Belted mag help

[Gray R]

Hey guys I just traded into a 7 mag and I plan on reloading for it cause I seem
To be incapable of leaving well enough alone. I've never had a belted mag before so I was going to ask how to set my die so it headspaces on the shoulder instead of the belt. I've reloaded for a few years now so I've got the basics I just never understood what people meant by set the die for the shoulder not the belt. Would I be doing it similar or completely different from say my 308 and 6.5x284? I appreciate the help and forgive what might be a rookie question

 

[Jud96]

Just buy a neck sizing die and neck size for it. This will get rid of any problems a belted magnum may have.

 

[Bullet bumper]

If you just neck size only eventually the case will get too tight to chamber and in some cases the body of the case will swell in front of the belt and cause hard chambering .
Sizing to head space on the shoulder is the same as for a non belted rimless round . The problem with the belted case is you have to make sure the body of the case is not jamming in the chamber so you can adjust the sizing die a little at a time on a tight case to just get it back in the chamber .
The good thing is the belt is always the fall back head space position if you over shoot the shoulder head space position .
You can't really create a dangerous condition as is possible with a non belted rimless case , the shoulder will mainly blow forward anyway on a belted case .
There is two dies that will make your life easy . Redding body die number 75136. This die will allow you to size just the body part a bit at a time to head space on the shoulder .
Larry Willis Innovative Technologies Belted magnum collet sizing die Innovative Technologies - Reloading Equipment This die will allow you to size down any potential swelling right at the belt but does not bump the shoulder. This die may not be absolutely required , it all depends on how the chamber is cut and how well the other size die works , like if it gets down low enough . However it's very handy to have to make sure you are feeling head space chambering on the shoulder when you adjust the other die and not jamming on the body above the belt instead.

 

[MudRunner2005]

I neck-size all my belted mags, but about the 3rd or 4th time I load them, I FL size them.

I set all my dies up just like I do for my non-belted calibers.

 

[Lefty7mmstw]

fl all the way here; set your dies up for slight resistance chambering (.002"- "003" or so setback) and forget it has a belt. As said earlier, you can use the belt as secondary headspace for fire forming or to correct brass you've bumped to far setting the die. The only belted I have that needs the belt at all is my 375h@h.

 

[Timber338]

Get a set of the Redding Competition Shellholders and FL resize with whatever dies you already have with the die making hard contact with the shellholder. Finite element analysis has proven they are the most repeatable at setting +.001 to +.002" of headspace and also eliminates the belt from coming in to play. Redding has detailed instructions on how to use them correctly.

 

[Gray R]

I appreciate that timber. Do they directions you're referring to come with the dies or should I look separately?

 

[Timber338]

I appreciate that timber. Do they directions you're referring to come with the dies or should I look separately?

I think both with the shellholders and on their website. Download their PDF catalogue and see what they say there. Just don't let their listed MSRP prices scare you. Much cheaper on midwayusa or wherever else they are sold.

 

[Timber338]

I just read over what Redding has online, and there's a few things I could add that might help you in selecting the right shellholder. First off, make sure you adjust the press so you are confident the top of the shellholder is firmly contacting the bottom side of the die at the top of the stroke.

Next, you want to eliminate the bolt spring from adding any force when you close the bolt. With a winchester action you can just put the safety in the third position and it will hold the firing pin and spring while you close the bolt. On a remington action you'll want to disassemble the bolt and remove the spring. Then get a feel for how easy the bolt closes with a fired case in the chamber as well as empty.

Then starting with the +.010 shellholder, perform a FL resize as you normally would. Clean the lube off of the case and insert into your chamber and close the bolt. It should feel VERY hard to close the chamber. At +.010, the body of the case will have been resized and pushed the shoulder of the case forward causing a high interference. Continue to resize with each progressively shorter shellholder, +.008, +.006, +.004, etc. Each shorter shellholder will push the case into the die +.002 further than the previous shellholder and bump the shoulder an additional +.002. Your goal is to find the shellholder where you first feel zero interference when you close the bolt. I do this with most of my rifles and it gets you right to within -.001 to -.002 of clearance between the shoulder and the chamber.

You can also use a headspace gauge to measure your fired case, and then simply find the shellholder that sets the shoulder back .001 to .002". On my custom rifles, I always have the gunsmith provide a chamber gauge and this is the most accurate tool to be 100% confident you are where you want to be. My gunsmith takes a rifled barrel section of the same caliber, and cuts into the the shank up to the shoulder with the same reamer he used to cut the chamber in my rifle. Then I insert a fired case in the chamber gauge and I have an exact reference to the size of a fired case without any guesswork. But just playing around with my custom rifle, I was able to determine the same correct shellholder just going by feel. Takes more time, but you can still get there just going by feel.

Good luck!