Since I'm relatively new at this caliber I'm checking out everything. This morning I noticed that my fire formed brass was right on 100 yard zero as expected. The next lot I shot was virgin brass that I did run through a FL sizer die as was the fire formed brass. However, the virgin brass on average was shooting .2 mils low at 100 yards. I was shooting .300 H&H. Each lot of brass was 20 rounds each. Each lot on average contained 67.6 grains H4831. All the brass was from the same manufacturer out of the same bag. Bullet was 190 SMK HPBT. I wasn't expecting that sort of result. All the bullshit I read on the "Internet" told me not to expect much difference if at all. They can't post anything on the Internet that isn't true.
Uhhh, Bonjour!!!
I don't know you, and I don't know your level of reloading experience, so please don't take any offense. What I observed so far--you say one batch was .2mil low. If I remember right, .2mil at 100 yd is about .73". If you are noticing that a group of 20 rounds averages .73" lower than another group, you are a very good shot. I sort my LC11 brass in 0.1gn lots. You say that "on average" each round held 67.6 grains H4831. If I may ask, how are you measuring your powder. I used to measure mine to 0.1gn on a Chargemaster, but I recently switched to a Sartorius GD503 and now measure to a single kernel of Varget. (scale is accurate to 0.005gn with no drift)
http://www.scalesgalore.com/sartorius_GD503_NTEP.cfm?this_selected_product_id=32931 . Do you run ladder tests? The barrel flexes each time you shoot and depending upon the interior ballistics, the bullet exits the barrel when it is effectively pointing in different directions. This can have a large effect on the elevation of the POI. 100yd is pretty close to have much of a drop due to velocity. Have you tried at 300-600yd. Do you sort your bullets by bearing length? I currently sort Ogive to base in .001" lots using a Sinclair Bullet Comparator Stand; however, I found something on David Tubb's site that I can use in conjunction with this stand
BSC insert .224 cal - BSC by Superior Shooting Systems to sort Ogive to boattail, since that is the only way you can measure bearing length. I went through 1000 77gn SMK HPBT bullets and found they varied in Ogive to base length by .014" (.483 to .496") Do you chrono your rounds during load development? I moved up from a Competition Electronics ProChrono to an Oehler 35P because I was tired of not trusting the number I was getting (repeated the same number, or skipped)
http://www.oehler-research.com/model35.html. The fireformed brass COULD have a larger volume, which you can measure by plugging the flashhole
Primer Pocket Plugs and filling them with water using a syringe, although I doubt that would help if you are not precisely measuring the amount of powder. I assume you are trimming both the fireformed brass and the virgin brass. Are you doing anything differently between the two such as trimming the flashhole, normalizing primer pockets, skimming/turning necks? I doubt the brass is work hardened in one firing. Most people go 3-4 firings between annealings; however, the best I have seen is from Giraud Tool Company,
New Page 1 . Are you shooting the two groups round-robin, or at least letting the barrel cool between groups. As the barrel heats up, it will shoot differently. Hope this helps.
