Dave Waits
03-15-2013, 02:02 PM
I've been attempting to develop a decent velocity JHP load for my 45s. While doing this I found something pretty interesting. We'll get to that shortly. I used two powders in this, Blue Dot and HP-38.
The Blue Dot load consisted of 8.8 grains, a Winchester Large Pistol Primer, a 230 grain JHP and an OAL of 1.220". Crimp was .470. Each charge was hand-weighed as a check after being dumped by my Pact Electronic Dispenser/Scale, which I completely calibrated for this load and powder. Each bullet was weighed beforehand and all were within .2 grains for the five rounds loaded. all cases were exactly .898 in length.
Results;
round one- 878fps
round two- 875fps
round three- 807fps
round four- 814fps
round five- 865fps
Very perplexing, each round was weighed as another check after loading, all were within .4 grains of each other, total weight. .2 grains being variation in bullets and the other in cases.
Second load was the same except that 5.2 grains of HP-38 was used. All checks were identical and all weights were identical. All weights and lengths were identical.
round one-807fps
round two- 812fps
round three-806fps
round four- 810fps
round five- 807fps.
Another perplexing occurance as this load with a 230 grain FMJ and a longer OAL of 1.265" gives a consistant ave.velocity of 835fps.
Here's what has me wondering. Aside from the erratic performance of the Blue Dot, these velocities with a shorter length showed an almost uniform loss of velocity, which means lower pressure. This got me to thinking, the JHP loads were a full forty-five-thousandths shorter than the FMJ loads. This is equal to what most see with severe setback but, no increase in pressure. AAMOF, there was a decrease in pressure.
First, I thought, maybe my Dispenser/Scale is off. So, I dropped three different weight charges with a RCBS #505 scale and checked their weight on the Electronic. All three were dead-on.
Now, looking at the Blue Dot load; I'm beginning to think that rounds three and four suffered setback as they showed the same lower velocities that the HP-38 load did.
Now, popular thought in both Reloading and Gunsmithing circles dictates that setback dangerously increases pressure. This was the main thrust in trying the HP-38 load, I was actually trying to increase pressure with the same charge by seating the bullets deeper and thus, increase velocity. what I found, as you read, was just the opposite effect.
As for JHPs versus FMJs, velocity-wise, the case,powder,primer and barrel don't care what the nose looks like, it's a 230 grain load. So, this doesn't enter into the equation.
So, the question is; Why did I see less pressure with these loads rather than higher pressure?
The Blue Dot load consisted of 8.8 grains, a Winchester Large Pistol Primer, a 230 grain JHP and an OAL of 1.220". Crimp was .470. Each charge was hand-weighed as a check after being dumped by my Pact Electronic Dispenser/Scale, which I completely calibrated for this load and powder. Each bullet was weighed beforehand and all were within .2 grains for the five rounds loaded. all cases were exactly .898 in length.
Results;
round one- 878fps
round two- 875fps
round three- 807fps
round four- 814fps
round five- 865fps
Very perplexing, each round was weighed as another check after loading, all were within .4 grains of each other, total weight. .2 grains being variation in bullets and the other in cases.
Second load was the same except that 5.2 grains of HP-38 was used. All checks were identical and all weights were identical. All weights and lengths were identical.
round one-807fps
round two- 812fps
round three-806fps
round four- 810fps
round five- 807fps.
Another perplexing occurance as this load with a 230 grain FMJ and a longer OAL of 1.265" gives a consistant ave.velocity of 835fps.
Here's what has me wondering. Aside from the erratic performance of the Blue Dot, these velocities with a shorter length showed an almost uniform loss of velocity, which means lower pressure. This got me to thinking, the JHP loads were a full forty-five-thousandths shorter than the FMJ loads. This is equal to what most see with severe setback but, no increase in pressure. AAMOF, there was a decrease in pressure.
First, I thought, maybe my Dispenser/Scale is off. So, I dropped three different weight charges with a RCBS #505 scale and checked their weight on the Electronic. All three were dead-on.
Now, looking at the Blue Dot load; I'm beginning to think that rounds three and four suffered setback as they showed the same lower velocities that the HP-38 load did.
Now, popular thought in both Reloading and Gunsmithing circles dictates that setback dangerously increases pressure. This was the main thrust in trying the HP-38 load, I was actually trying to increase pressure with the same charge by seating the bullets deeper and thus, increase velocity. what I found, as you read, was just the opposite effect.
As for JHPs versus FMJs, velocity-wise, the case,powder,primer and barrel don't care what the nose looks like, it's a 230 grain load. So, this doesn't enter into the equation.
So, the question is; Why did I see less pressure with these loads rather than higher pressure?