Crimp/Case Length Trial

I'm talking about .38 Special

Ever get a shot off during a slow fire target, and the recoil felt lighter than it should have? Then check your spotter and its an 8 or worse, a 7 in the five to seven o'clock range? 

Why would a cartridge recoil lighter than it should? First off, and very likely, the powder drop didn't drop the right amount of powder into the cartridge casing during the loading process. Second, inconsistent case length will give you an inconsistent crimp, which in turn causes inconsistent pressure, which translates to inconsistent velocity. 

How much will these two issues effect the end result? I know a wrong powder charge will cause anything from a squib load, up to a dangerously over charged cartridge. But what about crimp? How drastic will crimp effect the area of impact? 

I have a batch of once fired brass. I sized and de-primed 20 of them. Then I measured them and 14 of those measured between 1.1450" to 1.1480". I thought 0.003'' isn't much of a variation for 50 yard work. I loaded 50 casings that met these measurements. I'll use them for slow fire targets only. I'm probably going to chronograph at least twenty of those as well so I can see what range of velocities I get. I'll be watching for light recoiling rounds. 

I'm not going to say "stay tuned" because I have no idea when I'll get this done since work is getting busy right now. But today I felt like a simple reloading project and this is what I came up with. Maybe end of March or beginning of April I'll get this done.

Also, check powder position before each shot, I’d think down then up to level for consistency.
Or, use TrailBoss

james r chapman wrote:Also, check powder position before each shot, I’d think down then up to level for consistency.
Or, use TrailBoss

Change powders!? Come on now James, that’s a whole new rabbit hole to explore..

There’s an easier(?) way.  

https://m.youtube.com/watch?v=NzrAgRjYHps

Jason,

Do not overlook first part of Jim's suggestion regardless of what powder you are going to use.  With very low powder charge volume relative to case volume, distribution of powder within case play into relative accuracy.  I.e. I'd recommend raising gun to as close to vertical axial as possible and then slowly lowering it down to firing position without impacts when using RR.  With your level of hold and shot process, especially at SF, you can mimic same technique.

AP

Wobbley wrote:There’s an easier(?) way.  

https://m.youtube.com/watch?v=NzrAgRjYHps

That was cool to watch. Thank you very much. Now I have some other ideas I want to try in the future!

What flavor crimp will you be trying roll or taper?

chiz1180 wrote:What flavor crimp will you be trying roll or taper?

I use the Lee bullet seating die and crimp simultaneously. I think it produces a roll crimp. My curiosity comes from wanting to toy with uniform brass length to get a more consistent crimp. My normal process doesn’t include measuring my .38 Special brass and sorting it or trimming it. So I’m trying to see if an extra step might make things a little better.

PhotoEscape wrote:Jason,

Do not overlook first part of Jim's suggestion regardless of what powder you are going to use.  With very low powder charge volume relative to case volume, distribution of powder within case play into relative accuracy.  I.e. I'd recommend raising gun to as close to vertical axial as possible and then slowly lowering it down to firing position without impacts when using RR.  With your level of hold and shot process, especially at SF, you can mimic same technique.

AP

Long time ago I chronographed 38 spcl loads.  All the same loading except when fired, I tipped forward, back, and no tip.  The results were very different.  I forget the numbers but no tip was between the forward and back tipped shots
I think the powder was 231

I’m surprised you don’t crimp separately.

Tim:H11 wrote:

chiz1180 wrote:What flavor crimp will you be trying roll or taper?

I use the Lee bullet seating die and crimp simultaneously. I think it produces a roll crimp. My curiosity comes from wanting to toy with uniform brass length to get a more consistent crimp. My normal process doesn’t include measuring my .38 Special brass and sorting it or trimming it. So I’m trying to see if an extra step might make things a little better.

The 9mm LFCD produces a taper crimp.  Don't know about .45.
Dave

james r chapman wrote:I’m surprised you don’t crimp separately.

My habits come from when I was using a three hole turret press. When I got my four stage progressive press I just didn’t bother setting up a crimp die to try to replicate what I already had. “If it ain’t broke, don’t fix it” sort of thing. Just being lazy too lol

Tim:H11 wrote:

james r chapman wrote:I’m surprised you don’t crimp separately.

My habits come from when I was using a three hole turret press. When I got my four stage progressive press I just didn’t bother setting up a crimp die to try to replicate what I already had. “If it ain’t broke, don’t fix it” sort of thing. Just being lazy too lol

If you ever want to test crimping separately, shoot me a PM, I have a few 38 crimp dies on the shelf I could send for the cause.

If it was me, I’d look at velocity standard deviation.  In my testing, 2.7 BE, 3.0 452AA, and 2.9 RedDot gave SDs below 10.  They also gave best accuracy with BE and 452AA being overall best.  I haven’t tested WST yet, but I expect it to be similar to 452AA but the charge may be different.

I have a load that groups good. I’m just trying to figure out where the abnormal light load comes from. Because my standard practices don’t include case measuring or trimming, I thought I’d investigate that. That’s what this whole thing is about.