Headspace question

[rippit]

How much headspace is too much??

Yesterday the first two shots out of my custom 7saum the case heads separated. This was on brass that had been shot 6 times and full length sized twice. I'm not new to reloading but this is the first time I've ever had a case head separate.
So I decided to check how much my body die is bumping the shoulder back on fired cases . It is pushing the shoulder .025 back

. I thought that seemed like too much so I checked my 243 and it is only bumping the shoulder back .006 when full length resizing.


Does my 7saum have a chamber with too much headspace ?? Causing the cases to stretch too much and separate?

 

[buffybuster]

0.025"!!! That's excessive headspace to the point of being dangerous. The chamber is not your problem. Your problem is you are bumping the shoulders too far. You need to readjust the sizing die to bump 0.002-0.003". Any brass you have fired with the shoulders bumped back 0.025" is in imminent head separation. Throw it out and start with new brass.

 

[rippit]

That is what I figured. New unfired brass is .020 short of fired brass. Is it going to be a problem firing them the first time??

Trying to figure out if I have a serious problem and need to contact the gunsmith?

 

[rippit]

Also why would a redding comp body die bump the shoulder .25 . Thinking it has to be a bad chambering job?

 

[Powermac]

Most likely is that you have set up/adjusted the die way to far into the threads. Therby making the problem your self. Get a headspace gauge of some sort and do set up your dies before sizing any more cases

 

[rippit]

Yes I have already set up the body die to only bump the shoulder .002 on fired cases. The problem I have in new unfired cases are .020 short of my chamber.

Is firing new brass that is .020 short dangerous in my rifle??

 

[Milo 2.5]

.020 growth is way excessive, IMO. New saum grows .002 in my 2 chambers, that's new Rem brass. Are you getting the primer out before measuring, that can skew things.
I do suggest buying a Sinclair bump gauge, one that measures off shoulder angle, and actually get a definite measurement?

In the op, you said casehead sep on 6 times fired brass that was over bumped, best stay away from that stuff.

To me it sounds as though your chamber was over-reamed. 2 things you can do, fix it, or fire form your brass with light loads, or use a fire forming method, and take advantage of the increased case capacity. Just allot a certain number of cases for the rifle, and bump .002, and have a barn burner! If you go this route, you wont be able to use this brass in any other chamber.

 

[rippit]

I'm using a hornady lock and load headspace gauge to measure. Im assuming fixed means back to the gunsmith and rechamber?
I do reload but what if I needed to shoot off the shelf ammo is it dangerous?

 

[DAVETOOLEY]

You have two options as some have stated. Neither right or wrong.
1. Check the headspace and if it's off correct it.
2. Fire form brass by jamming bullets into the lands for the first firing. Then adjust your dies to fit your chamber. You can do this in the normal course of shooting as you don't have to change the load.

I've fire formed 10's of thousands of pieces of brass over the years of shooting wildcat cartridges.
Another way to fire form the cases would be to expand the necks to 30 cal. Then size back down to 7MM creating a false shoulder to push the case head against the bolt face. Put in 16 grs. of pistol or shotgun powder. I use Unique. Fill to the base of the neck with instant grits, plug the neck with a bit of paper towel and then fire them in the rifle.

 

[Milo 2.5]

I'm using a hornady lock and load headspace gauge to measure. Im assuming fixed means back to the gunsmith and rechamber?
I do reload but what if I needed to shoot off the shelf ammo is it dangerous?

Mr. Tooley just gave you some sound advice, put it into words I couldn't.
I'd lay off the factory loads, besides, that's kind of some over-priced crap anyway!

 

[DAVETOOLEY]

I'm using a hornady lock and load headspace gauge to measure. Im assuming fixed means back to the gunsmith and rechamber?
I do reload but what if I needed to shoot off the shelf ammo is it dangerous?

Obviously not dangerous since it took six firings before the head separated. I would think you could find a way to get the head space checked where you live. Then with that information consider your options.

