HELP!! 6mm ARC cases stuck after sizing?

[SMTGWKD]

About 40% of my resized cases stick hopelessly in the chamber of my rifle and I have to mortar them out with a mallet and wooden dowel. Same result in two separate rifles with different manufactured parts.

I've resized one piece 3 times to confirm that I didn't short stroke. Sticks after every resize. I then measured dimensions and couldn't find any notable difference between the stuck cases and the others.

Parts and Tools are:

Forster Coax Press
Hornady 6mm ARC Die
JP Bolt with Proof Barrel
Odin Bolt with Faxon Barrel

Your help is GREATLY appreciated.

 

[Precision Underground]

Case is likely not sized all the way down to the webbing. You may need a small base die if you’ve already run them to the base of the die you have. If you can add a turn more to the die you have and resize them again I’d try that.

Are you sure your bullet isn’t jamming in the lands?

 

[SMTGWKD]

Interesting - since I'm sitting here I tried turning the die 180 degrees and it changed them from hopeless to tough, but possible.

What small base die do you recommend? All my other dies are RCBS - start there?

 

[918v]

Do your fired cases chamber easily? They should. They were fired out of your chamber. Measure them at the base and at the shoulder. Then compare the base and shoulder diameters to your resized cases.

 

[Precision Underground]

Do your fired cases chamber easily? They should. They were fired out of your chamber. Measure them at the base and at the shoulder. Then compare the base and shoulder diameters to your resized cases.

Fired cases from a gas gun don’t always fit back in the chamber bc they are still expanding as they’re being extracted.

 

[918v]

Fired cases from a gas gun don’t always fit back in the chamber bc they are still expanding as they’re being extracted.

But sometimes they do. Maybe he should try it.

 

[SMTGWKD]

Tried 3 spent cases from today. Results:

1 went in and out cleanly
1 went in and stuck (bolt wouldn't go in battery) but came out with quite a bit of force
1 went in and stuck, then had to be mortared out with dowel and mallet.

I think we're on the right track here as I shoot suppressed 100% and I'm sure the case is being extracted a bit early. This should be resolved in resizing though, right?

I'll add buffer weight to see if I can slow it down some. I only run adjustable gas blocks so can tune easily.

 

[Precision Underground]

But sometimes they do. Maybe he should try it.

Do your fired cases chamber easily? They should. They were fired out of your chamber.

 

[SMTGWKD]

I don't think any of my semi auto cases will consistently rechamber due to what you described - especially since I run suppressed and higher pressure rounds like ARC and Creedmoor.

 

[Precision Underground]

Tried 3 spent cases from today. Results:

1 went in and out cleanly
1 went in and stuck (bolt wouldn't go in battery) but came out with quite a bit of force
1 went in and stuck, then had to be mortared out with dowel and mallet.

I think we're on the right track here as I shoot suppressed 100% and I'm sure the case is being extracted a bit early. This should be resolved in resizing though, right?

I'll add buffer weight to see if I can slow it down some. I only run adjustable gas blocks so can tune easily.

Resizing should make them fit. It’s not unusual for fired cases not to fit so it doesn’t mean there’s a problem. Are you sure your die is screwed in as far as it can go?

 

[SMTGWKD]

With a Coax it bottoms out. I'll try a slight cam over...gimme 5...

 

[SMTGWKD]

Ha! Ran 3 through with a cam over and voila. Fixed.

I always set them up with cam over on my old RCBS but didn't for some reason on the Coax.

Changing all sizing dies now...

Thanks Gents!

 

[Precision Underground]

Ha! Ran 3 through with a cam over and voila. Fixed.

I always set them up with cam over on my old RCBS but didn't for some reason on the Coax.

Changing all sizing dies now...

Thanks Gents!

 

[SMTGWKD]

Now if only I didn't have to size 400 perfectly prepped cases....

 

[Modoc]

Look on the bright side, at least they are not fully loaded cases. Nothing worse than having to pull several hundred because of an oops (happened to a friend).

 

[SMTGWKD]

Ha! I'm 200 into it... and your 1000% right. Tell your friend I'm sorry for his carpal tunnel.

 

[Modoc]

Ha! I'm 200 into it... and your 1000% right. Tell your friend I'm sorry for his carpal tunnel.

