Strut10 Posted December 27, 2004 Report Share Posted December 27, 2004 After a brief session with some handloads and my chronograph, I have two questions. 1. What would cause the first shot to chrono approximately 100 fps slower than the subsequent shots? 2. What is an acceptable "extreme spread" and "standard deviation" for a belted magnum? Quote Link to comment Share on other sites More sharing options...
AJ Posted December 27, 2004 Report Share Posted December 27, 2004 Re: Chrono / Reloading ?\'s 1. During this time of the year, the temperature can play havock with velocity. Colder temps can reduce velocities. As subsequent shots are fired, they are going off in a warmer barrel. As heat increases so does pressure. As pressure increases, so does velocity. Some powders are harder to ignite as temp drops. 1a. Barrel fouling can also have somethinig to do with speed deltas. If the first shot was from a squeaky clean bore, the following shots can give different readings. 1c. Chronograph just had a bad reading. Its possible. 2. The lower the better. I have had my .300 Wby loads down to a SD of 9 fps. Unless you are shooting very long range, higher SD numbers won't mean a lot. On big game hunting out to 350 yards or so, SD even with 50 fps won't mean too much. Quote Link to comment Share on other sites More sharing options...
Strut10 Posted December 27, 2004 Author Report Share Posted December 27, 2004 Re: Chrono / Reloading ?\'s It was in the mid 20's (temp-wise) when I was doing the shooting. However the gun and ammo had come straight outside from being at room temp. The barrel had one previous shot through it since a thorough, thorough cleaning. The charge was 82.0 gr. of 7828 in front of a Fed 215. Of the 5-shot string (not enough, I know........but it was cold out ) the low was the first round at 3498 fps. The other 4 were between 3557 fps and 3601 fps. Including the first shot, the S.D was 40.63. So I guess if I would have dropped that one slow shot from the string, the statistical numbers would have been pretty good, huh? This is all part in parcel to developing an accurate hunting load for absurd distances. So your insight is greatly appreciated, AJ. Do you know of one .284 hunting bullet that may be inherently more accurate than another? Preferrably a boattail to keep the BC high. Right now I'm trying Accu-Bonds. I haven't tested enough to give a verdict on them yet. Thinking about trying CT Ballistic Silvertips and Nosler Ballistic Tips. I think for downrange performance I'll try to stick with 140 grainers. Quote Link to comment Share on other sites More sharing options...
AJ Posted December 27, 2004 Report Share Posted December 27, 2004 Re: Chrono / Reloading ?\'s I have seen some big swings with 7828 in my .300 Wby. When I switched to N165, all things came together, very nicely. I take it this is in a STW? I really like the Scirocco bullet. They have given me some very nice groups, and do not blow up on close shots like the B-Tip will. The last time I shot my gun at paper at long range, I was able to get under 4" groups at 300 yards for 5 shots. Swift offers a 150 gr Scirocco. It has a BC of .515 and a sectional density of .266. That thing would be sweet for long range critter sniping. I also neck turn my brass casings to keep things as even as possible. This made a difference at the long range target. I take them to 80%-90% clean up. Quote Link to comment Share on other sites More sharing options...
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