FOGGER Report post Posted November 20, 2015 I built a .260 Rem and I've been building a load. I've gotten great groups, sub 1/2moa but my velocities are all over the board +/- 150fps. I double checked my chronograph with another rifle and it's working correctly. Any ideas how to get more consistent velocity? I'm using Lapua brass and 4831sc Share this post Link to post Share on other sites
FOGGER Report post Posted November 20, 2015 With WLR primers and Berger 140vld Share this post Link to post Share on other sites
STOMP442 Report post Posted November 20, 2015 Shoot it at longer ranges, if it holds half moa I wouldn't worry about what the chrony says. Share this post Link to post Share on other sites
Tac Report post Posted November 20, 2015 changes due to barrel temp? Share this post Link to post Share on other sites
308Nut Report post Posted November 20, 2015 Try the Rem 9-1/2 large rifle primer with 4831SC. Check neck tension consistency. Try another chrony. Make sure the sun shades are on properly and make double sure all or part of one or the other isn't shaded. Also agree with C. Test it at longer ranges. If it groups well, forget the chrony. M 1 Share this post Link to post Share on other sites
oz31p Report post Posted November 20, 2015 Just so I understand the question your getting a sd of 150fps(velocity spread of 300fps) and your groups shooting less than 1/2 inch at 100yards? Share this post Link to post Share on other sites
GreyGhost85 Report post Posted November 20, 2015 Shoot it out further and see how it groups. If it holds half MOA to 500, who cares. If there is that much deviation, i would think you would have a hard time shooting that well at 100 even. Chronos get you close, but best to true your velocity by shooting different ranges. Just 10-20 fps can make a lot of difference downtown 2 Share this post Link to post Share on other sites
rcdinaz Report post Posted November 21, 2015 Try different primers. 308 pointed out neck tension and I have had that happen as well, actually to loose so the bullets ended up being able to move a little. The result was them moving further from the lands on some of the cartridges. This was in my phase of constantly screwing with everything, trimming, chamfering, deburring, neck tension adjustment, meplat uniforming... too much of a good thing! Share this post Link to post Share on other sites
lancetkenyon Report post Posted November 21, 2015 Neck tension problems, with a standard die, require neck turning for consistent neck thickness. And unless you have a bushing die, you are stuck with one neck tension after turning. What is your jam/jump length? Are you measuring to tip of bullet or ogive? What scale are you using to measure charge weight? An electronic scale that reads to .1 grain is not very good for precision loads. You could throw one charge at the very low end, then the next at the high end and wind up with almost a .2 grains difference. It shouldn't make a 150 fps difference, but easily 50-60. Add that to neck tension, bullets jammed or jumping, and the 2% error of a chrono, and that all adds up. Try different primers, I like Fed GMM 210 or CCI BR-2. Share this post Link to post Share on other sites
FOGGER Report post Posted November 21, 2015 My jump is .040 off the lands. I'm measuring of the ogive. I'm using the RCBS chargeMaster and backing up ever charge with a Dillion manual scale. As far as neck tension I'm using a Redding competition bushing die. I had the guy at Bruno's measure my lot of cases and he picked out the bushing I needed. This is the first time using this type of die. I have always just used a standard RCBS die. Most of my other rifles are within 10fps of each other. Should I change my neck tension? Share this post Link to post Share on other sites
lancetkenyon Report post Posted November 21, 2015 I shoot a 6.5 SLR (almost identical to a .260 Rem), and have a redding bushing die too. I can pull it apart to see what bushing I have, but I am using Remington brass. I would think that if Bruno's told you what bushing to get after checking your brass, that is probably not the culprit. Since you are using a manual scale to check all of your electronically thrown charges, that is probably not it either. My next step would be to try a different powder and primer. The .260 Rem is known to love H4350, usually somewhere right around 43.0gr. And a match primer might help some too. What bullets are you shooting? When you say 150+/-, do you mean you have a 300 fps ES, or a 150 fps ES? Not that either one of those would be good for LR shooting. What chrono? Can you check using another chrono to be sure? What velocities are you seeing? Share this post Link to post Share on other sites
Mike S Report post Posted November 21, 2015 I'd be really suspicious of either the chrono itself or the lighting conditions when you took the readings. If you can get out mid day on an overcast day you may see different readings. Share this post Link to post Share on other sites
cactusjack Report post Posted November 22, 2015 do you know anyone with a Magneto-speed? Share this post Link to post Share on other sites
lancetkenyon Report post Posted November 22, 2015 Just remember, a chrono is to get you started on a drop chart, not to be used as a replacement for actually shooting at distances and recording your drop data. I think if you were to shoot at 500+ yards, if you truly have a 150fps +/- difference, it will show up very quickly. 2 Share this post Link to post Share on other sites
FOGGER Report post Posted November 22, 2015 I'm shooting a 140VLD Berger hunting 150ES Cheap pro chrono (it's dead on with my other rifles) 2726-2889 No I don't know anyone with a magneto-speed. Are those good? I'll have to just shoot it out to 500 and see Share this post Link to post Share on other sites
