Home Forums Reloading Big Game Rifles I think I have Headspace issues

After trying a few things, and reading a lot, I think I have discovered I have headspace issues.

So the barrel was replaced on my 7mm Rem Mag in April of 2011. Due to lots of "stuff" going on, After following the "break in" process recommended by Shilen, I quickly found an adequate load at the end of the summer last year with new brass and once fired brass with IMR7828 and 160 Accubonds. No obvious pressure signs and they shot well. Took my first branch antlered bull elk at a good long poke out there and cleaned it up nice and put it away for the year.

This fall, after bringing the rifle back out, I shot a few more of last years loads and checked zero. All was well and I loaned the rifle to my brother for a hunt he was doing. It worked well for him and after he was done, we met up on a deer hunt with our sons. I took the rifle from him then and then cleaned it up well.

Last month, I came here on the fire and expressed a concern I had with "wierd" pressure signs I was having. Shooting during a snowy November trip to the range, the rifle began exhibiting excessive pressure signs. I then resized the brass fully (normally only size enough to get a "crush fit" in the chamber)and dropped down the charge. I then fired a few more rounds, even over a chronograph, and was getting a bit of a hard bolt lift. It was then that I saw my first headspace expansion failure. Thinking my brass had become work hardened or was just beat up too much, I threw it out.

So, I loaded up some once fired Nosler brass, dropped the powder charge pretty significantly, and then went to the range.

Yesterday, I fired three shots, all different bullets with once fired Nosler brass. I used IMR7828 and 160 Accubonds, 160 Partitions, and H1000 with 168 Bergers. Choosing the lowest charge of the newly rolled loads, I shot my first shot. Case separated, So, I loaded a different load with a lower powder charge and a Partition bullet and fired. Case separated. So I tried the Berger and H1000 powder and again had a case separation. I was done. I put the rifle away and will now take it to the gunsmith to have the headspace checked.

The only thing I can think, is that all of the brass I used last year developing the loads etc., were stretching excessively and I didn't realize it. This year, after resizing it, it finished it off. Do you think I am correct?

Reading in the old Hornady manual, my Nosler manual and several other places on the web, it seems that I have a perfect example of "excessive headspace".

Any of you had this issue before?

FH

all reloads ? if you can take a factory new peice of brass or loaded round and measure to the datum line fire said round measure again , anything over .003 increase is a bit too much. if you dont have gauges to such you can use a .40 cal pistol case and it will read close enough to tell you if you have much of a problem. now if the problem is only with reloads you most likely just need to back the die off a bit

I agree with ID, It does sound like you need to back the sizer die out a bit.
Measure from the botton of a fired case to the shoulder.
I use a Hornady tool but the .40 cal case over the neck and resting on the shoulder of the 7mag will give you the reference number.
Size as usual and remeasure ,compare numbers.

I also bump the shoulder .002" max or brass suffers.

Headspace gauge

are you sure your barrel is not getting copper fouled clean it really well with montana extreme or remington 40x.I had pressure signs show up on arifle I thought was getting cleaned until I had it scoped and found out otherwise, changed to the two cleaners I mentioned and problem went away. Also you are not jamming these bullets into the lands,you mentioned trying different bullets they all have different ogives that will give you excessive pressure especially if you have different neck tension and some might get pushed back as they touch the lands to where there not jammed as tight as others.

Thank you folks. I am sure that the copper is okay. I used Barnes CR-10 last time to make certain of it.

As for setting the shoulder back, I have used the method described in both the redding and rcbs dies I own. They mention running the die to the shell holder in the upmost position. Then, back off the die one full turn and try to chamber a newly sized piece of brass. Then slowly turn the die back in until you can just close the bolt. I would assume this is the best way to do it.

That said, I did FL resize this last go around, because I wondered if I had done something wrong with the last batch of brass which I tossed out.

Also, I use the Hornady tool to determine where the lands are and then seat deeper. My magazine has been what determines the depth for me as all have a bit of a "jump" to get to the lands from the magazine enforced seating depth.

