mark I actually prefer the FB.
YMMV as well as preference.
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I'll argue your point to a certain degree......

I agree, typically BC is really of no concern inside of 400 yards for general applications in the hunting world.

As to outliers, when your world revolves around shooting itty bitty groups at 600/1000 yard Benchrest competitions, if your gun can't shoot small groups at close range, they certainly aren't going to get any smaller as the ranges extend.

A good example is my gun in 6 Dasher with Berger 105 VLD's during load development would shoot in the 3's at 325 yards, that's actual .300's, not MOA.

I wouldn't discount the sexy BC's of the heavier bullets when it comes to balls out accuracy.

As to the OP and lighter bullets, if your 55's shoot to your satisfaction, I don't think dropping down in weight will gain you much in MPBR, and will cost you barrel life chasing it.
 
Sgt_Mike said:
Just because it's old doesn't mean it's wrong or irrelevant. Honestly it depends on your goals, say the Varmint or what ever your shooting at is just a bit beyond 400 yards "on Paper" the Boat tail should perform better. But then reality steps in and kicks you in the groin.
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Totally agree to that. old doesnt mean incorrect. When I say old though, Im thinking, not taking into account current variables. As you mentioned, the trend now is sexy high BC bullets and all the R&D seems to be going to that, where does that leave FB bullets? Cant be totally obsolete if they are still making them. Are they still better at XX then the newer bullets in scenerio YY? Are the newer higher BC boat tail bullets blurring the line and slowing overtaking whatever advantage FB bullets have? Were FB indeed better in the past because of mfg/cost limitations?

Long range accuracy isnt what Im after, where I know the long boat tails shine. Same as you though, praire dogs, rock chucks, and occasional coyote with purpose built varmint bullets in mind is what Im after. Which happen to be on the lighter end and why I got the slower twist to accommodate. Was curious if anyone has seen noticeable changes based on their experience. Like when my rifle has X, Y, Z variables, this is where the FB really shines.

@alf I totally get it. I could settle with what I have. This is my first dabble into the wildcat world. Started with something easy, proven, that gets my hands into a little bit of all that goes with wildcats. Also plays well with my other hobbies. Ive accepted he fact that these small caliber, high velocity cartridges burn barrels and are just the cost of doing business. If I wasnt into tinkering though, I probably wouldnt have made it this far, and I have a curiosity of what its capable of with lighter bullets and more speed.
 
bronkorob said:
@alf I totally get it. I could settle with what I have. This is my first dabble into the wildcat world. Started with something easy, proven, that gets my hands into a little bit of all that goes with wildcats. Also plays well with my other hobbies. Ive accepted he fact that these small caliber, high velocity cartridges burn barrels and are just the cost of doing business. If I wasnt into tinkering though, I probably wouldnt have made it this far, and I have a curiosity of what its capable of with lighter bullets and more speed.
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I get it, I had a 26" slow twist 22-243 Middlestead back in the day, 55's at 4100. I did try 40's just for S&G's, and got those to 4600, but sold the gun as I built it too damn heavy to carry.

Also built a 22 Dasher slow twist, 40's at 4200, & was fantastic for calling coyotes. Kinda tough on barrels, sold the barrel & put a 6 Dasher barrel on the gun.

Just to put it all in perspective with a 200 zero & a guesstimate on velocities....

40gr - 4400 fps - 300 -3.70" - 400 -12.00"

50gr - 4200 fps - 300 -3.6" - 400 - 11.34"

55gr - 4000 fps - 300 -3.87" - 400 -12.04"
 
I think it is pretty much a crapshoot (sorry CS), as long as you stay within the twists that stabilize your bullet, your rifle will tell you what is the most accurate.

I have a 1-9 22-204 that dotes on 40gr NBTs and a 1-8 6mm ARC that shoots 75gr flatbase bullets great. I have a 1-12 223AI that likes 50gr boatails (NBTs
 
alf said:
As to outliers,
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Maybe NOT the best choice of words on my part when I read your response ALF ... to some that can mean exceptions in bullet choices (which is what I was actually referring to) , some it could mean those "fliers" what some refer to as in shooting groups.. If my choice of words caused confusion .. sorry


bronkorob said:
where does that leave FB bullets? Cant be totally obsolete if they are still making them.
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absolutely they are still making them .. and the fact that Berger is one whom is doing so should tell you something. and quite honestly @AWS hit it on the head with a 20 LB hammer.
AWS said:
as long as you stay within the twists that stabilize your bullet, your rifle will tell you what is the most accurate
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which summed up my war and peace post as accurate as can be.

Do I shoot both yep... and Just Like ALF and AWS if it's the Flat base that shoots as I want inside the range I engaging the vermin.. then that is what I use. if it the boat tail that shoots the best then it gets the nod. The whole purpose was of the formulas is a "Guide" for what is stable in the bullets flight. really nothing more nothing less. all it means is the bullet will be stable not accurate. but again as I stated to get accuracy it has to be stable.

The nail in the coffin is exactly as AWS posted. Your rig will let you know quickly if XXXX bullet is accurate.
 
Sgt_Mike said:
Maybe NOT the best choice of words on my part when I read your response ALF ... to some that can mean exceptions in bullet choices (which is what I was actually referring to) , some it could mean those "fliers" what some refer to as in shooting groups.. If my choice of words caused confusion .. sorry
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No confusion at all, I knew exactly what you were referring to.

Damn few absolutes in the quest for accuracy......
 
Good info. Figured it would boil down to, try em all and see what happens!! haha.

Just had to pick the brains of some wildcat wizards and see if there was some long lost bit of knowledge from the dark arts I could apply.....which actually I did get with the formulas mentioned, so thanks for that.
 
A lot of that old info, was probably pretty BR specific. And saying the BT was less accurate, was saying they agged in the high 2's instead of the low 2's. Big difference in a match. Very small difference in a dog town.

And there's no splat factor in a BR match. But it's a thing with colony varmints.

- DAA
 
DAA said:
A lot of that old info, was probably pretty BR specific. And saying the BT was less accurate, was saying they agged in the high 2's instead of the low 2's. Big difference in a match. Very small difference in a dog town.

And there's no splat factor in a BR match. But it's a thing with colony varmints.

- DAA
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You are probably right. Some of it was how the bullet seals gases as it traveling down the barrel. One tended to have more uniform jacket construction. One had less turbulence in flight. Lot of non obvious factors I have no way to see or measure myself. Which I suppose the effects can be seen and measured when your tracking deviations by .010"s. You stack all that up and the clear winner is, whatever works best for you.

End of the day, Ill pick some 40 and 50 grain bullets, FB and boat tails, off the local shelf and just see what happens! Consistent splat factor is my end goal, which I think I already have with the Blitzkings, but could it be better???? Only one way to find out.
 
The question is why the BTs work. Objective is to reduce the 'drag' of the cavitation at the base when supersonic. Twist is to put enough rotational energy into the bullet so that gyroscopic performance is maintained. Longer bullets need more twist to overcome the 'lever' fulcrum (wind effects). Realistically <300 yds, BT makes no difference IF the twist is proper for the 'normal' bullet weight and fps.
 
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