Stumped 308 headspace issue

[micj83]

Loading for a new rifle. HS Precision pro-2000 with a 26" proof 9tw carbon 308 Winchester. Loading with Forster co-ax, RCBS sizer (no expander), 21st century .3065 mandrel, Hornady OAL gauge, and headspace comparator. LC M118LR once fired cases. All annealled prior to sizing, neck turned, and weight sorted.

To start off. Took measurements of chamber. Chamber length came in at 1.6255" on my headspace gauge. Set my FL sizer to 1.6230 (.0025 bump). Resized a bunch of cases afterwards. Loaded up rounds and found I had a few that were hard to chamber. Went back to the bench and measured a bunch of cases. I did find a few that didn't get sized all the way (<~5%). Not sure how that happened.?.?.? I tried to chamber them after resizing a second time and no improvement. Hard time getting the extractor to latch over the rim and hard bolt throw down. Bolt will come 90% of the way up then stops. Gotta put some effort in to get the last 10% of movement. Thus, ensue chaotic thoughts. Brass? Sizer? Barrel?

Any thoughts on the subject? I'm assuming the barrel was a blank as the chamber info was never struck. No idea of the smith either. The one thing I'm hung up on is the barrel. It's a shooter, but when cycling the same hard to chamber round in the chamber repeatedly it would develop a shiny ring at the base of the case. That ring however was not concentric around the case. It would be almost all the way down to the rebated step and the opposite side is about 1/4" away from that step. I did that test with a sharpie to highlight it. Let me know what you think?

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[bcp]

Some thoughts:

Did you do the first firing, in this rifle, of these cases? If not, maybe they were fired in an oversized chamber and your die doesn't resize small enough on some cases.

Custom barrel: You may have a minimum or below chamber (not headspace but base diameter.)

Borrow a friends sizer die to try, just for some more information.

Maybe you need a small base die.

Bruce

 

[saxon]

cast your chamber and check size.

 

[micj83]

Yeah these are all mil-surplus. I had the same thought on being from an out of spec chamber. I also thought maybe run the small base option on those who aren't chambering. It looks like they are all tight at the base. I pulled out my mic and most were oversized compared to good ones. But there were also some that were exactly the same size and still didn't want to chamber. And lastly we don't have many good smiths around us anymore so casting the chamber will be another day lol. Thanks for all the input. I was just tired of racking my brain. I opted to just cull the brass that feels oversized.

 

[Local Loader]

Have you checked the angle of the shoulder?
I know it seems simple but some times that's the cause.
Also a small base die or a Hornady die as it seems to be small base by default(at least mine were).

 

[drstrangelove]

Try brand new brass and report back. Once your gun fires these they will be spec to your chamber and then you can neck size and shoulder bump with a Forster die meant for it. That's the easiest road to take.
On fired brass, I'm Not thinking your RCBS die is getting down far enough… particularly if you are setting your full length die to bump shoulder as opposed to reverting case to factory spec, as is what RCBS is meant to do.
Reducing the size of brass fired in a bigger chamber is going to be difficult the older and stiffer that brass is. A small base die is likely the ticket to reforming the brass bases.
I had similar issues with war vintage Mauser brass. I test fit all of those first and tossed the ones that wouldn't chamber because the brass was already so stiff, the cases were cracking necks on firing. Annealing only partially helped. Wartime metallurgical QC, not intended to reload, I imagine.

 

[Steel Head]

Is that brass fired from a machine gun?
They are famous for long chambers.
Annealing before sizing makes a huge difference.

Personally I'd skip unknown brass for new brass and start there.

 

[Member 361]

I have found that this slotted gauge: https://sheridanengineering.com/product/308-win-ammunition-gauge/ has really helped me diagnose issues.

 

[micj83]

Is that brass fired from a machine gun?
They are famous for long chambers.
Annealing before sizing makes a huge difference.

Personally I'd skip unknown brass for new brass and start there.

No they were all fired from M24 SWS or similar.

 

[Koda]

To start off. Took measurements of chamber. Chamber length came in at 1.6255" on my headspace gauge. Set my FL sizer to 1.6230 (.0025 bump). Resized a bunch of cases afterwards. Loaded up rounds and found I had a few that were hard to chamber. Went back to the bench and measured a bunch of cases. I did find a few that didn't get sized all the way (<~5%). Not sure how that happened.?.?.? I tried to chamber them after resizing a second time and no improvement. Hard time getting the extractor to latch over the rim and hard bolt throw down. Bolt will come 90% of the way up then stops. Gotta put some effort in to get the last 10% of movement. Thus, ensue chaotic thoughts. Brass? Sizer? Barrel?

Any thoughts on the subject?

How did you take measurements of your chamber?

