Bullet Velocity, Standard Deviation

[ricklovin93]

I've been reloading for 9 years now, and I just picked up my first chronograph.

I'm working up a new load for my Garand. 178 grn ELD-M, IMR4895.CCI200, mixed commercial brass. 6 shot groups (every group had a conistent flyer) so I omitted the flyer from the group size. So really 5 shot groups. off of a bag.

41.5 grns of powder:
-Average velocity: 2291
-S/D: 45.47
-Group size: 3.00

42.0 grns of powder:
-Average velocity:2291
-S/D: 18.41
-Group size: 2.30

42.5 grn of powder:
Average velocity: 2332
S/D: 20.21
Group size: 2.86

43.0 grns of powder:
Average velocity: 2351
S/D: 22.33
Group Size: 3.9

Is it normal to see velocity stay the same, with an increased charge, but the standard deviation to be substantially better? (like load 1 and 2)

 

[dsdmmat]

Not normally, the mixed brass maybe the culprit. Try separating out your brass by head stamp then by weight.

 

[dsdmmat]

I use 125 and 135 grain bullets and 47.5 grains of IMR 4895 in my Garand. Lot more pleasant to shoot all day.

 

[Carlos Hathcock]

Are those groups sizes at 100 yards?

 

[dsdmmat]

Are those groups sizes at 100 yards?

With A Garand probably. Unless you have a new Criterion barrel and a good load 3 moa is pretty standard.

 

[Podmonkey]

With A Garand probably. Unless you have a new Criterion barrel and a good load 3 moa is pretty standard.

What can a Criterion barreled Garand do? I have a CMP Special grade with a Criterion but I never put it in paper. Not seriously anyway.

 

[dsdmmat]

What can a Criterion barreled Garand do? I have a CMP Special grade with a Criterion but I never put it in paper. Not seriously anyway.

About an inch with a good load .

 

[Podmonkey]

About an inch with a good load .

Huh. That's pretty GD good.

 

[squib]

I've been reloading for 9 years now, and I just picked up my first chronograph.

I'm working up a new load for my Garand. 178 grn ELD-M, IMR4895.CCI200, mixed commercial brass. 6 shot groups (every group had a conistent flyer) so I omitted the flyer from the group size. So really 5 shot groups. off of a bag.

41.5 grns of powder:
-Average velocity: 2291
-S/D: 45.47
-Group size: 3.00

42.0 grns of powder:
-Average velocity:2291
-S/D: 18.41
-Group size: 2.30

42.5 grn of powder:
Average velocity: 2332
S/D: 20.21
Group size: 2.86

43.0 grns of powder:
Average velocity: 2351
S/D: 22.33
Group Size: 3.9

Is it normal to see velocity stay the same, with an increased charge, but the standard deviation to be substantially better? (like load 1 and 2)

I have seen the avg. velocity stay and even decrease with increased charge weight. Chronographs are funny gadgets, that are affected by many variables. Even the pressure of the hold of the rifle can change the averages. INMOP 6 shots are meaningless in regards to SD, too small of a sample. I would not jump to any conclusions until the data is repeated a few times. I would also not omit any "flyers" unless they are called.

 

[meketrefe]

Thanks for sharing.

I am thinking with a slower powder you should be getting a tad more speed with the standard barrel even from a gas gun.
IMO IMR4896 are a tad on the fast side and I would not go faster than varget and there are better powders than varget.
Something like R22 or H4350 or R19 are good powders for the 30-06.
you should be hitting the 2500 at the muzzle w/o any issues.

A good Garand is going to be a good shooter but never a super consistent shooter.
Same problem with the M1A, it can only go so far even after dumping thousands of dollars into it. It is not worthy.
~2.5 moa spreads are great for that rifle so it looks you have a good shooter.

 

[ricklovin93]

Brand new Criterion Barrel installed two years ago, less than 100 rounds through it. I haven't shot much lately. Last week was the first range trip I've made in a year and half.

I've shot 1.5 MOA with this using 168 Speer's Match BTHP.

Thanks for sharing.

I am thinking with a slower powder you should be getting a tad more speed with the standard barrel even from a gas gun.
IMO IMR4896 are a tad on the fast side and I would not go faster than varget and there are better powders than varget.
Something like R22 or H4350 or R19 are good powders for the 30-06.
you should be hitting the 2500 at the muzzle w/o any issues.

A good Garand is going to be a good shooter but never a super consistent shooter.
Same problem with the M1A, it can only go so far even after dumping thousands of dollars into it. It is not worthy.
~2.5 moa spreads are great for that rifle so it looks you have a good shooter.

I'm pretty finicky when it comes to powder and the M1. IMR4895 is pretty much my go to. I can get 2500 at the muzzle when I bump it up to 45.0 grains, but accuracy was subpar (could have been me, it was pretty cold today at the range.

 

[ricklovin93]

With A Garand probably. Unless you have a new Criterion barrel and a good load 3 moa is pretty standard.

