Why hollow points for match shooting?

[Dylan in AZ]

I tried using the search function for awhile but couldn't come up with a good keyword to find the answer.

Im not even sure if this is the correct place to post this but:

Im sure it's been discussed here before but why are bullets like the SMK or Berger's VLD lines with the hollow points more accurate than something with a pointed tip? Does the hollow point move the air a certain way that yeilds better results?

And if it is in fact a better way to go then why aren't solid machined bullets made with a hollow point?

Thanks in advance and sorry for my ignorance,
Dylan

 

[Niles Coyote]

Re: Why hollow points for match shooting?

The hollow point is simply a by-product of the manufacturing process. Just like the FMJ has an open/exposed lead base.

 

[mtm87tx]

Re: Why hollow points for match shooting?

I believe that alot of the ballistic tip ammo is the same boat tail design but it was manufactured with a polymer tip at the end instead of just being open

http://www.hornady.com/store/30-Cal-.308-168-gr-A-MAX/

has a good cut away picture

like niles said, its in the manufacturing, some just took it one step further to incorporate the tip.

I would believe that a solid machine bullet would be superior however the costs of materials and manufacturing process make them much more expensive compared to copper jacketed lead, not to mention they have little if any expansion and would have over penetration issues with any type of hunting

 

[Wild_Bill]

Re: Why hollow points for match shooting?

with the newest manufacturing proceses you can point a projectile up as tight if not tighter than the point of a plastic tip and also by reducing the extra component the petential for better accuracy is there this is one of the reasons that Hornady is using the HPBT design for a line of new projectiles because the more steps in making a projectile the more chances things can go wrong. i have shot A Max bullets that were amasing and others that were realy poor one friend had a batch of 140gr 6.5's and the tips would break off some and not others as they went down range Hornady actualy replaced them for him and the other ones he just put a small pressure against them and broke all the tips off and shot them at short ranges and they worked OK.

If you made up a conventional FMJ you could not point the projectile up as much so they tend to have a slightly lower BC aswell as having a problem when fired with high burn temperature propelants the exposed lead at the base can vaporise and become airborne causeing lead exposure and also leading in the bore.

So the easiest and best way to make a match projectile with a lacket and lead or composite core is to make them a HPBT design.

As for solid copper or brass projectiles unless you are starting at around 338 calibre you realy can not get any advantage over the HPBT lead cored bullet i have them in 6mm and up for testing and it is not until you reach 338 that there is an advantage in performance but they do have other properties that might be usefull for other than accuracy.

Hope that helps.

 

[BigMahi]

Re: Why hollow points for match shooting?

I remember reading somewhere that while a open tip is a manufacturing byproduct, one collateral benefit wqs that it reduced weight from the tip of the bullet, making it less likely to tumble. Having a higher mass concentration in the belly of the bullet made it fly straighter, as opposed to a leaded tip which would weigh down the front of the bullet (making it more likely to tumble at long range).

 

[Dylan in AZ]

Re: Why hollow points for match shooting?

Im just thinking of the benchrest guys who use whatever works best because money really isn't an issue for alot of those guys. So i knew there had to be a reason that an open tip is better but i still don't understand exactly what makes it better. I would think that just by design that they would be less accurate because the cavity would cause turbulence in the bullet but thats obviously not the case. There has to be a real reason.

And all bullets are assumed to be boat tail and FMJ by the way just to be clear.

Oh and on the subject of the solids, why do they only start improvements in 338 and up calibers? It would seem to me that any improvement in a larger caliber would effect a smaller caliber at an exponentially increasing ammount weather that be good or bad.

Thanks,
Dylan

 

[Wild_Bill]

Re: Why hollow points for match shooting?

Sorry you mentioned benchrest then Boat tail projectiles nearly all short range benchrest shooters use flat based bullets and some 1000 yard shooters also use custom flat based bullets so be carefull on genrealising.

