Varying OAL

[Nick_C_S]

Okay, here's a curious phenomenon. Maybe someone will have an answer.

Last night, I loaded 20 each of three different DEWC's for 38 Special. Not that it matters, but I used 3.3g of AA2 in all of the loads - so definitely not a compressed load - not even close. They're low power target rounds.

Missouri Bullet Co "PPC 2" BHN-10 148g Lead DEWC.
SNS Casting 148g Coated DEWC.
Rainier 148g Plated DEWC.

The press is a single-stage RCBS "Reloader Special 2" from 1984 and seems to be in excellent condition (I bought it new 30 years ago).

My RCBS taper crimp die is set for an OAL of 1.238" with the MoBuCo 148's. I seat and crimp in one step with these.

But when I load the SNS casting bullet, the OAL increases to 1.244." And when I load the Rainer's, the OAL increases to 1.250"

Mind you, the die was locked down and never moved between loadings. I did one batch right after the other. This isn't the first time I've notice this phenomenon. It's just the first time I've taken and recorded the OAL's for this post. It seems to me that the OAL is nothing more than the distance from the shell holder to the seat punch in the die - when the ram is all the way up, that dimension doesn't change. So how does the OAL change between different DEWC's??

BTW, I don't sweat this at all. That particular die is locked down and dedicated for loading 38 DEWC's only. I never use it for anything else - I just screw it into the press, and go. And I'm going to continue loading as I do with it. The ammo it produces is great, in spite of this anomaly. I just find this curious and want to see if anyone has an answer.

[MarkGlazer]

Take your caliper and measure your cases and your rounds. I have found inconsistencies in both.

Don't worry about being precise with your OAL. Work within an acceptable, safe range. Based upon the published Data, as long as your OAL range is within Min and Max, the powder weight is properly matched with the bullet weight, and of course the round fits the chamber, you're good to go.

Good luck.

[g.willikers]

No doubt you've checked, but,
Maybe the bullets from the different makers vary in length a little,
Like due to slight variances in the lube or crimp groove widths.
Or slightly different shape tops - maybe some are domed a little more.

[Don P]

As the previous post states, different bullet makers, different length, even varying weights by a couple of grains. Good rule of thumb to follow is every time you use a different manufactures bullet make at least one dummy round to confirm OAL and adjust as necessary.

[Unclenick]

If the OAL increases between seating and crimping, the crimp is likely distorting the bullet to make it longer. That's most likely with the Ranier as it has smooth sides and no crimp groove. In the case of a lubricated bullet, I've seen air compressed in the case during seating slowly push it up before it gets to the crimp die.

The first thing I would try is backing the crimp off until it just returns the case to straight sides and see if the COL's are still changing, then tweak it to the minimum crimp that does the job for you. With .38 WC target loads, that usually isn't much. You may find, in the end, that you don't actually want the exact same setting for your different bullet makes.

[Nick_C_S]

Thanks Unclenick. I'm fairly new to taper crimping revolver cartridges. My crimp setting may be a bit . . . assertive. (BTW, I'm seating and crimping in one operation).

I'm going to go "back to zero," so to speak, with the crimp adjustment and start over. OAL aside, I think I have it over-crimping.

I rather doubt it has anything to do with brass length for bullet length, or bullet shape (they are all flat tops). OAL is a function of the seater punch setting and the distance between it and the shell holder. Brass or bullet length should have no bearing on it.

[dickttx]

A slight change in the bullet nose would make it hit the seater plug in a slightly different place.

[Nick_C_S]

The bullet tops are completely flat; and so is the seater plug. The cavity at the end of the plug where the bullet meets it is filled in with epoxy - it's nearly perfectly flat - just like the bullet. It's flat against flat.

I think one thing that's going on is that the equipment is kind of old and there's probably a little "play." After all, we're only talking 12 thousandths. And to reiterate, this is all mostly an exercise in curiosity. The bullets shoot fine.

[Unclenick]

The bullet shape might be an issue if a crimp groove were present. I don't think I've ever examined one of the .38 seater dies with a taper crimp rather than a roll crimp built in, so I just assumed you were crimping separately for a taper crimp. Since you are not, the tight squeeze seems like it would have to be responsible for all observed effects.

BTW, target loads for wadcutters recoil so lightly, unless you run them in an Airweight snubby revolver you won't see bullets back out under recoil with even a light taper crimp. You may find you can get away with very little, and that gives you the least bullet distortion and the longest case life. Experiment. With those light loads you may find that when the bullet is copper plated and not lubed you need no crimp at all.

[Nick_C_S]

Thanks again Unclenick.

Yes, I'm going to re-approach my crimp process from square-one. You're right: very little crimp is needed. There's so much bullet being held inside the case, they're not going anywhere during recoil (lead, coated, or plated).

The crimp basically just needs to remove the flair.

Newbies take note: Here's a loader of 30 years, learning something new.