He already had Carpal Tunnel

He did throw away the kinetic bullet puller and bought an RCBS Collett style after that exercise.

 

[918v]

I asked him to do that so he can get a case to measure and compare to a sized case. He succeeded.

 

[Precision Underground]

Look on the bright side, at least they are not fully loaded cases. Nothing worse than having to pull several hundred because of an oops (happened to a friend).

This. OP pat yourself on the back for making sure the cases fit before you loaded them.

 

[SMTGWKD]

Sizing complete - deciding whether I toss them in the wet tumbler after hornady One Shot...Hmmm

 

[hlee]

So how does adding the cam over affect your head space? Sure, it sized down the web, but did you also push the shoulder back?

 

[Yondering]

Good grief. Yet another thread with someone refusing to measure shoulder bump, while complaining about the exact problem caused by not bumping the shoulder enough. And most likely solved by bumping the shoulder too much.

I thought we were beyond this, here on this forum? Is it just all the new people who haven't learned the basics, or what?

 

[MarkyMark007]

I thought we were beyond this, here on this forum?

retards are in majority on this planet, especially in america.

 

[Precision Underground]

Good grief. Yet another thread with someone refusing to measure shoulder bump, while complaining about the exact problem caused by not bumping the shoulder enough. And most likely solved by bumping the shoulder too much.

I thought we were beyond this, here on this forum? Is it just all the new people who haven't learned the basics, or what?

From my experience, a case bottoming out at the shoulder doesn’t stick. The case bottoms out and the bolt won’t close. You’d have a hard time even knowing you were .005 long unless you tried to close the bolt. A case with an expanded web does stick. This is (most likely) where his problem was. Also, how much shoulder bump is too much? That answer will be dependent on other factors. Micro-adjusting the die to bump the shoulder no more than .002 is not a requirement and is actually ill-advised in a lot of cases when you’re loading for gas guns.

 

[Yondering]

From my experience, a case bottoming out at the shoulder doesn’t stick. The case bottoms out and the bolt won’t close. You’d have a hard time even knowing you were .005 long unless you tried to close the bolt. A case with an expanded web does stick. This is (most likely) where his problem was. Also, how much shoulder bump is too much? That answer will be dependent on other factors. Micro-adjusting the die to bump the shoulder no more than .002 is not a requirement and is actually ill-advised in a lot of cases when you’re loading for gas guns.

In an AR? Of course they stick. Maybe not always, but often enough to be a common issue. Simple to try for yourself.
That's not at all the same as a bolt action with a lot of leverage to cam a round in and out of the chamber.

And it's a pretty basic and often repeated tenet of case sizing to bump .003-.004" for ARs, not .001-.002" for bolt guns. You seem to be giving a lot of advice that's not actually very good advice or grounded in solid understanding.

As to how much bump is too much? Do you really not know much about shoulder bump and case life? This stuff isn't rocket science, and solid answers are out there all over the web for anyone who cares to actually search and learn.

Don't pretend to be an expert on something if you're going to mess up the basics. The truth becomes really obvious, really quick.

 

[918v]

Sizing complete - deciding whether I toss them in the wet tumbler after hornady One Shot...Hmmm

Did you measure around the cases to see how the sized ones compared to the unsized one that chambered easily?

 

[Precision Underground]

In an AR? Of course they stick. Maybe not always, but often enough to be a common issue. Simple to try for yourself.
That's not at all the same as a bolt action with a lot of leverage to cam a round in and out of the chamber.

And it's a pretty basic and often repeated tenet of case sizing to bump .003-.004" for ARs, not .001-.002" for bolt guns. You seem to be giving a lot of advice that's not actually very good advice or grounded in solid understanding.

As to how much bump is too much? Do you really not know much about shoulder bump and case life? This stuff isn't rocket science, and solid answers are out there all over the web for anyone who cares to actually search and learn.

Don't pretend to be an expert on something if you're going to mess up the basics. The truth becomes really obvious, really quick.

Lmao.

