Headspace issues?

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dbsavage

Guest
Good morning all.
I'm new to the forum and I'm glad to be a part of something I can tap into a massive wealth of knowledge.
My question centers around headspace. I recently had a custom long-range build completed in 7mmWSM based on a Savage 10 action. I sent some ammo to the gunsmith who was doing the build so he could test fire it and make sure everything was on the up and up. I had him send back my brass because you can't find 7mmWSM brass ANYWHERE!
When I got my rifle back and the empty brass, I inspected it just like I would any brass, and noticed that I thought the primers had backed out a bit. They felt above flush with the rim. After putting them into my L.E. Wilson case gage, the rim was .008" above the top of the gage and the primer was another .004-.005 above the rim of the brass. My first thought is the headspace is off because everything I've read seems to point to that.
The ammo fired was factory Federal Premium with 140 gr. Nosler ballistic tip. The chamber was cut to SAAMI specs.
I'm new to shooting a magnum round, so I don't know if this is common with magnums, but I wouldn't think so. I have two other Savage bolt actions (22-250 & 7mm-08) and every fired case I've ever put into an Wilson case gage has measured out properly in regard to headspace. As far as my reloading practices, I neck-size only.
I wanted to ask you all before I hit up the gunsmith and have him rework the headspacing.
Please let me know if you need any other information.
I really appreciate your time. Thanks for reading!
 
Is the barrel fitted with a barrel nut or fitted with a shoulder? If it has a barrel nut, nothing to setting the headspace. Loosen off the barrel nut, set the barrel tight against the go gage with a stripped bolt, no ejector, no firing pin mechanism and tighten the barrel nut back down. If your primers are backing out, thats a sign of excess headspace. But, it can also be caused by pushing the shoulders back too much. As to finding 7 WSM brass, the brass is hard to find, but see if you can find loaded ammo from some of the vendors. Not the way you'd like to get brass, but better than nothing.
 
It's set up with a shoulder. No barrel nut. Sorry to leave that out. I haven't shot the rifle yet. I'm just going off of the brass the gunsmith shot in checking the function of the gun.
Yeah I've been buying ammo to use for my brass. If I wait around, I can find some good prices. I bought 10 boxes of that Federal Premium for less than $35/box from Midway back in March/April.
 
He might have got the headspace a tad loose. (I am defining "headspace" as the distance between the face of a chambered round and the bolt face with the shoulder of case against the shoulder of the chamber).

Simply put, the firing pin drove the case against the shoulder, the walls of the case gripped the chamber walls before the head of the case could be pushed back against the bolt face. Hence, the primer backs out a tad.

You could shoot it like this, just fire form all of your cases with a light load with some sizing wax applied to the body of the case, (this will let the case take the full form of the chamber), then set your full length die to "bump" the shoulder the correct amount.

But that being said, I think what you are seeing is a tad too much headspace with Factory ammo.

Strip your bolt, and chamber a round. Then cut some small piecees of paper and place them between the bolt face and the round. Keep doing this until you get some feel. Then measure the thickness of the paper strips.

Not exact, but it will give you an idea what you have. I would be concerned with anything over .006 inch, or at least concerned enough to give your gunsmith a call.
 
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A nogo gauge for your caliber would be a better way to check for excess headspace than your case gauge. Absent that, some tape on the back of a go gauge (assuming that you had no feel when closing on it) can be used to estimate how much longer than minimum your chamber is. Scotch tape, when doubled over on itself, sticky side to sticky side, measures about .004. By adding layers to the bottom of a go gauge, and checking as you go, you can estimate, clearance.

The protruding primer is commonly a sign of a low to moderate pressure load. I would add the amount of protrusion to the case measurement when estimating chamber dimension. In any case, I would use a nogo gage as my final word standard for determining if there was excess chamber headspace.

Just now, I went to the SAAMI site (Use Internet Explorer to get the drawings to come up properly.) and found the following information.
Maximum cartridge, head to datum line on case shoulder, was listed as 1.7680 - .007
Chamber headspace was listed at: Min. 1.7640 ; Max. 1.7740

I called Wilson just now, and the end of the gauge to the datum is specified at 1.768. The step is .005. I would imagine that case gauges might not be made to the same tolerances as headspace gauges.

Some time ago, I used a Hornady "headspace" gauge (actually a comparitor attachment for a caliper) to compare tight fired brass to a go gauge for my PPC. I found that that was a pretty good way to verify just how much over minimum headspace my chamber was. Generally, I much prefer the Hornady gauge for setting dies.
 
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Case gauges are a rough estimate, I wouldn't expect them to be any closer than 0.005". I have gauges from the same (reputable) maker that gauge differently enough that I labeled one 'tight'. I suspect they're made for relatively course visual inspection and not precise, quantified inspection. I'm not saying you don't have an issue, just that I wouldn't consider a case gauge to be definitive in making such a determination. Also, they're made to check sized cases, so checking a fired case doesn't necessarily tell you anything. As others have said, or implied, what you need are genuine go / no-go gauges.

GsT
 
Thanks for all the replies!
I got my no-go gauge in today, stripped my bolt, did quite a few test runs to get the feel of closing it without the gauge and then put the no-go gauge in. Closed fully without issue. Crap...
I repeated this several times to make sure I was doing it right and got the same results every time. I guess it's time to hit up my gunsmith to rework it.
Thanks again for all the help.
 
dbsavage said:
Thanks for all the replies!
I got my no-go gauge in today, stripped my bolt, did quite a few test runs to get the feel of closing it without the gauge and then put the no-go gauge in. Closed fully without issue. Crap...
I repeated this several times to make sure I was doing it right and got the same results every time. I guess it's time to hit up my gunsmith to rework it.
Thanks again for all the help.
Click to expand...

Before you do that stick a piece of thin tape of known thickness, one layer or more, on the face of the no go gage until you have a slight bolt feel so you can talk to your gunsmith from a position of knowledge.
 
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