First I'd like to say that I did a search on THL for everything I could find on this subject before deciding to post, but I could not find anything that correlates to what I experienced yesterday at the range. I realize that a chronograph has the potential of being very sporadic because of all the variables that can come into play. i.e. distance from muzzle, sky conditions, angle of the sun, etc., but I was seeing something very strange because it was only occurring when shooting my reloaded 9mm ammo.
I tried really hard to keep this short, but wanted to give as much info as possible so hopefully I won't lose your interest if it is too lengthy.
I had decided to test my 9mm reloads at the range yesterday to see how close they would get to the velocity readings from the manuals that I used to work them up.
I set up my Pro Chrono DLX 15-feet from the muzzle of my CZ P07. I was using a Caldwell sandbag rest and my target was set out to 25-yards. The temperature was about 75 and slightly overcast. I started out by shooting 10-rounds of Geco 115gr FMJ factory ammo (red box) to verify that the chrono was registering somewhat believable data.
According to the Geco specs on this ammo, it should be shooting somewhere close to 1,214 fps.
My 15-shots averaged 1,202 fps so I would consider the chrono to be fairly accurate as was also proven in past range tests when using factory .223 FMJ ammo. I would think that the Geco proves to be reliable enough to use as my control 9 mm ammo going forward.
My test loads consisted of Alliant BE-86 powder and Speer 115gr CPRN bullets. I used Data from Alliant and Speer because they both have receipts that use the exact bullet I'm using. I worked up the loads starting at 5.6 gr., which is 10% lower than the maximum of 6.3gr. I loaded 15-cases each at 5.6 gr, 5.8 gr and 6.0 gr.
The manuals show an OAL of 1.135" so to be safe and not create pressure issues, I loaded my ammo at 1.140" and the actual measured OAL of each of the 45 cartridges I reloaded was between 1.140 - 1.1415". I should let you know that everything was set up exactly the same as when I was shooting the Geco factory ammo, I didn't move anything.
According to the Speer info, at the max of 6.3 gr the speed should be around 1226 fps. Unfortunately no one lists the speed for lesser charges and I realize that would be asking for way to much anyway.
At 5.6 gr. my first shot registered only 665 fps even though my CZ cycled perfectly and ejected the round almost next to the Geco rounds I had shot first. The next 8- rounds were all "duplicates"
of the 1'st (665). Shots # 10 and #11 registered 3,950 fps and shots 12-15 registered 725 fps.
All 15- rounds cycled and ejected almost identical to the Geco control ammo. It was apparent that something was totally amiss because I seriously doubt that my CZ would operate at such a slow speed of 665 fps and I'm sure would have blown apart at 3,950 fps! I had also looked at the primers on all 15 as I shot them, for signs of flattening or flowing and ejector marks, but they all looked fine. I didn't see any unburned powder in the spent cases or in my CZ's action and the spent cases looked exactly like the Geco spent cases.
I decided before trying the next step of my reloads that I would shoot 10-more of my Geco control rounds. The 10 ended up having an average of 1205 fps, which basically matched the prior 15- rounds I shot in the beginning.
I went ahead and loaded the next 15, which were loaded with 5.8gr. of BE-86 and to my utter disappointment and amazement, the first 5 registered 665 fps. Shot 6 was 3,785 fps and shots 7-9 were 667 fps and 10 was 3,790 fps. At this point I was frustrated because I had no clue where to start trying to figure out what the issue (or issues) was. These numbers made no sense at all. I figured that the only thing I could do before giving up was to try the factory Geco again and because I also happened to have an AR-15 in 22 lr with me, shoot it through the chrono as well.
Every factory bullet that passed through the chrono was within 2-3% of the factory spec, but every reload was out in left field!
I decided to give up on the chrono and because none of the reloads that I shot showed any signs of being loaded over pressure, I decided to just shoot the last 5- loaded with 5.8 gr and check for accuracy and even though they were hitting about 3 1/2-inches low of the Geco POI, grouped really good. I also chose to shoot the last 15- loaded with 6.0 gr and checked each one of these spent cases after firing as well and again saw nothing wrong with them. The POI moved up
2" higher than the 5.8 gr shots and also grouped well.
Based on the POI alone of these reloads I can only assume that they had to be somewhere in the speed zone of my Geco factory ammo.
