Crazy Chrono

[Vulture]

I shot a match on Sat and when I get to the chrono station and the guy chrono's my gun my speed was all over the place. I had to use all seven chances to make it and did on the last one. The guy jokingly said "I told you guys to bring your chrono ammo not your league ammo." I needed 1000 fps and 4 of my 7 shots were low, some as low as 940. My load is .40 cal mixed brass Rainier plated RNFP 165 over 5.0 TG 1.17 OAL. .420 crimp. Lee sizer die and FCD and Dillion seater die. loaded on a 550b. Now I am assuming I am not always getting a full charge all the time. I only load about 100 at a time and then maybe won't load for a day or two then do a couple of hunderd more. Is it possible the loader needs to "warm up" because the powder has settled or something like that. Is it more consistant to load a large number at a time (500+) or does it matter. I'm just trying to use up these rainiers and will then be shooting 180 zero's. But I would like to address this issue before it is in a match that is more important than a club match.

[G-ManBart]

I'd suspect the mixed brass as the first possibility. I just did some chrono work last week. Ten shots, once-fired brass from the same lot, and the extreme spread was in the 21fps range. Take a case with a slightly larger volume and a powder charge a tenth of a grain or so low and you could probably see a shot as low as your 940 one.

Before doing anything serious I'd try sorting your brass, loading some that way and then run them over the chrono. On top of that, most people try to get a PF of 170 at least so they don't run into the problems you encountered. That would mean pushing those 165s to an average of 1030.

With the 180s you'll be loading next, I'd try to get 950fps and you'll be fine if a couple are on the low side. There isn't any noticable difference (for me) between a PF of 165 and 170 so it's not worth cutting it too close...in fact it takes a lot more difference in PF than that for most people to notice.

[benny hill]

The 165 with 5.0 tightgroup will make major out of my 6" but will not out of a 5" with a jacketed bullet.

[revchuck]

I load mixed brass in my token .40 S&W (Steyr M40) and separated them after loading, chronoing ten of each headstamp out of curiosity. The average velocities of my load (4.4 grains Bullseye, 185 Precision at 1.13" OAL) were within 15 fps among Federal, R-P and Winchester brass. Then again, this gun is stock; might an ignition system right on the edge of working (match gun) have caused the variation?

Is it possible the loader needs to "warm up" because the powder has settled or something like that.

Well, the guy pulling the handle might need to warm up to get consistent. Seriously, if you're emptying the powder measure each time and refilling it, then loading a hundred rounds, that could cause the variation if you got some of the rounds from when you first started mixed in with the ones toward the end of the batch.

[LPatterson]

If you are using TiteGroup and not empting the powder measure after each use it won't be long before you have a black plastic tube you can't see through.

[Chuck Merriam]

On a 550 you need to watch the safety plunger for the powder return bar. The little wing nut on mine kept backing off while I was not watching...leading to some undercharging. I got to the Area 6 last year and chronoed at 165.0 ! Blue lock tight fixed that problem! Just a thought...but I load with mixed headstamp and have never seen the flux's you are getting. Was the chrono open (no box), if so maybe the guy was shooting all over the array. If he's not constant the readings will not be either. Also if you have the sights set weird like shooting high. Just some thoughts.

[Vulture]

I haven't ever emptied my powder measure. when it gets low i just added more. It has only been in use less than a year so it can't have gunked up too much. But I will try doing larger runs and empty the powder measure when i am done and see how that works. It has also warmed up around here so I can chrono much more often. Thanks for the advice.

Edited March 27, 2007 by Vulture