FH

forget bullet depth for now, just try to get the brass to chamber with minamual shoulder sett back like .002 +/- .001 first than reset bullet depth ( but should not change COAL) in other words try to keep your brass working at a min.
if your die is not set up correctly you brass "streaches" too much and seperates at the head . if the gun has an issue it will still do this that is what it is imporant to know how much new brass is streaching on first fireing

Firehawk, I have measured 0.014 stretch on first firing of factory load in a factory fresh 7Mag. To load any fired belted mag cases You only need to push the shoulder back 0.001-0.002 on most rifles. You surely don't want/need to go back to original factory configuration.Rick.

I have come to believe no one should be allowed to reload belted mags without investing in a hornady head space bushing kit for $35.
It will never wear out or be used up but all the time you own it you will have quick ez answers to what is going on with brass growth, head space in a particular rifle, and accurate die adjustment.
I reach for mine almost every time I reload....it is one of the best $35 I've spent on reloading tools!

Firehawk,

Who chambered the rifle? A quick trip to a gunsmith with a set of GO/NO GO gauges would help eliminate a lot of questions for you.

Not true on a belted magnum case or an unbelted case

A belted magnum NEW case headspaces on the belt and the brass manufacturers know this and there is a lot of head clearance (gap between the case shoulder and chamber shoulder when case is seated against bolt face). Typically this gap is between .014" to .040"

example worst case of close to .040"




that is measuring to the datum line on a NEW FACTORY LOAD of 4.092" (really 2.092" since the insert attachement is zeroed on 2") and ONCE FIRED measurement of 4.129". The case will continue to expand another .003" or so on the next couple of firings if neck sized only before a crush fit develops. Do the math and get a gauge

I could look through my spreadsheet and give many other examples of belted mags that have from .014" (on a custom chambered rebarrel) to factory guns in 300 win mag 338 win mag that average around .020" or so.

Now these guns have HEADSPACE of .000" to .009" (remember forward movement of the case is stopped by the belt which is how headspace is measured)

Unbelted cases like '06 or other variants typically have headspace between .000" and .008" because the brass manufacturers know that if it was more than that the case is allowed to go too far forward in the firing process that the primer would back out and cause problems. The case is said to "headspace on the shoulder" as opposed to the belted mags "headspacing on the belt". If a rifle is slightly out of specs like my Steyr 30-06 (.011") then you will get slightly flattened primers which do no harm, but if the headspace on an unbelted case gets to .017" then the primers will get severely flattened

Example of .017" headspace on an unbelted case (firing Nosler 280AI brass in an older Ackley 280AI chamber)



Having .011" headspace on my '06 does not mean that it won't shoot




The go-no-go gauges are for use by the rifle gunsmith or manufacturer and will only tell you if the gun is "within SAAMI specs" and for a reloader are useless in that they don't provide the measurements we are talking about.

x2

To the original posters question

You do not have a headspace problem that is causing the case separations. Case head separations are caused by expansion at the pressure ring from too much stretching. Headspace problems cause primer flattening and misfires but not case head separations.

You may have a chamber problem in that there is an excessive gap between the case shoulder and chamber shoulder on new cases. Also case separations are from OVERSIZING and pushing the shoulder back too far which makes the case stretch more on each firing.

First you need to find out what the gap at the shoulder is on new cases because most of the stretching occurs on the first firing

I had a savage 300 win that "grew" the shoulder dimension over .020 from virgin spec. Using the stoney point gauge I'd set them up for a shoulder set back of .002 less. That brass still lasted as long as my other belted mags that grew the brass much less on initial firings.
Woods .....as usual....has given us a very good tutorial about sizing cases.

Tonight I made a quick trip to a buddy's house and used his Hornady Head space kit. Here is what we found:

New Nosler Brass, straight from the package....4.132" on my micrometer

New Nosler Brass, run through the reloading die to make sure case mouth was round.....4.134"

Fired Nosler Brass, with shiny mark just ahead of the bolt but not quite coming all the way through the wall.....4.162"

If I understand this right, I am seeing .03" difference. According to some of you, that is too much? Seems awfully excessive to me too, but again I am learning a lot through this process. I obviously have much more to learn still.

