reloading 380 - seating depth pressure change question

[Timmis2]

I am using Hodgdon published load data as a reference to reload 100 grain projectiles for 380. I am using the same powder (CFE Pistol) and the same grain projectiles (100 grain) as published, but will not be using the same brand projectile as in the data, and the projectiles will not be the exact same profile such as hollow bottom vs flat, or shape of the nose or ogive. Most reloaders will just say that you can use different projectiles as long as they are the same grain, and just start from the lower end of the published powder charge for the same grain projectile and work up when testing in your pistol.

One set of projectiles I have has a projectile length of 0.470", and another set I have has a projectile length of 0.519"...a difference of 0.049". The longer projectile has a pointier shape ogive which causes it to be 0.049" longer. They are both the same grain and diameter.

The projectile used in the published load data is a 100 grain Hornady FMJ round nose flat bottom. I cannot find how long this projectile is to compare it to the two projectiles I want to use. The published load data does not say the COL used.

If both of these projectiles are reloaded to a COL of 0.960", the longer projectile will be seated 0.049" deeper and thus causing potentially higher pressure from less internal case volume space.

Can anyone speculate what the difference in pressure may be between the longer projectile and the shorter projectile when both are loaded with the same powder charge and COL? is a difference of 0.049" seating depth a big variable? I do not have a chronograph yet, and I will inspect the cases for signs of overpressure with the starting load before working up.

 

[tommeboy]

If you have a newer 380 don't worry about it. The gun could be had with a 9mm chamber on a lot of newer 380s. So if it is available in 9mm also load whatever you want. Most all the 380 I have loaded is even at a max load are pretty weak. And way under the listed speeds even though my 380 has a longer barrel than all the tested loads use.

 

[Timmis2]

If you have a newer 380 don't worry about it. The gun could be had with a 9mm chamber on a lot of newer 380s. So if it is available in 9mm also load whatever you want. Most all the 380 I have loaded is even at a max load are pretty weak. And way under the listed speeds even though my 380 has a longer barrel than all the tested loads use.

I have a sig p238 and SW bodyguard 2.0 The Hornady published load data i'm using uses a 100 grain projectile sold as 9mm since the 9mm projectile diameter is compatible with 380 in lighter grains (typically 115 grains or less). Hodgdon also publishes 115 grain 9mm projectiles loaded for 380 with different powders which leads one to believe there is some allowance for deeper seating depths for different COL's

 

[GotRDid]

If your disparate length bullets are segregated into separate lots, simply load up the shorter bullets, then adjust your propellant charge down by .1 grains and load the slightly longer bullets. I can’t imagine such a small loss of combustion volume under the bullet would cause a significant “spike” in pressures, but applaud you for not only asking for assistance, but recognizing a potential issue.
Please keep us posted.

 

[Timmis2]

If your disparate length bullets are segregated into separate lots, simply load up the shorter bullets, then adjust your propellant charge down by .1 grains and load the slightly longer bullets. I can’t imagine such a small loss of combustion volume under the bullet would cause a significant “spike” in pressures, but applaud you for not only asking for assistance, but recognizing a potential issue.
Please keep us posted.

That's what I was hoping someone might recommend or suggest. Charge down .1 grains with the longer projectile to compensate for the potential pressure difference if you're attempting to achieve similar pressures as the shorter projectile. I will give that a go while still starting from the published starting load. An equation or calculation for reduced powder charge percentage for reduced internal case volume does not exist as far as I know. QuickLoad Ballistic Software may have some tool like that but I don't have it.

 

[bozo699]

I have a sig p238 and SW bodyguard 2.0 The Hornady published load data i'm using uses a 100 grain projectile sold as 9mm since the 9mm projectile diameter is compatible with 380 in lighter grains (typically 115 grains or less). Hodgdon also publishes 115 grain 9mm projectiles loaded for 380 with different powders which leads one to believe there is some allowance for deeper seating depths for different COL's

Sir,
How do you like your bodyguard? I just bought one but I live in s antiAmerican state and can’t have it for 10 days
Wayne

 

[Timmis2]

Sir,
How do you like your bodyguard? I just bought one but I live in s antiAmerican state and can’t have it for 10 days
Wayne

Haven't shot it yet. Just been doing drawing from concealed, dry fire drills, and reloading with published data I've tested on my Sig p238 (3.9 grains CFE Pistol, 100 grain Berry's RN and HHP). I'm buying a chronograph this week. Unintuitive to reload without one. I wish ballistic gel was cheaper! I just joined a fish and game club a few days ago and have access to a range now. I have large hands and it seems to be an okay fit with the 10 round mag. 12 would be better but I live in a 10 round and under state. YouTube reviews are all favorable. I'm sure you'll like it too

 

[JSH]

Be aware all 380 brass is not equal. There is some funky foreign brass out there.
I picked up on a big bulk buy of indoor range 380, sorted by manufacturers helped a lot.

 

[Timmis2]

Be aware all 380 brass is not equal. There is some funky foreign brass out there.
I picked up on a big bulk buy of indoor range 380, sorted by manufacturers helped a lot.

yes i've noticed some cases seem softer or thinner than others and bulges when seating projectiles can occur if you aren't careful.

 

[bozo699]

I’ve never loaded any but bought 1000 cases from starline and a bunch of bullets of different makes and gonna get started soon I hope. 32H&R magnum as well also a first for me! Always said I would never go smaller than 9mm and 38 special
Wayne

 

[divingin]

The projectile used in the published load data is a 100 grain Hornady FMJ round nose flat bottom. I cannot find how long this projectile is to compare it to the two projectiles I want to use. The published load data does not say the COL used.

If both of these projectiles are reloaded to a COL of 0.960", the longer projectile will be seated 0.049" deeper and thus causing potentially higher pressure from less internal case volume space.

The other option (assuming you have enough length in the magazine) is to load the longer bullet to a longer COAL. Your limiting factor on pistol is likely going to be either mag length or feeding reliability rather than pressure (unless you're one of those "bigger-booms-are-better" guys.)

 

[Coyotefurharvester]

What brand is the other bullet? I'm sure data is available concerning finished length.

 

[243winxb]

JBM Bullet Length Chart

Load Data

sierrabullets.com

 

[Timmis2]

What brand is the other bullet? I'm sure data is available concerning finished length.

it's also a Berry's 100 grain .356 but it's a "9mm" projectile with a hollow base and longer, pointer nose

 

[Coyotefurharvester]

I think you can go as short as .970 over all length and not get a bulge. With the velocity limitations of plated bullets, seems like they are more fragile than jacketed bullets, start at the minimum for the Hornady bullet and watch the target (7-10') feet from muzzle for small debris marks. If you are seeing plating marks, either to much crimp, or velocity.

 

[243winxb]

Use Hodgdon starting load for both bullets. Use OAL that feeds & fits chambers.

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