Blue Dot and Chronograph

[roadking85]

so, being new to 10mm reloading, I had some blue dot and Hornady 155gn XTP bullets. I loaded up 10.2 gns and went to the range with my Caldwell Chronograph. The Hornady reloading guide indicates for a load of 10.2 gn Blue Dot and 155 gn XTP that the FPS would be 1150 fps, however my Caldwell Chrono recored an average of 3132 fps over 9 shots (I forgot to hit start on the first shot of 10). I don't understand the huge difference. I was approximately 10 feet away from the chrono firing at approximately 15yds. I believe the load is safe but I want to understand the discrepancy in FPS from my chrono. I can't find anything on the web regarding my chrono. Any ideas? I trust the load data but suspect my chrono.

[Graybeard]

313.2 meters per second is 1028 feet per second. Any chance the units were the issue?

[fltbed]

Chronographs like your Caldwell, use light sensors to see the bullet pass by in order to figure velocity.  Things like, amount and angle of sunlight, powder ejecta and even muzzle blast can and do effect readings.

I suspect in your case, either the angle of the sun or powder ejecta giving you erroneous readings.  Or, like Greybeard suggested, you accidentally had it measuring in MPS.

Jeff

[Graybeard]

flbed gives some valid reasons for errors from optical chronographs. I've had errors for those reasons from the Chrony brand. They usually weren't consistent, like your 9 shot string.

One thing is for sure, you definitely weren't pushing a 155gr XTP at 3000+fps with 10.2gr of Bluedot. My top speed for that bullet was 1530fps out of a 5" 1911 using 800X. Recoil and muzzle blast were pretty stout. Your load should have felt fairly mild.

[roadking85]

313.2 meters per second is 1028 feet per second. Any chance the units were the issue?

That could be, I'll have to check that the next time I go out and test these loads again. I had a feeding problem and I think I didn't crimp enough. Thanks for the feedback.

[roadking85]

Chronographs like your Caldwell, use light sensors to see the bullet pass by in order to figure velocity.  Things like, amount and angle of sunlight, powder ejecta and even muzzle blast can and do effect readings.

I suspect in your case, either the angle of the sun or powder ejecta giving you erroneous readings.  Or, like Greybeard suggested, you accidentally had it measuring in MPS.

Jeff

Thanks Jeff, you could be correct, it was 3PM here when I was out testing, the chrono does have lights but I didn't use them thinking it was bright enough out mostly sunny. I was about 10 feet away when firing which is what they recommend.

Doug

[roadking85]

flbed gives some valid reasons for errors from optical chronographs. I've had errors for those reasons from the Chrony brand. They usually weren't consistent, like your 9 shot string.

One thing is for sure, you definitely weren't pushing a 155gr XTP at 3000+fps with 10.2gr of Bluedot. My top speed for that bullet was 1530fps out of a 5" 1911 using 800X. Recoil and muzzle blast were pretty stout. Your load should have felt fairly mild.

Yup, I agree on not pushing that at 3k+ for sure which is why I was really confused. I'm shooting these out of a RIA 1911 5". Iv'e since upped my powder charge to 12gns aiming to get 1300+ out of it.

Doug

[The_Shadow]

With Blue Dot I set my Chrony at 12 feet as some unburned flakes can trip a sensor.

That being said heavier loads tend to burn cleaners with Blue Dot.  Measure your crimp on the very edge of the case mouth, should be 0.4215" or 0.4220".

[Graybeard]

I?ve noticed that Bluedot has a very distinctive and somewhat nasty smell at lower pressures, too. You can tell you?re getting closer to the sweet spot in a work up when that goes away.

[roadking85]

With Blue Dot I set my Chrony at 12 feet as some unburned flakes can trip a sensor.

That being said heavier loads tend to burn cleaners with Blue Dot.  Measure your crimp on the very edge of the case mouth, should be 0.4215" or 0.4220".

Thanks for that info, mine are measuring right at .422

Doug

[roadking85]

I?ve noticed that Bluedot has a very distinctive and somewhat nasty smell at lower pressures, too. You can tell you?re getting closer to the sweet spot in a work up when that goes away.

I hadn't noticed that but will try to check it out. My smeller isn't always the best LOL.

Doug

[fltbed]

Thanks Jeff, you could be correct, it was 3PM here when I was out testing, the chrono does have lights but I didn't use them thinking it was bright enough out mostly sunny. I was about 10 feet away when firing which is what they recommend.

Doug

Using a chronograph this time of year can be troublesome as the sun is always low in the sky.  I have spent hours messing with distance, angles, even taping cardboard to the sun-ward side of the chrono to keep the sensors in the shade.  I even toyed with the idea of building a "chrono coffin" like we use at major USPSA matches.
 
What I do now is just wait for a calm overcast day with a nice layer of high white clouds with no discernible shadows.  Those are the days my CE chronograph works the best and I'll often take several guns and boxes of rounds to test and make a day of it.

Jeff

[jazzsax8]

Some brands have a lighting (LED) kit that helps in the Winter or in the basement.

[gunpost]

Anyone tried 180gr load work ups with Blue Dot? See, my dilemma is that I don't buy Hornady's so-called max load is really max load. They are saying 10.7gr is max, and gets you 1,250 fps. Yet I've seen factory load 180gr ammo hitting 1,350 fps. Plus, I had this experience with Hornady's so-called max load being way low in working up loads on my 357 magnum.

Problem is that I'm working up this load in my Glock 20. So how do you find out when you are getting high pressure sign in a semi-auto??? In my 357 magnum revolver it's easy because once the shells get a little hard to manually eject, you know you have to back off just a little bit, and that it a good and safe max load. And it was way higher than what Hornady load data claimed as the max.

So does anyone have any advice, or experience loading Blue Dot to the max with 180gr bullets in their 10mm pistols?

[fltbed]

Anyone tried 180gr load work ups with Blue Dot? See, my dilemma is that I don't buy Hornady's so-called max load is really max load. They are saying 10.7gr is max, and gets you 1,250 fps. Yet I've seen factory load 180gr ammo hitting 1,350 fps. Plus, I had this experience with Hornady's so-called max load being way low in working up loads on my 357 magnum.

Problem is that I'm working up this load in my Glock 20. So how do you find out when you are getting high pressure sign in a semi-auto??? In my 357 magnum revolver it's easy because once the shells get a little hard to manually eject, you know you have to back off just a little bit, and that it a good and safe max load. And it was way higher than what Hornady load data claimed as the max.

So does anyone have any advice, or experience loading Blue Dot to the max with 180gr bullets in their 10mm pistols?

Hello gunpost and welcome to the forum.

Many of us have worked up Blue Dot with 180 gr bullets.  Alliant's online data lists 11.0 as max but it's always wise to work it up yourself.  I can't speak for the others but for me, 10.8 was as much as I was comfortable with and my own personal max, with 10.4 gr being the accuracy node.

It is possible to get 1300+ fps with a 180 gr bullet but I would suggest Longshot or Accurate #9.  (or 800X but I have no experience with it)  You won't get the accuracy of the 10.4 gr of BD load but you will see the velocity.  (on a chronograph)

Their is no one thing to look for when determining a max load.  Without a pressure transducer hooked up to a laptop it's all just SWAG.  (Scientific Wild A** Guess)
That SWAG is based on a combination of things you learn from experience.  It's about the best way I can explain it.

Jeff