.357 Magnum COL

[Real Gun]

I did my first .357 magnum last evening and found that to get a good alignment with the cannelure of 125 gr XTP HP and using an average case trim length of 1.280 (didn't case trim) I was getting a COL of 1.690 instead of the book's 1.590. After crimping, the cannelure is barely detectable under magnification, so I believe the bullet is fully inserted to its intended alignment with the case mouth.

Am I okay here? I appreciate that the pressure may be low, but they dropped easily enough in my cylinder and compared pretty directly with purchased ammo COL.

On another note, I sorted out nickel plated cases that were way shorter than the 1.280 case trim length of brass. These apparently are the 1.240 trim length cases mentioned for use with 140 gr FTX bullets. So I'm just sayin' to watch out for those nickel plated jobbies. Might want to set those aside.

[Nathan]

That is very strange. I don't think my gun could fit this bullet at 1.690". Mine is a S&W. what is yours?

[Jim Watson]

Strange. Some .357s would not accept a round at 1.69".
If yours will, they will shoot OK.

But I do not know why Hornady would locate the cannelure there.
Most true revolver bullets with crimp grooves or cannelures load to standard OAL or shorter.

[Real Gun]

I would have to suggest that others measure some bought ammo, because the ones I checked were more than 1.590.

[Unclenick]

The reason the SAAMI limit exists is to ensure proper fit and feeding. I can't imagine any ammunition manufacturer wanting his product to be incompatible with lever rifles and self-loading pistols chambered for the round, so they can be expected to stay within the SAAMI limit. So I'm suspecting you have a measuring problem of some kind.

One thing you can do independently is calculate COL and see if your measurement matches.

COL = Case Length + Bullet Length - Seating Depth

I called Hornady, and their tech, Seth, said the HP XTP is nominally 0.550" long (bullets can vary several thousandths in length in manufacturing, but it won't exceed 0.560") and the cannelure starts 0.280" back from the nominal length nose, making seating depth a maximum of 0.270" just as the forward edge of the cannelure disappears. So that's maximum seating depth. If you allow the case mouth to be about a hundredth of an inch below the top edge of the cannelure, that makes seating depth 0.260". So, from the formula and your measured case length, which was reasonable, you have:

COL = 1.280" + 0.550" -0.260" = 1.570"

If your bullets were on the long side it would come out at about 1.580". That means that with a 1.290" long case it would be 1.590" exactly, when using a bullet on the long side.

So, that seems to verify that something's going wrong when you're measuring COL. I just don't know what it is without being there. See if you can borrow a second caliper.

[Real Gun]

Correct on the conclusion that there must be a measuring problem. Well done. I do usually know how to read calipers, and mine are good ones, but I mistook 1.569 for 1.69. We're good.

p.s. the load is 14.5 gr A2400, 125 gr XTP, SPP

[Unclenick]

Cool. I've done the mental decimal slip and slide dance more than once myself. So, my 1.570" calculation wasn't too far off then?

Alliant lists a load of 17.5 grains of 2400 with a 125 grain Speer Gold Dot as their closest equivalent bullet. Their load has 1.580" COL and uses a CCI 500 primer, which is a standard primer and not a magnum primer. Magnum primers are not required with 2400, as it ignites more readily than the spherical magnum powders do. Alliant does warn about pressure differences caused by different brands of primers, but at -17% from their listing (their listings should be treated as maximum in the absence of other reliable load data to the contrary), you are very close to Accurate's general recommendation that, except where instructed to the contrary (H110/296, for example) pistol and revolver loads be started 15% below maximum for load workup. So you should be at a very safe level for a starting load, regardless of primer make, case make, and bullet make differences, and lot of powder. The difference in COL is too small a percentage of the powder space in this case to be an issue. Just work your load up in 2% steps while watching for pressure signs, and you will be safe.

