Brass Case Head Separation after 6 firings

[bigngreen]

Any case can stretch on the first firing? The distance between the bolt face and the end of the belt in the chamber isn't controlled for in every bolt/action combination, just like headspace to the shoulder isn't consistent in certain bolt designs. When fireforming if you don't pull the ejector and the firing pin overcomes whatever jam method was used the shoulder's don't blow forward as far on the first firing. I can measure that with a headspace comparator by running a false shoulder case, a jammed case, and a poorly jammed case back to back to back. If the shoulders don't move as far forward on the first firing, then it takes a second fireforming load to get it right or it's the same as if you excessively resized a case. Maybe that's where we're different - the second firing is when the problem is induced, not necessarily by resizing but by not letting the case fully form?

A belted mag can't be jammed as far forward , but try forming shoulders using a bolt head where you can change out the bolt face like a Savage and consistency can be hard to get. This is partly why I use false shoulders, because my Savage target action has enough slop in the bolt face that I couldn't get a jam method to be consistent enough. I wasn't going to waste barrel life running multiple rounds of fireforming loads, so it now has a standard SAAMI chambered barrel on it that runs a weak 20* shoulder because IMO the action isn't tight enough to handle a better chamber. Definitely not the 30-338 LM Improved that I was hoping for, I got a Defiance target action to handle that amount of case shoulder movement.

There is no difference between any action, the back of the bolt lugs seat on the front of the integral action lugs in every conventional bolt action and it's solid steel from the lugs to the bolt face so there is literally no way to create slop!!
I've seen multiple Definace actions set back so far the handle is acting as a recoil lug with a 338 Lapua round, the Savage built for the Lapua actually is stronger with more lug!!

 

[QuietTexan]

Ha. Yes, that's why there are so many aftermarket replacement bolt heads for Savage, because they fit so tight and so well from the factory Never a single case was dished by a Savage bolt. Must be an internet myth inside the dial of my caliper.

it's solid steel from the lugs to the bolt face so there is literally no way to create slop!!
set back so far the handle is acting as a recoil lug with a 338 Lapua round,

So wait, if what you described is true and the handle is acting as a recoil lug, doesn't that imply there's a gap between the rear of the lugs and the recess? You can't have it both ways - it's either solid steel from lug to action or there's a gap because the handle holds the lugs off the action. Smells like hyperbole. Show one of these Defiance actions that the lugs don't contact, because per you there's literally no way to create slop like the lugs not contacting.

 

[bigngreen]

Ha. Yes, that's why there are so many aftermarket replacement bolt heads for Savage, because they fit so tight and so well from the factory Never a single case was dished by a Savage bolt. Must be an internet myth inside the dial of my caliper.


So wait, if what you described is true and the handle is acting as a recoil lug, doesn't that imply there's a gap between the rear of the lugs and the recess? You can't have it both ways - it's either solid steel from lug to action or there's a gap because the handle holds the lugs off the action. Smells like hyperbole. Show one of these Defiance actions that the lugs don't contact, because per you there's literally no way to create slop like the lugs not contacting.

Your making this painful!! When a bolt handle becomes a lug is when the forward lugs are pounded back into the action till the bolt handle starts taking a beating.

I've built extremely accurate elr rifles on Savages, never once needed a new bolt face to do it, I've trued some bolt heads but over all no difference was made. The bolt fit in the body has zero to do with anything in front of the bodies fit to the action!!
A PTG bolt head is a last resort IMO.

 

[Mike Matteson]

