Forming 7mm-08 Rem Brass from Federal Brand 308 Win Brass

[lightload]

My 308 brass is once fired. I will resize cases in a 308 Win die and then run the cases into a 7mm-08 Rem resize die. Then I will trim cases. Also, I will remove the expander from each die. Later I will expand in a separate operation. I will trim cases. Zero cast bullits will be loaded--J words only.

My concern is increased neck thickness that would create excessive pressure. I'm seeking advice on the total process and ask for dimension criteria for case necks. Is annealing required?

I realize that I could buy 7mm-08 Rem cases but wish to experiment.

[eastbank]

works well as .243 will too. i have half a bucket of once fired.308 BHA MATCH CASES GIVEN TO ME BY A BLACK HAT SHOOTER FRIEND.

[jdsingleshot]

Why do you plan to run them through the .308 dies first? Seems unnecessary.

If the formed case with a bullet in place will chamber without resistance, I would not worry about neck thickness. Worth checking, though.

[Mk42gunner]

My semi-educated guess is you will be fine with normal .284" j-words. I have necked down .30-06 to 6.5-06 without having to thin necks.

To be absolutely sure, you will need to do either a pound slug or a chamber cast of your rifles chamber then compare to one of your necked down cases with a bullet seated.

I would wait until the case forming is done before annealing, I have never had good luck annealing before hand.

Robert

[redriverhunter]

here was my experice, sized 308 to 7mm08 by the 3 firing as a 7mm08 if I remember correct I started getting alot of vertical stringing. I turned my necks of the 7mm08 vertical string went away. My understanding it is as the brass is fired and sized the brass moves forward making pressure spikes.

[Dom]

In 1994 I built a 6.5x308 wildcat which became known as the 260 Rem. I form my cases direct from fired 308 brass. One pass thru my 260 FL sizer, load & shoot. Never once have I had necks that were too thick. Always had the neck expand-er in place. Only thing I check for is, length, & that has never been a problem. Simple..

[Rapier]

If you lube the neck in and out, keep the expander ball in place and run the FL resize with the 7-08 FL die. If you pull the expander first and lube it then reinstall, it helps. You can also use a shot bottle with powdered graphite to lube the neck in and out.

[Texas by God]

Neck up .243 brass and no worries about thick necks. We tried .308 brass through a 7mm-08 die to feed a Remington 788 when the 7mm-08 was new.
Hard bolt lift on starting loads. Then we noticed that a fired case wouldn’t accept a bullet…… they would require turning.
We then necked up .243 brass and used those happily until my brother was able to find 7mm-08 brass.


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[pworley1]

All my 7mm08 brass started out as 308. I run them through a 7mm08 file trim die then a 7mm08 full length sizing die and load and shoot.

[MarkP]

You should be fine unless the rifle was chambered with a custom reamer having a smaller diameter non standard neck. I know for sure one company uses the same final draw punch for 308 and 7-08. (Same mouth thickness before tapering) Not sure what you have to take measurements with so a comparison may be better. If you only have calipers; Measure the neck of a fired 7-08 cartridge and compare to the neck of a loaded round using a reformed case. Your loaded rounds should be 0.002 to 0.003" smaller than the fired necks. If you have a micometer, Measure the neck of a loaded round and compare to SAAMI max cartridge.

[BK7saum]

You should be fine unless the rifle was chambered with a custom reamer having a smaller diameter non standard neck. I know for sure one company uses the same final draw punch for 308 and 7-08. (Same mouth thickness before tapering) Not sure what you have to take measurements with so a comparison may be better. If you only have calipers; Measure the neck of a fired 7-08 cartridge and compare to the neck of a loaded round using a reformed case. Your loaded rounds should be 0.002 to 0.003" smaller than the fired necks. If you have a micometer, Measure the neck of a loaded round and compare to SAAMI max cartridge.

This!!!

A simple measurement of a fired case with calipers to confirm that the loaded neck is at least 0.003" smaller for margin of safety.

i just formed 250+ 260 remington from Lake City 308.

While not necessary, I neck turned them midway at 7mm-08.

Step 1. size in 308 die w/o expander (not necessary but 308 sizes the base slightly smaller than the others)

Step 2 size in 7mm-08 w/o expander

Step 3 Anneal

Step 4 expand with expander mandrel

Step 5 turn necks

Step 6 Size in 260 remington die with expander in place

Load and Shoot

I turn necks at 7mm so that when I neck down to 6.5mm, i do not have to worry about a donut at the base of the neck.

My cases necks on loaded cartridges are approximately 0.006-7" smaller than a fired case neck. This is an AR10 platform and I like a little extra clearance since it is shot suppressed and gets a "wee bit filthy"

Point blank range on coyote is a little over 300 yards based on experience with 95 VMAX at about 3100 fps.

[lightload]

I appreciate the many good suggestions. Thank you.

[ebb]

The oal of the case must be right cause if the case is too long when you chamber it the neck will get pinched down on the bullet and cause very high pressure. I say this to you cause when i first started reloading I thought i knew it all and severely over pressured a Ruger 25-06 making this mistake necking down 270 win brass. The other thing that can be a problem is too thick of a neck. Assembling a loaded round is easy measuring the inside of the chamber not so much. If a loaded round of your formed brass is vey much bigger than a loaded factory round i would do more research to find out how much is too much before I pulled the trigger. if you want to assure that the neck diameter is small enough instead of necking down 308, neck up 243 or 260 Remington.

[country gent]

Measure a few factory 7-08 loaded rounds and compare to your sized down reloads if they are larger you may have to ream or neck turn them, better would be a chamber cast to get the actual neck dimension. Make sure and get back as far to the shoulder as you can.

Sizing down thickens brass sizing up thins it.

WHen you set your die set it so the sizes case has a little resistance in the bolt closing to hold it snug when fire forming