Riveting

[rays308]

I've noticed a couple of posts that mentioned riveting as a possibility when a patched boolit is seated into the case. This sounds like it could be a dangerous thing.

Started patching some 311299 from my new NOE mold. I patched them out past the ogive which leaves about .312 of the boolit in the case when seated into my 308.
I cast them from water dropped wheel weights with some some magnum shot added. I'm thinking they are about 18bhn.

I would have thought that the gases would put pressure on all exposed points of the boolit in the case, preventing expansion from rear forces until the boolit is in the neck.

Has anyone experienced riveting of their boolits?

What are the signs of riveting?

Should I patch them just forward of the bands and leave the bore riding portion bare?

[303Guy]

I was wondering the same thing. Trials have been done with rebated and boat tail boolits and those got squeezed thinner, supporting the idea that riveting might not occur for the reason you mention. Riveting does seem to occur in the gap between case mouth and throat and in the chamfer.

[geargnasher]

Yes, I've had what I believe is riveting in the throats too when using undersized boolits, or when the loaded case neck diameter was too small for the chamber neck. Sometimes this forces me to use way oversized boolits so they extrude into the rifling, but I'd rather them start too large than start just right, rivet into a lump, and THEN extrude into the rifling, especially with PP boolits.

As far as loading below the case neck, I haven't done it with cast. I recall some people have reported doing so and not having any problems. I think it all depends on the powder choice, loading density, and overall pressure of the load. As far as safety goes, I seriously doubt you could rivet a cast boolit enough to cause dangerous problems, but if you extract a case and the neck tore off and departed the gun with the boolit, you know you have a problem!

Gear

[pdawg_shooter]

I started PPing in the late 60 and have never had a problem with riveting yet. But then I use the old fashioned "twist the tail and trim short" method. I also size to fit the throat, the patch will compress easy in the bore.

[leftiye]

Like gear said - powder choice. Unless you really have an obstruction (like the rifling) that some part of the boolit is against, and high pressure, I doubt that you would be able to expand a part of the boolit due to pressure from the rear. The exception would be long heavy boolit and/or just plain fast pressure rise that obturates the boolit. Therefore, fast powders may run this risk and be worse the hotter the load.

[rays308]

Thanks all, I was afraid I might have been risking a rare phenomenon.

I have 45 rounds loaded with W748. Used the lowest charge recomended for jacketed.

If these dont perform well I'm gonna pick up some W760 to try. I've seen several posts recomending progressive ball powders over stick.

I have loaded many a bare boolit below the neck without issue however that is at lower pressure.


I could understand swelling at the throat, all pressure would be from the rear at that point and the tail would be trying to catch up with the nose.

Throat swelling should play havoc with the patch but still allow the boolit to swage back down or cut a ring. Wouldnt I see leading at the throat if thats the case?

[303Guy]

I have a few samples of fired pp boolits that shoe evidence of having riveted into the case mouth/chamber end gap. The patch compresses more than lead evidently.



I have one that actually twisted at the 'riveting' point as could be seen by the width of the rifling groove above and below the riveting.

Here it is.


Maybe this is why harder alloys are sometimes indicated?

[geargnasher]

Probably not leading, the front part of the patch will maintain obturation (seal against gas cutting) but your groups will fall apart if the patch near the base gets mangled at high pressure.

Slow-for-cartridge powders seem to work best in my book, I've tried it different ways, but slow powders, especially double-base ball powders seem to have the right stuff for PPCB. I've also had good luck with RX22 in several calibers, it's really slow and still easy to light.

Gear

[pdawg_shooter]

Probably not leading, the front part of the patch will maintain obturation (seal against gas cutting) but your groups will fall apart if the patch near the base gets mangled at high pressure.

Slow-for-cartridge powders seem to work best in my book, I've tried it different ways, but slow powders, especially double-base ball powders seem to have the right stuff for PPCB. I've also had good luck with RX22 in several calibers, it's really slow and still easy to light.

Gear

+1 on the slow powder. I always get my best accuracy from a powder that gives near as possible to 100% load density for the velocity I want. At times that calls for a powder no one but a paper patcher would consider for cast in a given cartridge.

[rays308]

303Guy,

Very interesting pics.

Are both pics the same boolit?

Did the boolit start out tapered?

I'm wondering if the lead flowed back to the point that the patch failed(broke) since the back end still looks so well formed and the rifling marks are not as deep behind deformation.

If the tail of the boolit was pushing forward, wouldn't it swell up into the rifling?

I think I could see the tail end not twisting in the rifling as fast as the nose if the patch failed on soft lead.

The lead flowing backward would make a very good seal also.

[CJR]

Rays308,

Another one bites the dust! Looking forward to see how your first PPCB shooting goes. What's the actual weight of your CB? W748 charge? PP material, lube? For what's it's worth, the NRA shot PPCB seated past the neck and into the case with good results.

When I started PPCB shooting I got leading in front of the chamber. It turned out to be poor PP wrapping on my part and the PP was stripping in the bore with resultant leading. Once I PP correctly, I was on a roll. Enjoy your new PPCB journey. It's an understatement to say that PPCB is a blast!

Best regards,

CJR

[rays308]

CJR,

I think I enjoy casting and now wrapping more than shooting. I spend alot more time with them.

Actually I do very much like the idea of making my own. I think I like the independence of not relying on manufacturers.

I would really like to get a boolit shooting well at long range out of my savage 10.

I loaded with 42gr of W748.

I sized the boolits down to 304
I'm using notebook paper that miked about .0025.
soaked in water.
2 times around the boolit.

I lubed them with JPW and sized to 311.

I'm hoping that the patch will cause less stress on the boolit and leave it as close to cast as possible so that good accuracy will be acheivable.

I've probably wrapped 150 boolits and haven't shot any of them yet. LOL

I do seem to be getting better at getting them tight. Practice makes better.

The loads I have use 311299. I want to try 311365, 311332, 311413 also.

It will be a lot of testing and re-testing. Darn it.

[303Guy]

Same boolit. Other than the cutting on the driving face of the groove, the patch did not fail. It simply preserved the bump formed, being a rather thick and compressible paper. I should mention that it was fired in a two groove with a rough bore. That means the paper can and does wear through on the driving edge. It was because of that that I was reducing the charge to capture the boolit. The charge was i think shotgun powder which has a sharp pressure rise.

And yes, this paper patching is fun and challenging!