 

[Rocketvapor]

LMAO, also
How can people troubleshoot a stickage problem without knowing headspace of sized cases in their own chamber?
Shooting an AR, suppressed, and a 'high pressure round' like an ARC (huh?) and yes you will get case expansion.
I shoot a NO-GAS AR for mid range prone. Cases are blown out full length. I run pretty hot loads. I need about 0.004" headspace to reduce stickage. 0.002" and cases are blown out to the bolt face and tough to extract.
Pressure is zero when I extract and cases are cool. Case body spring back eliminates that as a cause.
I size to dummies made to fit my chamber length (headspace).

Just this week I've seen several threads about sized cases sticking. Everything from peened necks, bullets sticking, cases blown out oversize, and bumping more and more until stickage is eliminated. How much is too much? How would you know if you didn't know how much is just right?
Bumping more and more just to size down the body just doesn't sound right to me. And, this 'Cam over' thing.

 

[Mike Casselton]

Good grief. Yet another thread with someone refusing to measure shoulder bump, while complaining about the exact problem caused by not bumping the shoulder enough. And most likely solved by bumping the shoulder too much.

I thought we were beyond this, here on this forum? Is it just all the new people who haven't learned the basics, or what?

I'm glad the OP got it solved...

With that said, back when Christ was a Corporal, people would buy actual reloading books and guides.

Then, they would sit down in their favorite chair with a hot toddy.

While sipping on the concoction, they would begin at page 1 and actually read the process, the how-to section and the troubleshooting.
Then, they would read the cartridge descriptions and load data.

If they got really curious, they would even check out the trajectory charts.

They knew the cause and effect before the first pull on the handle.


Most questions were answered before they ever got asked.

Nowadays, it's hit EweToob and watch a bunch of videos about how to really complicate a very simple process, while ignoring the primary steps.

New reloaders are overwhelmed and totally confused as to which process will make simple, reliable ammunition.

People need to learn that first, then start heading into the rabbit hole.

 

[Rocketvapor]

I won't resort to calling people (on this forum) retards.
A lack of knowledge is just that.
This thread, and another recent one was solved by bumping more, and I saw no objective evidence that actual headspace was determined.
Solved? Maybe, maybe not.

 

[SMTGWKD]

Glad you never encounter mistakes as you learn. I also appreciate your condescension to add valuable insight. Thanks!

 

[SMTGWKD]

Wow - just read the entire thread. Guess guys like me who are learning what they can aren't too welcome (I shoot some PRS and am an enthusiast who runs maybe $150k in rifles/pistols/suppressors). Am I a "retard" for not knowing what you know? Would you be a retard if you didn't know core competencies I posess?

For the sake of our gun community at large I genuinely hope our community doesn't treat others with the same bullying. We need more curious and thoughtful dialogue - you know, the kind men used to have face to face when both are carrying a sidearm?

 

[Rocketvapor]

I'm sorry if I am one of those that came over as condescending. MY comments are primarily to those that offered advice. Advice that may not be completely accurate or safe.
There's plenty I don't know.

 

[Precision Underground]

LMAO, also
How can people troubleshoot a stickage problem without knowing headspace of sized cases in their own chamber?
Shooting an AR, suppressed, and a 'high pressure round' like an ARC (huh?) and yes you will get case expansion.
I shoot a NO-GAS AR for mid range prone. Cases are blown out full length. I run pretty hot loads. I need about 0.004" headspace to reduce stickage. 0.002" and cases are blown out to the bolt face and tough to extract.
Pressure is zero when I extract and cases are cool. Case body spring back eliminates that as a cause.
I size to dummies made to fit my chamber length (headspace).

Just this week I've seen several threads about sized cases sticking. Everything from peened necks, bullets sticking, cases blown out oversize, and bumping more and more until stickage is eliminated. How much is too much? How would you know if you didn't know how much is just right?
Bumping more and more just to size down the body just doesn't sound right to me. And, this 'Cam over' thing.

Serious question bc I’ve never shot no-gas AR. If all of your cases are blown out, wouldn’t that be a sign that you’re overpressure? A no gas AR is essentially a bolt gun, right? When we shoot bolt guns and get a blown out case(assuming blown out means stretched to the point of fitting tightly in the chamber) it’s usually a sign of excessive pressure. Does that not apply to a no gas AR? I guess I’d need to know your definition of blown out.