Onve the cavity has pressurised it almost becomes a solid piece of the projectile, as mentioned you can add or remove the lead from the projectile and adjust the ballance to be best suited but the issue with the solids is the mass of the smaller calibre projectiles the mass has a lot to do with stability and also contributes to BC so the realy light projectiles in smaler calibres just dont come close to a conventional design and also to make a higher BC you then have to spin it faster when in 224 and 8mm we already use 7 and faster twists then you are looking at 6 twists and things realy start to go backwards if you have to spin projectiles that fase.

 

[Dylan in AZ]

Re: Why hollow points for match shooting?

Allright thank you, so is there no effect on the tip of the bullet? Or is it negligable.

 

[DAVETOOLEY]

Re: Why hollow points for match shooting?

Yea be careful bashing flat base bullets. They said it couldn't be done, I couldn't hit the paper they laughed their asses off but I've won a lot of loot with those flat base bullets. I hold the NBRSA 1K heavy gun group world record and a friend, who was one of the doubters, holds the IBS 1K heavy gun group world record. We were both shooting the same flat base bullet. Give me enough BC to get the job done then I want <span style="font-weight: bold">THE</span> most accurate bullet I can find.
A flat base bullet is way easier to make, so lot to lot it will be more accurate. No one has ever or will ever make a <span style="font-weight: bold">mass</span> produced lead core bullet that is more accurate than a hollow point bullet, again lot to lot. Hornady is doing a good job with A Max's but there is still more to learn making a plastic tipped bullets. That's the reason for the new line of HP's. HP's are accurate,they're easier to make, they're accurate lot to lot they make money off of them.

Meplats have a huge effect on the flight of the bullet. I've measured BC spreads as high as .039 before. To make a long story short years ago I got some test data from an F-Class shooter who tested 30 different bullets with Dr. Ken Oehler at 1K yds. While not conclusive it led me to conclude tipped bullets(A-Max's) had more uniform BC's than HP. I then developed a meplat trimmer to trim off all the irregularities off the meplat. I also purchased an Oehler model 43 with acoustical screens and began testing bullets myself. That led to a test for Sierra where I tested stock, trimmed and bullets with tips manually installed.

Results, stock bullets can suck, trimmed meplats cut the BC spread way down but decreased the BC by about 2%, tipped bullets were the best of both worlds-uniform and you get an increase in the BC. Over the years the pointing dies have been developed. As a bullet maker I was leery at first but I've come around, done properly it decreases the BC spread and increases the BC slightly and this can be done by anyone reloading their own ammo.

 

[bohem]

Re: Why hollow points for match shooting?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TerrorInTheShadows</div><div class="ubbcode-body">
Oh and on the subject of the solids, why do they only start improvements in 338 and up calibers? It would seem to me that any improvement in a larger caliber would effect a smaller caliber at an exponentially increasing ammount weather that be good or bad.

Thanks,
Dylan </div></div>

Hi Dylan, I'll take a short crack at this question.

The problem is scalability. Simply taking a superb 50cal bullet and scaling it down to say 7mm or 30cal, while keeping the same rifling twist and everything else scaled (ie a 22cal/turn 50 and a 22cal/turn 7mm, etc) doesn't necessarily mean that the 7 will be stable.

I believe that this has been discussed in various threads that the behavior is not identical and just because everything was normalized on a "calibers" basis doesn't net you a similarly superb small caliber bullet.

 

[nova-birdman]

Re: Why hollow points for match shooting?

I've always explained it as such:
In supersonic aerodynamics, the dominant source of potential side loads is due asymmetry in the angle of the nose shock to the nose itself. Thus, for a mass produced bullet, it is far easier to flatten the tip to result in a flat (or hollow) that is perpendicular to the bullet axis, than it is to make a point that is perfectly symmetrical to the axis (except when lathe turning a bullet). So, to get the best possible accuracy, without precision machining of the projectile, the the best tip choice will either be a dimensionally stable, reproducible insert (amax tip), or a flat made perpendicular to the axis---this is why meplat uniforming results in the improvements it does--axisymmetric tip and shock angle = minimal side loads and destabilization

 

[RobertB]

Re: Why hollow points for match shooting?

