How much variation in shoulder from chamber to chamber?

[entoptics]

Any of you have base-to-shoulder data on a couple (or more) rifles for the same cartridge? What kind of variation is normal?

Got a 7mm Mag coming, and want to load a few rounds for "w000h000, I got it" as well as break in.

I have a couple hundred once fired brass from an older Remington 700, and am hoping to get a handle on how far back to bump the shoulder, without being excessive, so the first 20-30 reloads will function properly.

I have a rule, that I shoot a new gun the day I get it, so I need to have a couple dozen rounds loaded before I get the rifle in hand. Obviously, once I have a few down the pipe, I'll measure its headspace, and size accordingly.

What's do you think the typical variation among rifles is? 0.002", 0.004", 0.010"?

 

[Black Hat]

Removed

 

[MNbogboy]

Why not just run a box of factories through it?
You could look up the saami chamber specs & tolerance for the variation in shoulder to base that is "allowed". Then FL size your old brass to the saami min.
Shoot it!
Good luck

 

[Black Hat]

Removed

 

[just country]

morning, look up the blueprints of the cartridges in question.
justme gbot tum

 

[L.Sherm]

That's a crap shoot trying to guess, if your have a Smith spinning on a new barrel try and get a print, some headspace tight some dont.
Generally factory guns are on the " loose " side that I've got and loaded for.
The once fired brass may not need it at all. Sizing cases to far back is were people get head separation on belted cases hence the bad rap.
I'd just wait untill you get the gun and try some cases then load some the same day.

 

[lancetkenyon]

From about 15 I have loaded for (custom amd factory rifles), most factory virgin brass, with my Hornady 420 comp insert, will be about 2.103-2.105".
Most fired brass I have seen are 2.121" to 2.124". So 2.119" usually fits in most chambers.

 

[shortgrass]

Start with new brass. Cartridge cases that were fired in another rifle are often a waste of time, especially if that 'new' chamber is custom cut. Your question was about lengths, but you need to take diameters into consideration, also. Sizing dies for the belted mags don't 'size' all the way to the belt unless you have an Accurate Innovations collet sizing die, and it only sizes at the belt and nothing more. A new chamber deserves new brass. Cutting corners trying to save a couple of bucks isn't worth it.

 

[J E Custom]

Start with new brass. Cartridge cases that were fired in another rifle are often a waste of time, especially if that 'new' chamber is custom cut. Your question was about lengths, but you need to take diameters into consideration, also. Sizing dies for the belted mags don't 'size' all the way to the belt unless you have an Accurate Innovations collet sizing die, and it only sizes at the belt and nothing more. A new chamber deserves new brass. Cutting corners trying to save a couple of bucks isn't worth it.

Exactly !!!!

The only real way to find out everything about a chamber is to fire a new case in it.

Older cases fired in another may not exactly fit your chamber and give you false readings. Once you fire the new case, you can try it for fit and size it just enough to chamber well or not at all.

J E CUSTOM

 

[milo-2]

That's a crap shoot trying to guess, if your have a Smith spinning on a new barrel try and get a print, some headspace tight some dont.
Generally factory guns are on the " loose " side that I've got and loaded for.
The once fired brass may not need it at all. Sizing cases to far back is were people get head separation on belted cases hence the bad rap.
I'd just wait untill you get the gun and try some cases then load some the same day.

If you need to use fired brass from a different chamber, follow this advice. No reason to do or try anything till you have the rifle in hand.
I'm not going to lecture on using fired brass in a new chamber as there are dies to make brass fit.

 

[Frog4aday]

<SNIPPED STUFF> I'd just wait until you get the gun and try some cases then load some the same day.

This seems the simplest and most prudent course of action. Doesn't take long to load up 20 rounds once you see if the brass you have will chamber.

 

[shortgrass]

correction: Innovative Technologies (larrywillis.com) makes the collet sizing die, not Accurate Innovations. They make stocks.............

 

[entoptics]

Thanks for the replies, particularly @lancetkenyon's data. The new rifle is a Savage 110 High Country, so factory "SAAMI" chamber.

Why not just run a box of factories through it?...
Good luck

Don't wanna spend $35 for 20 chamber molds.

From about 15 I have loaded for (custom amd factory rifles), most factory virgin brass, with my Hornady 420 comp insert, will be about 2.103-2.105".
Most fired brass I have seen are 2.121" to 2.124". So 2.119" usually fits in most chambers.

Exactly the type of information I'm after. From your data, it looks like I can aim for a 0.004" bump, and likely be able to chamber.

Start with new brass...A new chamber deserves new brass. Cutting corners trying to save a couple of bucks isn't worth it.

I have 200 brass, so it's not exactly "a few bucks". More like 25% of the cost of the rifle.

Also, in my experience new brass is WAY smaller than most chambers, and requires at least one fire form before it's close to the chamber. Based on lancetkenyon's data, and my own experience with other cartridges, fired brass will be much closer to the final chamber size than virgin brass. Unless I have a particularly tight chamber on the new gun, and a particularly loose chamber on the old rifle, it seems like once fired would actually be a better place to start load development than virgin brass.

This seems the simplest and most prudent course of action. Doesn't take long to load up 20 rounds once you see if the brass you have will chamber.

Where I shoot is 5 minutes from my FFL, and both are 25 minutes from my house, so having a handful of rounds ready would save me a bunch of driving. Also, with the stupid time change, it gets dark around here at 4:15PM. Depending on when I can pick up the rifle, I might not have time to make the trip.

I'm a seasoned reloader, and understand the consequences/implications of brass sizing and chamber variations. If I truly get terribly unlucky, and the brass can't be FL sized down correctly, then of course I'll have to bite the bullet and start from scratch. Not gonna drop $200 till I know that for sure though...

 

[entoptics]

From about 15 I have loaded for (custom amd factory rifles), most factory virgin brass, with my Hornady 420 comp insert, will be about 2.103-2.105".
Most fired brass I have seen are 2.121" to 2.124". So 2.119" usually fits in most chambers.

Unfortunately, all I have is the 0.41 hornady comparator insert. I'm getting 2.137" on the once fired. Using the magic of trigonometry, I calculated what it would be at 0.420, and I got 2.126". Pretty dang close to your results.

Think I'll knock em back 0.005" with my FL die and hope it's enough. I've dealt with two OEM Savage 300WM chambers, and both were significantly longer than a Shilen pre-fit and a factory Rem 700 Long Range, so my guess (i.e. wishful thinking) is I'll be fine.