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Posted: 2/7/2011 5:42:48 PM EDT
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I am new at reloading. I am confused on this topic.
RIght now I only have a Lyman 49th edition manual. I have a few more manuals on the way, but in the meantime I would like to learn and understand this issue: Can I use load data for 9mm 115 grain JHP to load a 115 grain FMJ? I am trying to understand the theory here - and from what I am thinking, which is probably wrong, the bullets are both jacketed and have the same exact weight, so the powder charge should be the same for both. I can understand that OAL could be different depending on the length of each bullet, but would it be safe to start loading 115 FMJs with the data for the 115 JHP? (I would start with the lowest powder charge in the manual and use the same OAL, 1.090). I know the JHP bullets are longer than FMJ's, so seating at the same OAL would theoretically mean lower pressure in the FMJ case - there is less bullet in the case with the FMJ (asking, not telling). I understand that if I wanted to use lead or plated bullets, the load data would be totally different, but I think I am comparing one FMJ to another, with the exception that the JHP has a hole in the end. I have the same question regarding .40SW, the Lyman manual lists only 180 grain JHP and I want to use 180 grain FMJ. I look forward to understanding this issue so I can learn to reload safely, thank you. |
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Bad idea as OAL of the bullets will often be different which means different seating depths which means massive changes in pressure.
Find a load for your bullet and powder of choice... It's not that hard thanks to the Google and much safer for your weapons and you in the long run. The sectional density of a FMJ is going to be much different from a JHP... |
| Bullet company manuals such as Hornady, Speer, Sierra and others most often list THEIR same weight bullets with the exact same data. Whether they are hollow poiint, flat point, round nose FMJ's they list the same data, BUT, they give different overall lengths for each. With 9MM different overall lengths can change pressure dramatically and the same for other cartridges. Bullet company manuals also list rifle bullets with the exact same data for Spire Points, hollow points, or FMJ's for same weight bullets. Key is to work up loads from near starting data working up to higher charges to check that loads are safe in your guns. And starting out reloading you need to keep overall lengths to suggested lengths in the manual. Data for a 115gr. Hornady bullet may be different than a Speer 115 gr. bullet. Jacket differences, bearing surface, etc. from one bullet manufacturer to another usually means different charge levels. Good idea to have a few different manuals. I like to have the powder company manual as well as the bullet company manual. Lyman's 49th is a good resource too. A lot of powder company data is available on-line or in free pamplets. |
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