JHP vs FMJ for loading


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Old 11-16-2013, 09:26 PM   #1
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Default JHP vs FMJ for loading

If a load recipe says for instance, "115 grain JHP" as the bullet, is there any reason that a 115 gr FMJ wouldn't be exactly the same as far as pressures and all? As long as the diameter is the same? Yes I am a total newb and am trying to learn by others' mistakes rather than making my own.



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Old 11-16-2013, 09:29 PM   #2
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Yes and no. Different bullets from different makers have different bearing surfaces (the area of the bullet that actually contacts the rifling). Different bearing surfaces equate to different pressures.

Generally speaking an FMJ has less bearing surface than an equal weight JHP so you "should" be OK.

WTS, ANY COMPONENT CHANGE REQUIRES A NEW LOAD BE WORKED UP!!!



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Old 11-16-2013, 09:46 PM   #3
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Quote:
Originally Posted by robocop10mm View Post
Yes and no. Different bullets from different makers have different bearing surfaces (the area of the bullet that actually contacts the rifling). Different bearing surfaces equate to different pressures.

Generally speaking an FMJ has less bearing surface than an equal weight JHP so you "should" be OK.

WTS, ANY COMPONENT CHANGE REQUIRES A NEW LOAD BE WORKED UP!!!
I hadn't thought of that thanks! I haven't started reloading yet, just educating myself first. I will definitely be working up to loads!
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Old 11-16-2013, 09:47 PM   #4
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long as you arent loading max you can generally interchange same weight jacketed hp and fmj. dont swap data for non-jacketed and jacketed ammo.

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Old 11-16-2013, 09:59 PM   #5
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Any lead-core jacketed bullet will use the same loading data. COL needs to be adapted for each bullet and you ALWAYS start with the lowest starting load and work up.
If you are asking if you can just blindly load Max or near max loads, then NO. If you check out a couple of manuals (you do own more than ONE right?), you will see that the max load varies in each. Since you are not using the same gun that was used to develop the loads and you do have the exact same lot number of the components, your loads will vary from theirs. Thus, you need to always check at least two sources and work up from the lowest starting load.
This should be covered in any decent manual.
Plated bullets, unless the have very thick plating like Speer Gold Dots, should be loaded like lead bullets (or no more than mid-range jacketed and usually not to exceed 1200 fps).



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