A lot of times our fired gas gun brass won’t fit back into the chamber without resizing due to the base of the case being expanded. I know it’s the base of the case bc when I drop it in the chamber it sticks before the shoulder would bottom out if it just needed a few .001 bump. I always assumed it was bc it’s being ripped from the chamber while still under pressure and the base of the case is the first thing to leave the containment of the chamber. I have no scientific proof of this concept but I’ve read about it and it seems to line up with reality bc I can fire our bolt gun brass several times while only neck sizing and have no problem with cases expanding too much to fit back in the chamber easily. Shouldn’t no-gas gas gun cases behave in this same way? Maybe AR chambers (typically) being slightly larger is a factor because more expansion is allowed before brass expansion is contained by the chamber walls, I don’t know.

From my experience loading for gas guns… and just from using reasoning, if a case drops into the chamber and obviously sticks before the shoulder bottoms out, the base of the case is expanded. Turning the die further in is not necessarily bumping the shoulder more and more if the base of the case is being sized before the shoulder ever contacts the die. Either way, the OP got his cases to fit in his chamber.

Should he get a headspace comparator and fine tune his die assuming he will only use this ammo in a single rifle and wants to minimally size his cases? Sure. But some are assuming we all want to minimally size cases. The OP said he tested the cases in multiple guns. If he wants to use the ammo in multiple guns he shouldn’t fine tune the cases for a single rifle. To say that using the full length of a sizing die is unsafe is not accurate unless you have big problems with your die or your chamber. A lot of our 5.56 ammo is made to minimum spec because I want to be able to shoot it in any of our rifles(or any rifle that happens to be available in a pinch). The guy pontificating and calling the OP a retard without considering this needs to check the mirror. And guess what, the ammo made to minimum spec shoots pretty much as good as the ammo that I meticulously bump the shoulder on.

Id be willing to bet his shoulder bump is fine. He essentially tuned his die without even meaning to. The cases wouldn’t fit. He turned the die in more and it helped a little bit but still wouldn’t chamber. He then cammed over and it now chambers. There’s no way camming over is adding more than .001-.002 bump so it’s not likely that he added a massive bump there.

OP- read up on fine tuning headspace by turning your die in small increments. Grab a headspace comparator and next time you resize these check the headspace of a fired case vs the ones you just sized and report back.

 

[918v]

“From my experience loading for gas guns… and just from using reasoning, if a case drops into the chamber and obviously sticks before the shoulder bottoms out, the base of the case is expanded. Turning the die further in is not necessarily bumping the shoulder more and more if the base of the case is being sized before the shoulder ever contacts the die. Either way, the OP got his cases to fit in his chamber.”


Using your own reasoning, when a case expands during extraction it is going to expand in every direction, including shoulder length. Therefore the die will contact the shoulder and will size the shoulder more and more as you screw in the die.

 

[918v]

I think, based on the totality of OP’s posts, it could have been too much shoulder length or too much case diameter or both. There has been a lot of chamber/die mismatch with all these new calibers .

 

[Rocketvapor]

@Precision Underground (only)
The extraction of an AR/gas round relies on gas force to unlock the bolt, often a little early, allowing the body to expand a little outside the chamber. A No-Gas AR, almost like a bolt gun, leaves the case inside the chamber but does not have the decocking advantage of rotating the bolt with a big ass handle.
0.002" headspace results (in my case) in a case stretched by the 0.002" (datum to base) and a tight extraction. 0.004" and stickage is pretty much eliminated. I have a bore swab on a 90 degree handle I use after every 20 rounds or so to clear some carbon from the neck area that also helps
( I shoot 60+ rounds per match).
Yes, that would tend to equate to a little heavy bolt lift in a bolt gun.
Factory rounds start out with about 0.004"- 0.005" headspace and don't stick.
Regardless of stretch, I size to my chamber plus what I think I need for headspace.
The commonly accepted 0.004" for a gas gun (with gas) stretches cases more than a bolt gun and requires watching for body thining.
I tend to to get loose pockets long before I have to worry about head separation. Some cases might make 5 or 6 reloads where I lose 10% of the pockets that feel loose.

Getting cases that won't chamber is annoying but not knowing the headspace of loaded ammo could be unsafe.
Or, at the very least, wear out cases sooner than expected.
A full length sizing die should be set for bump. If the base isn't sized enough then use a small base die.
Long story short,
KNOW how short your sized cases are.