I find this interesting. I used a 308 Norma Mag for years and do. At the start I use 300 WM case and sized them back to 308 Norma Mag sizing cut the case to length. I was FL sizing for awhile. I have case separation and very early in, using those cases. Generally in three firing the case was done. I change to a 300 WM neck sizing die, and stop the separation at the belt. If look you'll will see that the 308NM case is shorter to the shoulder, than the 300WM case. The neck is shorter with the 300WM case, due to lengthening the case to the shoulder. So my fix was to FL the 300WM case to 308 NM, then fire form them to chamber. There after I used a 300WM neck sizing die to size the neck only. That only sized about half of the neck length. It stopped the case separation in it's tracks. The only problem after that was primer pockets would get to large after about 10 firing. The moral of the story is getting the belted mag case to form to the shoulder quickly as possible. Only bumping back by a .001 or .002 is needed to extend the case life for sure. Just how you get there is another thing. Jammed or pushing the bullet into the lands is one way. Double shoulder is another way. I also several other belted mag's. Rem, Win, and M-98 actions. My son has a browning action, and we haven't gotten that far yet.
Now I never used the double shoulder to fire form the case. Not totally up on doing that either. I am not with just how to set that up. Being your allowing the neck to be at a different size than what the chamber size is. Seem like there could be and should be some problems there. Getting the bolt to close. I would think that probably need to use a mandrel to expand the neck some then size the neck down a portion to chamber size. That what causing me a lot of concerns. Probable I don't fully understand. I see I am going to get some up coming. So be it. Learning at 74. It's hard to brake an old dog of old habits, but can be trained for new tricks.

 

[QuietTexan]

The bolt fit in the body has zero to do with anything in front of the bodies fit to the action!!

Not sure where you're getting this, no one is talking about bolt fit in the action past the lugs? Other than you saying that Defiance lugs can get pounded so hard the charging handle takes on the bolt thrust apparently, that still sounds fishy to me.

I really don't understand what you're arguing here? It's a fact that the Savage floating bolt head allows forward and rearward movement separate from the bolt body - awesome for your bolt heads that they fit out of the box, that doesn't mean every Savage has come out tight and square. It's a two-piece design - there are multiple tolerances stacked up between the action lug recess and the bolt face. It's a design that several writers have touted as being better than a one-piece bolt design because they claim dynamic lug contact is better than fixed. I think that the one piece design is better because there are fewer interfaces by at least one - the fit between the two bolt head components. It's the same argument as Savage/Rem-age barrel nuts versus a shouldered barrel - two sets of threads versus one set and a hard shoulder.

Let's go back to what I said:

my Savage target action has enough slop in the bolt face that I couldn't get a jam method to be consistent enough.

Either the face was dished from too many high pressure rounds, or wasn't cut square, or it didn't sit square on the second piece of the bolt head that contacted the lugs, or the lug contact itself was shifting under pressure. Any way you cut it, whatever was moving was moving inconsistently enough the bullet would move inconsistently in the neck to the point fireforming wasn't consistent when done trying to jam a bullet. Different shoulder measurements with everything else set the same. Changing to a false shoulder fit tight enough that whatever was moving couldn't overcome the crush fit of the brass case, end result was much more consistently formed cases. The new bolt face might have helped, but like you said Savage bolt faces don't tend to make a ton of difference.

This isn't insane fantasy talking about the bullet moving in the neck, there's a finite amount of grip a neck can put on a bullet, it's not challenging to set a bullet back into a case with an action.

 

[nksmfamjp]

Ha. Yes, that's why there are so many aftermarket replacement bolt heads for Savage, because they fit so tight and so well from the factory

You should look into this a bit more. I have talked to a well known Savage gunsmith who offers truing on Savage actions. When I replaced a Savage bolt head on my rifle, he refused to true it saying their bolt heads are usually good out of the box.

The reason the 2 piece bolt head is better is covered well in Harold Vaughn's book. Basically both sides of the lugs will touch regardless of trigger pressure. The is a know issue with 1 pc rigid bolts.

When lugs are set back, they yield. If they yield enough, something has to catch. Usually the bolt handle. Mauser had an extra lug for that!

 

[bigngreen]

@QuietTexan , there is not a difference in tolerance stack between the action integral lugs and bolt face of a Savage vs any other action, they ALL have the integral lugs and bolt lugs seated together then it's the bolt face. What happens behind the lugs is different ya but a lug seated on a lug is the same!
What I'm saying is there would be zero difference in fire forming in a Savage action vs any other action. I've used multiple savage action for fire forming all kinds of rounds including 338 Lapua AI and 30-338 Lapua AI because I can chamber it to spec then set it back .002 for fire forming then have cases that drop right in what ever gun they were for. The action isn't was is causing your issue!!