Question about bullet shapes and ballistics

[meshugunner]

At this point, I've cast, loaded and shot about 5000 rounds of plinking ammo in .357/.38Sp & 9mm. I've collected a number of Lee molds without any real plan. It's been great fun. I've learned a lot. Now it's time to get more serious. I'd like to develop some accurate loads for my revolvers. I could really use a rundown on the inflight ballistics of the various bullet shapes. I'm target shooting, not hunting so I don't care that much about wound channels etc.

At this point I have no idea how to make an educated choice of SWC over RF or RN or anything....

Thanks

[fecmech]

If you simply want to hit a target at extended range the round nosed bullet such as the H&G #39 or Lyman 358311 are good choices. I use the former for 100 yd Silhouette work in a .38 spl. A light weight bullet that is even more accurate in my experience is the 9MM truncated cone bullets of 120-130 grs such as Lyman 356402, Lee 120 TC and RCBS 124 gr CN. Just about any handgun bullet is literally a "ballistic brick" with BC's under .2 so they are all pretty wind sensitive at extended ranges. Where you live would be a great place to really wring out some long range loads.
RN's and TC's are not considered "sexy" by the heavyweight big meplat school but they do shoot accurately.

[Artful]

This might help ya.

http://castboolits.gunloads.com/showthread.php?94638-Cast-Bullet-Ballistic-Coefficent-Table

[Skunkworks]

Here you can see the effect of speed.

http://i295.photobucket.com/albums/mm153/Chickenthief/Skydning/lapuadrags_zps9ab1643a.gif (http://s295.photobucket.com/user/Chickenthief/media/Skydning/lapuadrags_zps9ab1643a.gif.html)

[meshugunner]

Thank you for the chart. I was aware of the rapid increase in drag just before Mach 1 - drag divergence - but what causes the sudden drop in drag just before this happens? Is this shape dependent?

I looked at the BC numbers in the link that Artful posted (thank you) and it seems that the flatter the nose the lower the BC with wadcutters being the worst. Which is what I would have expected. Now I read here and there that WCs are often favored for target shooting at short range. Would this be because more of their mass is far from the axis of rotation giving more angular rotation and stability from spin. Is this perhaps why people sometimes mention HPs as giving tight groups? Is there a trade off between stability from the spin and aerodynamic performance and the sweet spot depends on the range?

Is there a significant difference between SWC & RF ?

Lots of questions. I have a lot to learn

[williamwaco]

Thank you for the chart. I was aware of the rapid increase in drag just before Mach 1 - drag divergence - but what causes the sudden drop in drag just before this happens? Is this shape dependent?

I looked at the BC numbers in the link that Artful posted (thank you) and it seems that the flatter the nose the lower the BC with wadcutters being the worst. Which is what I would have expected. Now I read here and there that WCs are often favored for target shooting at short range. Would this be because more of their mass is far from the axis of rotation giving more angular rotation and stability from spin. Is this perhaps why people sometimes mention HPs as giving tight groups? Is there a trade off between stability from the spin and aerodynamic performance and the sweet spot depends on the range?

Is there a significant difference between SWC & RF ?

Lots of questions. I have a lot to learn


I have shot nothing but Keith type and wad cutters in .38 special for 50 years I have recently tried the Lee 358-158-RFP and find it to be as accurate as any bullet I have ever used.
In fact I put three of them in a 2.25 inch group at 100 yards just this morning from my Thompson Contender.

I got so excited, I didn't have the nerve to shoot the next two.

[Le Loup Solitaire]

The round nose shape is aerodynamically pretty good, but not as good as the pointy one. The problem with RN's is that they cut raggedy holes which are difficult to score in the BE game. SWC's do almost as well and cut sharp holes which are easier to score. The conical nose, including the truncated version do well too. Full wadcutters are popular in BE; they are loaded light and cut the cleanest holes of all which makes them desirable for scoring, but they are the worst aerodynamic shape possible. They can and do skid in windy conditions and a blustery day at the range...save your ammo for a better day. Usually BE is shot at a max of 50 yards, but can be shot at shorter or longer ranges. It would seem a better choice for longer ranges to choose a pointy, RN or CN design and SWC's and WC's for shorter ranges. A factor that should be kept in mind is barrel length (and sight radius). A two inch snubbie is not going to perform as well as a four inch and neither will do as well as a six inch or longer barrel. Other factors can include bullet bearing surface, relation of weight to twist and velocity. It is not a simple subject and there is much to read and the necessity for careful experimentation and patience. And don't forget lots of practice. Good shooting. LLS

[flintlock62]

What distances are you shooting at? If you're shooting at around 25 to 50 yards, keep your loads sub sonic. I have never found any load to perform as well with a maximum charge. In my experience, 90 to 95% of a maximum charge has the best accuracy, no matter the projectile shape.


