9X23Guy Posted January 4, 2014 Share Posted January 4, 2014 So I ran a few rounds over a chrono today just to get into the ball park for a load combination I never used. Normally I'd run ten rounds to get a velocity but like I said just trying to get in the ball park. What I noticed was that velocities kept climbing the more I shot. Not abnormally high but noticeably higher as the string of fire went on. My question is is this common for moly coated bullets? I have not noticed this with jacketed bullets. It seems as the barrel heated up velocities rose. Hot barrel burning more of the coating off? Accuracy was fine. Notice the first three rounds or so in each string are consistently lower. What do you all think. STI Tactical, 5" Bull barrel .40 S&W 180 grain Bear Creek FP WSF powder 1.185" OAL Winchester SP primer 4.5 grains 143 PF 1. 755 fps 2. 777 fps 3. 827 fps 4. 807 fps 5. 811 fps 5.0 grains 158 PF 1. 862 fps 2. 867 fps 3. 894 fps 4. 865 fps 5. 902 fps 5.5 grains 176 PF 1. 960 fps 2. 955 fps 3. 976 fps 4. 1003 fps 5. 1007 fps Link to comment Share on other sites More sharing options...
blaster113 Posted January 4, 2014 Share Posted January 4, 2014 I shoot a lot of BBI molys through my 6" gun, but never noticed velocities climbing as I shot over the chrono. I dont use WSF but Solo and N320. I noticed that when I adjust the powder measure of my 650 it takes a few throws for it to settle in and get the powder drops to be consistent at the new weight. Link to comment Share on other sites More sharing options...
9X23Guy Posted January 4, 2014 Author Share Posted January 4, 2014 (edited) Yeah, thought about that. I threw 5 or so charges before i loaded at that charge. Maybe a few more is needed. Then again I didn't shoot them in the order they came off of the press either. Edited January 4, 2014 by 9X23Guy Link to comment Share on other sites More sharing options...
joshxdm9 Posted January 4, 2014 Share Posted January 4, 2014 I recently switched from 124 gr mg to 124gr bayou. Like you I started with what I was loading the mg at. I shoot a xdm 5.25 and the velocity was consistency higher with the same charge of titegroup. So I was actually able to load down with the coated bullets. Link to comment Share on other sites More sharing options...
9X23Guy Posted January 4, 2014 Author Share Posted January 4, 2014 I knew velocities overall would be higher with moly. Just can't figure out the variation within the string. Link to comment Share on other sites More sharing options...
Sarge Posted January 4, 2014 Share Posted January 4, 2014 Here is an out in left field possibility. Could the bullets be setting back into the cases due to recoil as you shoot the string. I doubt it's the culprit but worth checking by measuring 5 or 10 before loading them in a mag. Then after a few rounds pull them out of the mag and measure. It might be the top round in the mag getting dragged forward against the mag or frame as well. Maybe even try loading them by hand one at a time to eliminate to weed out possibilities of set back. If you think it's heat just shoot one and wait 5 minutes between shots. Might make for a long chrono session but it will help figure out the problem. Link to comment Share on other sites More sharing options...
Russellhjoy Posted January 5, 2014 Share Posted January 5, 2014 Do you use case lube? Link to comment Share on other sites More sharing options...
9X23Guy Posted January 5, 2014 Author Share Posted January 5, 2014 Yes, Hornady One Shot. Link to comment Share on other sites More sharing options...
Russellhjoy Posted January 5, 2014 Share Posted January 5, 2014 Perhaps, another long shot, some of the powder is clinging to the inside walls of the case but the vibration of shooting knocks it off and allows for a more complete burn. I've noticed this in my 1911 but it was only the first round of every mag. I assumed it just wasn't seating as hard from slide lock. Link to comment Share on other sites More sharing options...
dauntedfuture Posted January 8, 2014 Share Posted January 8, 2014 With mixed brass 50-60 fps ES is quite possible. Lead build up can contribute to pressure and velocity. Yes, you get some lead with bbi bullets. It's weird. Link to comment Share on other sites More sharing options...
TH3180 Posted January 8, 2014 Share Posted January 8, 2014 With mixed brass 50-60 fps ES is quite possible. Lead build up can contribute to pressure and velocity. Yes, you get some lead with bbi bullets. It's weird.Interesting I've gone through cases of BBI bullets and haven't had leading once. Link to comment Share on other sites More sharing options...
Sarge Posted January 8, 2014 Share Posted January 8, 2014 With mixed brass 50-60 fps ES is quite possible. Lead build up can contribute to pressure and velocity. Yes, you get some lead with bbi bullets. It's weird.Interesting I've gone through cases of BBI bullets and haven't had leading once.same here. Got some moly residue though Link to comment Share on other sites More sharing options...
9X23Guy Posted January 20, 2014 Author Share Posted January 20, 2014 (edited) That's what I've seen in the barrel, moly residue, not lead. I've also noticed that the first mag there is no smoke but by the second or third it pretty noticeable. I've pulled a round to make sure I'm not scraping the coating off when I load and I'm good there. I'm going to try some BBI or Bayous next. Just trying to find an acceptable substitute for jacketed since limited is my secondary division. Edited January 20, 2014 by 9X23Guy Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now