I need help understanding bullets

[foolproofoak]

When the reloading manual gives the powder charge data on bullets it specifies the type of bullet such as fmj or jhp, etc. My question is do these matter, or is it simply the weight (and diameter of course) that matter. Sorry if this question is stupid, but i am new to reloading and am simply exploring my options. Thanks for any help.

 

[Sunkist]

The nose doesn't matter. Go by the weight and whether jacketed or lead. If the velocity isn't too fast you can use the same data either way but keep in mind that often times a lead bullet will move faster than the same weight jacketed bullet. Hope this helps.

Welcome aboard.

 

[duckloads]

You'll get a better answer soon. There is great difference between a jacketed bullet (FMJ, JHP, etc) and a lead bullet (LRN, SWC, etc.) of the same diameter. There can bg a little bit of difference between brands of jacketed bullets. Not all jackets are the same thickness or hardness. So starting low and working up is a safe way to do things.

The man who taught me how to reload shotgun shells told me that, "its all about chamber pressure". So, for a given chamber pressure, a hard jacketed bullet takes less powder than does a soft lead bullet. The hard jacketd bullet gives less velocity than the lead bullet given the same chmber pressure.

Some of this info might even be right

.

 

[foolproofoak]

Sorry I wasn't very clear. I understand the difference between jacketed and lead bullets, and how critical pressure is. My question is is it ok to substitute a fmj for a jhp or a lrn for a lswc. Thanks again for any help. This forum truly does have some of the nicest and best people who have helped me so much in getting into not only firearms but reloading as well. so thanks.

 

[Amici]

Weight is the single most critical factor to verify when reloading; both charge weight (powder) and bullet weight (projectile).

However, even with the same class (jacked vs. plated vs. lead), weight alone is not the whole issue. Bullet SHAPE determines how much contact it has with the bore; that friction factor affects pressure.

Bullet shape also affects overall length, meaning a longer bullet in the same overall CARTRIDGE length will have a higher pressure because more of the bullet is seated into the case, reducing its volume. This is particularly true with rifle bullets.

SO, whether a given weight bullet is RNFP, HP or SWC will have some effect and a comprehensive manual will show loads for jacked and lead bullets, as well as SWC, RN and HP profiles.

 

[armadillo]

The depth of seating will also effect pressure. A wadcutter seated flush to the mouth of the case uses a lot more of the available space in the case than the same weight RN bullet.

A RN or SWC lead bullet should be pretty close to each other.

 

[DonD]

Edit: Amici did address the subject of bearing surface, perhaps I added some extra detail.

One point that was not addressed in the responses is that the profile of the slug does matter, it can change the length of the bearing surface that engages the rifling. More bearing surface all other things being equal means higher pressures.

The construction of the slug is also critical. A solid copper slug like a Barnes XPB will obturate less than a typical jacketed slug and for the same velocity will create greater pressure or lower velocity at the same pressure. Don

 

[Steve C]

Reloading manuals are guides and not cook books. You should use data for the type (jacketed or lead) bullet and the weight specified OR if you have an odd bullet weight then use data for the next heavier bullet.

In all cases use a start load, either the one listed or a 10% reduction from the maximum load, and work up to maximum, stopping if pressures signs start appearing. The start load will be a safe level even if the bullet isn't the exact same as used in the data development.

Pressure signs will only appear with excessive pressure when loading magnum pistol and rifle ammo. One should never see pressure signs with low pressure cartridges like the .38 spl or the .45 acp. Seeing pressure signs like flattened, pierced or cratered primers with these cartridges means that you are way beyond the maximum allowable pressure limits for those cartridges.

 

[Skip Sackett]

Good basic information given by most already. One thing I want to clear up though is the thought that bullet nose shape doesn't play into the loading issue. Nothing could be further from the truth.

How much of the weight is "up front" matters a bunch. Why? 'Cause if it is light in the front end, guess where it is heavy at? The rear! If it is heavy in the rear that means that it is longer than a bullet that is configured with a "slighter" shaped nose.

Bullet OAL, not cartridge OAL, bullet OAL, is something that needs to be understood. If a RN bullet is a "1R" it is going to have a shorter, fuller nose, thus making a shorter OAL bullet. If it has a "2R" nose just the opposite is true. The bullet is going to be longer, weight for weight.

