[CaptMarine]

First Shot 38 spl. Starline Brass in S&W 357 Mag 686. SAAMI spec. = 1.155 - .020 (range 1.135-1.155). Now reload manuals state trim length to be 1.145" for loads listed. My brass barely meets the minimum SAAMI spec. Question is: what would be a safe thing to do with respect to trimming this brass? Select my shortest case and trim to that length or select a case length that falls somewhere else. Shorter the case length to me would increase pressures especially once a crimp is applied. I don't want to have to keep adjusting dies to get my crimp in the cannelure of the bullet.

 

[mrerick]

The .357 magnum headspaces on the rim, not the mouth of the cartridge.

Leave the cases alone. Just load the cartridge to the correct OAL. The OAL determines the volume within the case (along with the case's thickness, including it's base).

Don't over crimp.

The cases are within spec.

 

[Forester]

I don’t think I’ve ever trimmed handgun brass.

 

[Abby'sDad]

I have never trimmed any handgun brass, there's no need to constantly adjust the seating die for that tiny difference.

 

[jonesy814]

I also have never trimmed or messed with OAL of handgun brass. Just load and shoot until the brass fails

 

[series guy]

What jonesy said.

 

[mrerick]

The OAL of brass that headspaces on the mouth of the case is important. Typically 9mm, .40S&W and .45ACP. The length of these cases is important.

Revolver brass headspaces on the rear rim at the head of the cartridge, so the case length is less an issue.

 

[Engineer1911]

When you have to "pound" too long brass out of a cylinder, you will trim your straight walled revolver cases.

 

[DocWyatt]

Okay, I'll admit that I've trimmed handgun brass and basically to get a more consistent crimp. I don't try to over do my expectations, satisfied at +/- 0.010 or better at +/- 0.005. I also usually only do this once when I first buy new brass, after that I don't worry about it. I think it results in a smaller standard deviation when checking velocities over a chronograph. Not that it has improved my shooting that much as far as I can tell, as I'm just an ordinary shooter, plinking at cans and shooting at paper at my home range.

 

[SidecarFlip]

I don’t think I’ve ever trimmed handgun brass.

Neither have I, ever. Straightwall cases by design and use don't 'grow' unlike a bottleneck case. Bottleneck cases by design and use do grow, but some more than others. 'Growth' depends on various factors like tightness of chambering and the angle of the shoulder.

When you fire a bottleneck case, the internal pressures cause the brass to 'flow' (for lack of a better word) from the shoulder into the neck and that equates to case growth (OAL). Consequently, some calibers of bottleneck cases do require trimming to length, but again not all. Some calibers actually recede in OAL.

None of that applies to a straightwall case.

On a straightwall case, the necks will crack and the primer pockets will get sloppy, long before anything else happens. Why I anneal the case mouths on my heavy crimp calibers like the 460 and 44 Rm cases.

Heavy crimps workharden the case mouths and workhardened case mouths are prone to cracking.

If I purchase once fired or more than once fired brass (and I do but have not lately), first thing I do is run them in STS wet media, inspect the case mouths for cracks (and discard any suspect cases) and then take the rest and anneal the case mouths. Just the case ends to about 1/8" back and no more.

 

[SidecarFlip]

When you have to "pound" too long brass out of a cylinder, you will trim your straight walled revolver cases.

Tight straightwall cases as it pertains to ejection, has nothing to do with OAL and everything to do with case expansion under pressure and tight or dirty chambers (as in buildup). Time to clean your cylinder bores and/or discard weakened cases. Actually had that issue with my 460 and I took some Clover fine lapping compound and a bore mop and lapped the cylinder bores a tad. It also has to do with workhardened case mouths, where the case mouth is unable to 'relax' because the hard brass cannot relax after ignition, so it 'sticks'.

Not all cylinder bores are created dimensionally perfect. They are all produced with a tolerance in mind so if they are on the negative side and the brass is tight to begin with (because the the brass, like the bores) are made to a tolerance, they may be tight (or loose) depending on which side of the go-no-go tolerance they were swaged at.

 

[Engineer1911]

Well Flip, this time you are wrong. The stuck cases were 0.030" to 0.040" too long when they came out of the cylinder. When I loaded the rounds, I thought the roll crimp looked excessive. Your dissertation on cleanliness is much appreciated.