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Surprised by the amount of loose primer pockets I'm getting on some brass that's been fired only twice.
Brass is Lake City 2010, originally from MidwayUSA (the unfired stuff they were selling a couple of years ago).
First loading was Rem 55gr FMJ, AA2230 25.0gr, and CCI #41 seated to cannelure. Nothing earth shattering here.
Brass then cut at the shoulder, run through an RCBS small base die, trimmed to SAAMI spec with WFT.
Second loading was 125mg SMK, 5744 18.8g, and CC #41 seated to 2.255". Worked up to this load. No problems. Haven't chronographed them yet but I would like to know how fast they're going. This was a fun round to shoot and something to change things up a bit from the 5.56 world.
I liked that load so I figure I'll just repeat everything exactly the same.
First surprising thing I noticed was that all of the brass were about 3-5thou longer, still not in absolute need of trimming but it's something I went ahead and did. I guess what surprised me here it that such a short little case grew so much with one firing.
Anyway, here's what really disappoints me... I noticed about 1/6 of the brass were really tough to get to slide into the shellholder (Lee). So difficult in fact that it would often take off the slightest shaving of brass on the rim. Rotating the brass would not help these cases slide into the shell holder.
Another 2/3 of the brass had a little "snap" going into the shell holder. Did not require any true effort to slide them in or out, but there was a little "snap".
And half of the cases slide in and out with perfect ease.
I pulled out the calipers and started measuring extractor groove diameters. The truly difficult to seat (in the shell holder) cases measured 0.333" at the groove. The cases that seated easily in the shell holder but with a little "snap" measured 0.331". And the cases that slid effortlessly in and out of the shell holder measured 0.330".
There were corresponding differences in primer pocket looseness, completely subjective and based on "feel", of the three groups. When seating primers in the cases with the 0.330" extractor grooves a "normal" amount of resistance was felt. When seating primers in the cases with the 0.331" extractor grooves a decreased amount of resistance was felt but it was still noticeable. When seating primers in the cases with the 0.333" extractor grooves, a significant decrease in the amount of resistance but these primers weren't falling out- it just took very little effort (comparatively speaking) to seat them.
Cases from all three groups drop in fine in a Wilson case gauge. I have no doubt they'll all chamber and fire just fine. I didn't want to discard the whole batch because of amount of work involved in forming these cases. I think I'll use the extractor groove diameter to screen for loose pockets and discard only those cases.
I was using Hornady's loading manual. Without going down to the basement I can only tell you the max load for 5744 is in the ballpark of 19.5ish, so I'm under the max load in that respect. There were no other pressure signs. However, I wonder if I might be overpressured because I'm using 5.56 brass which has less case capacity.
Do any of you load 300BLK, especially those who use 5744. It's not my ideal choice of powder, but it's what the LGS had on hand at the time. I think I'm generating too much pressure. I wouldn't expect to get so many loose primer pockets from the second loading. Or is this typical for this case?
Finally, another curious observation. Attached is a picture of some of the cases with loose pockets. I primed these cases using a Lyman Ram Prime die. I previously used the RCBS universal hand held priming device, but the Lyman Ram Prime die was just a new accessory I wanted to try out. You may have to zoom in, but you'll notice on cases #2,3, and 4 especially, the primer cup is not flat. It has a convex deformity to it. These only occurred with the cases that had loose primer pockets. One final observation- these appear to be almost compressed loads. I don't recall the Hornady manual stating that the 19.something max load was compressed, but I know if I worked this load up any more it'd be compressed. Can anyone help me gain some insight into what's going on here exactly? Thanks, and Merry Christmas!
Brass is Lake City 2010, originally from MidwayUSA (the unfired stuff they were selling a couple of years ago).
First loading was Rem 55gr FMJ, AA2230 25.0gr, and CCI #41 seated to cannelure. Nothing earth shattering here.
Brass then cut at the shoulder, run through an RCBS small base die, trimmed to SAAMI spec with WFT.
Second loading was 125mg SMK, 5744 18.8g, and CC #41 seated to 2.255". Worked up to this load. No problems. Haven't chronographed them yet but I would like to know how fast they're going. This was a fun round to shoot and something to change things up a bit from the 5.56 world.
I liked that load so I figure I'll just repeat everything exactly the same.
First surprising thing I noticed was that all of the brass were about 3-5thou longer, still not in absolute need of trimming but it's something I went ahead and did. I guess what surprised me here it that such a short little case grew so much with one firing.
Anyway, here's what really disappoints me... I noticed about 1/6 of the brass were really tough to get to slide into the shellholder (Lee). So difficult in fact that it would often take off the slightest shaving of brass on the rim. Rotating the brass would not help these cases slide into the shell holder.
Another 2/3 of the brass had a little "snap" going into the shell holder. Did not require any true effort to slide them in or out, but there was a little "snap".
And half of the cases slide in and out with perfect ease.
I pulled out the calipers and started measuring extractor groove diameters. The truly difficult to seat (in the shell holder) cases measured 0.333" at the groove. The cases that seated easily in the shell holder but with a little "snap" measured 0.331". And the cases that slid effortlessly in and out of the shell holder measured 0.330".
There were corresponding differences in primer pocket looseness, completely subjective and based on "feel", of the three groups. When seating primers in the cases with the 0.330" extractor grooves a "normal" amount of resistance was felt. When seating primers in the cases with the 0.331" extractor grooves a decreased amount of resistance was felt but it was still noticeable. When seating primers in the cases with the 0.333" extractor grooves, a significant decrease in the amount of resistance but these primers weren't falling out- it just took very little effort (comparatively speaking) to seat them.
Cases from all three groups drop in fine in a Wilson case gauge. I have no doubt they'll all chamber and fire just fine. I didn't want to discard the whole batch because of amount of work involved in forming these cases. I think I'll use the extractor groove diameter to screen for loose pockets and discard only those cases.
I was using Hornady's loading manual. Without going down to the basement I can only tell you the max load for 5744 is in the ballpark of 19.5ish, so I'm under the max load in that respect. There were no other pressure signs. However, I wonder if I might be overpressured because I'm using 5.56 brass which has less case capacity.
Do any of you load 300BLK, especially those who use 5744. It's not my ideal choice of powder, but it's what the LGS had on hand at the time. I think I'm generating too much pressure. I wouldn't expect to get so many loose primer pockets from the second loading. Or is this typical for this case?
Finally, another curious observation. Attached is a picture of some of the cases with loose pockets. I primed these cases using a Lyman Ram Prime die. I previously used the RCBS universal hand held priming device, but the Lyman Ram Prime die was just a new accessory I wanted to try out. You may have to zoom in, but you'll notice on cases #2,3, and 4 especially, the primer cup is not flat. It has a convex deformity to it. These only occurred with the cases that had loose primer pockets. One final observation- these appear to be almost compressed loads. I don't recall the Hornady manual stating that the 19.something max load was compressed, but I know if I worked this load up any more it'd be compressed. Can anyone help me gain some insight into what's going on here exactly? Thanks, and Merry Christmas!
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