Belted Magnum issue

[Luckus]

A buddy who just got in the handloading is having problems with a 7 Rem Mag. The area of the case just ahead of the belt is galling in the chamber and cases are hard to chamber and extract. They mic well under book spec when resized. Rifle is a 20 year old Rem 700 with maybe 200 rounds thru it. Any ideas? Luckus

[Apache]

New brass or old brass that has been shot several times?

[Luckus]

Old brass, not sure on firings, but I think twice. Luckus

[Stevens M200 30-06]

trim the brass to spec. probly the problem. alway trim the brass after shooting it.

[Apache]

If that's not it, it could possibly be that the FL size die isn't sizing down all the way to the belt.....sometimes takes a special die for that. Can't remember the name of the outfit that makes it though.

That's one of the problems with belted magnums. After several reloads or a couple high pressure loads will cause the case to swell just after the belt and a lot of dies will not size that portion of the brass.

[Luckus]

Apache, I think you are right.

[bigedp51]

See link below, it has a Belted Magnum Collet Resizing Die that sizes the case above the belt.

Innovative Technologies
http://www.larrywillis.com/

[Apache]

Thanks bigedp51..........that's the one I was thinking of.

[1983Weatherby]

This is common with magnum reloads. You need to full size the brass when it won't chamber. Make sure you bump back the brass. It should load after that.

[Luckus]

He is going to bring all his gear down to my place, and hopefully we can get it cured. I mic'd my die at the point ahead of the belt and it measures .511, that should work, Thanks to all. Luckus

[bigedp51]

Your problem is "cartridge headspace" aggravated by cases with a short belt which increases headspace. When full length resizing the shoulder gets pushed back too far and you are then depending on the undersized belt to control cartridge headspace. Set your dies up to only bump the shoulder of the case back .001 to .002 and let the case headspace on the shoulder and not the belt.

This is where the collet die come into play and is use the squeeze the case just above the belt where a normal FL die does not touch.

Below is a rimmed .303 British case being fired, a rimmed case and a belted case both have the same problem with undersized cases. Both type cases should be resized so the cases headspace off the shoulder and not the rim or belt for longer case life which helps prevent case head separations.

Below pay attention to the words "headspace" and "head Clearance" as these two words are what you are fighting with, and need to correct.

http://i122.photobucket.com/albums/o254/bigedp51/headspacestretch-c.gif

By only bumping the shoulder back .001 to .002 the case will headspace on the shoulder and the excess head clearance or "air space" behind the case is eliminated and the case will not stretch in the web area.

http://i122.photobucket.com/albums/o254/bigedp51/zeroheadspace.jpg

http://i122.photobucket.com/albums/o254/bigedp51/case-bulge.jpg

http://i122.photobucket.com/albums/o254/bigedp51/headspace-2.jpg

http://i122.photobucket.com/albums/o254/bigedp51/Headspace_2_lg.jpg
http://i122.photobucket.com/albums/o254/bigedp51/Headspace_1_lg.jpg

As you can see above if the belt is short it can create too much head clearance or air space behind the case. Not matter what type case you have above, you will get longer case life by letting the shoulder control cartridge headspace in the chamber.

[Luckus]

bigedp51, I understand completely what you are saying. I just corrected 50, 300 Win mag's for another buddy of mine by doing what you have so thoughtfully described above. The 7MM mag is another friend who is new to handloading, and I cannot scope out his problem until I have the rifle and his cases in my hands. As soon as I do, I will let you all know what I found. Thanks, Luckus

[Luckus]

My buddy brought the rifle, dies and cases down to my place on Sunday afternoon. I mic'd everything and found his dies were fine and resized cases chambered fine. His problem was very hard bolt lift after firing. His load was 56.5 gr imr 4350 and 139gr Hornady sp. Should have been a no problem load,but it's not. I pulled a bullet and recharged with 55 gr 4350, pulled the trigger and the case extracted perfectly. I don't recall the measurement, but the fired neck OD vs sized neck OD was .001-.002 difference, which indicates a real tight neck clearance, and maybe the reason for excess pressure. I told him to load a few more and this spring we will chrono this load and see where it's at. Hopefully the problem is resolved. The data on this cartridge in several books is all over the place. Luckus

[bigedp51]

Lets see, I loaded 55 grains of 4350 with a 130 grain bullet in my .270 Winchester.

This makes his 7mm Remington Magnum slower than my .270 Winchester and his loading density is way low.

This is why Jack O'Conner said the .270 Winchester was the best non-belted magnum in the world.

Start looking for problems starting with case length, the Hornady Number 7 manual lists 61.9 grains as maximum and the Hodgdon's website lists 63.4 as a maximum load with IMR4350.

[maclowry]

Tag
As I will start reloading .300wm