Where is the case when ignition begins?

For any who want to check whether or not the bullet can be "held in place with neck tension) all's ya' got's to do is set your loaded round on the table and drop a 20lb cinderblock on the nose........ there, did she hold??

OK, this isn't egg'ZACKLY how I tested these myownself but hey.... I don't want to make it too complicated. I want folks to TEST stuff!
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Bullet pull for the 5.56mm is 45lbs. My test showed that the bullet could be pushed(apply pressure slowly) into the case using between 35 to 45 lbs or more. Rounds were not crimped. Loaded with standard RCBS dies, expander .0015" under bullet diameter. Now looking for cinderblock. :D Link to gov info on 45#. http://www.bradfordherrick.com/sitebuildercontent/sitebuilderfiles/m855.pdf The shoulder of a 223 round can be set back by the action on loading in an AR15.
 
Would this work?

Wouldn’t a way to test it be to soak some primers in Kroil for a couple days. Then seat them in cases that are shoulder bumped .005” and load neck tensioned bullet that is seated so it’ll be jammed into the lands. Close the bolt on the no powder round and measure a rod that is dropped down the barrel. Then pull the trigger and see if the rod is pushed out .005”, nothing changes, or the cartridge OAL changes?
 
tricrown said:
Wouldn’t a way to test it be to soak some primers in Kroil for a couple days. Then seat them in cases that are shoulder bumped .005” and load neck tensioned bullet that is seated so it’ll be jammed into the lands. Close the bolt on the no powder round and measure a rod that is dropped down the barrel. Then pull the trigger and see if the rod is pushed out .005”, nothing changes, or the cartridge OAL changes?
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Yeahh,

This is closer to what I've done although "dropping" a rod down the barrel scares me :)

Gently, GENTLY wit' da' measures me' frien'!!!

al

Note that primers can go off with variations of fizzle down to near zero. IMO it's important to seat primers below the surface of the casehead for these experiments and to pull apart EVERY round after measuring to see did the primer bugger the read.
 
Okay....riddle me this.

Assuming some of these postulations are correct, how is it possible to blow the shoulders forward on cases without using a false shoulder and using only neck tension and bullet 'jam' to seat the case firmly against the bolt face? Let's add some lubricity on the cases to the mix, just to make sure we've touched all the bases. :)

To qualify things a bit more, we're talking about blowing the shoulders forward a significant amount, here........

Good shootin'. :) -Al
 
I have tested this and there is no way in hell the bullet can be seated tight enough on my Dasher. I was turning 6mm BR brass into 6mm Dasher brass which is .100" longer. A super tight neck and jamming the bullet into the lands so hard the bolt had to be forced closed simply did not stop the case from moving forwards when the firing pin hit. Repeated closing and measuring to stabilize the oal reading then pulled the trigger. I killed some primers and tried this method with uncharged rounds to see if it worked.


Years ago I experimented with killing primers and many of the "killed" primers went bang, most were a subdued bang but some were very loud and no doubt most would have ignited a round. My changed lathe oil seemed to kill primers very well, various other spray solvents etc did not kill a primer.
 
Al Nyhus said:
Okay....riddle me this.

Assuming some of these postulations are correct, how is it possible to blow the shoulders forward on cases without using a false shoulder and using only neck tension and bullet 'jam' to seat the case firmly against the bolt face? Let's add some lubricity on the cases to the mix, just to make sure we've touched all the bases. :)

To qualify things a bit more, we're talking about blowing the shoulders forward a significant amount, here........

Good shootin'. :) -Al
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Thought this was covered back in my first post.....:confused:

Yeahh, it's well understood that greasing cases will result in a case that looks like one's chamber.

al
 
alinwa said:
Thought this was covered back in my first post.....:confused: al
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alinwa: My post was meant more along the lines of a devils advocate reply. :D

Like many things mechanical, assigning absolutes to all situations can be a sticky thing. If all of this were true, how is it possible for me to f-form a 30BR case into a 30BRX (shoulder blown..yes, blown...forward .100) w/o using a false shoulder? 50 cases fired and z-e-r-o issues. Fired and dissected cases show z-e-r-o thinning foward of the case head. Here's a pic for reference:
brx.jpg


My 30WolfPup cases are f-formed the same way. In this case (pun intended) the shoulder went foward a whopping .240. :eek: Again, a reference pic with ready to f-form case (lt.) and f-formed case (rt.):
unfiredpup.jpg





There are a couple things that make this possible. One is mechanical and the other serendipitous. The serendipitous part has to due with circumference. Here's some numbers to mull:

.224 bullet circumference: .7037
.243 bullet circumference: .7634 (9%> .224)
.308 bullet circumference: .9676 (37%> .224 and 26%> .243)

Assuming that .250 of the bullet is in the neck in all three scenarios (a reasonable assumption), it's clear that there's a big difference in how much surface contact area difference there is between the three examples. Let's simplify things even more and say the firing pins impact force is the same on all three examples and connect the dots accordingly. ;) I ciphered out some surface area figures, but no need to bore anyone with that data. I had to take my socks off and use the toes on both feet to get an accurate answer......it's the South Dakota way, dontcha' know? We only have three calculators in the whole state and today is not my day to use one of 'em......:D

Guys making .30 cal. Hunter class cases from 308W or 300 Savage parent cases have been shoving the shoulders back .020-.030 before f-forming them to the chamber for decades, so it's not exactly a new process.

I'll let 'ya ponder the remaining piece of the puzzle. ;) :)

Good discussion and good shootin', guys. :) -Al
 
Al Nyhus,

I think you're insinuating that whilst a .243 bullet may not hold back the case, a .308 bullet WILL.........

And I'm OK with this. Folks have been doing it this way for years.

And you DO get a case that looks like the chamber.

And while I'd never really thought it through, yes it does make sense that the 30's will hold back better.

And I DO hope that competitors everywhere find this method to be appropriate. :)

That said..... if your caseheads are perfectly square then I can't fault your method. I've not managed to achieve this.


al
 
alinwa said:
Al Nyhus,
That said..... if your caseheads are perfectly square then I can't fault your method. I've not managed to achieve this. al
Click to expand...

The remaining piece of the puzzle is the extractor. :)

A sliding plate style extractor/coned bolt setup keeps the case head firmly against the bolt face when f-forming, allowing the shoulder of the cases to indeed....blow forward. With a good amount of neck tension, a solid 'jam seat', lightly lubed cases and a powder that is a bit faster than generally used in the parent case's standard configuration, blowing the shoulders ahead is a pretty straight forward deal.

A Remington 700 bolt nose/extracor may not give the same results for obvious reasons....depends. A 700 bolt fitted with a Sako or M16 extractor may or may not....depends. This is what I meant earlier about assigning "absolutes" to all scenarios. ;)

Hope this helps. Good shootin'. :) -Al
 
OK..... so I'll amend my absolute.

UNLESS THE CASE IS HELD IN PLACE by something more than a jammed bullet, it will move forward :D

I won't give in yet regarding the jammed bullet thing because I've spent too much time trying to get it to work in a .308. So I'll say this, I've tried many different bullets, increasing neck tension to the point of JB Welding the bullet in place and two different leade angles and I cannot get it to hold.

And the reason for all this fooferaw is that IMO UNLESS you can hold the case back solidly the result will be canted caseheads.

al
 
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