I've been working on a load for a 20" AR15, and recently ran into an issue of split necks. All in all, I've shot around 150-200 rounds of new and reloaded ammo through the rifle. Well, over the last two range visits, I've had 9x pieces with linear splits in the neck. These aren't single splits, either, as some will have as many as three splits (with a few extending the full length of the shoulder and terminate at the case mouth).
Its important to include that these have occurred only on factory brass/factory loaded ammo. The majority of them were with Winchester 45gr HPs (the kind Wally World used to sell in 40rd boxes), with a few being red box Black Hills 68gr BTHP ammo (marked BHA Match brass). I have not had an incident of split necks with any of my reloads, which include the use of LC, WCC, PMC, Winchester, and other assorted brass. Now, I must also mention that I have shot a lot of the Winchester 45gr HP ammo through various other .223 rifles without issue. The BH match ammo has been fired in my 10FP, and no split necks were seen. IIRC, I fired one 5-shot group with the BH, with 2-3 of the cases splitting.
As you can see in the pics, the brass is also very dirty, with an almost sooty appearance. The last pic below shows how the ammo appears prior to firing, which is pretty clean. I have noticed in load development on this rifle, that the first round of five fired out of the magazine will be relatively clean, with the remaining rounds looking fairly "sooty".
So, I guess my questions are this. Any ideas on the cause of the split necks, and why is the brass this dirty? I've loaded for quite a few .223s, and don't recall seeing this with other rifles (including ARs). Is it indicative of anything? Thanks!
Its important to include that these have occurred only on factory brass/factory loaded ammo. The majority of them were with Winchester 45gr HPs (the kind Wally World used to sell in 40rd boxes), with a few being red box Black Hills 68gr BTHP ammo (marked BHA Match brass). I have not had an incident of split necks with any of my reloads, which include the use of LC, WCC, PMC, Winchester, and other assorted brass. Now, I must also mention that I have shot a lot of the Winchester 45gr HP ammo through various other .223 rifles without issue. The BH match ammo has been fired in my 10FP, and no split necks were seen. IIRC, I fired one 5-shot group with the BH, with 2-3 of the cases splitting.
As you can see in the pics, the brass is also very dirty, with an almost sooty appearance. The last pic below shows how the ammo appears prior to firing, which is pretty clean. I have noticed in load development on this rifle, that the first round of five fired out of the magazine will be relatively clean, with the remaining rounds looking fairly "sooty".
So, I guess my questions are this. Any ideas on the cause of the split necks, and why is the brass this dirty? I've loaded for quite a few .223s, and don't recall seeing this with other rifles (including ARs). Is it indicative of anything? Thanks!
