I'm working up loads for a FN Mauser chambered .30'06. Most of my loads so far, and the factory loads I originally tested it with, chamber fine. But, I just loaded 15 rounds and 11 of them are difficult, to near TOO difficult to close the bolt fully.

COL is fine, same or shorter than any other loads I've run through it and over .2 shorter than max. Same sizing die I used for all the other loads, as well.

Considered maybe I didn't deburr the brass cleanly enough, but it doesn't seem to be that. The case necks are smooth.

The only time I've encountered this in the past was when I had a COL issue; a load for one rifle loaded almost to max length, tried out in another, and the chambers differed just enough to be an issue. I figure somebody here has encountered a similar problem, might have an idea of something else to check.

Thanks Much-
Andy

New brass? Fired brass? Sizing die setup properly? Seater die setup properly?

How many times have the offending brass been reloaded and has it always been shot in that gun?

Only time I've ever had that happen I didn't set the sizing die down far enough so the the shoulder didn't get pushed back properly. If the sizing die was set the same for all the brass, I don't see how this could have happened.

Twice fired brass, and no, not always in this rifle.

Sizing and seating dies set up properly; no problems from other loads in the same rifle with the exact same dies. Some scuffing on the brass, but now impossible to say if it was already there.

As will be volleyed back and forth across the net: you are either full-length sizing too much or not enough.

Check your brass length. Though its only been loaded twice it could have been near max from the factory and a couple of passes through a FL dies might grow it enough to pinch the neck.

I have had my dies loosen on the press in use, check to see they are screwed in tight

When you fire brass in differnt guns you may set yourself up for problems like this. If the other gun had a looser chamber than yours and more headspace your dies may not be pushing the shoulders back enough on the brass that was in the other gun.
I highly recomend getting a stoney point headspace bushing kit so you can see how much you are working the shoulders of your brass when sizing. Its the best $35 you'll spend on reloading equipment.
If it was me in your shoes my best guess would be to crank the die down every so slightly and run that brass through again.
Long story short...don't reload brass from another gun without checking to see if they chamber after resizing cause it ain't fun pulling bullets.

Freshly trimmed to spec before loading. Dies tight in the press. I check the dies routinely every few rounds.

I reckon I can check the sizer setting again, but doesn't make sense why the 10 rounds I ran through it before these 15 are fine (with a slightly longer bullet), not to mention the 4 in this batch that do chamber okay.

Not much else makes sense, either, though. A couple of them, I'll have to pull. They're just too tight. The others are tight, but the bolt closes, so I'll shoot 'em and set the brass aside so it doesn't get comingled.

Smart thing to do would be to keep brass with the same rifle for it's life span. I very abruptly see why that might not be such a detail-loony thing to do, after all.

. . . and, yeah, the head space bushing kit wouldn't be a bad investment. I've been lookin' for another toy, anyway.

I'm gonna beg you not to fire those sticky chambering brass till you know for sure it's just a shoulder dimension thats a hair long. Odds are it is but even a 5% chance that something is pinching on the bullet or neck of the brass could make for some bad high pressure. It isn't worth it. Park those shells till you get the gauge and can check it out.
I just bought some once fired brass to use in a tight chambered 270 win that I own. It was too cheap to pass up and I found out with the gauge that the brass was fired in two different guns. Some had the shoulders blown forward .002 more than my chamber and some was blown out .007. Long story short....I could use my normal die setting to chamber the shorter stuff but had to crank the die in a bit to make the .007 chamber in my gun. I might not buy any more brass like that for that particular gun.
Something thats been working good for me is I set my dies to work with at least one of my guns for a shoulder pushback of about .002. Then I put a mark on the threads of the sizing die right above the set screw on the lock ring. If I'm loading for another gun....maybe a buddies....and I need to adjust I find that moving the marks about 1/4" apart will make a change of about .004" on the shoulder. Also if you ever get into annealing you'll find that the brass softens up to the point that you will most likely need to make a die adjustment.

I assumed you were full length resizing the cases after firing in a different rifle. If not, then what Kraky said.

Make sure you didn't get some bullets with a different ogive (hitting the rifeling), I have found differences in batches of nosler partition over runs. I check every bag now.

Also make sure your seating die is not hitting on the case mouth causing a bulge.

The die is a full length sizer, don't understand why it would matter between rifles. I'm just gonna pull all of them and start over with these loads in once fired brass. I'll reset the die and see how the first couple chamber before I continue for another 15 round mess.

Thanks, guys. Have a great night and a good weekend!

Sometimes the inside neck sizing button pulls the neck
shoulder junction out a tad. it is hard to see it. Lube the
inside neck/ shoulder with Imperial Die wax with a Q-Tip.
If there is any amount of resistance or sound you button is dry.

Even if the COL is longer measured on the bullet tip with the cartridges that chambered, the shorter COL bullets could be longer if measured at the ogive because of a different bullet design. Check the sticky rounds for shiny marks on the ogive to indicate that you're jamming the lands. DON'T SHOOT THEM UNTIL YOU FIGURE IT OUT!!!

I think that is your issue. Also, COL had little to do with chambering, more with fitting into ones magazine. Chambering difficulty is mostly linked to chartridge dimensions.

Probably right on the different rifles point. If the chamber in the other rifle is bigger (not necessarily longer), your FL die will be squeezing the case body and pushing the shoulder forward when you size.

And BTW, COL can cause difficult chambering if the bullet is seated into the lands.

Your seating die may be set a touch low and crimping the case mouth to the bullet as you seat.
A little too much crimp will bump the shoulder back on your sized brass and slightly bulge the case just behind the shoulder.
The loaded round may or may not chamber of course.

Don't ask me how I know.
Just a thought, Good Luck!

Compressed powder charges? Compare internal volumes with known easy chambering samples?

It's a Mauser..are you feeding them from the mag or dropping them on the plate and trying to push feed them?

Minimum chamber dimensions on new rifle. Max. dimensions on sizing die, and max chamber on the rifle cartridges were originally fired in.

Brass is not being sized down enough in the body of the case. This is a common problem when using brass fired in another rifle.

Try to borrow another die from someone. By chance, you might get a die with Min. dimensions and can use the brass.