300 win mag headspace

I have read that the 300 winmag actually head spaces off the shoulder unlike other belted magnums but the Forster .535 head-space gauge looks to just be the belted rim part.

I was wondering if I could head space off of a fired or unfired round but I have already removed the factory barrel. Supposedly after firing that shell then head-spaces off of the neck since it has expanded to that area. But I probably wouldn't want to use a case formed to the sloppy old 111 300 winmag barrel to headspace a new ER Shaw barrel. But if it headspaces off of the belted rim I should be able to get pretty close with a factory round.

Bonjour!
Believe everything you read on the internet. It's all true. And no, it does not headspace on the neck. It would headspace on the shoulder.

If you're ok with having case head separation 3" from your face, by all means go right ahead and set the headspace using any old piece of brass you can get your hands on. Otherwise, use the headspace gauge and set it correctly and just neck size only. You'll be accomplishing the same thing without the possibility of early case head separation.

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Originally Posted by Hotolds442

Bonjour!
Believe everything you read on the internet. It's all true. And no, it does not headspace on the neck. It would headspace on the shoulder.

If you're ok with having case head separation 3" from your face, by all means go right ahead and set the headspace using any old piece of brass you can get your hands on. Otherwise, use the headspace gauge and set it correctly and just neck size only. You'll be accomplishing the same thing without the possibility of early case head separation.

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What he said. For a lot of things I'll substitute tools but this is not one of them. For your own sake spend the cash to buy or rent the proper tool.

Sent from my SM-T330NU using Tapatalk

X3. Headspace your barrel with the gauge. Size your brass to the chamber just bumping the shoulder a few thousands. Or neck size, whatever works for you.

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Originally Posted by Robinhood

X3. Headspace your barrel with the gauge. Size your brass to the chamber just bumping the shoulder a few thousands. Or neck size, whatever works for you.

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I have only reloaded for straight walled cases before but I plan on doing 223,308,and 300 winmag. How exactly would you determine how far back to set the shoulder? I would like to get away with just neck sizing if possible on bolt actions.

Let the shoulder set itself. After firing, smoke the case with a candle. Back your sizing die off and run the smoked case into the sizing die. Continually run the sizing die in until you achieve full neck sizing. At that point, you're not bumping the shoulder at all and will be headspaced to the shoulder. 1/32 of a turn in on the sizing die should bump your shoulder .002" if closing the bolt on a loaded round seems tight.

That pretty much sums it up. I use a Hornady head space gauge cause I have one. If you get there and need more help just post up the question.

Belted magnums are suppose to head space on the belt. However it seems that is not always the case. What most do is size the case to headspace on the shoulder which saves working the brass a lot. (less stretch)
One thing that shows up with belted magnums is case swells just ahead of the belt and you have hard chambering as the dies cannot size it back.

Anyone who does not set the initial head space on the belt is uniformed and Should not be installing a belted magnum barrel. As stated above, when installing the barrel it needs to be head spaced by the belt. You will find that all brass is manufactured within a couple of thousands of the belt head space dimension. The shoulder dimensions vary more than .010 from manufacturer to manufacturer. Once the brass has been fired then it is neck sizing or full length sized to bump the shoulder to your desired clearance, hopefully no more than .003.

You really need to measure some belts on cases.....they vary all over the place.

I've headspaced 300winmags with out go-nogo-gaguges. Initial headspace is set from the belt, therefore I took several types of factory ammo, took them apart and used their brass as go gauges. During this process I had to figure out which of the factory brass had the belt farthest up from the head, then used that brass for final headspace,... Then taped 1 or 2 pieces of masking tape on the head to use as no-go gauge (1pc of masking tape gives you >0.002" working headspace and 2 pcs = >0.004"). Works perfect every time. I use 1 piece of masking tape for target rifles and 2 pieces for hunting rifles.

Getting the proper go-gauge is better because it simplifies everything. I use go-gauges for regular bottleneck cartridges, it's the only way I trust to do it.

I don't plan on any belted magnum ever, but have found the discussion interesting as supposedly the belteds head spaced on the belt but lot of anecdotal says not. Having had a 7mm some years back and not having had that discussion......

Zero333: Not to be argumentative but I am confused that you would use the gauges on the bottle neck non belted but not the belteds as it seems to be the same thing?

I like how you went about it, logical and I believe safe.

I would like to add to this that the Model of 1917 30 caliber (aka 1917 Enfield 30-06) is extremely loose and you don't even bother with the first two gauges and jump right to the filed reject and the bolt almost closes on that!

While I don't claim it as definitive, my take is that you are better off with excess than too little.

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Originally Posted by RC20

I don't plan on any belted magnum ever, but have found the discussion interesting as supposedly the belteds head spaced on the belt but lot of anecdotal says not. Having had a 7mm some years back and not having had that discussion......

Zero333: Not to be argumentative but I am confused that you would use the gauges on the bottle neck non belted but not the belteds as it seems to be the same thing?

I like how you went about it, logical and I believe safe.

I would like to add to this that the Model of 1917 30 caliber (aka 1917 Enfield 30-06) is extremely loose and you don't even bother with the first two gauges and jump right to the filed reject and the bolt almost closes on that!

While I don't claim it as definitive, my take is that you are better off with excess than too little.

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I used factory ammo for headspacing 300winmags because after careful measurement, all factory ammo was within 0.0015" from base of the head to top of the belt. By using the brass that had the biggest space from the base of head to top of belt ensured that All other ammo would fit after setting the headspace as little as 0.002" (1 piece of masking tape).

After I fireformed 220 pieces of F.C. brass (Federal Premium FGMM 190gr SMK), now I just bump the shoulder no different than a non-belted case. This ensures the case doesn't stretch and thin right above the belt, which is what would happen if the belt controlled the working headspace, eventually after as little as 4 or 5 reloads it could rupture right above the belt from the thinning.

I use the Hornady headspace comparator to verify the amount of shoulder bump, which I keep around 0.002". This extends brass life and feeds smoothly into the chamber. Full length sizing can bump the shoulder more than 0.008", returning the job of controlling the working headspace back to the belt.

Only New never fired brass can be used for setting the headspace on a belted case because once you fire a piece of brass you can't guarantee the FL die will size the body right above the belt, leaving a slightly bigger diameter than original. Putting that sized brass in a chamber that's 0.001" tighter than the chamber the brass was originally fired in will not allow the brass to be seated right up to the belt because of that "bulge". But in case anyone has a "bulge" issue...there are a couple of specialty body dies that can remove the bulge.

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all factory ammo was within 0.0015" from base of the head to top of the belt.

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This was my finding as well.

Zero333: Thank you for the detailed explanation. I never reloaded enough 7mm to find out those issue (30+ years ago)

Funny part was that working up to go hunting one weekend and found I had no reloads and all the gear was packed away from a move.

Off to the store, grab 2 x 20 rounds of Federal something on sale, off to the range, dial in, and kind of hmmm, these aren't bad.

When I got back I did a 3 round accuracy check, as good as anything I ever reloaded, left the gear in storage and just bought another box of the Federals each year.

Out to 300 yards or so it's hard to better some of the factory ammo.

I actually use factory hunting ammo for a couple of my hunting rifles because not only do I not shoot them often but when I can't better the factory ammo I don't even bother.

Here is an example.

http://i464.photobucket.com/albums/r...ps6eocdjhz.jpg

http://i464.photobucket.com/albums/r...psdkpsetmw.jpg