The question is headspace for rifle cartridges.
I am not a complete newbie, but I would like some clarification from the experts on "headspace"
ESPECIALLY for rifle cartridges using a controlled feed action. I believe, from Michael 458 and others experience, that with CRF actions, the "shoulder" is not important.The Cartridge is held by the extractor, and cannot go forwards with the primer strike.
Am I missing something?
If so, I am very lucky. I inadvertently fired a 9.3x57 round in a Husqvarna 9.3x62 action, with a slight "poof", but no other sequelae. Like firing a 243 in a 308 chamber, completely safe, if inadvertent.
SO
Is it true that with a controlled round feed action,the head-space is not AS important?

A NEW REASON FOR CRF, if correct?

While it is possible that the extractor on a CRF rifle can hold a round firm enough that it will fire, that is not it's purpose.
It is possible that you could chamber a short .358 Win in a .270 chamber with disastrous results.

A CRF does not change the need for correct head space!

If the cartridge is belted it is designed to headspace on the belt and headspacing on the shoulder, while not required for proper ignition, may influence brass life (if reloaded) and may influence accuracy. A non belted cartridge with slack headspace on the shoulder may fire, or may not fire, or may hang fire, or may sort of fire but have low velocity as a good primer strike can not be relied upon if the cartridge is solely retained by the extractor. The long and short of it is that proper headspace is important.... more important if you may be betting your life on it.

The only answer is; NO, headspace is very important no matter what type of action the rifle has.
Excessive headspace can cause a case head separation on the first firing, even if the case is held by the extractor.
When it comes to fireforming a cartridge in an improved or altered chamber with factory loads, yes, the CRF action can assist with this, but cases like the those that have the shoulders moved forward a considerable amount require mechanical means of holding the case against the bolt face, belted magnums don't require this, though, as the belt controls headspace near perfectly, even when blowing the shoulder forward.

Cheers.

Also consider that the belt dimensions aren't held to particularly tight tolerances and you will see it is usually best to make your belted ammo seat on the shoulder.
Also, if most people knew how much variations are allowed from min ammo to max chambers, they would shudder.
And, I have fired many .308s through 30-06s and 7.65 Argentines, without issues; the ammo being held back by the extractors. Still, it is always a good idea to minimize the distance from the bolt face to the case head. Everything is happier when you do.

Well think about the 450 Bushmaster, 50 Bewolf used in a AR rifles. Both head space on mouth.

Headspace is your guide to safety. It is a must, but it can be on the belt or the shoulder with a belted cartridge..It was designed to headspace on the belt, end of story BUT you can also safely headspace it on the shoulder just like a 30-06 or any non belted round.

The extractor has nothing to do with the equasion other than holding an improper round against the bolt face when the primer strikes, and I'm not sure that's such a good idea as one has no business shooting such a case in his rifle.

Belted cartridges that are headspaced on the shoulder by the reloader tend to be more accurate and cases definitely last longer as the brass is not stressed as hard with each firing.

I always recommend setting up your reloads to have the shoulder just a hair off the chamber, just enough to chamber with little effort.

This is done by using a match to blacken the neck area of the case, and using the resizing die as it will mark the neck a bit at a time until you reach the shoulder junction, then back off ever so little until the case chambers with ease. Now you have a perfect fit. If its still a bit snug chambering then take the neck down in the die just a tad more. Now lock your die in place. Some folks resize very snugly and compress the case very tight in the chamber for accuracy and that's Ok, but not good for a hunting rifle as more important than accuracy in a hunting rifle is dependability and feed and function is best every time.

This is definitely NOT a silly question.

Headspacing off the case mouth in Big Bore rifles is not thought of highly by most of us. Personally I will never do it! unless the Case length is rigorously measured and maintained, you can get a case that's too long and crush the case mouth into the bullet resulting in a huge pressure spike when the cartridge is fired. If that load is at the max end of pressure,a kaboom is quite possible.
As others have said,headspace is extremely important and it's usually done in big bores off the belt or off the shoulder. I've seen people headspace off the rim with shell holders and off the case mouth, but that's not how I was taught to do things. However you do it, most accurate rifles have a headspace of 0.003 or less.
You can make a lot of stupid things go boom even with crazy headspace up to 0.030.however, my head isn't going to be anywhere near it!

CRF is about feeding and extraction
headspace datum is about headspace

these aren't actually related

Think of headspace as how well the shoe fits the foot.If the shoe is to big or too small it is going to hurt.If the shoe does not fall off the foot it makes no difference and you should still go by fit.