Author Topic: Bullet's..Flat base VS. Boattail (Read 993 times)

PJ · « **on:** August 08, 2003, 02:33:19 PM »

Has anyone chrono'd these to see if there is a differance in velocity...? I have not tried it yet.. :oops:

KN · « **Reply #1 on:** August 08, 2003, 03:41:48 PM »

Generally speaking you should get a little more velocity from a BT design since there would "generally" be less bearing surface traveling down the bore with a BT vrs a FB design. All things being equal,such as bullet nose profile, weight, powder charge, etc. KN

PJ · « **Reply #2 on:** August 08, 2003, 03:46:21 PM »

Makes sence.....Thanks

Duffy · « **Reply #3 on:** August 08, 2003, 06:47:25 PM »

Tried some 140 Sierra FB and BT and the difference was very small like about 25-40 fps. You have to take into consideration that the BT bullet is longer and will/can take up more case space at a given depth changing pressure too! But then the boat tail should take up less space and balance things out. More or less it's a trivial thing that dosen't make a squats worth of difference. I asked the Sierra reps why they still made flat based bullets if the boat tails are so superior and he said that some guns just shoot them better! Unless you are shooting at over 300 yards I don't really think it matters that much.

WW1 · « **Reply #4 on:** August 10, 2003, 05:00:38 AM »

I personally have 3 rifles in my safe that refuse to shoot BT's with accuracy....they just seem to like the flat base better and with the FB will group under 1" @100 and 2"or more with the BT's......go figgure.....leave it to me I can buy a firearm that will do the opposite as expected everytime......hahaha

Duffy · « **Reply #5 on:** August 10, 2003, 07:14:47 PM »

WW1

You must only have half of the picky/finicky guns because I think I have the other half!

smoky · « **Reply #6 on:** August 11, 2003, 03:53:50 AM »

Also realize that the boat tails are generally easier to reolad, due to the tapered base entering the case mouth. That said, in short action cases, I am reloading almost exclusively flat base as I am just not comfortable seating those long ogive bullets that deep in a small case in order to get the overall length right. In response to the original question, the differences I have seen on velocity between flat base vs. boat tail (IN THE SAME BULLET) have been marginal across my chronograph. However, some boat tails (ie ballistic tips) generally are much faster.

Smoky

Duffy · « **Reply #7 on:** August 11, 2003, 05:19:43 AM »

Smoky,
I also noticed that the Noslers were a bit faster. The FB & BT bullets that I refered to above were Sierras but when compared to the Noslers there was quite a jump in vel. I think bearing surface and jacket material has more to do with it than the BT design though.

Questor · « **Reply #8 on:** August 11, 2003, 05:43:35 AM »

I want the highest ballistic coefficient I can get and that's usually a boat tail spitzer of some kind. My reason for wanting the higher BC is that I want minimum wind deflection on long shots. Granted, the difference is not great.

KN · « **Reply #9 on:** August 11, 2003, 03:54:19 PM »

Some one correct me if I'm wrong, but I don't see how BC would have anything to bo with wind deflection. BC describes the amount of drag the bullet has on it in flight, I don't believe it would have any signifigance as to side forces. KN

Duffy · « **Reply #10 on:** August 11, 2003, 07:12:48 PM »

Load data suggests that a high BC means it will lose less velocity over a given time thus arriving quicker and having less time for influences of wind drift. Clear as mud huh.

It probably amounts to .00025 seconds.

KN · « **Reply #11 on:** August 11, 2003, 07:28:46 PM »

I stand corrected!! KN

helobill · « **Reply #12 on:** August 18, 2003, 08:14:35 AM »

And Duffy answered the original question at the same time. The BT design is an advantage at longer ranges because of lower drag (higher BC)...meaning less velocity loss due to drag. Muzzle velocity should be the same if the weight/composition of the bullets are the same and they are accelerated with the same type/amount of powder. However at 200 yards the retained velocity would be measureable and significant at 400 yards. So in a 300 RUM at 400 yards or a long range varmit gun it will make a difference, but as said already, "won't amount to squat" on shorter range targets.
Bill

X-man · « **Reply #13 on:** August 24, 2003, 04:21:01 PM »

You should check out the latest copy of "Rifle" magazine. They have an article in there that basically says we've all been mislead by the BT mythos. FB bullets are the only way to go, unless you are target shooting at extreme ranges and/or military sniper. All hunting situations under 300 yards should be solved with a FB bullet according to the article. Made for an interesting read.

myronman3 · « **Reply #14 on:** August 24, 2003, 04:48:08 PM »

i cant see how i have been mislead. the ballistic tips that hit deer i shot at dumped everyone of them instantly. and as one alread stated, they start into the case mouth really easy. whethter the boat tail part of the design is signifigant or not i cant say for sure; either way i am happy with the end result.

xphunter · « **Reply #15 on:** August 27, 2003, 05:43:44 AM »

Another reason that FB bullets shoot better out of most production guns is that they are not as finicky as the BT designs with less than perfect crowns. I can't explain all the reasoning but am sharing what I have learned. And even with good crowns as the benchrest boys have shown us the flat base bullets are highly accurate at hunting ranges. That deer can't tell difference at most specialty handgun distances.

Ernie