I am hoping that one of you fine gentlemen might have had a similar experience with a chrono that reads accurately with factory ammo, but takes a big gigantic dump while using reloads? I would sincerely appreciate any explanation or suggestions of what I can try, to solve this problem.
I tried really hard to keep this short, but wanted to give as much info as possible so hopefully I won't lose your interest if it is too lengthy.
I had decided to test my 9mm reloads at the range yesterday to see how close they would get to the velocity readings from the manuals that I used to work them up.
I set up my Pro Chrono DLX 15-feet from the muzzle of my CZ P07. I was using a Caldwell sandbag rest and my target was set out to 25-yards. The temperature was about 75 and slightly overcast. I started out by shooting 10-rounds of Geco 115gr FMJ factory ammo (red box) to verify that the chrono was registering somewhat believable data.
According to the Geco specs on this ammo, it should be shooting somewhere close to 1,214 fps.
My 15-shots averaged 1,202 fps so I would consider the chrono to be fairly accurate as was also proven in past range tests when using factory .223 FMJ ammo. I would think that the Geco proves to be reliable enough to use as my control 9 mm ammo going forward.
My test loads consisted of Alliant BE-86 powder and Speer 115gr CPRN bullets. I used Data from Alliant and Speer because they both have receipts that use the exact bullet I'm using. I worked up the loads starting at 5.6 gr., which is 10% lower than the maximum of 6.3gr. I loaded 15-cases each at 5.6 gr, 5.8 gr and 6.0 gr.
The manuals show an OAL of 1.135" so to be safe and not create pressure issues, I loaded my ammo at 1.140" and the actual measured OAL of each of the 45 cartridges I reloaded was between 1.140 - 1.1415". I should let you know that everything was set up exactly the same as when I was shooting the Geco factory ammo, I didn't move anything.
According to the Speer info, at the max of 6.3 gr the speed should be around 1226 fps. Unfortunately no one lists the speed for lesser charges and I realize that would be asking for way to much anyway.
At 5.6 gr. my first shot registered only 665 fps even though my CZ cycled perfectly and ejected the round almost next to the Geco rounds I had shot first. The next 8- rounds were all "duplicates"
of the 1'st (665). Shots # 10 and #11 registered 3,950 fps and shots 12-15 registered 725 fps.
All 15- rounds cycled and ejected almost identical to the Geco control ammo. It was apparent that something was totally amiss because I seriously doubt that my CZ would operate at such a slow speed of 665 fps and I'm sure would have blown apart at 3,950 fps! I had also looked at the primers on all 15 as I shot them, for signs of flattening or flowing and ejector marks, but they all looked fine. I didn't see any unburned powder in the spent cases or in my CZ's action and the spent cases looked exactly like the Geco spent cases.
I decided before trying the next step of my reloads that I would shoot 10-more of my Geco control rounds. The 10 ended up having an average of 1205 fps, which basically matched the prior 15- rounds I shot in the beginning.
I went ahead and loaded the next 15, which were loaded with 5.8gr. of BE-86 and to my utter disappointment and amazement, the first 5 registered 665 fps. Shot 6 was 3,785 fps and shots 7-9 were 667 fps and 10 was 3,790 fps. At this point I was frustrated because I had no clue where to start trying to figure out what the issue (or issues) was. These numbers made no sense at all. I figured that the only thing I could do before giving up was to try the factory Geco again and because I also happened to have an AR-15 in 22 lr with me, shoot it through the chrono as well.
Every factory bullet that passed through the chrono was within 2-3% of the factory spec, but every reload was out in left field!
I decided to give up on the chrono and because none of the reloads that I shot showed any signs of being loaded over pressure, I decided to just shoot the last 5- loaded with 5.8 gr and check for accuracy and even though they were hitting about 3 1/2-inches low of the Geco POI, grouped really good. I also chose to shoot the last 15- loaded with 6.0 gr and checked each one of these spent cases after firing as well and again saw nothing wrong with them. The POI moved up
2" higher than the 5.8 gr shots and also grouped well.
Based on the POI alone of these reloads I can only assume that they had to be somewhere in the speed zone of my Geco factory ammo.
I am hoping that one of you fine gentlemen might have had a similar experience with a chrono that reads accurately with factory ammo, but takes a big gigantic dump while using reloads? I would sincerely appreciate any explanation or suggestions of what I can try, to solve this problem.
.
