Boat tail bullets

[Saddlemaker]

A couple of shooters on this site have complained about the accuracy of their rifles when using boattail bullets. A number of years ago I was told by a Sierra Bullet engineer that to shoot well,a boat tail bullet needed a good muzzle crown on the rifle. It seems a flat base bullet is more tolerant of a poor muzzle crown.

If your rifle shoots flat base bullets well but not boat tail it may be worth a few dollars to have the barrel re-crowned by your gunsmith.
Walt

[Kenny]

G'day Walt and welcome to the forum

Just wondering how you would classify a 'poor' crown...?

Is it cut crooked or just plain worn out ...and is there a preference that boattails like such as an 11 degree job??

KY

[Saddlemaker]

Kenny,
Other than poor cleaning technique the biggest problem I've seen is a poor factory crown job. The first thing I do to any rifle I buy is have my Machinist friend put a recessed crown that has a shallow taper. My reasoning is to keep muzzle damage to a minumum if I accidently strike the muzzle while hunting. My machinist friend, Grady, does a lot of work for the benchrest and longrange crowd. He has saved a lot of us from buying a new barrel simply by recrowning a poor factory job. He has a scope he puts the muzzle under and is able to see miscut or cuts that aren't square or have minute pieces of chipped steele ect.

As far as what taper he uses I'll ask him and let you know. It is interesting to note that most benchrest bullets are flat base.
Good hunting...Walt

[Kenny]

Walt....okie dokie

KY

[Tim]

Is it correct that boattail bullets only offer an advantage when shooting at ranges over 500yards.

And dont flat base bullets create a better gas seal between the bullet and bore

[kjd]

I wouldn't say that if a boat tail is more streamlined ie: has a better BC then it will help at all ranges and shoot flatter thus increasing the likelyhood of a hit. For example a 52gn HP BT from hornady in .224 has a ballistic coefficient of .229 where as its flat based counterpart the 53gn HP has a BC of .218. Which would have to make a difference as it is roughly 5% better BC.


As far as the gas seal I have never noticed and I'm sure it would only be a small difference that would be overcome by the more streamlined boat tail designed.

Having said that I mostly used flat based bullets just because I try to get the cheapest varmint bullets to shoot. ie: Nosler shots.

[shane]

Flat base projectiles that shoot better than boat tails in a particular rifle do so mainly because they stabilize better in that particular barrel mainly due to an increased bearing surface among other things.

Yes boat tails usually dont start to show an advantageous effect from drag until around the 300m mark. But flat base proj's work very well for long range also.

Yes a poor crown is bad for accuracy and can have slightly more of an effect on boattail proj's than flat base.
cheers,
Shane

[Ned Kelly]

G'Day all,
I'm NO expert, far from it, but I'll try to explain it as I understand it....................assuming the bullet is travelling down the barrel true and square (properly aligned) so to speak...... as it leaves the barrel, if the crown is not square & true to the BORE the bullet will loose contact with barrel at the point where the crown has been cut "deeper".

This loss of contact at this point allows the expanding gas to blow past the bullet and the gas momentarily pushes against the bullet BEFORE it clears the barrel on the other side (remember, it is still in contact with the barrel) thus creating unwanted instability in launching the bullet.

Especially as the bullet is translating from spinning inside the mechanical centre of the barrel to the gyroscopic axis of the bullet (slightly different due to jacket thickness variations).

Now, if your using BT bullets, this is potentially is more of a problem because the BT "corner", located between the BT taper and parallel shank, may NOT be exactly same distance from the actual bullet base.

So, lets assume this longer BT side of the bullet exits the barrel exactly at same spot of the "deeper" crown, the propellant gas WILL leave the barrel much earlier than say a flat base bullet therefore the tilting/sideways effect will be at its worst! That is the gas acts on the bullet for a longer time.......for more effect. Now imagine, exactly the same bullet exits 180 degrees away on the other side at the "shallow" side of the crown and the effect may well be neutralised! Naturally, the assumption is ALL THINGS BEING EQUAL!!!!!!!!! (deep breath! Are you still with me?)

So, if the crown is cut perfectly square & true to the BORE (NOT the outside of the barrel), this cannot happen to the same degree and there are those in competition who recrown their barrels regularly to remove damage from cleaning/wear & tear etc.

REGARDLESS of whether you choose to shoot flat base or BT bullets a perfect crown is a good thing!

To tell how good your crown is look at the pattern of powder residue on the face of your crown after shooting........is it even? symetrical? It should look like a star pattern with each "point" of the star being the same length.Then its reasonable to assume the crown is ok, otherwise a recrown is a good starting point to improve accuracy in your rifle

I hope this helps.......

Cheerio Ned

[roscoe]

G'day All,

I have shot boat tail bullets in two varmint rifles, 22/284 and 22/243 Imp without problems. Probably up to 300 metres or so there is not that much advantage but at the longer distances the boat tail is invaluable. Over
300 M IMHO you need every advantage you can get to assist in a one shot kill.

Practical use shows they open up in the approved manner.

Shoot safely

Roscoe

[Ned Kelly]

G'Day All,
essentially every shooter should at least try boat tails or any bullet that takes their fancy to see if it will shoot in their rifle.

If your rifle shoots BT's/FBase bullets accurately, then FEED the rifle what it prefers and everyone will be Happy! Except the varmints of course!

Cheerio Ned