In my M700 Varmint in .223, I am using some Win brass, which started its life as factory loaded 40 grs HPs (White Box). I have reloaded it a total of 3 times, and the last time I reloaded, I decided to FL size it all and trim to the same length, as some of the cases were hard to chamber - possibly fired in other rifle(?). I used a Collet die with an undersize mandrel for NS and a Redding Body die set up for partial FL sizing. I used the undersized mandrel, as some of the cases refused to hold bullets when sized with the regular mandrel. This was a tad earlier than I had expected, but not unheard of for a Collet die.

Shooting the loaded rounds (a fairly light load of 23 grs of VV N130 behind a WW 55 gsr SP), I sometimes get gas leakage around the cases - maybe 10% of the rounds? The resulting soot in particular shows up at the rear of the case (extractor groove and on the part of the case not supported by the chamber itself). I have not got a clue where the gas leakage is coming from. Initially, I thought I was seeing case head separation. But cleaning the cases and inspecting them revealed no compromised material, nor did an inside inspection with a bent and sharpened paperclip. There is no indication of gas leakage around the primer - no soot on case head or around the primer, besides primer pockets were nice and tight. I see some soot also on the body of the cases, but I'm not sure whether the gas leakage comes from the mouth of the case (due to insufficient case expansion/grip) and simply shows up on the rear part of the case or what is the matter??? The gas leakage does not seem to be related to an oily chamber for the initial shots. If the gas leakage comes from the case mouth, why would some cases have such problems expanding and gripping the chamber walls, and others not??? That particular chamber is probably pretty wide - cases fired in this chamber refuses to chamber in any of the other .223 Rems I have (expanded too much at the rear of the case). Before I FL sized the cases, I did not experience this problem (NS-only is my regular way of resizing).

Anybody care to share their experience of such mysterious circumstances??

- mike

It seems you load is too light to properly expand the case, so that gas flows back. Try upping the charge.

I'll second that.

This was a common problem in Norway with match shooters using the krag Jorgensen rifles, very accurate guns but weak and had to be loaded down somewhat. The common solution was to switch to a faster powder or seat the bullet a little deeper.

With my brand new 6,5 I have also experienced a little soot on my cases with good loads and suspect my chamber is on the large side and the cases rather small (I�m still shooting factory ammo to get my hands on some fireformed cases) Maybe you size your cases a little to much?

Tron

Yep, increasing the load should solve the issue, not that I think it's anything to worry about. Cast bullet shooters get the same phenomenon a lot due to the reduced loads.

I will also agree with the reduced load being the cause.

as well as the faster powder idea that has been mentioned,..you can also increase the neck tension with that same load and see if it rectifies the situation.

Thanks guys, you seem to agree pretty much on the possible cause. Since I originally posted, it also occurred to me that I'm seating out the bullets almost as far as I can to get anywhere close to the lands in my 10-12 year old barrel - paired with cases trimmed .005" below SAAMI minimum. This combined with the fact that the Collet dies normally don't work the brass as hard as regular dies do, probably means I don't have too much neck tension on some of my loads. Paired with what somebody pointed out, that it is quite common for necks to vary could well explain why I only see the problem on some loads, and not on others.

In all likelihood, there are probably several options for fixing this. Size the necks a tad harder, let the brass grow a bit longer (to allow deeper seating), don't size the case bodies as much to allow them to grip the chamber walls more easily, up the load a tad. Any or all (?) of this might just do the trick.

Thanks for all the feedback - not least the comforting news that cast bullets shooters experience the phenomenon fairly regularly.
-mike

Anneal the necks. Problem will go away.