Same brand, same weight, virtually the same bullet. Same charge?

P

Pond James Pond

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I have loaded a hottish load in the past for some wide meplat PRVI FMJ 240gn bullets. These have an open base so the core is visible.

I have also bought some wide meplat PRVI JSP 240gn bullets. These are soft points with the core visible, but the base is fully copper sealed. Both have the same crimp groove at the same point.

So the question is do I change the charge? Do I need to drop by a grain and work up again, or are these so close to being the same bullet, that it is not necessary?
 
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It's always safe when changing any component to drop down a grain or two and work back up. You should be around same charge to end with but its best to drop back and workup again.
 
Wow. That response was... fast!

Were you on the starting block or something? :D

A cylinder at a grain below, then 0.5gn and full charge?

I'll try to match velocity too.
 
If that's how you do your workups then yes.

You probably already realized this, but you'll more than likely have a different OAL as well.
 
You probably already realized this, but you'll more than likely have a different OAL as well.
Click to expand...

The FMJ is only 0.15mm longer than the SJSP, and the crimp groove (rippled band in the copper jacket) is also that much higher on the FMJ.

A difference, yes, but I could seat both to the same OAL and still be crimping well within the cannelure on both.

In doing that there would actually be more case space with the SJSP, so pressure should me a smidge less when all other things are equal.
 
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I can't tell you for sure about your bullet, but I load 3 different 75gr .223's all with the exact same charge, and they all shoot equally as well, with only a slightly different POA at 100yds.just about a half an inch. When I load 9mm, I always use the same charge when shooting fmj rounds of equal weight. But none of these bullets are at max loads, if they were than I would work back up.
 
I had 12 cases that I'd just reprimed so I've done 4 at 19.5gn, 4 at 20n and a final 4 at the existing charge of 20.5gn of N110.


I'll check them out the next time I go to the outdoor range.
 
Same weight, but even a small difference in the ogive will affect distance to the lands if you use the same "overall length", which was discussed in one of your prior threads. If you have an OAL gauge, check to be sure that you wouldn't be jamming the bullet into the rifling- not a good thing with a "hottish" load.

Putting those two different bullets into the cases without adjusting the seating die will have different results if the FMJ and the JSP have even slightly different profiles.
 
Are you talking about safety or accuracy?

I can't speak to your exact situation, but I can say this about my .223 loads:

I load 3 different Sierra Match King 69gr bullets; the regular Match King, the Match King with the plastic tip (TMK), and the Match King with the Moly coating. My first guess is that they would all shoot the same, but they don't. I load them with different amounts of IMR 8208 XBR and each bullet has it's own preference for best accuracy, in spite of them being very close to the same bullet.

Furthermore, one type, the Moly coated one, constantly outperforms the other two, at least in my Howa 1500 bolt gun. In addition, to get them to .005" off the lands, requires a unique CBTO measurement for each type.

I would worry not so much about safety, especially if you fire a few light ones and work up. But I would be concerned that shooting a different bullet with the same recipe you found to be good with a very similar (but not quite identical) bullet might not be giving you the best accuracy. The only way to know for sure is to do a load development routine for the new bullet.
 
The hornady manual lists, for the most part, all of their bullets of the same weight together using the same load data. But hornadys load data i have found is on the conservative side compared to lyman and speer data. I measure all my stuff at the ogive and seat everything to the same ogive. There will be differences in accuracy of diff bullet types obviously, but from a safety side of things i wouldnt worry unless loading super hot. And if goin by hornadys data with their bullets, you will be fine.

This is assuming you are using jacketed and not cast bullets. Now that data IS different.
 
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