I had loaded 50, 5.56 LC cases with Hornady 55 grain fmj-bt, Winchester SRP and 25.2 grains Varget. This load is 95% of Hornady’s published maximum load and I had previously worked up from a reduced load. C.O.A.L. is 2.200” as published by Hornady.
Rifle is a Savage 10T-SR. Replacement barrel 1:7, Wylde chamber. Probably about 100 rounds through it. Cleaned after each range trip, about every 40 rounds. No carbon ring.
Before loading I plugged numbers into GRT and it told me pressure should be 40,197 psi, well within 223 Rem maximum of 52K. FPS should have been 3,044.
Yesterday I fired 22 of them, all went well and accuracy was OK. Then on the 23rd round I got a little sting on the cheek below my shooting glasses. Not real bad but enough to feel it. The bolt handle initially wouldn’t lift until I forced it, then it popped loose. It did not withdraw the case from the chamber. I tried to close the bolt to see if the extractor would pick up the case but the bolt wouldn’t close. It stopped about ¼” shy of closing. I tried to remove the bolt but it wouldn’t come out of the action. More on that later, I turned my attention to the case in the chamber. The primer was still in place but the case head and primer were black.
Quite coincidentally I had just put up a new target. The bullet did hit the target.
The case easily pushed out with a cleaning rod, it was not stuck at all. It fell onto the magazine as I pulled the rod out.
I dropped the mag and the case and primer, now separated, fell out. I looked at the primer first. It looked entirely normal except it was black all around. Then I looked at the case. It was easy to see the enlarged primer pocket. Later at home I placed a new primer into the pocket with just finger pressure and it could fall right out with a good shake. A no-go pocket gauge wallows around in the pocket like a stick in a bucket. Well not that bad but you get the idea.
The entire shot string including that last round had an average 2,932.5 fps, a high of 2,968 and a low of 2,887. The shot in question chrono’d at 2,896 fps. (less than the average). Plugging that data into GRT the adjusted output was a maximum average pressure of 35,943 psi. By all accounts this is a mild load.
I found the reason for the bolt trouble was the extractor had been pushed outward and was sticking out from the bolt head. The ball and spring were still there but the extractor was off the ball. I had to reach in with a small punch and push the ball in to get the extractor to snap back in to place. Then the bolt operated as normal. It was not damaged, just black soot.
That cartridge case measures 1.759” in length. Measured at the rim it’s .378-.379” dia. The case head /200 line is .379. Other cases from that group measure .376 on the rim and .375 on the 200 line. This one is clearly expanded. No brass flow at the ejector, just a little shiny spot and visible brass flow at the extractor.
So any way, I never experienced anything like this. It appears to be an over pressure round but some of this evidence suggests that’s not the case. Also I would have had a seriously compressed load to create an over pressure and I certainly would have noticed that when loading. I am pretty sure the primer pocket was not loose when loading, I check each one with a go/no-go tool and prime with a hand tool. I can easily feel a loose one. This is brass I bought on line as “once-fired” from a known supplier but a good portion of it obviously had been fired more than once.
Rifle is a Savage 10T-SR. Replacement barrel 1:7, Wylde chamber. Probably about 100 rounds through it. Cleaned after each range trip, about every 40 rounds. No carbon ring.
Before loading I plugged numbers into GRT and it told me pressure should be 40,197 psi, well within 223 Rem maximum of 52K. FPS should have been 3,044.
Yesterday I fired 22 of them, all went well and accuracy was OK. Then on the 23rd round I got a little sting on the cheek below my shooting glasses. Not real bad but enough to feel it. The bolt handle initially wouldn’t lift until I forced it, then it popped loose. It did not withdraw the case from the chamber. I tried to close the bolt to see if the extractor would pick up the case but the bolt wouldn’t close. It stopped about ¼” shy of closing. I tried to remove the bolt but it wouldn’t come out of the action. More on that later, I turned my attention to the case in the chamber. The primer was still in place but the case head and primer were black.
Quite coincidentally I had just put up a new target. The bullet did hit the target.
The case easily pushed out with a cleaning rod, it was not stuck at all. It fell onto the magazine as I pulled the rod out.
I dropped the mag and the case and primer, now separated, fell out. I looked at the primer first. It looked entirely normal except it was black all around. Then I looked at the case. It was easy to see the enlarged primer pocket. Later at home I placed a new primer into the pocket with just finger pressure and it could fall right out with a good shake. A no-go pocket gauge wallows around in the pocket like a stick in a bucket. Well not that bad but you get the idea.
The entire shot string including that last round had an average 2,932.5 fps, a high of 2,968 and a low of 2,887. The shot in question chrono’d at 2,896 fps. (less than the average). Plugging that data into GRT the adjusted output was a maximum average pressure of 35,943 psi. By all accounts this is a mild load.
I found the reason for the bolt trouble was the extractor had been pushed outward and was sticking out from the bolt head. The ball and spring were still there but the extractor was off the ball. I had to reach in with a small punch and push the ball in to get the extractor to snap back in to place. Then the bolt operated as normal. It was not damaged, just black soot.
That cartridge case measures 1.759” in length. Measured at the rim it’s .378-.379” dia. The case head /200 line is .379. Other cases from that group measure .376 on the rim and .375 on the 200 line. This one is clearly expanded. No brass flow at the ejector, just a little shiny spot and visible brass flow at the extractor.
So any way, I never experienced anything like this. It appears to be an over pressure round but some of this evidence suggests that’s not the case. Also I would have had a seriously compressed load to create an over pressure and I certainly would have noticed that when loading. I am pretty sure the primer pocket was not loose when loading, I check each one with a go/no-go tool and prime with a hand tool. I can easily feel a loose one. This is brass I bought on line as “once-fired” from a known supplier but a good portion of it obviously had been fired more than once.