At this point, I've cast, loaded and shot about 5000 rounds of plinking ammo in .357/.38Sp & 9mm. I've collected a number of Lee molds without any real plan. It's been great fun. I've learned a lot. Now it's time to get more serious. I'd like to develop some accurate loads for my revolvers. I could really use a rundown on the inflight ballistics of the various bullet shapes. I'm target shooting, not hunting so I don't care that much about wound channels etc.

At this point I have no idea how to make an educated choice of SWC over RF or RN or anything....

Thanks

[frnkeore]

Thank you for the chart. I was aware of the rapid increase in drag just before Mach 1 - drag divergence - but what causes the sudden drop in drag just before this happens? Is this shape dependent?

I looked at the BC numbers in the link that Artful posted (thank you) and it seems that the flatter the nose the lower the BC with wadcutters being the worst. Which is what I would have expected. Now I read here and there that WCs are often favored for target shooting at short range. Would this be because more of their mass is far from the axis of rotation giving more angular rotation and stability from spin. Is this perhaps why people sometimes mention HPs as giving tight groups? Is there a trade off between stability from the spin and aerodynamic performance and the sweet spot depends on the range?

Is there a significant difference between SWC & RF ?

Lots of questions. I have a lot to learn

Bullets are nothing but round wings. If you study airfoil design, you'll find that in subsonic flight the C/D is dependant on a continued boundry layer containment. Anything that disturbs it causes drag. A radius on the leading edge promotes this and any flat distrubes it. The other thing in subsonic flight is that your not pushing a shock wave. That shock wave takes a lot of energy to over come, hince the big spike on the graph. Supersonic also takes a different profile with a very sharp leading edge to minimize the pressure on the point of the bullet but, they both benefit from long, gental ogvies.

Frank

[meshugunner]

Again thanks for all the comments. I feel I now have a better, though still very limited, understanding of this question. I understand that turbulence requires more energy than laminar flow. I don't understand much more than that about aerodynamics. But this prompts a naive question, why aren't handgun bullets pointy nosed and boat tailed? And why have any kind of flat on the nose - e.g RF & TC ? And what about the lube grooves? It seems to me they could be designed so that the don't "scrape" the air as badly as square cut grooves.

Also, it seems from this discussion that the only reason to use a flat nose design is for easy scoring.

Yes, I want to start stretching out to 25 & 50 yds. To date I've been shooting at "tactical" distances and mostly rapid fire where fine accuracy is not the primary concern. I have three .357 revolvers with 6" +/- that I want to try this with. I also have a BlackHawk chambered in .356 GNR which should be fun. I haven't started reloading that caliber yet. I have a mold for a 170gn Keith style RN. I haven't cast any of those either but now is the time.

But .357mag & certainly .356 GNR are intended for supersonic velocities. Are you guys saying this is not the best choice for shooting at those ranges? What bullet design is suited to this kind of performance?

[fecmech]

I think you may be worrying about the wrong things here as far as BC's and such. Anything shoots well at 50 yds, sub sonic,supersonic,wadcutter, round nose,semiwadcutter etc. YOUR grip,YOUR sight alignment,YOUR trigger break are the most important factors in hitting a long range target. YOU have to develop these skills before you can judge good long range loads. To do that I would suggest a good .22 target pistol like a Buckmark or Ruger semi as these with decent .22 ammo are capable of less than 3" 50 yd groups. Using these guns with good .22 ammo takes the gun and ammo out of the accuracy equation and helps you develop the skills for long range shooting. Then you can determine for yourself good accurate centerfire loads.

[meshugunner]

fecmech, I completely agree with your advice and I have tried to do just that. I started shooting in Feb '12 with a Ruger MKII. I put about 15000 rounds through that little pistol and made a lot of progress. Then I bought a S&W 686 which I love, but I realized that I couldn't afford serious practice with this caliber unless I reloaded so by July '12 I was cranking out plinking grade .38Sp & 9mm. I've shot over 5000 of those.


Anyway, I have these revolvers with 6" barrels. They need to be shot at distance :). Also, these days, my reloads are a lot cheaper than .22lr. (What .22lr do you recommend? I've been using CCI).

All I really want right now is to know that my reloads are better than I shoot and when I miss, it's my fault. I would also like to have some understanding of this subject.

[fecmech]

You're right about the cost of .22's, what was I thinking! Maybe the easiest way for you would be to cast some wadcutters and load them over about 3 grs of Bullseye or 3.2-3.4/231 and continue to practice along with dry firing. IMO shooting close and fast is not all that helpful from an accuracy standpoint. The game of Bullseye is much more conducive to sharpening marksmanship skills and in the end will do more to improve your close/fast shooting. I'd recommend getting some bullseye slow fire targets, setting them at 25 yds and go for it. Keep track of the targets so you can see your progress and don't be discouraged if things don't happen overnight. Very few people have the talent to shoot pistols well in the beginning. As you progress you will see that handguns can be very accurate to 100 yds and beyond. Good luck