Can you sub FMJ when JHP in a reloading recipe?

[CanuckShooter]

I just bought the newest Lyman 49th Edition Reloading Manual and was looking for a load using a 124gr FMJ bullet, but all that is listed is a 125gr JHP. Since both bullets are the same weight, can I just substitute a FMJ in place of the JHP? Is this true for all rifle and handgun bullets (can substitute any bullet type as long as it is the same weight and jacketed assuming they are the same weight in grains)?

If they CAN be substituted for each other, does the fact that they list the bullet weight as 125gr when I will be using a 124gr bullet make any difference? Do I have to adjust the powder charge or seating depth at all for a 1gr difference?

If they CAN'T be substituted for each other, I just don't understand how Lyman could leave out 124gr.... I mean how many bullet weights are there really for 9mm that are common? Cripes...

 

[Canuck223]

When using a reloading guide, you really can't substitute components. What this means is while the people creating the guide have proven results, you are experimenting using thier findings as a starting point.

In your case, switching bullets with different profiles means a start at the starting load.

I would load 5 each from the starting load up to .5 under max in .2 gr increments, and chrony each round.

 

[sunray]

Yep. Load for the bullet weight. Who made it of what jacket is has doesn't matter.
For your 124 grain bullets, use 125 grain data. One grain of weight won't make any difference.
Like Canuck223 says, if you change any one component, you have to work up the load again. Your firearm may not like JHP's. Or it may not like FMJ's. In either case, you'd have to work up a load for each type of bullet, but you can use the same data for like weight bullets.

 

[B]

It should be stressed not to simply switch components and go on your way. Start low and work up slowly watching for pressure signs. A chrony will help immensely as well.

 

[H4831]

I'm sure glad I learned to handload in the days when most loading charts made no seperation of bullets, cases or primers. That is, a loading chart would show a 30-06, say, with a 180 grain bullet and xx grains of zzz powder. No mention of what brand of case, what brand, or type of bullet and no mention of what kind of primer.
I have never had a speck of trouble using that method, not did I ever hear of anyone else getting in trouble. However, I will seperate the cases by weight, if there is much of a change.
An example of this way of doing things was when Jack O'Connor stated in Outdoor Life magazine that 60 grains of 4831 worked great in a 270 with 130 grain bullets. We all went to the bench and loaded 60 grains of 4831 in our 270s and shot them. Every type and combination of components was undoubtably used.

 

[Ganderite]

I have had the advantage of working with pressure barrels. Any time any part of a load is changed (including changeing the powder lot number and sometimes even the primer lot number) there is a measureable difference in the average velocity/pressure of the load.

To answer your question, it is unlikly to make a difference.

But it could make a huge difference. This is why you must start lower and work up, so that if there is a problem you don't find it with a case full of powder.

What could be different, you wonder, with just one grain? Well, the ogive could be very different, and the load that was 5 thou off the rifling could now be 5 thou into the rifling. The bullet that was the same as groove diameter could be bigger. The bullet than was soft could be harder.

In the case of rifle bullets, there is a very big difference in the lenght of bullet engaged in the rifling between a round nose flat base and a spitzer boatail.

I can now step outside my back door and test a work up before committing to making a pile of ammo. The joy of a farm. In the old days I had a big block of firewood at the back of my loading bench. Faced with the question you just asked, I would have loaded at least one of five increments of .2 grain and tested. Warn anyone home befre shooting.

 

[blindman]

When using a reloading guide, you really can't substitute components. What this means is while the people creating the guide have proven results, you are experimenting using thier findings as a starting point.

In your case, switching bullets with different profiles means a start at the starting load.

I would load 5 each from the starting load up to .5 under max in .2 gr increments, and chrony each round.

X2 Better safe than sorry.

 

[CanuckShooter]

Thanks very much guys. I was planning to start at the starting load as I would when loading any cartridge.

Appreciate all the responses!

PS - For those interested, Al Simmons in Hamilton sells this book (Lyman 49th Edition... it's the newest one that came out this year) for $32 which is a damn good price (most stores don't even have them in stock!).