I think I will be taking it back to the gunsmith. You all agree?

FH

Take it back and have him check it, but he'll likely find that the headspace is OK. The headspace is set by the belt on a belted magnum, not the shoulder. It seems you have a lot of excess room in your chamber's shoulder area, but that's not "headspace" in your cartridge. In my custom chambered 7mm rem mag the dimension change in the shoulder area measured with comparators from Norma brass is .012" after the first firing, it looks like yours is .030". What you really need to do is take a once fired piece of brass, which measured 4.162" on your caliper, and set your die to where it only bumps the shoulder back to measure 4.160". That way you've now set your gun up to control the headspace by the shoulder instead of the belt and the case can't stretch with each firing. As it is now you're squeezing the shoulder back by .030" then blowing it back out on the next firing, so something's gonna give and you're getting case separation.

I would say that's excessive. You actually haven't even reached the full length yet...you have another. .002-.003 to go as it takes 2 firings to make the full transition. I know this cause I always use a lee collet die for the the 2nd loading.
I would want my barrel spun on a bit tighter.
You wouldn't know where your die was pushing them back to unless you sized a fired round

When you say the fired Nosler case was .030 and already had the shiney spot, how many times had it been fired and sized?

I agree with others, you always want to get the stretch on the first firing, then leave it be until it needs set back. I would recommend neck sizing after the 1st couple firings witha Lee collet die. You can go many more if not loading hot. Once you get resistance on closing the bolt, measure to see where you're at. Then take a Redding Body Die and start long, keep adjusting the die in about 1/8 turn at a time until you get a slight bump. Chamber that case and make sure the resistance is minimal. You now have custom fit cases that will go for several more firings whether you are neck sizing or bumping each time. The LCD/RBD combo is the real deal for case life, great concentricity, and good accuracy.

Good Luck and don't get too bummed, we all(well, most of us) learn something new every day.

Have a good one,

loder

So I called my gunsmith and explained what was going on. He asked me to bring the rifle in and he would check the headspace. I brought it up to him this afternoon and he proceeded to use his "Go and No Go" gauges to check. Everything checked out fine.

He suggested neck sizing only and then checked a few other things out. Everything checks out okay and he said that a neck sizing die would probably be the best route and then only bump the shoulder back as needed.

He did think that the .03 difference was more than he would like to see, but everything was headspacing correctly.

So....I will now go buy a neck sizing die and a Headspace kit and see if I can do this better.

FH

Read that 3 times, then pick apart each sentence until you fully understand exactly what it says because it is entirely correct.

.030" is not unworkable. For example off my spreadsheet on rifles I reload for I get the following:

Beretta Mato 300 win mag
New case - 4.253"
Once fired - 4.270" - neck sized with Lee Collet
Twice fired - 4.272" - very slight crush fit, again neck sized with Lee Collet
3 times fired - 4.2725" - crush fit, neck sized with Lee Collet and shoulders pushed back with Redding Body Die
TOTAL MOVEMENT - .0195"

Beretta Mato 338 win mag
New case - 4.097"
Once fired - 4.120" - neck sized with Lee Collet
Twice fired - 4.123" - very slight crush fit, again neck sized with Lee Collet
3 times fired - 4.124" - crush fit, neck sized Lee Collet and shoulder pushed back with Redding Body Die
TOTAL MOVEMENT - .0270"

Even with .030" of head clearance you can load and reuse the cases many times as long as you let the case fully expand in a couple of firings and push the shoulder back only .001" on each sizing. However you will need to be able to measure that, keep the cases segregated according to how many firings each case has on it (work hardening from firing will effect the dies ability to set the shoulder back and vary springback) and continually chamber the cases in your rifle as you size them. .001" difference will make a difference in how well a case chambers and die/press surfaces and joints will compress as you use them. Sorta a dynamic situation.

So I picked up a Redding Neck Sizing die today. Now I read that I should use the Lee collet die and a Redding body die.

If i pulled the expander ball etc. from my RCBS Sizing die, would I essentially have a body die? Or..are there other differences in that die?

Thanks!
FH