For anyone following the belted mag tight bolt chambering, mystery solved. Problem is Redding shoulder die is apparently long, or Remington rifle chamber is slightly short.

I Dykem blued up a case which I verified was tight like most. Interference is on the shoulder (long to headspace). Plans are to surface grind 0 .005" off the shoulder die to enable pushing back shoulder and hope that there's enough belt clearance (can bump back if necessary). I can then use Redding competition shell holders to adjust if necessary.

Thanks for the ideas and feedback, Mike K.

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K.I.S.S.

Full length resize you multi fired brass to be smarter than the equipment that you are attempting to operate.

Grinding .005" off the body die will not size the web of the case.
Redding body dies only size the body.

You do have an option since you elected to use Win brass.
Measure from head to forward surface of belt...should be .220"
You'll be lucky if your (junk)Win brass measures .212"

Unfortunately there are few choices in 264 Win Mag for brass. Don't ask why I'm shooting a 264 and not something else more popular. I deburr, trim, ream, and turn my brass and have had a problem with Winchester brass. In fact, I favor it over Remington brass and some others. Ok.

Before thinking of altering the die, I decided to look at my RCBS shell holders, I had three of them. Measuring them, I found 0.005" variation in length from where the brass head resides and where the ram bottoms, and coincidentally the one I'd been using would result in the longest head space.

I switched to the "taller" of the three shell holders and sized through my Redding body die, which DOES size the case body and shoulder. It does not size the neck (as bushing sizes that). Tried the sized case and chambers effortlessly.

Verdict - Be aware that RCBS standard shell holders have length variation high enough to cause head space trouble in belted magnums.

Case closed!

There alot easier way to do this, you still going to have chamber problem when you get to 4 to 5 firings

After comparing results from neck and full length sizing, I now size every firing.

How did you figure it was a headspace problem when a belted magnums headspace off the belt, there's no way to resize the belt

They can quite easily headspace off the shoulder once they've been fired, even though that's not the official use of the term for a belted cartridge.

Headspace interference causing tight bolt closure was on the neck shoulder and not the belt. I discovered this by Dykem bluing a case, showing contact witness. I can't say that now the neck is bumped back that I've verified contact to the belt, but it doesn't much matter as the bolt closes freely now.

The belt may/not be in contact but it really doesn't matter whether it's in contact with the chamber or if it's the bolt face to bottom of the case. Belted mags were developed around the 300 H&H as they had no shoulder. They really serve no purpose in a shouldered cartridge and most rifle mfg headspace off the shoulder, which is better for accuracy anyhow. Even if the headspace is initially set up off the belt,case expansion functionally drives it to the shoulder.

Even if you set your die to bump the shoulder your still going to have bolt resistance after 3 to 5 firing and a small base die won't take care of the web expansion. You need a collet die

True.

Here's a solution to sizing the area ahead of the belt. FL dies don't always get that area properly sized. Just another "reward" from belted cases. Don't see it in non-belted cases...

Not cheap, but it does work Good thing, one dies does all the std. belted magnums. I bought mine back when they were a bit cheaper. You don't have to use it every time, use it to rehab hard to chamber cases. They may do OK for several loadings before needing it again. And, IME, some rifle chambers don't have this issue, but some do.

http://www.larrywillis.com/

DF

Gemby58 is correct. I just recently picked up a collet die for my 300WM loading. Works great and keeps the bases of the cases from swelling past the point of being useable.

Maybe Redding revised their body dies, but mine sizes right up to the belt, and that was never my problem. I've measured cases and they are to spec right up to the belt shoulder itself. My body die has a small 90 deg counterbore to cover both the belt and size right up to the belt shoulder.

At any rate, it looks like I'm out of the woods for now, and will continue to body size every time using the "tall" shellholder to keep the shoulder off the chamber for just enough clearance.

My .264 thinks it's a 7mm Rem Mag based on headstamps it normally sees.

Just tested today. 100 yd with 95gr VMax with H4831 with 68.Xgr known load and 120gr ELD with 70.0gr Ramshot Magnum. 0.005" off, 4 -shot groups all touching, can cover with a dime. Between having action on the Sendero bedded and bumping the shoulder back 0.005" with shell holder, fun is a tack driver. Very happy. Time to step it out to 400, 500, 700yds. Scope is Nikon X1000 6-24x X 50mm MOA reticle. Love this scope, have 3 on rifles, hate that Nikon got out of scopes. If anyone has one they would like to sell I'm interested.

So does my 257 Weatherby

You're talking about the Larry Willis collet die, right?