Over pressure and velocity with standard data

Background, used powder manufacturer data for one year for 1 1/8 oz loads to 1200 fps. Set powder and shot bushings to exact suggested weights using digital scales.
Then wanted to bump 1 1/8 oz load to 1235 fps to match Nitro 27 factory loads.
Added .3 gr to the 1200 fps data, loaded 6 rounds, hand weighed. This powder weight was less than the suggested weight for 1250 fps. Sent to a laboratory for testing.
WOAH, when I received the ballistics test results.
The 1 1/8 oz load average velocity was 1328 fps (ATA max 1290 fps) and 12,745 psi (SAAMI max is 11,500 psi).
Obviously, I needed to make adjustments.
As a standard, using an optical sensor chronograph I shot 6 rds of factory Nitro 27 in a .732” bore 34” barrel for 1251 fps, SD 30, ES 70.
My long term load 1 1/8 load at expected 1200 fps chronographed at 1305 fps, SD 19, ES 44.
I reduced that 1 1/8 oz powder load by 1 grain (1200 fps load data) (1.3 grain from the lab tested load). The chronograph result was 1270 fps, SD 12, ES 34.
I suggest you start with lowest powder load and chronograph it, with small increment increases to obtain desired velocity. (Limited space in thread)

 

Did you know that an 1150 fps load will smoke targets all the way back to the 27 yard line?? They will
And on a side note 35 fps means absolutely nothing.

 

Update on reloaded data.

Reduced manufacturer suggested 1200 fps powder weight by 2.3 grains which choreographed at 1228 Avg, 17 SD, 49 ES, 1225 High, 1207 Low. Each hand weighed.

Lesson learned;
Do not use manufactures published data without independent validation. Lot to Lot variation, and other variables, will result in reduced or increased velocities and resulting pressures. Some may be excessive by ATA or SAAMI standards.
Consider sending precisely weighed loads to a laboratory for verification of velocity, and resulting pressure,

ps, I did not identify hull, primer, powder, exact powder weight, wad, lead weight or any other variables on purpose. The focus of this thread was only upon verification of manufacturers expected velocity (lot to lot variation) in contrast to actual reloaded ammo, without regard to other, multiple variables.

 

Edit did not work.
Change 1225 High to 1255 High.
Change choreographed to chronographed.

 

New shell manufactures claim a + or - of 5%, which at one time was accepted according to the rule book of the ATA , I do not know if that is still the standard or not being as I quit reading the rule books when I quit shooting registered ...
The Data posted by jesflorida is impressive but to make a point without graphs and charts backing up the data just seems so lacking (half baked ) in a way ... I had some new Handicap loads tested (several years ago) and was really shocked by the different stats they produced (again no graphs and charts) out the of the same box , it was not only one manufacture of shells but several and some of the Data exceeded their standard of + or - 5% ... Based on the findings people can be shooting illegal loads and not even know it ... Maybe the rules should say on Average a plus or minus of 5% is acceptable if presented with Charts and Graphs to confirm such Data or unless they are new shells ... WPT ... (YAC) ...

 

ATA Rule Book, pages 48-49 set the maximum velocity of any single 1 1/8 oz load at 1290 fps.

All chronographs I am familiar with report velocity data in fps and determine average, standard deviation and extreme spread. These are helpful to the reloader but do not guarantee that a given load will not exceed the ATA velocity limit.

I have settled on a load that uses 2.7 grains less powder than the powder manufacturers load data for 1200 fps.
It chronographed at 1219 fps AVG,14 fps SD, 42 fps ES. I also recorded the highest velocity at 1235 fps and lowest velocity was 1193 fps. I am confident my load provides adequate performance and are ATA legal.

A chart or graph of that data would be single points on the x-y axis. It would require multiple tests to create charitable data.

 

My point exactly (half baked ) ... WPT ... (YAC) ...

 

You are welcome.

 

So, after the shell has been shot how are they going to check it ..? I shoot all handicap loads (factory) (assume 1250 fps, per the manufacture) , years ago had them checked and got the reports on the Data which have long since disappeared ... I seem to recall I had shells test out over 1300 FPS to less than 1200 FPS out of the same box, on more than one type ... I would hope the manufacture has improved over all with the consistency as progress and technical support improved ... They say this is not "Rocket Science" obviously that is a good thing ... I was never one to give the ammo much thought or consideration being as it was new and I probably could not be held accountable for what the factory does or does not do ... I have NEVER had anyone contest or check any of the shells I used ... WPT ... (YAC) ...

 

Years ago I shot USPSA and IDPA. Many of the major matches (equal to our regional Grands) required all shooters to have a random sample of their ammo chronographed during the match. All major matches had a chronograph available for challenged loads.

Anyone have a similar experience at ATA shoots, like the Regional Grands or the All American Grand?

 

I have been a Life Member of the ATA since 1975, have never had a shell checked even at the Grand when it was in Vandalia (required new shells back then ) ... One time a shooter next to me said my shells sounded loud, I handed him a shell out of the box and told him they are brand new Federal papers, take one and have it checked ... He never did, or if he did I was not aware of it ... It is a rule that takes up space in the rule book, based on my own experience it is not enforced or I am sure I would of been checked at least once in over 40 years ... WPT ... (YAC) ...

 

the speed differential with a 1200 fps and an 1145 fps from the 27 yd line is 6 fps figure that smokingtom said it best

Mac

 

The gathered information is great and appears to be reasonably accurate ... I always wondered if people who pattern and use a 30 inch circle as their intended coverage area are counting on the pellets on the fringe of the pattern to break targets or would it be best to try and utilize the "hot spot " which is usually pretty dense ... I'm a hard head and stubborn in some ways but be damned if I would count on pellets outside of the 20 inch center of any given pattern to break targets with authority, but be thankful that they did on occasion (part of the game ) ... Thanks all for the information ... WPT ... (YAC) ...