I just finished developing my load for my 7mm remington mag with 162gr SST's. I worked the load up the old way of loading 4 rounds at .5 grain increments up to 1 grain over book max charge. Even at the highest load, no pressure signs were seen. The best shooting load (.402) was with 69.5 grains of H-1000 and a regular Fed 215 primer, which is .5 grains below book max. I loaded up 20 more of these and went back to the range to test at some longer distances and remembered to bring my chrono with me this time. DAMN, I was getting speeds in the 3285 - 3303 range. My E.S. was 20 and S.D. was 9. Is this possible, I had a few 150 grain factory rounds that claimed 3150 as a velocity and they were running about 30 fps faster at 3180ish. My chrono was set at 15 feet as to not get any interference from the muzzle blast. Thats 300 fps faster than what it's supposed to be running.
- Thread starter jsthntn247
- Start date
Re: Is this possible?
What barrel length?
Which Chrono?
Did you get some where the MV was about 3500+ fps in the same string where they were 3100?
If you're using a significantly longer barrel than the book data came from it's entirely possible.
If you're using a chrono with adjustable sensors or one of the folding style ones you could have the sensors closer together than the little chrono brain thinks they are, making the calculated speeds higher.
The last question would indicate that you're getting muzzle blast screwing up the results.
What barrel length?
Which Chrono?
Did you get some where the MV was about 3500+ fps in the same string where they were 3100?
If you're using a significantly longer barrel than the book data came from it's entirely possible.
If you're using a chrono with adjustable sensors or one of the folding style ones you could have the sensors closer together than the little chrono brain thinks they are, making the calculated speeds higher.
The last question would indicate that you're getting muzzle blast screwing up the results.
Re: Is this possible?
Barrel Length is 24 inches. Was using a Beta Chrony. It is possible that I didn't have the chrony completly flat, didn't think of that. Still can't figure why the factory rounds were so close to advertised speeds and mine were so far off. MV only ranged from 3274 to 3320. I threw the 3274 and the 3320 out because they were fouling shots after cleaning, all other shots were in the 3285-3303 range. I also shot a few of the same load with CCI 250's. It was running about 100 fps slower, and was stringing shots vertically.
Barrel Length is 24 inches. Was using a Beta Chrony. It is possible that I didn't have the chrony completly flat, didn't think of that. Still can't figure why the factory rounds were so close to advertised speeds and mine were so far off. MV only ranged from 3274 to 3320. I threw the 3274 and the 3320 out because they were fouling shots after cleaning, all other shots were in the 3285-3303 range. I also shot a few of the same load with CCI 250's. It was running about 100 fps slower, and was stringing shots vertically.
Re: Is this possible?
I checked in Quickload and while it is usually off by some, the numbers are generally a lot closer than 300fps (50-60fps usually on first try).
I'm getting appx 2950fps with the load you mentioned above.
I suspect you have a chrono issue.
How was the light that you were shooting in? Those BETA Chrony's are very fussy I've found.
I checked in Quickload and while it is usually off by some, the numbers are generally a lot closer than 300fps (50-60fps usually on first try).
I'm getting appx 2950fps with the load you mentioned above.
I suspect you have a chrono issue.
How was the light that you were shooting in? Those BETA Chrony's are very fussy I've found.
Re: Is this possible?
I shot at about 6 o'clock p.m on a sunny day. My initial thought was the light angle may be affecting the chrony results (i.e. because of the setting sun,the light was shining in below the screens). I'm going to test again early on a cloudy day and see what the results are.
I shot at about 6 o'clock p.m on a sunny day. My initial thought was the light angle may be affecting the chrony results (i.e. because of the setting sun,the light was shining in below the screens). I'm going to test again early on a cloudy day and see what the results are.
Re: Is this possible?
I would start with a new battery in your crono. I had the same thing happen to me with a f1 chrony. after I changed the battery my readings went back to normal
I would start with a new battery in your crono. I had the same thing happen to me with a f1 chrony. after I changed the battery my readings went back to normal
Re: Is this possible?
I have a chrony beta POS and with my tripod setup, with a quick mount thingy that came with the tripod, it is easy to get the chrony in a position where the base is not level/even. It hinges a little bit thus moving the sky screens closer together, thus falsely indicating high velocities.
I had been chasing 3000fps in my 300WM with 208AMAX and thought I was there, magically. WRONG!
I have a chrony beta POS and with my tripod setup, with a quick mount thingy that came with the tripod, it is easy to get the chrony in a position where the base is not level/even. It hinges a little bit thus moving the sky screens closer together, thus falsely indicating high velocities.
I had been chasing 3000fps in my 300WM with 208AMAX and thought I was there, magically. WRONG!
