by Hoot » Thu Jun 27, 2019 10:00 pm
Welcome n aboard offrink!
I don't own a Lyman chamber gauge but I do check my reloads against my chamber as its what ultimately decides what sizing is appropriate. SAAMI specs generally come in slightly smaller than the minimum a chamber will accept, to guarantee that the reloads will chamber in even the tightest of chambers. Sounds to me like your sizing die is not reducing your cases to the precise SAAMI specification set forth by that gauge but in your case, your chamber isn't overly tight, My original Bushmaster upper also had a generous chamber. About the only downside that came from that was that my brass got worked a little more each time it was sized and I seemed to produce empties that had experienced excessive case head growth that other members using the same recipe were not experiencing. Eventually, I got over worrying as much about what readings other members got when they measured their case head growth compared to mine. Never had an issue with cases failing in over 2k of reloads over an 8 year period. If the inability to check your finished loads using your gauge troubles you, send the sizing die to Hornady and tell them you're concerned that it isn't properly sizing your cases. They'll check it out and they're pretty generous about replacing dies that trouble their customers. If you opted for the less expensive Lee die set, I san't speak to how they receive customer's concerns.
How far into your Lyman gauge does your sized cases go before they seize up? Is is a fit problem only after a bullet has been seated? Are you screwing your sizing die down to where the shell holderbumps up against it at the top of the ram stroke to generate a small amount of "cam-over"? Lastly, you are lubing your cases prior to sizing right? If so, how much lift resistance do you feel as they're being sized? even with slippery Imperial Sizing Lube that I prefer over 1-shot, there is a distinct amount of resistance as the cases go up into the dies from the moment they entire it, until they bottom our, not just down where the wall almost reaches the web. Some things to ponder. Also, is you have a precision micrometer, not digital caliperwhat is the widest case diameter you see as the case passes through the micrometer? If after sizing, your cases are still .5015 or more at their widest point, then your sizing dies definitely has an issue. There is a trick I perform where I shorten the height of the shell holder, to encourage a slightly greater insertion into the sizing die, to squeeze that last little bit of resultant diameter down abouty .050 more. This is consistent with what is known as a small base rezsizing die when referring to a 5.56 caliber sizing die. It buys you a little more wiggle room when trying to fit a sized case into a chamber gause. While it is a bandaid to an overly generous sizing die, it is a cheap workaround if you want to use the chamber gauge for your "thunk" test, as opposed to using your rife's chamber.
Just throwing ideas out there to see what sticks and to coax more information from you. As I said, the ultimate test is whether your finished rounds "thunk" your rifle's chamber. If that's the case, your are not in any danger. you just own a chamber gauge you cant rely upon to get the warm fuzzies. Straight walled cartridges are in a league that's different than botteneck calibers.
Hoot
In Theory, there is no difference between theory and practice. In Practice, there is.