The No-gas AR I am referring to is a 22 Nosler using Nosler and Dogtown brass.
My loads are pretty stiff. No obvious pressure signs and at or near the upper range of published reloading data.
I send 88's and 90s at high 2900s from a 28 inch barrel.
Check reloading data for the 22 Nosler, usually listed with a 24" barrel, and Staball6.5 powder.

90 grain Sierra:

Winchester

StaBALL 6.5

0.224"

2.460"

29.3

2,649

42,500 PSI

32.3

2,889

53,500 PSI

SAAMI pressure for the 22N is 55k
Plug an 88ELD (.224) with a muzzle velocity of about 2970fps into your favorite calculator.


I do not own a 6ARC, in AR or bolt gun. Watch out for gas gun vs bolt gun reloading data.
In a bolt gun the 6ARC cuts the mustard

 

[SMTGWKD]

Appreciate the thoughtful replies. I'm very interested to learn from others on this as I have 3 rifles with JP BCG (VMOS, and 2 LMOS) each with Proof Carbon barrels for which I've experienced identical case "stickage", but only after switching to the Coax. Two 6.5 Creedmoors and one 6mm ARC. I've never encountered it with any other combos till the 6mm ARC situation (two sets of manufacturers, etc). I have one of the JP BCG and Barrels back at Proof and they are checking headdpacing, etc as it was blowing Primers with factory ammunition. I don't have the tools to confirm, but it appears the combo is on the tight side. Will be interesting to see what Proof determines.

For clarity, the sticking cases are occurring on chambering in that the bolt cannot go completely into battery and requires sharp force to eject. This spoke to what is mentioned above about the bottom of the case not being completely sized and I'm guessing is exacerbated by suppressed use - even with heavy mass and adjustable gas my cases are extracting sooner than I'd like.

As I alluded to above, in my excitement to load with my new Coax Press, I set all my sizing dies to contact, but not cam over like the RCBS instructions indicate (i.e. screw till it touches, then add a quarter turn). As a result, I've been relying on my downward force, and not the mechanical advantage of the press, to completely size brass. Sometimes it was enough, sometimes it wasn't. The input above reminded me of my mistake and after following the same process (touching, then a quarter turn) every sticky piece of brass chambered and ejected with ease.

For reference, I've shot 400 rounds of factory ammunition through the 6mm Arc rifles without issue so I don't think headspace is off, but certainly correct me if I may be wrong. Luckily, I found this issue when 2 of the 10 round I loaded to confirm loads at 1200 yards would not chamber, fire, nor eject. Had I loaded the lot I'd still be camming...been there, done that.

 

[SMTGWKD]

I may have missed intent somewhere - skim read posts before my son's baptism and saw some strong assumptions/words. Thought they were directed at me.

Regardless - I do appreciate advice and look forward to studying up on headspace/etc.

 

[918v]

What tools do you have to measure cases?

 

[Rocketvapor]

Let us know what Proof says. Head space with quality parts is likely to be OK even with a somewhat new caliber.
By blown primers you are referring to primers blown back out of the pocket, or pierced by the pin?
Over gassed ejection could be a cause of blowing out a primer. Pressure still high when case is being pulled out.
Cutting back gas will slow down ejection and since you mentioned 1200 yards, cycle speed (pew, pew, pew) is not your intent
I don't run a suppressor but you will read about many ARs with gas issues when suppressed.
I have never been to 1200 yds (yet). Still trying to Master 600.
Have a 600yd match on the 15th.
Wife will be shooting a 22 Nosgar, similar to mine but with minimal gas.
Dribbles cases about a foot or so.

 

[Mike Casselton]

I won't resort to calling people (on this forum) retards.
A lack of knowledge is just that.
This thread, and another recent one was solved by bumping more, and I saw no objective evidence that actual headspace was determined.
Solved? Maybe, maybe not.

Solved...
Probably a poor choice of words, but I agree with you.

He got his brass to fit into the chamber, but they may not fit well.

Sorta like shoes. I wear a 12.
I can squeeze into 11-1/2 with some effort, but it's not a correct fit. They are harder to take off too.

I can slip my feet into 13s without issue, but it doesn't solve the proper fit issue. It's a sloppy fit.

