New chronograph, interpreting 9mm loads

[ericuda]

Just purchased a prochrono chronograph and would like input on my results from my reloads. Shot 5 shots each with a ruger 6 1/2" blackhawk and walther pps.

1. American Eagle Factory 124 fmj
ruger: 1138 avg, 32 es, 13 sd
walther: 1045 avg, 33 es, 12 sd

2. MBC 125 lrn at 1.060 oal and 3.9 gr hp38
ruger: 1061 avg, 29 es, 11 sd
walther: 956 avg, 14 es, 6 sd

3. xtreme 124 plated rn at 1.130 oal and 6.5 gr hs-6
ruger: 1120 avg, 32 es, 14 sd
walther: 1038 avg, 66 es, 31 sd

4. xtreme 124 plated rn at 1.135 oal and 5.2 gr cfe pistol
ruger: 1081 avg, 26 es, 11 sd
walther: 1024 avg, 29 es, 10 sd

5. xtreme 124 plated hp at 1.120 oal and 5.2 gr cfe pistol
ruger: 1058 avg, 41 es, 16 sd
walther: 990 avg, 53 es, 20 sd
I need to shorten oal to around 1.090 to chamber in my cz.

6. For fun factory cci quiet 22lr in a ruger sp101
565 avg, 76 es and 24 sd. Very quiet round.

 

[moxie]

Nice consistent results. You usually but not always get a bit more velocity from the longer barrel on the Ruger. Keep doing what you're doing!

 

[Dudedog]

Chronos are fun, and usefull.

 

[steve4102]

There are two types of shooters that use a Chrony.

Those that have shot their Chrony and those that Will shoot their Chrony.

 

[ATLDave]

It's interesting that the xtreme HP ran a touch slower in both guns versus the RN of the same weight and manufacturer. Anyone know what that's about? Or, with only 5 shots of each, is this all within the margin of measurement error?

 

[mavracer]

It's interesting that the xtreme HP ran a touch slower in both guns versus the RN of the same weight and manufacturer. Anyone know what that's about?

Length of bearing surface and exactly how far base of bullet is in case play a big roll in velocity, even though the RN is loaded to a longer length because of the nose profile it still may have less room for powder and a shorter bearing surface

 

[ATLDave]

mav', he says the powder charge was the same. I think that takes out "less room for powder" as an explanation.

I suppose a longer bearing surface has more friction, so I guess that could be the answer.

 

[vaalpens]

I don't have a chrono so I don't know if there is a difference between my Xtreme 124gr CPRN or CPHP loads. When I load them I load the HP with about a .05" lower COL which is the difference in bullet length. The CPHP is also a thicker plating and should be able to handle higher velocities. I loaded my CPRN to a 1.145"/1.150" COL and the CPHP's to a 1.091"/1.10" COL.

 

[mavracer]

mav', he says the powder charge was the same. I think that takes out "less room for powder" as an explanation.

How much room you have for powder and how much powder you put in that room are two different things, the deeper you seat a given bullet the less room the powder charge has and the more pressure you'll have

 

[ATLDave]

OK, I don't disagree with that, Mav', but he's seating the HP deeper, which should increase peak pressure. Yet he's getting slower readings with them. Again, I think "less room for powder" is excluded as an explanation.

 

[mavracer]

Is he seating them deeper in the case? The bullets have a much different nose profile so that while OAL may be shorter less of the bullet may be in the case.

 

[vaalpens]

OK, I don't disagree with that, Mav', but he's seating the HP deeper, which should increase peak pressure. Yet he's getting slower readings with them. Again, I think "less room for powder" is excluded as an explanation.

ATLDave, you are correct that he is seating the HP deeper but it is not the complete picture.

xtreme 124 plated rn at 1.135 oal and 5.2 gr cfe pistol
xtreme 124 plated hp at 1.120 oal and 5.2 gr cfe pistol

The difference in the COL is 0.015".

The average length I have found for the RN is .5888" and the average for the HP is .5385". The difference in length is .0503".

So it seems the RN is seated about .0453" deeper into the cartridge than the HP, which should create higher pressure. If the HP was seated with a COL of 1.0847", then they would have been seated about the same depth.

I'm not saying he should change the COL, but this is just my observation regarding the seating depth.

 

[mavracer]

Thanks vaalpens, it would seem my guess was accurate.

 

[ATLDave]

OK, that all makes sense. I wouldn't have guessed the RN being substantially longer than the HP. And, yes, that would support mav's guess. I retract my prior dismissal of that possibility.

 

[Walkalong]

I logged the X-Treme 124 Gr RN & HP at .536 & .582, very close to what vaalpens measured. I always log the bullet diameter and length. That way I can use the length of the bullet and the OAL of the round to determine how deep one is seated in relationship to another if these kinds of questions come up.

 

[ericuda]

vaalpens, thx. You confirmed what i was thinking in the oal of the hp. I did the plunk test on my walther which passed but my cz wasn't even close. I will load some up this weekend at 1.09 and see if the velocities are more in line with the rn.

Steve, i suppose you are right. Hope i don't have bad luck for awhile. Looking at the results i can see where the velocities come in handy when experimenting with different loads.

 

[mavracer]

It's also a real good reason to back off charge weight when changing bullets or using a different bullet than called out in the manual

 

[ericuda]

5. xtreme 124 plated hp at 1.120 oal and 5.2 gr cfe pistol
ruger: 1058 avg, 41 es, 16 sd
walther: 990 avg, 53 es, 20 sd

Retested today with the above and a 1.090 oal. Interesting what a change in oal does. I am kinda surprised it didn't match the xtreme 124 rn results closer though.
ruger: 1152 avg, 39 es, 17 sd
walther: 1062 avg, 30 es, 12 sd

I also shot 5 5.7x28 with 4.9 cfe pistol out of fn pistol.
1636 avg, 79 es, 28 sd

 

[vaalpens]

Nice to see the change in fps with the OAL change. Obviously all bullets are not exactly the same length so that is one variable. Also the Xtreme RN and HP bullets are not the same plating. The HP has the thicker plating and is rated up to 1500fps. Not sure what impact the plating has on the pressure, but it probably does.

Be safe.