Case head separation?

[bigedp51]

I have bigedp51 on my ignore list. Theres a reason for that. To much BS.

But yet, someone quotes it, making me see it.

243winxb who would have ever guessed that you graduated first in your class from the Attila the Hun School of Diplomacy.

I can't believe you posted this and then talk about too much BS.

 

[bigedp51]

I sent this link to my oldest son who is a forensic psychologist or criminal profiler and asked what I did to 243winxb to set him off.

What he replied to me I never expected and really shocked me.

My son said 243winxb response was because engineer40 thanked me for my posting and 243winxb wanted all the credit and be in the spotlight for what he posted.

Its nice engineer40 thanked me for my "senior moment" but 243winxb and his childish reaction was uncalled for. And I still can't believe how he reacted and his adolescent response for being thanked.

 

[WildRose]

. ...

 

[4xforfun]

Right out of the gate I am going to admit i did NOT read all of the replies, so if it was covered, please forgive me.

In your OP you stated that you have a "strait walled case". You then state that you bump the shoulder back .002.

How is this posseble..there is no shoulder to bump. Or did I miss something? lightbulb

Thanks,
Tod

 

[engineer40]

Right out of the gate I am going to admit i did NOT read all of the replies, so if it was covered, please forgive me.

In your OP you stated that you have a "strait walled case". You then state that you bump the shoulder back .002.

How is this posseble..there is no shoulder to bump. Or did I miss something? lightbulb

Thanks,
Tod

Sorry, I can see how that was confusing. Yes this cartridge I'm having the problem with is a straight walled cartridge that I am shooting out of a rifle even though the 460 S&W Magnum is a revolver cartridge. What I meant was when I reload rifle cartridges that have a shoulder, I bump them back .002. The 460 S&W Mag does not have a shoulder.

After some additional reading yesterday I'm leaning towards this being excess headspace on the TC Encore platform. I found a website that sells shims to put behind the firing pin stop so I might give those a try.

 

[243winxb]

The rim thickness, if different between brands, changes the cartridge. headspace.

 

[Pdvdh]

You should be able to inspect the interior of your fired cases and see the thinning of the side wall near the web/case head -[FLOATRIGHT][/FLOATRIGHT] without having to section them longitudinally. Of course you can also cut them in half.

But I've inspected the interior side walls of cases in the web area for decades now, even on calibers as small as .277, simply with a small focusable flashlight.

On a case as short and large in diameter as your .460 casings, it should be very simple/easy, compared to inspecting 270 and 280 cases. Then you can toss the ones close to separating instead of wasting them all, even the useful ones. More importantly, you'll be able to prevent damage to your firearm by avoiding case head separations by culling the bad ones.

BTW, I agree your problem is due to excessive headspace. The only other plausible explanation is defective brass casings, in my experiences and in my opinion.

 

[bigedp51]

Engineer40

If your die is reducing the case diameter too much it will over work the brass and cause it to fail. Measure a new case a fired case and a resized case and see how much the brass is being worked.

Next take a resized case and measure the cases overall length and write it down.

Next take a fired spent primer and just using your fingers start the primer into the primer pocket.

Now chamber this case and let the bolt face seat the primer and remove the case.

Now measure the case again from the base of the primer to the case mouth and write it down.

Now subtract the first case measurement from the second and this will be your head clearance or the air space between the rear of the case and the bolt face. This will be the distance the case can stretch when fired. With thin rims and at maximum headspace your case could stretch .010.

This is where you want to know your head clearance and how much lengthwise stretch the case has. Add this to your base diameter increase and you will have the total case stretch.

Using the primer trick is the cheap bastards headspace gauge. And if you measure your rim thickness and add it to your head clearance measurement you will have your rifles actual headspace reading.

Measure OAL of case

Fully seat spent fired primer with bolt face and remeasure to get head clearance.

 

[Pdvdh]

Excessive headspace will by far and away be the cause of case head separations, compared to the affect from a slightly large chamber diameter.

 

[bigedp51]

Excessive headspace will by far and away be the cause of case head separations, compared to the affect from a slightly large chamber diameter.

Buy a .303 British Enfield and some Winchester brass and measure the case thinning with a RCBS case mastering gauge. When the case stretches and thins more than your head clearance the rest is due to radial expansion of the case.

 

[Pdvdh]

And it will be a very minor contributor to case head separation, as the radial swelling any resizing is perpendicular to the longitudinal stretching that's primarily responsible for tearing the case head off the sidewall of the casing. Particularly on a straightwalled .460 S&W. My guess is 90% of case head separation is due to excessive headspace. Less than 10% due to any radial expansion.

 

[RoadKill]

High pressure 'sticks' the more forward portion of the case wall to the chamber wall all whilst blowing the case head rearward 'til slowed by collision with the T/C's firing pin bushing but continues on rearward a bit more as the rearward thrust causes the T'C's frame to stretch, adding that much more to the stretching of the case body and so there's even more thinning of the case wall just forward of the case head. Mr. Bellm's firing pin bushing shims can rid that particular T/C frame & barrel combination of its excessive head space.

 

[WildRose]

High pressure 'sticks' the more forward portion of the case wall to the chamber wall all whilst blowing the case head rearward 'til slowed by collision with the T/C's firing pin bushing but continues on rearward a bit more as the rearward thrust causes the T'C's frame to stretch, adding that much more to the stretching of the case body and so there's even more thinning of the case wall just forward of the case head. Mr. Bellm's firing pin bushing shims can rid that particular T/C frame & barrel combination of its excessive head space.

Hmm, very interesting.

 

[243winxb]

Seen a 222 Rem TC Contender Barrel /Frame Hinge Pin wrapped with aluminium foil to get a better frame to barrel headspace fit.

It was traded in that way and sold before a test fire.

Not recommended as a permanent fix.