Forming 7mm Creedmoor brass from 308

[CanSniper]

The 7mm Creedmoor is pretty new uncharted teritory and not alot of info, so I thought I would share my experiance.

For most that venture down this road the simple answer will be to use Hornady 6.5CM brass and simply run it through a full lenght die set up for 7CM. Simple wham bam done. Nothing at all wrong with Hornady brass and makes it very easy. I however am a habitual tinkerer, and can never leave well enough alone. SOooo I started thinking...(oh no not again), I sure do like Lupua brass to bad I could not use Lapua in my new 7CM. This along with the fact that many shooters probaly have 308 brass laying around might make this info usefull to some one. Or some may just find it interesting.

So here we go.
I started with a Piece of 308 FGMM 1x fired brass (because I had one). Here is a side by side with a piece that I formed from Lapua Palma small primer brass.

Next step, I found it to work better to trim the 308 brass first. Rather than after it has been formed. Seems to run through the die better and come out straighter. Here is the 308 case on my trimmer with the RCBS 3 way cutter head.

And here it is after the trim job. Expect them to grow a little after forming.

Here is the modified 6.5CM Redding die from Mark Gordan @ Short Action Customs

Here is the case after a trip through the die. Lube is the key, I like the redding stuff both out side AND inside the neck.

Quick check of run out shows almost .003

Quick trip in the Expander Die to be neck turned. The necks at this point are to thick to even chamber. I set my neck turn tool to allow for .002" clearance in the chamber with a seated round.

After

One thing I like about the 21st Century tool is that it cuts the radius into the shoulder.

Quick trip through the annealer.

One last time through the sizer.(since we expanded it). and also seems to help take the last bit of run out away. Then back on the dial to check.

This one came out @ .0015

I know I will get the "what a waste of time" comments but like I said, I enjoy this type of stuff. And also I think it makes a very strong stiff case. Especially with Lapua brass. But there it is take it or leave it.

 

[Nortex]

Re: Forming 7mm Creedmoor brass from 308

Very nice, I've been wondering how well this works.

 

[CanSniper]

Re: Forming 7mm Creedmoor brass from 308

One thing I should make clear, All this is not required If you run Hornady 6.5 brass it is as easy as full lenght sizing. Just another option.

 

[Mgordon]

Re: Forming 7mm Creedmoor brass from 308

I see you have things figured out really well. Here is what I was/am doing.

Federal GMM x1 fired brass, 308.
Size in the 30 TC die
Run in my modified 6.5 CM to 7mm CM die.
Trim the brass in a lathe to length.
Resize brass with 7mm CM bushing F/L die to final size.
Trim brass to length to ensure its square and to the proper length after the lathe cutoff.

There you have it!

Mark

 

[CanSniper]

Re: Forming 7mm Creedmoor brass from 308

Thanks Mark! glad to see I am not the only one.

 

[Marksman]

Re: Forming 7mm Creedmoor brass from 308

I'm curious why you would want to form brass this way? I thought the Creedmoor brass had a different web design that allowed it to withstand higher pressures?

 

[Cmonroe]

Re: Forming 7mm Creedmoor brass from 308

I think the small primmer Palma 308 brass is proving it can hold the pressure very well. 2800 does not even flatten the primmer.

 

[turbo54]

Re: Forming 7mm Creedmoor brass from 308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">I think the small primmer Palma 308 brass is proving it can hold the pressure very well. 2800 does not even flatten the primmer. </div></div>

My 260 and 284 will both smoke a primer without flattening it.

I've found primer flatness to be meaningless in all cartridges BUT 308. Even with 308, its not a consistent thing.

 

[The Lawn Ranger]

Re: Forming 7mm Creedmoor brass from 308

Regardless of how you do it, my compliments on an outstanding set up.
I feel like I am working in the bronze, or possibly the stone age.

 

[Cmonroe]

Re: Forming 7mm Creedmoor brass from 308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">I think the small primmer Palma 308 brass is proving it can hold the pressure very well. 2800 does not even flatten the primmer. </div></div>

My 260 and 284 will both smoke a primer without flattening it.

I've found primer flatness to be meaningless in all cartridges BUT 308. Even with 308, its not a consistent thing. </div></div>

If your pushing primmers before they are becoming flat then your pockets are most likely loose already, this is one major reason that Cansniper and I both like Lapua brass. I can make a primmer pocket loose with one firing with Federal, Remington or most other brass for that matter.

 

[Boltfluter]

Re: Forming 7mm Creedmoor brass from 308

CanSniper,

Great article and pics. Gotta love the Lapua brass. Very interesting caliber. The wheels are turning.

Regards,
Paul

 

[TC260]

For data on a 7mm Creedmoor, a 7mm IHMSA is basically the same thing with a 38 deg shoulder angle. You may have to dig a little but there's quite a bit of information out there on it since it was a very popular handgun silhouette round 25 yrs ago.

Lapua 22-250 brass might be a good candidate for making cases also. Just a thought.

 

[JGorski]

Or 30TC brass.

 

[sentry1]

I know I will get the "what a waste of time" comments but like I said, I enjoy this type of stuff. And also I think it makes a very strong stiff case. Especially with Lapua brass. But there it is take it or leave it.

Thanks for the post! I heard a lot of the same when I asked about making Lapua 6.5CM brass, but I like to tinker and develop new skills.
Of course, I plan on wrecking some range brass before I start mucking with expensive Lapua brass.