I have a Savage 12LRP in 6.5 Creedmoor that shoots very well.  I also have a home-built Savage in 6.5x47 with a Rock Creek barrel in which I set the headspace pretty tight.

The issue I have is that the brass grows significantly on the factory Creed compared to the 6.5x47.  As a matter of fact, my Lapua brass for the x47 has been loaded 9 times and I've never had to trim the brass - not even once.  FL sizing the x47 is also almost effortless.  In comparison, the Creedmoor takes A LOT more force to resize and I have to trim the brass every one or two firings.

I load the Creed with Whidden FL bushing dies and Redding Competition shellholders for a .002" bump.  On the x47, I use Hornady FL bushing dies with the same shellholders for a .001" bump.

So here are my questions:

1)  Is the easy sizing and lack of trimming on the x47 Lapua because of the tight headspace or because of a tighter body spec?  Or both reasons?

2)  Would removing and re-installing the factory Creedmoor barrel to a tighter spec (virgin Lapua small primer brass grew .004" - .005" in headspace after firing) be a good idea to make my brass life longer and brass prep easier?

3)  Would I be a fool for messing with a rifle that already shoots 1/2MOA or better regularly even if I have to trim and replace my brass more often?

Thanks guys.

1) Maybe, maybe, or maybe, but the headspace is the main suspect if what you're saying is correct. The only problem I've run into with too little clearance was neck diameter. Bolt opening became stiff, and the primer started to crater.

2) Yes, but you only need to loosen the barrel nut and adjust properly, not remove the barrel completely.

3) No, it's almost guaranteed there will be an increase in accuracy. There really isn't any downside to adjusting headspace below .001 to barely touching.

I checked my Savage rifles and didn't hesitate to dive right in.

Thanks, wtfboombrb - that was very helpful!

So are you saying that when you tightened your headspace down to or near zero, it affected your neck clearance?  If so, what did you then do?

No, sorry for the confusion.

I pulled a barrel off a rifle and installed a match barrel for a change in cartridge. Went from .223 to .260. I used Lapua brass and got those pressure signs from the start.

The match barrel apparently has a match sized chamber. The Lapua brass has thick necks. I didn't want to get into the added hassle of neck turning so I switched to another brand of brass. Worked great.

That 0.002 bump is going to stretch every case 0.002 each time it is fired.

I have reset the headspace on every factory rifle I have ever owned.  So easy to do, once you have the proper tools, I don't see any reason to not do it...

I always set to zero headspace on barrel nut guns.

Thanks guys.  I'm going to reset my headspace.  Did resetting headspace affect the performance of your gun?  Did it change the harmonics at all?  Or did your tried and true loads pre-reset still shoot great after adjusting headspace?

It can increase pressure on a given load. I’d carefully watch using hot loads at first. Several of my rifles show a lot of pressure signs with factory ammo like gold medal match.

What signs? How much did you shorten?

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I never compare new brass length to my first firing length simply because virtually all brass comes shorter than it needs to be brand new.

Set your die up to bump the shoulder -.002" for a bolt action, -.004" for semi-auto based on your once fired case measurement.

I would consider sending the barrel back to manufacturer with a dummy cartridge using the Lapua brass. No powder, no primer. Tell them you want .003" to no more than .004" of neck clearance. They should fix it for free unless you ordered a custom neck dimension.

The signs were there from the tight chamber, not the headspace. Factory GMM is pretty damn hot even compared to the max loads in the loading books from my usage. You will typically get noticable ejector marks on the headstamp of the brass.

I am not trying to dissuade you from properly adjusting your headspace to minimum, just letting you know that factory ammo tends to be hot, not in the middle like many would expect.

Maybe I'm misremembering FGMM being referred to as "weak" (like 150fps slow).

Not in the 308 stuff that I have shot. Perhaps 2600-2650 range.