Case in point:
This picture is of the Rainier and Berry 230gr TMJ bullet. I did my best in a hurry to align the noses of the bullets. I will try to get better pictures after church, if they are needed.

The Berry bullet is much "rounder" in the nose. More of it's weight is in the nose, making it shorter in OAL. The Rainer bullet is more "pointy" making it's weight more in the base. The bullet is longer, not by much but it is longer. Guess where the longer part ends up when seated to the same cartridge OAL? That's right, in the case. What happens when you cram more bullet into the case? Pressures rise. Why? Because of bullet nose shape!

I hope this is understood, it can be critical if you are already loading towards the top of the data. Bullet setback is the biggest cause of KB in firearms with unsupported chambers. It would seem foolish to cause the same condition on purpose.

Food for thought.

 

[acl864]

Not a stupid question at all. I had a similar question. How do identical bullet styles from different manufacturers differ. Here is how I did some testing.

I ran three different bullets loaded identically through the chrono. These were medium hot 357 mag loads shot out of a M19 with 2 1/2" barrel.

Hornady XTP 158 Gr. JHP - Avg. velocity 976 fps
Speer 158 Gr. JHP (bulk pack not Gold Dot)- AV 925 fps
Winchester 158 Gr. JHP - AV 945 fps

As several people have already stated. Work up to max loads.

 

[gregintenn]

Bearing area, weight distribution, hardness, shape, and other factors all combine to decide how much pressure it takes to push a bullet from the bore. Molybednum sulfate, and other coatings can work to reduce pressures. I would not substitute bullet types. I would search for loading data for the exact components you wish to load and adhere to it strictly. This is a great question, not a dumb one.
Other factors that determine pressures to varying degrees are: Case brand, Primer Brand, Bullet seating depth, Barrel lengths, Bore diameters, Temperature, and a host of others I've surely forgotten. Reloading is a fickle science.

 

[Amici]

Originally posted by gregintenn:
Bearing area, weight distribution, hardness, shape, and other factors all combine to decide how much pressure it takes to push a bullet from the bore. Molybednum sulfate, and other coatings can work to reduce pressures. I would not substitute bullet types. I would search for loading data for the exact components you wish to load and adhere to it strictly.

Jacketed ammo data is readily available. For any but the most common lead bullets, however, finding "loading data for the exact components you wish to load" is not feasible. I've never seen load data for the poly-coated bullets I use, and there are many different bullet casters who make many variations on a theme. Reloading manuals cannot address them all.

What one must do is find the bullet with the shape, weight and material which most matches the bullet you intend to load in a manual - preferably, several manuals - and online sources. Take that data, compare across the sources (if you can find more than one) and start at the LOW end.

Then work up - carefully.

 

[harry carey]

THANK YOU smithcrazy !!! i really caught it, was called a liar, on another forum for telling my experience while working in a range about 45acp unsupported chambers etc. THANKS. new loaders should buy Zedikers book "handloading for competition" and get a Sinclair Intl catalog. you will learn more and get farther , quicker. Naramores old book is very good. check out the used book stores for out of print books, and old manuals.

 

[Skip Sackett]

harry,
My caution isn't so much about the 45ACP and unsupported chambers as it is about bullet length/shape/case fill.

I'm not aware of KB's being very prevalent in the ole' 45 as they are in the higher pressure rounds, such as 9mm and 40S&W. I'm sure they can happen, they are just much less likely at 20k/psi versus 40k/psi.

I guess I need to go downstairs and look at the differences in my 9mm and 40S&W bullets.

Anyway, thanks for the kudos.

 

[NFrameFred]

No stupid questions, only stupid answers !

I think you've already been given some very good information, so I won't bother repeating it.

I learned to reload my first shells from a self appointed 'expert' ( I found out too late ) but I was smart enough and lucky enough to check multiple sources and use common sense, so I avoided mishap.

The thing is, there are lots of very experienced knowledgeable folks here, and should someone give advice that doesn't quite measure up - you'll see it debunked pretty quickly, so 'posers' don't last long in here.