Size 12? Most of them fit correctly, but might need different socks to fit just right.

It's ^^^^^^^ like the difference in that last .0005 of sizing whether it is correct, or more like, uh, that'll work.


Here's how simple it is:

My older brother, bless his heart, has always worn 10-1/2 shoes.
A few months back he bought some new shoes for work and the guy brought him size 11.
He said they felt perfect so he bought them without realizing the guy sold him a pair that was in his opinion, a half size too big.

After getting home he noticed the size, so he tried them on again.
That's when he said he realized that all his adult life he's been wearing the wrong sized shoes.

He confirmed it by trying on the numerous 10-1/2 sized ones he already owned. They hurt his feet.

When he related the story to me, I couldn't help feeling like I needed to say "how fucking dumb can you be?"


Anyone, no matter how ignorant they might be can post EweToob video and literally confuse half of the population.

Getting your knowledge from actual experts is the proper way to learn. Those experts usually work for ammunition and component manufacturers.

 

[Rocketvapor]

Wearing shoes that are too small?
That's just retarded.
Sorry, just had to

 

[Mike Casselton]

Wow - just read the entire thread. Guess guys like me who are learning what they can aren't too welcome (I shoot some PRS and am an enthusiast who runs maybe $150k in rifles/pistols/suppressors). Am I a "retard" for not knowing what you know? Would you be a retard if you didn't know core competencies I posess?

For the sake of our gun community at large I genuinely hope our community doesn't treat others with the same bullying. We need more curious and thoughtful dialogue - you know, the kind men used to have face to face when both are carrying a sidearm?

I can only speak for myself.

I hope my response didn't come across as condescending. It wasn't meant that way. It's more of a general observation over the last 20+ years of using forums.

Somewhere along the way, people stopped trying to truly learn. (Your post isn't like that. You simply reached out for some assistance.)

What was once a slow learning curve has become a congested highway of bad drivers dispensing even worse advice.


One of the best learning tools are the old chamber cutaways.
It gives people a chance to look at how brass and loaded rounds are supposed to fit together.
It makes improper sizing, case length and seating stand out like a sore thumb.

The thing that stands out for your post is that you took some of the advice and made it work.

Now it's time to fine tune your knowledge and brass fit.

 

[Mike Casselton]

Wearing shoes that are too small?
That's just retarded.
Sorry, just had to

Dude, you have no idea how hard it was to just bite my tongue...

 

[SMTGWKD]

Anecdotally - when I started reloading 6 or so years ago (I'm 41 and started when my father gave me his old scale and press - decided I had to earn the privilege and started reading and studying up) I only loaded for bolt rifle chamberings. I measured all kinds of things for my rifles then and set dies to bump the shoulder back just enough and load projectiles at the ideal jump for each rifle after seating depth tests - and for the most part it was pretty straightforward.

Fast forward 50+ firearms later, add a stable of suppressors, and a multitude of different length semi loaders/gas systems and oh how things have complicated! The import of headspace, timing, gas, etc is magnified and I frequently hit my knowledge limits.

I've since paired down my reloading chamberings to the 4 I shoot most and worked to find loads that all my rifles shoot well enough (like 140 ELDM over 41.5 h4350 or 147 ELDMs over 42.2 RL16) to load in bulk and hold out the specialty loads for my competition rifles. I borrowed a friend's comparator then, but need to add some tools to my arsenal to troubleshoot and diagnose.

As mentioned above, this simple catch was the result of a few things I HAVE learned, one of which is to check chambering/ejection of a random sampling of sized brass before loading them up. I had to pull 300 rounds of creedmoor once and never want to repeat that if I can help it.

For comedic relief, I made this neat ornament when I switched from seating 108 ELD to 58 VMax in the 6mm...

 

[Rocketvapor]

I think everyone has a few 'ornaments' like that

 

[Yondering]

Appreciate the thoughtful replies. I'm very interested to learn from others on this as I have 3 rifles with JP BCG (VMOS, and 2 LMOS) each with Proof Carbon barrels for which I've experienced identical case "stickage", but only after switching to the Coax. Two 6.5 Creedmoors and one 6mm ARC. I've never encountered it with any other combos till the 6mm ARC situation (two sets of manufacturers, etc). I have one of the JP BCG and Barrels back at Proof and they are checking headdpacing, etc as it was blowing Primers with factory ammunition. I don't have the tools to confirm, but it appears the combo is on the tight side. Will be interesting to see what Proof determines.

