.357 oal

[Battis]

Here's a very basic reloading question (I've searched and read and found differing info).
I loaded some .357 mag rounds for my Ruger Speed Six using 4.7gr Titetgroup (suggested load: 4.5grs - 5grs) and cast 158 gr RNFP bullets. The cartridge OAL is approx. 1.56" - 1.57".
Does the pressure increase a lot from an OAL of 1.59" to the 1.56" that I used?
The reason I ask is because I'm seating the bullet to the crimp groove which seats it further than the depth listed. When I searched that question different opinions show up - some say seat to the suggested depth, some say they never worry about OAL. I'm not too concerned about accuracy, just safety.

[slughammer]

The depth does matter and the bullet profile also matters. Both affect the case capacity. (With so many available designs the distance from the crimp groove to the base).

Pressure changes quickly using faster powders. So even if you were using exactly the same components as the data, always start low and work up. You are tailoring loads for your gun.

Become more concerned with accuracy....

[BCRider]

The change in pressure in such a case is related to the percentage of volume change. And 5 gns of Tightgroup in a .357 casing leaves LOTS of open room. S

Ooops, the rest of my original reply was based on a .003 difference... :D

The .030 difference you posted would show up for sure. But likely not at your shoulder with a big change. Instead if you shot over a chrono the decrease in volume along with the extra neck tension from the deeper seating would show up as an increase in muzzle velocity. Likely not a huge change but enough that you'll notice it right away. But in terms of damage to the gun? Nope, it won't even notice anything

[GP100man]

I agree with BCRider , you`ll have to have a chrono to see it.

The speed six is as strong a 357 as they come & the load ya speakin of should run in the mid to upper 20k pressure wise, if memory serves rite. Titegroup can & will get very "spiky" when the pressure gets up on it in the 357, I found this threshold (& no I`m not putting it in print)by increasing powder .1gr until I had an unexplained/illogical jump in fps at this point cases weren't stuck but wouldn't fall out either. I done this with a GP100 & after firing 15 times on the same brass(5 cases) the average case head expansion was just .0003" ,but just too many variables to guess at pressures , variables such as brass hardness, chamber differences ,internal volume of each case ,boolit variables

I promise you if a straight walled cartridge is over pressured it`ll be stiky extracting.

[Battis]

I'd been loading DEWC and SWC but decided to try the RNFP (gotta think about those letters before I type them). I kept the powder in the mid-level range but then I started thinking about the seating depth after they were loaded. Crimping below the groove didn't make sense - that's too nice a groove to waste. I'm also going to use those bullets in my .38 Colt Official Police but I'll load the minimum charge (Bullseye) for that older revolver.
Thanks for the replies. I had visions/nightmares of pulling those 100 or so bullets.

[gray wolf]

Does the pressure increase a lot from an OAL of 1.59" to the 1.56" that I used?

I may stand corrected here, but, I believe the 1.590 is a sort of standard for max OAL in a 357 so the bullet does not stick out the cylinder and lock up the pistol.

Using a RNFP and crimping in the crimp groove will most likely give a shorter OAL cause the tip of the bullet is gone do to the flat point shape.

Many times if you look at a bullet that is crimped in the crimp groove and still measures an OAL of 1.590 it's because the front band and the tip of the bullet presents a longer profile.

Most 357 bullets are made so that even with a shorter OAL the same amount of bullet is in the case. try putting some bullets of a different shape next to each other and compare the distance from the crimp groove to the base. seating deeper in that instance such as crimping over the front band will reduce case capacity and increase pressure.

It's the reduction of case capacity not necessarily the shape of the bullet.

A full WC that seats flush with the case is a different story and most times the load info is taking into account the reduced case capacity.

[Battis]

Flat point, shorter bullet, still an equal amount of bullet in the case...that's the point that was nagging at the back of my brain. Thanks for bringing it out. This was my DUH moment.

[BCRider]

By the way, if you had the same variation in OAL in a 9mm the results would be far more dramatic. While testing for OAL vs muzzle velocity in my IPSC loading I found that with even a .010 change in OAL I was seeing a 50 to 60 FPS change. I tested for loading in my CZ over a three step OAL variation of .010 steps and saw the velocity change by just shy of 100 fps from the shortest to the longest. And that's a heap.

Because I was aiming for a low 130 PF I didn't need to fret over finding the pressure trip point mentioned by GP100man. But you can see that it was producing a very noticeable change in pressure by the variation in speed just from that total of .030 change in seating depth.

Another fellow I know actually blew up a 1911 due to bullet setback. At least that's what he figures it was. He figures from examining some remaining ammo that the crimp wasn't setting hard enough and the neck tension wasn't enough. So as he was shooting the rounds still in the magazine were being set back by the recoil. So the last couple of rounds, which he apparently shot in rapid fire, increased in pressure and before he knew it the gun broke the slide and barrel and shot the magazine out the bottom hard enough to partially bury in the ground. His hands were badly bruised but he never had any broken bones. We call him "Lucky" now.... :D

After hearing that story I checked my own .45acp loads and there's about 300 set aside with a note to re-crimp them.... :oops:

[gray wolf]

BCRider
Interesting story but not sure if it totally applies to the OP's question.
I suspect the problems you spoke of may be caused by a different set of circumstances.
I have always been under the impression that under recoil a bullet moves ahead of the case mouth and not to the rear, ( action RE-action ) However if an insufficient crimp is used the bullet may be ( could be moved forward ) and then be pushed back when it
it's entering the chamber because the proper seating dept has been disturbed. If it's set back enough, yes the pressure will rise.

Also seating a round deeper than the recommended length for a specific bullet can raise pressure. But with different bullets if the bearing surface remains the same and the amount of bullet inside the case remains the same I don't think a problem will arise.

There is a big difference in seating deeper as apposed to having a shorter OAL because the bullet nose profile is different.

[slughammer]

".................................................. ....After hearing that story I checked my own .45acp loads and there's about 300 set aside with a note to re-crimp them.... :oops:
The taper crimp that a 45acp die applies only does a little to hold the boolit. Case tension from sizing and more precisely the tension remaining after the expander has been used is what holds the boolit. (If your expander is too big in dia you will loose tension).

When setting up new handgun dies I use the edge of my bench and push a loaded round against it to see if I'm getting enough case tension to prevent setback. If I'm getting enough to keep from pushing it in, I'm getting enough for good ignition.