Resizing .357mag, not enough tension.

[Tommy Gun]

Hey folks,

The last two batches of .357 from Diamond K have had a few cases not resizing like the rest. Hornady Nickle Plated was first batch and a few randoms in the second batch. Basically not enough tension to hold the bullet 100% and it's got me concerned. I'm looking to buy an undersized die, as I think that will fix it but anyone else expierence this?

Using RMR 158gr .357 flat noses. No Cannelure. Shoukd have checked with my XTPs I have but didn't.

[SoCalRayJr]

Are you buying reloaded ammo or are you reloading this yourself?
If you're reloading sounds like you need to add a taper crimp to your round

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[Tommy Gun]

Reloading myself. I full size and bell the mouth then run a roll crimp. If it had a cannelure I'm sure would alleviate this issue but the RMRs are smooth bodied.

[SoCalRayJr]

You have pm

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[sofbak]

For a rimmed cartridge, roll-crimp is definitely the proper method.
If you're not getting sufficient "bite" in the bullet, you may have either some thin-wall cases or slightly short cases.
For roll crimp, a thousandth or two reduction in either of these case dimensions will affect the depth of the crimp into the bullet OD.
If you can, adjust your crimp die down just a little and check result.
You didn't indicate if the bullets are lead, plated lead, or fmj. For plated, you have to finely adjust the crimp die to bite deep enough to hold, but not so deep you bite through the plating.

[Tommy Gun]

It's only a few cases I've ran into this problem. I use FMJ cause I only load full power .357. The projectiles do not have a canelure, but most of the cases crimp fine on the smooth body of the bullet. I'll just toss em as it's not worth it to take a chance.

[pacrat]

It's only a few cases I've ran into this problem. I use FMJ cause I only load full power .357. The projectiles do not have a canelure, but most of the cases crimp fine on the smooth body of the bullet. I'll just toss em as it's not worth it to take a chance.

"sofbak" is correct. You should follow his suggestion.

A cannelure is not required for using a "roll crimp". It is more effective with a cannelure. Because the case lip easily folds into the groove.

Adjust down a little at a time. until the lip just bites into the bullet.

In full power Mag revolver loads, I suggest you roll crimp ALL ammo. If not, sooner or later you will have a bullet walk out of the case during recoil and "lock up" your cylinder. Especially with 'nickle" plated cases. In my experience nickle cases are a bit thinner than brass, and Nickle is a VERY HARD SLICK metal.

A taper crimp would be useless in your application.

[sofbak]

^^^And to add to pacrat's suggestion, if OP is feeding these rounds thru a tube-mag lever gun, bullet seating below minimum OAL is also a problematic possibility.

[tabascoz28]

I make my own ammo too but when I bought some once I noticed that the factory crimps the hell out of the 357 ammo. I asked the clerk at the range and he said that they do this to cover their bases. I've also noticed that on my LCR357, if I don't crimp like hell then I get bullet extension.

[Paseclipse]

I'm looking to buy an undersized die, as I think that will fix it but anyone else expierence this?

Lee has an undersized die for 38/357- https://www.midwayusa.com/product/1012827841?pid=687452

[ysr_racer]

Lee has an undersized die for 38/357- https://www.midwayusa.com/product/1012827841?pid=687452

I use a U die in 9mm. It's just what I needed.

[Tommy Gun]

Lee has an undersized die for 38/357- https://www.midwayusa.com/product/1012827841?pid=687452

Just purchased the Die. Also grabbed a Kinetic Bullet Puller. 99.9% of the cases had resized just fine and had sufficient tension on the smooth body bullet before the roll crimp and solid after. Just a few were not working. Ill test the USize die on the special cases and see if it fixes it.

And no thanks on increasing my roll crimp just for 10 rounds. The roll crimp is perfect for Cannelure projectiles I have like the XTPs, etc. And like I said above it perfect for 99.9% of the recently bought cases from Diamond K. Bought 500 like 3 years ago and only the 10 cases of the 400 cases bought over the last 2 months were an issue.

[pacrat]

Just purchased the Die. Also grabbed a Kinetic Bullet Puller. 99.9% of the cases had resized just fine and had sufficient tension on the smooth body bullet before the roll crimp and solid after. Just a few were not working. Ill test the USize die on the special cases and see if it fixes it.

And no thanks on increasing my roll crimp just for 10 rounds. The roll crimp is perfect for Cannelure projectiles I have like the XTPs, etc. And like I said above it perfect for 99.9% of the recently bought cases from Diamond K. Bought 500 like 3 years ago and only the 10 cases of the 400 cases bought over the last 2 months were an issue.

If just for 10 cases. I would crap can them. It doesn't make a lot of sense to spend $30+shipping for that few. That's $3+dollars per case just to size them.

Another metallurgical issue with nickel plated cases being thinner and harder. Also makes them "springier" for lack of a more concise term.

Have you measured your "expander"? And the ID of cases before seating the bullet? Compared to the OD of your bullets?

Since the issue is just a few cases. Another remedy with no cash outlay at all. Would be to take those 10 and only load cannelured bullets in them.

Your case neck after expanding. Should measure .002" LESS than your bullet dia. If it was a larger volume of problem cases, I would suggest just dressing down the expander a few thou.

[Beelzy]

Too much roll crimp can loosen the neck tension. Had it happen with some heavy 44 magnum loads.