I am going to start reloading for my Finnlight 300 WM. I havn't tackled belted cartriges before so i'm riding on training wheels. What are the important points of reloading them. I have a set of RCBS F/L dies for them. I'm hearing that you can headspace off the shoulder instead of the belt? Any knowledge would be appreciated.

You're on the right track. I set all my dies to headspace on the shoulder, and it's especially important with the belted magnums.

The easiest way to do that is to use a fired case that WON'T chamber in your rifle. Start sizing it with the shell holder 1/16" away from the bottom of the FL resizing die. Size and try...if it won't chamber, screw the die another 1/4 turn deeper in the press. Repeat this procedure until the case will chamber without undue pressure on the bolt handle and then set the die lock ring.

My belted magnum brass lasts 10 or more reloadings using this method.

I will say, never ever belted caliber to me.

As much trouble as belted cases are, makes you wonder why they were ever designed...

quote:

Originally posted by homebrewer:
As much trouble as belted cases are, makes you wonder why they were ever designed...

The .375 H&H didn't didn't have enough shoulder to headspace off of so the Brits added the belt. Most magnums in one form or another have been derived from that case so the belt is merely vestigial.

quote:

Originally posted by icemanls2:
I am going to start reloading for my Finnlight 300 WM. I havn't tackled belted cartriges before so i'm riding on training wheels. What are the important points of reloading them. I have a set of RCBS F/L dies for them. I'm hearing that you can headspace off the shoulder instead of the belt? Any knowledge would be appreciated.

Iceman, If you are loading Virgin brass you might want to carefully examine or measure the shoulders on your brass. Since they are spec'ed to headspace on the belt, some virgin belted mag brass has very short shoulders. Some that I measured in 338 Win mag had shoulder .040 short of fired cases.

They will function OK with the short shoulders but they won't be as accurate as cases that headspace off the shoulder. Some people like to make a false shoulder by expanding the neck to 8mm or so and then resizing the neck partially until it will snugly chamber with the stepped neck acting as a false shoulder. It won't be an issue with fired brass since they will have expanded to your chamber.

I've seen this problem more with 338 brass than 300 Win brass but it's just something to remember if your accuracy with Virgin brass doesn't seem as good as once fired.

If I'm loading for a new 300 Win mag, I load from 74 to 77gr of RL-22 and a good 180gr bullet (try Accubonds). I've had great luck with RL-22 and 180's in several 300 Win Mags...................................DJ

Right now all i'm gonna load are once fireds from my rifle, no virgin brass. So if the rounds were fired in my rifle i should be ok to F/L resize as long as i don't bump the shoulder back? Or should i bump the shoulder back a couple thousanths like my normal bottlenecks? RL-22 is what i was thinkin of going with, I've heard alot of good about it with 180's.

If anyone is having a problem with a Belted Case, the problem is with the person - not the Case. You treat it the same as any other Case and it will do fine.
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Nice post by DJ about creating the False Shoulder. I normally just Seat an El Cheapo Bullet(hard to find now days) so it is 0.005"<->0.010" Into the Lands and Fire Form the new Cases. Works well for me.

By the way, the 300WinMag is one really fine cartridge. Has enough Recoil to know you shot it and enough Energy way down Range so it makes a significant Impact on the Game. Works well with a number of Powders too, which is also real nice. And provides long Case Life if Reloaded properly.

Doesn't have the "Feeding Problems" associated with some of the Short Fat designs either. And it has that excellent Belt.

quote:

Originally posted by icemanls2:
Right now all i'm gonna load are once fireds from my rifle, no virgin brass. So if the rounds were fired in my rifle i should be ok to F/L resize as long as i don't bump the shoulder back? Or should i bump the shoulder back a couple thousanths like my normal bottlenecks? RL-22 is what i was thinkin of going with, I've heard alot of good about it with 180's.

+2 to what dj and HC said.

The only thing about what you asked is that you may not be able to bump the shoulder back until you have fired the case 3 or 4 times. IOW the case does not develop a crush fit until it has been fired that many time.

You can set your die to FL or PFLR size but it will not bump the shoulder until the case has expanded enough. If you set your shoulder back before the case has fully expanded then you are pushing it back too far.

For example a typical measurement with the Hornady Headspace Gauge on a 300 win mag of mine goes like this

new case - 2.253"
once fired - 2.270" (neck size)
twice fired - 2.272" (slight crush fit, still neck size)
3 times fired - 2.273" (crush fit, time to push the shoulder back)

The problem would lie that if you set your die to push the shoulder back .001" on once fired to 2.269" then you would actually have a gap of .004".

Short story, don't push your shoulder back until your case has expanded to hit the shoulder and you have a crush fit.

Now there is the fact that once your die starts to size the case body it will push the shoulder forward, but in my tests it is usually .001" or at most .002". That will shorten the expansion sequence but you will still not be able to get a crush fit with once fired cases.