I have always been under the impression that the hollow point design was to keep as much of the weight of the bullet to the outside of the projectile.

 

[Dylan in AZ]

Re: Why hollow points for match shooting?

bohem, thank you, i think im starting to understand the differences a little more now.

Dave, i don't see anywhere that i bashed flat based bullets.

I understand that they are regarded as more accurate but in my question i didn't ask about the differences between a flat base and a boat tail and i say that with no disrespect intended. Im simply trying to find out why the tips are made how they are.

I understand that the hollow point is just a byproduct of the machining process but i know that if it caused problems they could easily fix that problem. I guess what im getting at is how can a bullet with a cavity in the nose fly as well as a bullet with a pointed tip. And by pointed tips im reffering to not plastic tips but tips formed out of the jacket like a flat base but assuming all bullets are equal besides the tip. I doesn't really matter wheather they are flat or boat tail. They just have to be the same as to isolate the one part of the bullet that is theoretically being changed.

Thanks,
Dylan

 

[Dylan in AZ]

Re: Why hollow points for match shooting?

Sorry didn't see the 2 most recent posts, thanks guys.

 

[vman]

Re: Why hollow points for match shooting?

tag, interesting read

 

[Dylan in AZ]

Re: Why hollow points for match shooting?

Isn't it? Credit for the question goes to my dad, he inquired about it several times but i couldn't ever give him an answer.

 

[Dogtown]

Re: Why hollow points for match shooting?

I think the supersonic shockwave that forms at the nose of HPBT prevents air from getting into the hollow portion and being a drag issue...but that's a bit of CFD induced speculation.

 

[Noel Carlson]

Re: Why hollow points for match shooting?

Dylan,

If you think in terms of center of gravity, rather than the existence of a cavity in the nose, then your question will be more easily answered.

Supersonic airflow will *see* a hollow point as a solid meplat. As mentioned earlier, there is a slight trade of efficiency, for symetry, in using either. The nature of jacketed bullet structural rigidity necessitates designs that are less than six calibers long, which is fine given that the twist-rates necessary to stabilize a longer jacketed projectile would create rpm values too high for the jacket to hold together in flight. This design limitation has the side benefit of making a dynamically unstable bullet difficult to construct, especially given the relatively high specific gravity of lead in comparison to the copper alloys used in turned solids. For this reason, hollow noses are a non-issue , from a stability standpoint, in jacketed bullets.

The scalability phenomena is a function of differing laminar, and turbulent, fluid flow properties around an object based on it's *size*. Size differences are denoted by the assignment of a Reynolds number.

For example; to simulate the flow characteristics that a 50 caliber projectile would produce at 2,000 fps, a 25 caliber model would have to be run at 4,000 fps. Fluid flow is not scalable, and projectiles in smaller calibers must account for this.

 

[groper]

Re: Why hollow points for match shooting?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Noel Carlson</div><div class="ubbcode-body">Dylan,

For this reason, hollow noses are a non-issue , from a stability standpoint, in jacketed bullets.

</div></div>

This is not the main reason either... from a stability standpoint, the reduced transverse moment of inertia of a hollow point design, more than offsets the greater pitching moment caused by shifting its center of gravity rearward in the process.

Another benefit that also goes hand in hand with the above, includes a shorter raduis of gyration and this helps with better damping of the epicylic arms so that the projectile yawing 'goes to sleep' sooner and you get better accuracy, particularly at shorter ranges. All good things for match projectiles obviously.

The improved mass inertia properties of a hollow point projectile, or a plastic tip projectile, effectively makes it behave more like a shorter projectile than it really is and allows designers to construct a slightly longer nose with reduced wave drag and higher BC, whilst still maintaining good stability and accuracy benefits of shorter designs.

 

[nova-birdman]

Re: Why hollow points for match shooting?

Good thread! I'm in agreement with Noel and groper, but thisnreminds me too much of conversations way back when in school

I must hit the range soon to make up for it