Take your measurements off of fireformed brass. Start with a fully sized brass if needed. Keep setting the shoulder bump back until an empty sized case closes easy, thats your shoulder bump size target. Maybe even add a thou or two to that for tolerance as most people squeeze calipers +/-.002 depending on their mood that day.

 

[NeoBlackdog]

SAAMI puts a standard .308 Win chamber at 1.630" – 1.6340". If I read the above right your chamber is starting off at 1.6255" or 00.0045" short. Given that 7.62x51 brass is fractionally longer to start with I think I'd be starting with .308 brass and making sure it was getting bumped back enough to accommodate what sounds like a short chamber. Does the gun chamber factory .308 rounds alright or do they have some resistance?

 

[P7M13]

• What year code follows the LC head stamp? Some years have more spring back than others due to metallurgy, like @drstrangelove suggested.
• Do you have a case gauge? I use a LE Wilson one. If a case doesn't fit after a first sizing, or not drop out cleanly, I cull it.

On an aside, I stopped turning necks. I could not find any statistical correlation to ES/SD or accuracy.

Maybe even add a thou or two to that for tolerance as most people squeeze calipers +/-.002 depending on their mood that day.

That's some gorilla shizzle right thar....

 

[Stomper]

• What year code follows the LC head stamp? Some years have more spring back than others due to metallurgy, like @drstrangelove suggested.
• Do you have a case gauge? I use a LE Wilson one. If a case doesn't fit after a first sizing, or not drop out cleanly, I cull it.

On an aside, I stopped turning necks. I could not find any statistical correlation to ES/SD or accuracy.


That's some gorilla shizzle right thar....

I believe you're referencing the "Ham Fists" troupe of gorillas mainly located in the dense jungle forests of Waconda.

 

[Spitpatch]

If it chambers, fires and ejects factory ammunition and brand new factory brass, there's nothing wrong with the gun.

Measuring chambers, etc. maybe somebody's idea of fun, but not necessary.

A tiny fraction of what was spent on the rifle would buy some brand new brass for it (that it deserves).

"Problem" (false economy using brass fired in another gun) solved.

 

[Aught Six]

We used to loadem weak, then use those cases and neck size only.
"Oh darn honey, I have to go out to the range again"

 

[micj83]

How did you take measurements of your chamber?

Take your measurements off of fireformed brass. Start with a fully sized brass if needed. Keep setting the shoulder bump back until an empty sized case closes easy, thats your shoulder bump size target. Maybe even add a thou or two to that for tolerance as most people squeeze calipers +/-.002 depending on their mood that day.

Using a standard case gauge setup. Measured a couple dozen of fired cases. Mean ended up where it was. Initially seat bump to -.002 but after setting lock screw it ended up being -.0025. Close enough for me.

 

[micj83]

SAAMI puts a standard .308 Win chamber at 1.630" – 1.6340". If I read the above right your chamber is starting off at 1.6255" or 00.0045" short. Given that 7.62x51 brass is fractionally longer to start with I think I'd be starting with .308 brass and making sure it was getting bumped back enough to accommodate what sounds like a short chamber. Does the gun chamber factory .308 rounds alright or do they have some resistance?

I don't have any factory stuff laying around but it will chamber some new 7.62X51 ammo. I will have to measure it for size comparison. Like I said most chambered fine after annealing and sizing. Just a say 10% of total, as I'm sure these weren't all fired from the same firearm.

 

[micj83]

• What year code follows the LC head stamp? Some years have more spring back than others due to metallurgy, like @drstrangelove suggested.
• Do you have a case gauge? I use a LE Wilson one. If a case doesn't fit after a first sizing, or not drop out cleanly, I cull it.

On an aside, I stopped turning necks. I could not find any statistical correlation to ES/SD or accuracy.


That's some gorilla shizzle right thar....

These are all LC '19 batch. Sorted to ensure that. I'll have to look for that post info on spring back. And no I don't have a case gauge. I haven't had a 308 for good while. Had to re buy everything to get going… kinda avoiding spending more lol.

As for turning. I've seen a positive improvement from turning. But it was inconsistent at points till I started running the mandrel first. Hypothetically maintaining centerline while trimming the fat. That being said, hand loading is a labor of love that I enjoy so I will endure the pain. Thanks for the input

 

[micj83]

If it chambers, fires and ejects factory ammunition and brand new factory brass, there's nothing wrong with the gun.

Measuring chambers, etc. maybe somebody's idea of fun, but not necessary.

A tiny fraction of what was spent on the rifle would buy some brand new brass for it (that it deserves).

"Problem" (false economy using brass fired in another gun) solved.

I understand the argument, but 4 kids and a working for the government doesn't leave a lot left to play with… however free brass that is once fired. With plenty of time to play with it to make it right works for me… save what I can for a nice optic.

 

[Mono1]

I believe you're referencing the "Ham Fists" troupe of gorillas mainly located in the dense jungle forests of Waconda.