Truncated Cone vs. Round Flat Nose?

[Canuck Bob]

For my education I have been wondering about the truncated cone nose compared to the Round Flat Nose while playing with the program at Mountain Molds.

Assuming the meplat is the same is there a big difference between the two with 44 or larger bullets?

[VenomBallistics]

the RNFP might be a little slicker and can leave a hair more case capacity, but with the metplat being equal its a dern close race

[Bullshop]

I dont qualify to answer but just wanted to make an interesting point.
I have a Freedom Arms mold, yes that right from Freedom Arms for the 454 Casull.
Way back when they used to include a load data book with their guns.
It listed loads for both their jacketed bullets and their cast boolits.
The interesting thing is they chose the truncated cone design for both their bullets and their boolits. Would you suppose that was just by chance or was there a good reason?
BTW anyone ever see one of the Freedom molds? I have the only one I have ever seen.

[onondaga]

I like the truncated cone or even a semi wad-cutter because of the sharp top edge before the point starts. The sharp edge cuts the edge of the hole and leaves a clean hole for bleeding. Look at the sharp edge on my favorite .500 S&W rifle bullet, it is the Lee R.E.A.L. 50 Cal muzzle loading bullet sized to .501" for my rifle:

http://i30.photobucket.com/albums/c338/rhymeswithwhat/TLsized.jpg
unsized and sized

These cut a good hole and the nose is flat enough to thump hard and punch over deer.

Gary

[noylj]

The ogives can not be the same. The cone has straight edges up to the point and a round nose has a meplate that is in a continuous curve up to the point. The meplate (the nose of the bullet) would be the same only as a coincidence.

I have never found any difference in COL whole loading them.

[44man]

The ogives can not be the same. The cone has straight edges up to the point and a round nose has a meplate that is in a continuous curve up to the point. The meplate (the nose of the bullet) would be the same only as a coincidence.

I have never found any difference in COL whole loading them.
If the meplat is the same, both kill the same. As far as accuracy difference between them, there is none. Both are good choices.

[onesonek]

If the meplat is the same, both kill the same. As far as accuracy difference between them, there is none. Both are good choices.

While I haven't the experience with game and cast of yet, I would tend to agree.

I seen some pic's of test done in B-gel with the nose painted on both boolits in question. After impact the paint remained on the leading edge of the front driving band on the TC design, wasn't much in the way of a edge on the RNFP. But some paint remained on the RN as well (other than the meplat's on both), so seemingly, it is the meplat doing all the work. In both, the resulting wound channel appeared about the same. I would tend to think, it is up to the firearm's discretion, which shoots best. Other than that, it seems merely a personal choice in design.

[Piedmont]

I seen some pic's of test done in B-gel with the nose painted on both boolits in question. After impact the paint remained on the leading edge of the front driving band on the TC design, wasn't much in the way of a edge on the RNFP. But some paint remained on the RN as well (other than the meplat's on both), so seemingly, it is the meplat doing all the work.

If you ever need to kill a blob of jello, you have your answer. Animals, however, are not homogenous. Think deeper.

[onesonek]

The deeper thought is,,,it's the mass's frontal area and momentum, that does the displacement, whether that mass has expansion or not. That is dependant on a host of other criteria. While I agree B-gel is not ideal, and that body tissue is not homogenous,,,, it still shows equally, the impact results with different designs.
The point was, the cavity was opened by the meplat, wider than the body diameter of the boolit itself. Providing the meplat is the same dia., (and or expansion), velocity the same, weight the same, and alloy the same, I see little difference in the two designs when it comes to impacting an animal.

[Mk42gunner]

My thought is that most of the truncated cone designs originated with people trying to get a projectile that is more effective than a fmj ball round for auto loading pistols, while the RF boolits are meant to feed easier in lever action rifles and carbines. A SWC shoulder can hang up while feeding in either type of gun.

Robert

[Canuck Bob]

This question is an outcome of some reports with levers that often require crimping ahead of the driving band and on the ogive with the longer Remington brass. Some levers as most taught me here can have abrupt leades with small or almost no throat. A secant ogive appears to offer more latitude than a tangental ogive. The TC might match up with the abrupt leade rather well.

Just trying to learn about bullet design and characteristics of shape of the nose. The feeding issue does add an interesting element for a lever.

It appears that equal sized meplats are likely to offer very similar real world performance.

The level of varied experience is staggering to a new guy and very much appreciated. You guys are supportive of new guy questions and not all forums are.

Thanks

[Bret4207]

Bob, I thin you've struck the reality of the issue. There's probably a lot more difference in feeding and fit than in performance on game given the same metplat, speed, wt, etc. Common sense says that since no 2 shots will be alike on game that the variables add up a little too quickly to make a concrete evaluation of one being way better than the other. Now, one may fly a lot better from your gun and load, but that's not the question.

[44man]

My thought is that most of the truncated cone designs originated with people trying to get a projectile that is more effective than a fmj ball round for auto loading pistols, while the RF boolits are meant to feed easier in lever action rifles and carbines. A SWC shoulder can hang up while feeding in either type of gun.

Robert
No, No, No. The nose shapes allow a boolit to align a revolver cylinder and enter the forcing cone on a straight path into the rifling.
Nothing at all to do with an auto.

[Canuck Bob]

I stumbled on Fryxel's book on the stickies. that is some serious help for a guy as new as me. He discusses some interesting points about cast bullet design. It lead me to another article of his about SSK bullet designs which use a TC nose. The SSK design uses a short nose ride before the turn to the nose keeping the nose proper short. It puts a lot of lead in a compact package.

Apparently the designer noticed that his bullets recovered from some serious hunts all looked the same. So he just had them start out looking like they would finish with a TC nose. I think his name is J D Jones and has quite a rep for design and wildcats around the Contender line of handguns and some heavy lead thumping revolvers.

[Doble Troble]

My 1911s all feed TC bullets reliably. Only 1 feeds a RNFP 45 Colt bullet. Two out of three feed SWC, and that's my personal favorite. But all I do with them is kill cardboard.

[Bass Ackward]

For my education I have been wondering about the truncated cone nose compared to the Round Flat Nose while playing with the program at Mountain Molds.

Assuming the meplat is the same is there a big difference between the two with 44 or larger bullets?


It's real simple. Look at what old time (Lyman classic molds) cast bullets looked like for each caliber. Back then people had a idea of what a common weight range was for handguns. And what sane velocities were to run lead. To make bullets in this weight range with maximum bearing area and room for lube capacity you had three nose shapes: Semi-wadcutter, wadcutter, and trunicated cone.

Two of these shapes took valuable weight off the nose and moved the center of balance BACK so that it would be easier to stabilize and have some type of aerodynamic properties for flight at sane velocity levels of the day. Everyone knew that the wadcutter went wacky beyond some short distance.

The olgival was from the BP days when case capacity was precious. Problem was that they couldn't run it up fast enough to stabilize in short barrels, but then handguns in those days just had certain limitations.

As we changed our expectations for what a handgun was and could be used for, we took steps to increase velocity to levels where the C of B wasn't as critical as long as you stomped on it. Weight then became a velocity issue, more case capacity (or barrel length) became essential.

Pick a 200 grain weight in 44 caliber and try to design a bullet and see how many options the program will let you have. Then you will understand.

The design needs to taylored for the intended purpose of the slug or it will be finicky to get to perform. So a design (weight and shape) for a 3" barrelled 44 would have less design options and probably should look different than the options you have for a 10" or 20" launcher.