Range Report use of 'open tip' bullets ?

[tedbiv]

i have been reading a number of articles comparing accuracy of open tip vs. spitzer tip. specifically m118 173-grain match grade full metal jacket boat tail, ogival spitzer tip bullet, vs the M852 is the Sierra MatchKing 168-grain match grade boat tail, ogival spitzer tip bullet with an open tip. the articles seem to speak more to the 'legality' of open tip bullets more than the design that makes open tip more accurate at distance.

can someone enlighten me as to the physics of the open tip design that helps improve accuracy. on the surface, i would have expected the spitzer tip to be better performing. the open tip seems to have a better ballistic coefficient, i can't understand why...

thanks in advance.

tedbiv

 

[tedbiv]

Re: use of 'open tip' bullets ?

i think i found the answer...

Where target shooting accuracy is the prime consideration, some bullets such as the Sierra "Matchking" incorporate a cavity in the nose section. This has the effect of lightening the bullet's forward section and shifting the center of mass towards the tail of the bullet, to give an improved ballistic coefficient, greater down-range velocity retention, and greater resistance to deflection by crosswinds.

gotta love wikipedia...

sorry for the spam.

 

[tedbiv]

Re: use of 'open tip' bullets ?

interesting tidbit, didnt know there was a place named dum dum...

The hollow point and soft-nosed bullets are both sometimes also referred to as dum-dums, so named after the British arsenal at Dum Dum, in present north Kolkata, India, where it is said jacketed, expanding bullets were first developed.This term is rare among shooters in North America, but can still be found in use, usually in the news media and sensational popular fiction.[18] Recreational shooters sometimes refer to hollow points as "JHPs", from the common manufacturer's abbreviation for "Jacketed Hollow Point".
To be most correct, the term "Dum Dum Bullet" refers only to Soft-point bullets, not to hollow points, though it is very common for it to be mistakenly used this way.

 

[MitchAlsup]

Re: use of 'open tip' bullets ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tedbiv</div><div class="ubbcode-body">can someone enlighten me as to the physics of the open tip design that helps improve accuracy. </div></div>

The HPBT bullets have the lead swaged in from the front, and then the front of the bullet is swaged down to its nominal point. Durring this time, the BT is held in a die. This leads to better concentricity, and better placement of the center of mass at the radial center of the bullet. There can be "issues" with the nose of the bullet because the bullet has to be pushed out of the final die with a tiny pointed tool from the pointy end of the last forming die.

The 173 style bullet has the lead pushed in from the back and the swaging of the BT is the last in the line of events. This leads to runout on the BT and troubles keeping the center of mass concentric with the radial center of the bullet.

Neither bullet is typically 'designed' to exapnd at impact.

 

[Bob 964]

Re: use of 'open tip' bullets ?

This may be a stretch but...

In an effort to get more speed and better hook-up, while my jet ski engine was out of the hull to be rebuilt, I lightly sanded the hull. The principle behind this is that the rough hull moving through water creates a layer of bubbles. As the hull moves forward, the layer of bubbles actually cushions the hull and lifts it up a bit, which permits it to move through the water with less drag.

I would think this principle might permit an open tip bullet to fly with less drag.

 

[gstaylorg]

Re: use of 'open tip' bullets ?

Here you go:

Now if only there was a way to put dimples on a boolet...

 

[kraigWY]

Re: use of 'open tip' bullets ?

If anyone has studied Dr. Franklin W. Mann (inventer of the Mann Accuracy device, still used today by the military to test ammo, and author of "The Bullet's Flight from Powder to Target")
you would understand that buttet tip, open or closed, has little to do with accuracy.

Dr Mann decated his life, to the point of destroying his family, trying to find out why each and every bullet shouldn't go into the same hole.

He proved conclusively that a misshapen bullet point had little or no ffect on grouping, a cocked, cut, or slanted base destroyed it completely.

Its not the tip, but the base, the base and the ability to seat the bullet perfectly, consistantly each and every time.

So it matters little if the bullet is open or closed tip.

 

[9H_Cracka]

Re: use of 'open tip' bullets ?

It has to do with the weight distribution front to back in the projectile.

The 173 is a rear loaded bullet - the core goes in from the ass end, hence at the base you'll see some grey of the lead core.

The 168 and 175 are front loaded. The copper cup is open on one end, has the core pressed in from what ends up being the front, and then the front is closed, leaving an air space at the front of the bullet.