neck tension and pressure

[Battis]

Lots of info out there on this subject, and differing opinions...
I found a way to increase neck pressure when loading WSL .351 rounds, and I was wondering if the tighter neck might make the pressure too high.
The rounds chambered and ejected perfectly when loaded my "old way", but there was never enough neck pressure to keep the bullet from spinning (by hand) in the case. The powder (IMR 4227 compressed slightly) held it from pushing in and the crimp kept it from moving out.
As a test, I ran some cases (357 Mag) into a 9mm crimp die before loading the bullet, which tightened the neck for the length of the bullet, then I expanded the case mouth slightly, then loaded the powder and bullet, and crimped with the .38 sp die. Seems to work great. Dummy rounds load and eject. I'll test the rounds Monday with a chronograph.
I don't know how these rounds compare to the original rounds as far as pressure.

[Tatume]

Neck tension on your cast bullet ammunition will not by itself cause undue pressure. Too much tension may slightly reduce the accuracy of your ammo, so you don't want to use so much tension that it reduces the diameter of your cast bullets.

That said, be certain that the charge of IMR 4227 that you are using is safe. Hodgdon does not list data for this cartridge on their web site, so I have no idea what is appropriate, and you don't say your charge weight anyway. IMR 4227 is used to load high pressure ammo, so you may want to reexamine your charges.

[Tatume]

Lead bullets can be cast from #2 alloy using Lyman mold #350319. These bullets weigh 171 grains with a .348 caliber gas check. According to the 45th Edition of the Lyman Reloading Handbook, IMR 4227 proved to be the best overall powder for the .351 WSL.

Using a 180 grain JSP bullet, Lyman data shows a starting load of 17.0 grains of IMR 4227 for a MV of 1400 fps. The maximum load is 19.5 grains of IMR 4227 for a MV of 1751 fps.

With a 171 grain cast lead bullet and IMR 4227 powder, the starting load is also 17.0 grains and the MV 1658 fps. The maximum load for that bullet is 19.5 grains for a MV of 1904 fps.

https://www.chuckhawks.com/351_WSL.htm

[Idz]

I think neck tension is overrated. A quick calculation will show you that at pressures around 1000 psi the yield strength of brass is exceeded and the case lets go of the bullet. The inertia of the bullet, engraving, and throat condition can have a bigger effect. All normal neck tension does is set the initial burn conditions which will tweak the final pressure a little bit. Most neck tension calculations I've seen are incorrect in that they only look at the stretching of the brass. The correct interface pressure calculation is a shaft in hub (bullet in case) which involves the Poisson ratio of the materials and gets quite complex since that requires knowing a lot more about the material structure than can be easily determined.

[Battis]

I use 17 grs IMR 4227, which is just enough to work that heavy bolt. I bought some loaded ammo online once, and pulled the bullets to measure the charge - it ranged from 17 grs to 21 grs, way too much of a difference for me.
Thinking back, I'm pretty sure I got the load data from the Chuck Hawks site. There's not much info out there besides Hawks on this cartridge.
I have 7 vintage rounds - maybe I'll use the chronograph on one.
Thanks for the tension info.

[onelight]

Neck tension is for more than controlling burn it also helps the cartridge stand up to handling and helps support the bullet from set back during feeding on repeaters and in tubular magazines . There is a reason for the recommendation of bullet being approximately .002 larger than the ID of the case it is being loaded in.
It sounds to me like you neck expander is to large or your bullets are to small.
Can you load bullets with 0 neck tension and shoot them ? Sure you can , even in a repeater but you give up part of the integrity of the cartridge and are totally dependent on a perfect crimp on every round to prevent setback.

[Battis]

More of the story...
I use .357 mag brass to load for the .351 WSL (and .38 special brass for the .35 WSL). If true .351 brass exists, I haven't found it, other than vintage rounds. You can buy .351 brass sometimes online, but it's made from .357 Max brass. I had a set of .351 Lee dies (special order dies, sold on ebay) that did not work on the .357 brass (Mag or Max), so I just used .38/.357 dies. I have an Accurate mold that casts .352 bullets, which are perfect. Getting neck tension on .357 brass to hold a .352 bullet is tough. I was using a .223 die to tighten the neck, and it works to a point. The compressed 4227 powder kept the bullet from setting back, and the crimp held it from pulling out. But the bullets spun in the cases.
The 9mm crimp die does a good job downsizing the necks of the .357 cases. I run the case through the 9mm crimp die, then open it slightly to accept the bullet, then crimp with the .38 die. The bullet doesn't spin in the case, but I wondered about the pressure from the tighter case.
I found that the case mouths of the .357 Max brass got destroyed when used in my rifle. The shorter .357 Mag brass works better.
The chronograph info should answer some questions.

[onelight]

Battis your explanation makes sense , and it certainly sounds like you know what you are doing to keep that old rifle shooting . Wish I could think of a case and bullet that would be a better fit. We have people here that are great at finding solutions to these problems maybe they will chime in if they know of anything that would work better.
Good luck with it.

[Battis]

The bullets and brass are fine, it's the pressure issue I was wondering about with the tighter neck. The rifle has new buffers and recoil spring, so it should be fine, but I know little about pressures in cases.

[onelight]

Battis have you considered trying 223 brass for your 351 ? The case diameter is very close if the rimless case would function in your rifle.

[Battis]

The .357 mag brass is perfect. The hardest part is reducing the case rim with a drill press and file.

[Battis]

I found some .351 brass for sale. Am I reading that price correctly? $4.19 each?
I think I'll stick with the .357 mag brass.


https://www.rccbrass.com/product/351-winchester-self-loading/

[Tatume]

On my computer it says $3.91 ea. Big savings! :-)

[Battis]

I went to the range with the chronograph. I had a bunch of rounds with loose neck tension and the newer ones with tight neck tension. There was no difference in average velocity (1400 fps - 1600 fps). I fired off one vintage round - 1879 fps. I fired off a few longer rounds made from .357 MAX brass - no difference from the ones made with shorter .357 MAG brass.
The rim of the vintage case measures .408" diameter. The rims on the cases that I made ranged from .404" to .411", and surprisingly, ejection was not a problem with any. I did make two cases from .223 brass (I tried it many years ago) but they would not eject (rim - .375"). That's too bad because making cases from .223 is easy.
That rifle is a crowd pleaser. The range was crowded.

[onelight]

Those are neat old rifles it would be a lot of fun to have one to shoot occasionally . Really glad you have a load that works for you.