Can I safely use FMJ loads with a JHP bullet of the same grain? I understand the JHP will be a bit longer due to it's contruction, should I make the round a bit longer than FMJ specs, but within the range for that round?
Can I safely use FMJ loads with a JHP bullet of the same grain?
- Thread starter 41 Colt
- Start date
I've been loading both 230 grain FMJ and 230 grain JHP in my .45 ACP for years with the exact same load and overall length with not a single problem. Like any reloading practice, though, it's best to test everything yourself with as much margin for safety as possible. What I did originally was to work both loads up separately to test for pressure, and when I found that both bullets worked identically, then I just kept them at the same level. Probably the safest route.
Erik.
Erik.
mudgunner49
CGN Ultra frequent flyer
Not necessarily true. A JHP will be longer than a FMJ of the same weight (that material from the HP has to go somewhere) but may not make a great difference depending on the width and depth of the HP. If the bullet is in fact longer then it will end up seated deeper in the case in order to maintain the same overall legth and attendant pressures will climb - bearing surface of the bullet will also affect this (here is where differernt manufacturers become important). This may be relatively insignificant or possibly unnoticeable in a low pressure round like the .45 ACP, however in a round that operates at high pressure with a very peaky pressure curve (like .40 S&W) it can be dangerous/disastrous. For instance, seating a 180 gr .40 projectile as little as 1/8" deeper can increase chamber pressuer as much as 100%.
The best way to check this is to use a chronograph - if the velocity has jumped appreciably then in all likelihood so has the pressure. Any changes in components must be taken into account...
blake
JohnC
CGN Ultra frequent flyer
A recipe for disaster if you try to use JHP or FMJ powder weights withlead bullets. Also TMJ or plated bullets are different again. the plated ones are some where between lead and jacketed.
the only way to be safe refer to a published manuals.
When switching bullets, there are 2 factors that can change, max pressure and velocity.
If the substituted bullet is longer, and is seated to the same OAL, pressures WILL increase. Obviously this is much more important if you are at a max load, and if using fast burning powders.
Peak pressure in most handgun rounds occurs before the first 1/4" of bullet travel. (a couple large magnums, with lots of slow burning powder, reach peak pressure a little farther out, say 1/2" to maybe 3/4" out)
A longer bearing surface on a bullet will not affect peak pressure (much) but will affect velocity.
As said above, use published loads.
Sunray, you are only partially correct. The bullet construction is not as important as length of the bullet and seating depth (volume remaining within the cartridge). Going from an IDENTICAL jacketed to plated/lead bullet might raise peak pressure a couple thousand PSI, but only IF the volume in the cartridge below the base of the bullet doesn't change. This is where the biggest problems arise in substituting bullets.
If the substituted bullet is longer, and is seated to the same OAL, pressures WILL increase. Obviously this is much more important if you are at a max load, and if using fast burning powders.
Peak pressure in most handgun rounds occurs before the first 1/4" of bullet travel. (a couple large magnums, with lots of slow burning powder, reach peak pressure a little farther out, say 1/2" to maybe 3/4" out)
A longer bearing surface on a bullet will not affect peak pressure (much) but will affect velocity.
As said above, use published loads.
Sunray, you are only partially correct. The bullet construction is not as important as length of the bullet and seating depth (volume remaining within the cartridge). Going from an IDENTICAL jacketed to plated/lead bullet might raise peak pressure a couple thousand PSI, but only IF the volume in the cartridge below the base of the bullet doesn't change. This is where the biggest problems arise in substituting bullets.
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