 

[Pinecone]

If new brass is 20 thou short of your fired brass, I would have your rifle headspace checked.

 

[Brasscow]

Dave offered very sound advice. One thing I will say about this option number two is that if you are going to jam the bullet into the lands, make sure you jam it a good .020 and that you have enough neck tension that it doesn't slip back into the neck. You want to make sure that the case head is solid against the bolt face, even if that means running without the ejector until they're formed.

 

[rippit]

Thanks for all the info guys

 

[MikeeBooshay]

x 2 to the advice here - another little trick to minimize the case stretch when fire forming cases is to NOT clean the case lube off before firing. Obviously do not fire a full house load, the idea is to have the case slip in the chamber, against the bolt face. A case would normally grip the chamber, with the brass fwd against the shoulder, then the combustion pressure pushes the case back to the bolt, that is why it stretches the case just above the web. Using a false shoulder, or string neck tension against a long seated bullet also works.

Using the 6PPC, and sizing .0005, no more than .001 setback, it is not unusual to get 100+ firings from a batch of Lapua 220 Russian cases. As long as it still holds primers. GTG.

 

[blackfoot]

I question the accuracy of the measurements in some cases. I have a Hornady tool and a Sinclair tool, and they give me vastly different measurements from a fired case to a sized case, as in one shows .004 shoulder bump and the other one shows .015 shoulder bump. I don't trust the .015 number because I can "feel" slight resistance with the striker mechanism removed from the bolt. Surprisingly it's the Sinclair gauge that shows what I believe to be the erroneous measurement. Just sayin' before you jump to conclusions you might want to get a second measurement opinion.

 

[427Cobra]

Don't measure the shoulders on virgin brass, unless you like pissing into the wind then eating yellow snow

 

[rippit]

I just got the bolt to close with 10 layers of scotch tape on the bottom of a piece virgin Norma brass. So there is about .020 so the hornady tool seems to be pretty accurate. And I can't believe virgin Norma brass being .020 off

 

[bax]

New brass is commonly short.

Mr. Tooley has it right. Load a moderate powder charge. Seat the bullets just into the lands. That insures that the case base is forced against the bolt face. When you fire the case, the shoulder will expand to fill the chamber -- also known as fireforming. Measure that case. Set your sizing die to bump the shoulder back 0.001 or 0.002. Sizing more than that will cause "rapid brass aging" -- you will get head separations. Your excessively sized brass is probably injured but it will probably soldier on for a few more firings. It will tell you when it is too exhausted to go on.

Silly story. I have several 308 FL dies. For various reasons, I decided to buy a new Dillon carbide FL die. I have about 100 Lapua cases that I bought in the mid-1990s. I have been shooting them several times a year since then. They are faithful friends. I popped that die into my press and screwed it down until it caused a slight cam-over and sized 20 pieces of brass. I loaded and shot them. I had 14 head separations and 6 incipient separations. I went home and checked. Turns out that die was not designed for my press setup and it was bumping the shoulder back by 0.014 too much. I pulled out a Redding die stop, set up the die correctly with a specific case holder, and it has made perfect brass ever since. I kept the box of decapitated Lapua to remind me not to make assumptions.

 

[ArmyJerry]

tagged

 

[MitchAlsup]

In any event,
A) it is never necessary to push the shoulder more than 0.002 when sizing an already fired case.
B) it is fairly dangerous to push the shoulder more than 0.005 when sizing an already fired case.

 

[rippit]

Thanks for all the help again. I understand that I can fire form the brass and set up the dies to only bump the shoulder .002 and be fine shooting that way. I just wanted to know if I was shooting factory ammo or copper creek loaded ammo would that be unsafe?. Sounds like it would be .

I am going to send the rifle to the builder and have him check the chamber and reset the headspace correctly.

 

[427Cobra]

You can take a fired piece of brass, measure it, then check the cartridge prints online to see if you do have excessive headspace, or buy a No Go gauge and see if your bolt will close