5.7 Reloading w/Flat Base Bullets

[f4epilot]

New member. Some of us here in northern MN have been doing reloads for the 5.7x28 for a few years. I have chatted with Jay at Elite Ammo and the use of flat base bullets came up. I use CH4D dies. As for the expander, they are very knowledgeable and can custom make them for you. One of the other guys uses Redding dies. I am going to copy and paste some info that discusses an expander made by RCBS and some measurements he made after crushing a few cases with flat base bullets. Flat base bullets are cheaper for target practice and usually in stock.
Also, RCBS makes a die with an expander, part # 39803.
Flat based are cheaper and more plentiful. Below are some numbers from the guy I partner with to
experiment and find tooling that will work for the rest of our 5.7 followers.
Figured I’d share the following just as an FYI……………
Regard, Bob
Here is the measured observations from a couple years ago.
The following was from Sept. 2022
Subject: Re: tales of the 5.7
Not sure if I answered this but CH4D has a taper crimp die

Hi Bob,
The RCBS ex-pander came in.

Started mic-ing things up.

My 5.7 resizing die leaves the neck OD at .244-.2445 very consistently. (Redding dies used)
The neck walls I measured typical was .012-.0125 Which leaves the neck ID .219-.220, which give a neck tension of .004-.005.
With this much neck tension I usually don't do a final crimp.

The mandrel section of the ex-pander die mics up at .2235.

I took some brass I had, that I have tumbled, trimmed and primed and as a test I ran the brass over the ex-pander mandrel section only (not flaring the brass at all). Then tried loading them with 40 grain Sierra HP which have a flat base.
I loaded up dozen with out any neck collapsing just fine. The Neck ID of
.2235 is just enough to get the flat base bullets started with a little manual effort to line up the bullet and case.
With only about .0005 case neck tension, crimping is going to be required. I used a Colet chuck style crimp, a taper crimp would work too, if one exists, to stay away from any kind of roll crimp

Putting a .001-.002 flare would make starting the bullet a bit easier, but does add a bit of additional working of the brass. If your going to flare the case, the trim length is going to be critical, especially on a case this small.

I will try these out at the range hopefully this week, I ran them through an the all chambered fine. I don't expect them to extract since the coating has been removed.

Tom

[panzermk2]

Thank you for sharing!