My Sheridan Engineering 300 BLK ammunition gauge arrived today. Fast shipping!
My intended use for the gauge is not to check 100% of all my 300 BLK ammo, but to check 100% of ammo to taken out for hunting, spot check ammo when setting up my dies, checking to see how unknown/not used by me before headstamped cases will work, and checking when I experiment with new bullets. Measurements listed are from my Lyman caliper...don't have a way to make sure it's calibrated accurately, but I did zero it. I also extrapolated 4th digits where any are listed, so the 4th digit could be off a hair.
1st test: Had 7 rounds left over that I had not pulled the bullets from that wouldn't chamber due to too large of neck diameter (case neck wall too thick). Necks measured .3369-.3378". The gauge properly rejected all. SAAMI max spec is .334" for the neck diameter. I no longer even try and use a variety of headstamps in which I've determined the case neck wall thickness can be too thick. These 7 rounds didn't come near to fully entering the gauge.
2nd test: How big can the neck diameter be before it starts to get harder to go into the gauge? Looks like it will take up to something about .3345" (SAAMI max spec is .334"). I found this on both sized but empty brass and loaded rounds.
3rd test: What happens when I gauge ammo I've always thought was good-to-go, in particular my hunting ammo with LC formed brass (brass resized by me) and Nosler 125gr Ballistic Tips for which I've never had a failure to chamber and my 220gr SMK subsonic loads in LC formed brass (brass resized by me). Well, about 10% failed to fully chamber in the gauge (the case rim would be partially sticking out). I had an ah ha moment and examined the case rim. In each instance I found a tiny nick on the case rim which prevented the round from going fully into the gauge. While I don't think it would cause a malfunction as I feel the bolt face is larger than the case head width, for ammo to be taken hunting, those with case rim nicks will be set aside for shooting at the range and only the perfect ammo will be used for hunting.
4th test: Randomly checking my practice/plinking loads (loaded in a variety of brass that has always worked for me). Here and then I would find one that needed a little "push" to fully enter the gauge (but none would stick out like those in test #1; part of the rim would be above the gauge, but no rim nicks big enough to matter). Measuring the cases, I could find no reason for them to not easily enter fully. My speculation is that because I'm using pulled GI bullets for plinking, the bullets are not perfect in roundness or maybe perfect in seating in the case. I also tend make my 300 BLK rounds longer in oal than some reloaders. I don't have problems chambering my practice/plinking loads in which I have resized the brass prior to loading. I don't intend to normally gauge this ammo providing that I use brass that is known to me to be OK.
Finally, someone has offered a 300 BLK ammunition gauge. Thank you. And again, let me mention that measurements were with my Lyman reloading caliper, and I don't have a way to ensure its accuracy. This gauge is what I've been waiting for.
Regarding my #4 test. I think I found the answer as far as my USGI M160 frangible bullet reloads go. The bullets are supposedly made of compressed lead particles mixed with bakelite fibers. In other words, the bullet is not as hard/sturdy as a jacketed bullet. One can see/measure where sometimes the portion of the bullet begins that was not originally seated in the GI brass has a slight ridge or raised area that would have been right at the edge of the GI case neck. I'm seating them in the BLK case where that area is .075" out from the edge of the case neck. Whether the raised area is a result of the original GI case neck squeezing the seated portion or it's a result of the seating process scraping some bullet material forward when the original GI case was loaded or even a result of the demilling process, I don't know. By measuring the raised area before putting the round in my ammunition gauge, feeling for increased resistance at the very end of the gauging process, and then remeasuring the raised area, I found that 1) I could predict which rounds would be harder going into the gauge and 2) The raised area would have been reduced by the act of putting the round into the gauge (the bullet is a lot softer than the metal of the gauge).
In any case, I don't have failures to fully chamber with those loads. I just wanted to find what was going on. Since possibly only 1 in a thousand 300 BLK reloaders use those bullets, it's a non-issue and not the fault of the gauge. I bet I could get it to go away by simply seating the bullets .075" deeper, but I've already worked up my seating depth vs powder charge vs AR feeding vs accuracy combinations and have no need to change them.
Hopefully everyone else that ordered it last weekend will get it today.
I am heading out to visit family for Thanksgiving, so I won't be doing any more shipping this week. But I will definitely still be logging in here if there are any questions.