For clarity, the sticking cases are occurring on chambering in that the bolt cannot go completely into battery and requires sharp force to eject. This spoke to what is mentioned above about the bottom of the case not being completely sized and I'm guessing is exacerbated by suppressed use - even with heavy mass and adjustable gas my cases are extracting sooner than I'd like.

As I alluded to above, in my excitement to load with my new Coax Press, I set all my sizing dies to contact, but not cam over like the RCBS instructions indicate (i.e. screw till it touches, then add a quarter turn). As a result, I've been relying on my downward force, and not the mechanical advantage of the press, to completely size brass. Sometimes it was enough, sometimes it wasn't. The input above reminded me of my mistake and after following the same process (touching, then a quarter turn) every sticky piece of brass chambered and ejected with ease.

For reference, I've shot 400 rounds of factory ammunition through the 6mm Arc rifles without issue so I don't think headspace is off, but certainly correct me if I may be wrong. Luckily, I found this issue when 2 of the 10 round I loaded to confirm loads at 1200 yards would not chamber, fire, nor eject. Had I loaded the lot I'd still be camming...been there, done that.

Look, nobody's gotten on to you about wanting to learn. (My original comments were to the other people giving you "advice".)
But at this point in the thread, you should have figured out by now that you need to be measuring your shoulder bump. If you're not sure how to do that, just ask - it's very easy to do and you can even do it with just a sized 9mm case if you don't have the right tool.

But throw away the instructions for the "contact plus quarter turn" crap for the sizing die. That's old school b.s. for lowest common denominator reloaders who can't understand headspace. That method sucks, and is horribly inaccurate. Instead, measure your shoulder bump and set your die for the amount of bump you want. You'll discover that even when camming over there's a significant range of adjustment. Measure, don't guess.

On the subject of headspace - headspace for your brass in your rifle is NOT about a reference to a headspace gauge, instead it's completely about how you adjust your sizing die. Bump the shoulder back too much - you've got excess headspace. Didn't bump it enough, and cases stick - you've got zero headspace because the brass is crushed into the chamber and now it doesn't want to extract.

 

[Rocketvapor]

I bump 0.002" for the wife's gasser. I can live with that due to the low gas setting (set for the load).
I separate the upper and hold the case under the extractor and ease the BCG forward.
Sizing past no close, to close with a click, to easy close, then my desired headspace.
I usually run mine with a little more for the skickage issue.
Point being, I KNOW what my actual head space is with my loaded rounds.
The belled X39 case also goes over seated bullets.

Bumping a 6mm Hagar case to a 22 Nosler chamber with a body only die is more than normal bumping

I think where we are failing to communicate the concept of bump for headspace is thinking running the die down to fix a swollen case fixes a sizing problem. It fits so it must be good (not exactly ).
Size for bump/headspace .
If the case still won't chamber all the way go to a small base die and
size for bump/headspace.
Know the headspace of YOUR reloads in YOUR chamber.

 

[Yondering]

Id be willing to bet his shoulder bump is fine. He essentially tuned his die without even meaning to. The cases wouldn’t fit. He turned the die in more and it helped a little bit but still wouldn’t chamber. He then cammed over and it now chambers. There’s no way camming over is adding more than .001-.002 bump so it’s not likely that he added a massive bump there.

That sentence in bold says that you haven't spent much time measuring bump with cammed over setups. Different amounts of cam over does still change shoulder bump by more than that. And you're completely guessing about where his die was set before and where it is now. Literally, you have no idea, but are continuing to "give advice" that is of zero value. Just stop.

Also, you still seem to be missing the fact that most bolt actions have leverage to cam a sticking round out of the chamber, but the AR15 platform does not, at all. A round that doesn't even stick enough to be noticeable in a bolt action can completely lock up an AR. This is why you can get away with neck sizing only, or partial full length sizing, etc without any shoulder bump in a bolt action, but not in an AR.
You're making bad assumptions about what a sticking round means in an AR, and giving bad advice as a result.