[Real Gun]

UncleNick - Alliant lists a load of 17.5 grains of 2400 with a 125 grain Speer Gold Dot as their closest equivalent bullet. Their load has 1.580" COL and uses a CCI 500 primer, which is a standard primer and not a magnum primer. Magnum primers are not required with 2400, as it ignites more readily than the spherical magnum powders do. Alliant does warn about pressure differences caused by different brands of primers, but at -17% from their listing (their listings should be treated as maximum in the absence of other reliable load data to the contrary), you are very close to Accurate's general recommendation that, except where instructed to the contrary (H110/296, for example) pistol and revolver loads be started 15% below maximum for load workup. So you should be at a very safe level for a starting load, regardless of primer make, case make, and bullet make differences, and lot of powder. The difference in COL is too small a percentage of the powder space in this case to be an issue. Just work your load up in 2% steps while watching for pressure signs, and you will be safe.

I use Hornady bullets and the Hornady manual. For the 125 gr HP XTP and 2400 powder they show a range of 13.9-16.9 grains. Using a Lee case activated powder measure, the closest I could come using the set of apertures was 14.5 while aiming for the 1300 fps, second step load of 14.9. I am using the Lee .109 aperture.

My manual is the latest one (9th edition).

After redoing the setup on the insertion and crimp, I now get a COL of 1.585 and see about as much of the crimp groove peeking out as you show in the recommendation picture. I will shoot a few sample rounds and then crank out a batch.

I just bought a chronograph, although I am not sure where I can use it. I want to properly rate these loads.

I also have IMR 4227, Win296, H110, and Power Pro 300-MP, along with the magnum primers for those. I have other powders, but loads for them are not listed by Hornady for that bullet. I can also consider using my Power Pistol on the box of 110 gr HP XTP.

[Slamfire]

It is my opinion that you do not have to worry about OAL if:

Your length is longer than reloading book recommendations and you are not exceeding maximum powder charges.

This is because longer reduces pressures. Shorter raises pressures. Shorter is bad if you don't cut your loads.

The ammunition chambers in your revolver.

[Unclenick]

Real Gun,

That kind of difference in load data maximum recommendations isn't uncommon. They don't use the same brands of cases or primers, which alone can account for the difference before the bullet even gets involved. In either case, though, reducing the maximum given by 15% creates the necessary overlap of the data to prevent a problem. So you are good to go.

[wogpotter]

I just loaded up a lot of XTP 125 grainers, let me check the dimensioning independantly & see what I get.

The brass case measures 1.2888"
The bullet overall length is 0.534"
The cannnelure is 0.217" up from the bullet base.
The width (front to rear) of the cannelure crimp is 0.046"

seating to 1/2 way up the cannelure groove I get a measured overall length for a loaded round of 1.591"

'Course that was a digital caliper & so harder to mis read than a dial type

[rclark]

As long as the bullet had a crimp groove, I never (and still don't) worry about COL. That is what it is there for to begin with . Only time I check COL with a calibers is loading .45 ACP. In fact up until just a couple years ago, I never even owned a calibers. Loading the straight wall revolver cases, I never bothered. Crimp into the crimp grove and your golden.

[Unclenick]

Rclark,

You just have to be sure the bullet was designed for the cartridge you are loading. This can get you in trouble in some instances. The most common one is the .44 Mag and .44 Special, which both have almost the same maximum COL, but different case lengths, with the .44 Magnum case being 0.12" longer. That's the reason you see two cannelures on some .429 bullets. One for each case length to produce the same COL. Ruger cylinders, at 1.75" long, will allow you to use a .44 Special bullet in the longer .44 Mag case, which produces a 1.725" long cartridge, exceeding the 1.610" SAAMI COL for the .44 Magnum, but allowing more powder space for higher performance. The S&W m. 29 cylinders are too short to allow that, IIRC.

[mikld]

Rule of thumb for revolvers; seat to cannalure or crimp groove and if it fits cylinder (length), disregard OAL measurements/dimensions. Most OAL dimensions quoted in reloading manuals is what the techs measured during testing, and not necessarily a "loading/design tolerance". I only know of one bullet that poses a problem in revolvers; that is a cast lead bullet for the .357 Magnum/38 Special and it has two crimp grooves and if the lower crimp groove is used it may be too long for some cylinders.

K.I.S.S.

[Unclenick]

Mikld,

That's for the same reason I just described in .44 Magnum/Special with two-crimp-groove bullets, except in .36 caliber. The groove nearer the bullet base is for the shorter .38 Special case, while the one nearer the nose is for the .357 Magnum.

[mikld]

Yessir!