weirdish 40 minor chrono results

[motosapiens]

4.0 gr ba9.5 @ 1.018 , 180 gr blue bullet = 750fps average, and brass ejecting 5-6 ‘.

 

same exact load on the same day with 165 gr berrys = 530fps average and brass doesn’t eject at all.

 

I know plated bullets are not as slippery as coded, but I have never experienced such a large disparity. I’m wondering if I am just at the ragged edge of low pressure.

[ChuckS]

Check the bullet dia? 

[IHAVEGAS]

24 minutes ago, motosapiens said:

4.0 gr ba9.5 @ 1.018 , 180 gr blue bullet = 750fps average, and brass ejecting 5-6 ‘.

 

same exact load on the same day with 165 gr berrys = 530fps average and brass doesn’t eject at all.

 

I know plated bullets are not as slippery as coded, but I have never experienced such a large disparity. I’m wondering if I am just at the ragged edge of low pressure.

Interesting. 

You thinking that the brass is not expanding enough to get a good seal on the chamber with the lighter and slicker bullet? 

 

Not sure how fast the powder you are using is. I'm getting ready to try and find the bottom limit for my gun (Glock 23, only need 105 pf for IDPA CCP division) and am going to use Clay Dot. 

[motosapiens]

1 hour ago, IHAVEGAS said:

Interesting. 

You thinking that the brass is not expanding enough to get a good seal on the chamber with the lighter and slicker bullet? 

 

Not sure how fast the powder you are using is. I'm getting ready to try and find the bottom limit for my gun (Glock 23, only need 105 pf for IDPA CCP division) and am going to use Clay Dot. 

I also was wondering about the seal with the brass. I was getting an occasional extra light round when I was at 133 power factor, which I guess might be a stiffer piece of brass, not expanding enough to seal. So I bumped the original 180g load up to 140 power factor. i’ve been shooting that for about a month and just tried the 165s today To get a baseline.

 

The lighter bullets may leave the case just quickly enough to start letting the pressure out earlier.

Edited January 1 by motosapiens

[IVC]

I wouldn't correlate the two since you're at the low end of PF and things can deteriorate quickly.

 

Normally, I would check the chrono first (direct sunlight can make it go crazy), but since you're getting FTE and no cycling, it appears that it's working correctly. The rest is about the load - before you get into brass, consider that you're comparing 165 to 180, bullets that are not only different weight, but significantly different length. If you're keeping OAL fixed, the 165s will have quite a bit more space in the case and will yield lower pressure. In fact, this alone could explain what you're seeing. 

[IHAVEGAS]

Got to the range yesterday to chrono a couple attempts at minimum power factor using clay dot. With 180 Bayou and 3.0 clay dot I got 650,676,698,705,720 fps.

 

With 155 grain Bayou and 3.3 Clay Dot I got 683,699,735,747,787. 

 

Accuracy was ugly in a Glock 23. 

 

Will up the horsepower a bit and try again. Previously had liked the recoil impulse of 3.4 Clay Dot pushing 180 bayou in a 40ish ounce gun (about 140 power factor in the STI 2011 I had at the time) but was wanting something more mouse fart for the lighter G23.