Informative thread on reloading experiences w/ 5.7x28

Some excerpts:

#1

I hope that my experience will give anyone pause before jumping into this.

I now have Five-seveN number 2. While at the gun shop, the dealer mentioned hearing a rumor that FN was going to begin manufacturing heavier grain bullets for the pistol. That should prove interesting. Mine showed no signs of stress until the 40 grain slug was fired. I don't think I'll be the first to try out any heavier bullets.

I spoke to Browning this morning (apparently they supply parts for FN in the US). They have SOME parts listed for the Five-seveN, but not all, and they could not disclose which parts, or what the prices are (??). I am considering sending the gun to them for a repair estimate. Haven't decided yet, but I hate to just write the first one off.

I have not given up on the concept of reloading this round, but I don't think I'll be pioneering anymore on a polymer gun.

#2

I was using Alliant 2400, 4.5 grains of powder. I expected this to be a very low charge. It did seem to be; the muzzle velocity was in the 400's of fps.
I expected the end charge to be on the low end between 6 & 7 grains.


#3

Perhaps I was not clear enough in my earlier posting. My first Five-seveN didn't blow up, it broke.

Before I fired a shot, I miked the overall length of an SS192 round, so my rounds would be seated at the proper depth. The slugs I used were shorter than the SS192 slugs (I extracted one), so I know that it didn't extend too far into the case. The FN slug is surprisingly long (.810!) to only be 28 grains. I have 231, Red Dot, Bullseye, Unique, and a bunch of IMR powders, but I have used 2400 the most by far, and selected it in an attempt to have the case be nearly full on a normal load (for consistency of performance).

As nearly as I can tell, the sequence went something like this:
Shot number one:
There is a piece of metal that blocks the slide, which is rolled forward by the grey plastic take-down button.
Upon firing the slide moved backwards (likely too hard), striking that piece of metal. This impact on the metal broke the plastic mechanism which is a moulded part of that take-down button.
The shot "felt" fine. Not too light or too hard. On this shot, my chrony reported an error and didn't give a good reading.
Shot number two:
Slide retracts after firing. At this point, the metal block is not held in the correct position by the plastic. The slide strikes this block, and the block rolls backwards (as if the take-down was slid rearward). This applies leverage to the slide while moving backward. The front of the slide lifts, partially dislocating the 'T'-rail on the front of the grip frame. The slide comes to a stop with the metal block firmly jammed under it.

After some amount of work, I have managed to get the gun apart, assess the damage, and (mostly) reassemble it. The only part that is obviously permanently damaged is the grey plastic take-down operator.
I am planning to send it to Browning (who does repairs for FN pistols) and get an estimate for repair and test firing.

I have pistol #2 now, but getting #1 repaired would be nice.