I would call them with following additional descriptions:
1. FMJ - Concave or "dished" lead base
2. FMJ - Flat lead base with lip
3. FMJ - Flat lead base
4. Plated RN - Solid base (or TMJ if bullet is verified to be trademarked Speer TMJ)
1. FMJ - Concave or "dished" lead base
FMJ with flat lead base pushed in to form a concave cavity done to help expand bullet base to better seal with barrel and reduce gas leakage around the bullet.
Hollow Base - If the cavity is deep enough, bullet will become "Hollow Base" as shown below left that also increases the length of bullet base/bearing surface to improve neck tension (same intent as Berry's Hollow Base RN on the right) and better engage the rifling (reasons why 124 gr FMJ/RN bullets are favored over 115 gr FMJ/RN with shorter base for accuracy). So with 115 gr HB FMJ/RN, you end up with similar bullet base length as 124 gr FMJ/RN. Notice both hollow base bullets are longer/taller compared to solid base bullet in the center.
Here's Federal (.FC. headstamp) 9mm 115 gr FMJ pulled to show hollow base bullet -
https://www.thehighroad.org/index.php?threads/factory-rounds-pulled.706260/
2. FMJ - Flat lead base with lip
FMJ flat lead base with jacket that forms a "lip" around the base. Winchester 115 gr FMJ shown below right shows more defined lip around the base. The "lip" may have been intended to form a concave or dished base to better trap expanding gas to better expand the bullet base to seal with the barrel.
3. FMJ - Flat lead base - FMJ with exposed lead base.
Here's Remington (RP headstamp) 9mm 115 gr FMJ pulled to show flat lead base -
https://www.thehighroad.org/index.php?threads/factory-rounds-pulled.706260/
4. Plated RN - Solid base (or TMJ if bullet is verified to be Speer TMJ)
Number 4 is described by some companies as "Total Metal Jacket"
4. TMJ
All so called “TMJ”s that I have seen personally were actually plated, not jacketed ... Do you know who manufactured that bullet?
I pulled that bullet from a cartridge with an AMT-97 headstamp. That was a small ammunition manufacturer in South Africa called Ammotech.
Bullet number 4 definitely looks plated. If the ammunition came from South Africa, plated bullet used could have been made by Frontier Bullets/FMP Bullets (
Frontier Metal Processing), which is also based in South Africa -
https://fmp-bullets.com/collections/cmj-bullets
Frontier Bullets said:
Bullets are completely coated in pure copper ... plated bullet
As to TMJ (Total Metal Jacket), it is trademarked originally by Alliant Techsystems Inc. (Now Vista Outdoor) -
https://trademarks.justia.com/738/33/tmj-73833272.html
TMJ bullets are "thick plated" and I believe originally intended to produce projectiles with no exposed lead to reduce lead exposure (supplemented by use of non-toxic primers) but as demonstrated by Gold Dot HP bullets (which are even thicker plated bullets), showed no jacket separation from lead core that some other JHP bullets suffered. TMJ, as best as I can find have around .015" thickness copper plating which is around the thickness of gilding metal used for jacketed bullets (which is around .015"-.030" in thickness) -
https://www.thehighroad.org/index.p...ng-at-25-50-yards.808446/page-3#post-10470195
TMJ bullets are sold by Speer in bulk and also used to manufacture factory ammunition -
https://www.speer-ammo.com/en/bulle...ndgun-plinking-bullets/355/355-115-tmj-bullet
Here's Blazer (BLAZER headstamp) 9mm 124 gr "FMJ" pulled to show solid copper plated base -
https://www.thehighroad.org/index.php?threads/factory-rounds-pulled.706260/
Speer TMJ bullets could be used by other manufactures to produce "FMJ" ammunition. Here's Remington 45ACP 230 gr "FMJ" pulled to show solid copper plated base -
https://www.thehighroad.org/index.php?threads/factory-rounds-pulled.706260/#post-8782418