My 1903 with its original barrel from 1918 will outshoot my M1 all day. Fantastic rifle.

 

[meketrefe]

Brand new Criterion Barrel installed two years ago, less than 100 rounds through it. I haven't shot much lately. Last week was the first range trip I've made in a year and half.

I've shot 1.5 MOA with this using 168 Speer's Match BTHP.

I'm pretty finicky when it comes to powder and the M1. IMR4895 is pretty much my go to. I can get 2500 at the muzzle when I bump it up to 45.0 grains, but accuracy was subpar (could have been me, it was pretty cold today at the range.

I have been reloading for more than 30 years and when it comes to powders I also have my favorite powders.
H4895 and Varget are both suitable for the 30-06 and both match winners and the most imprevious powders to temperature
changes but they are on the hot side for the longer and heavier bullets.
When it comes to performance with those bullets the R22 can push those to 2750 fps with a bolt gun and on top
accuracy loads but like R19 they behave better in cold weather.
With 2000 MR and a 20" 308 bolt action I can get the 180gr bullets pushed to 2700fps in accuracy loads.
This combination is another match winning powder in the PRS and F-class competitions because of the added speed
with latest generation bullets, including CNC ones.
Like with everything consistency and predictability is the name of the game no matter what recipe.

 

[ricklovin93]

I have been reloading for more than 30 years and when it comes to powders I also have my favorite powders.
H4895 and Varget are both suitable for the 30-06 and both match winners and the most imprevious powders to temperature
changes but they are on the hot side for the longer and heavier bullets.
When it comes to performance with those bullets the R22 can push those to 2750 fps with a bolt gun and on top
accuracy loads but like R19 they behave better in cold weather.
With 2000 MR and a 20" 308 bolt action I can get the 180gr bullets pushed to 2700fps in accuracy loads.
This combination is another match winning powder in the PRS and F-class competitions because of the added speed
with latest generation bullets, including CNC ones.
Like with everything consistency and predictability is the name of the game no matter what recipe.

I've been wanting to get my hands on some Varget. Hasnt happened yet.

If I wasnt loading specifically for the M1 I would be able to open up my powder options a bit more. Varget and 4064 are about the slowest I can use with the gas system.

 

[Tisto]

I'm going to ask the question that no-one else has asked yet, and it may actually be the source of your concerns.

What type of chronograph are you using ?

Most chronographs use the shadow of the bullet breaking a plane to start a timer, and then again to stop the timer. The measured time is used to then calculate velocity. There are inherent problems with this system. First, if the path of the bullet is different as it goes through the measurement points, it changes the distance between the points thus changing the calculations. Next, measuring such minute amounts of time lends itself to a high error rate, again translating to incorrect calculations. Most of the chronographs on the market have a +/- 0.5% accuracy. Hypethetically, two bullets traveling the exact same path through the measurement zone at the exact same real velocity, could produce very different results. Example: real velocity of each of these bullets is 2600 fps. The chronograph may give a reading of 2613 fps ( + 0.5 % ) or a reading of 2587 fps ( - 0.5 % ). The difference here is 26 fps. That is the possible acceptable error in the chronograph alone, not accounting for any other external factors. Using a chronograph with this error rate will drive you absolutely insane.


For decades, the chronograph designed and build by Dr. Oehler was the industry standard. The model 35 Proof chronograph was used by every ammunition manufacturer because it was the most accurate. It had an accuracy rate of about +/-0.25 %. It was actually two chronographs stacked together. The bullet would pass through the two measurement zones and the readings would automatically be compared. If they did not fall within a specified limit, the shot was discounted from the results.

Today, the LAB RADAR chronograph is king. It uses dopplar radar to measure actual velocities, and has an error rate in the area of 0.1 % @ 1000 m/s. This system has a few drawbacks of it's own, but is far superior to any other on the market.

You can drive yourself crazy trying to make sense of numbers that are nearly meaningless.


Also keep in mind that temperature and barometric pressure can have a dramatic effect on ballistic measurements. A load that chronographed 2875 fps on a 75° day may drop to 2825 fps on a 50° day.

 

[Tisto]

As others stated, 6 round strings are too small to gather a good sample. They will give you an idea of what you are producing, but only just a general point of reference. Also, pick one type of brass and use that to develop loads. Mixing headstamps is sure to produce variations that will destroy your best efforts to produce an accurate load. Try this test : take 5 pieces of every type headstamp brass you have and weigh them. Average the weight of every headstamp group. Now compare the groups. Since the external dimensions of all the cases are the same, the extra weight must be on the inside of the case, reducing case capacity. Consistancy is the biggest factor in producing accurate ammunition. There are far more factors, but consistancy is the king of them all.

 

[ricklovin93]

I'm going to ask the question that no-one else has asked yet, and it may actually be the source of your concerns.

What type of chronograph are you using ?

Most chronographs use the shadow of the bullet breaking a plane to start a timer, and then again to stop the timer. The measured time is used to then calculate velocity. There are inherent problems with this system. First, if the path of the bullet is different as it goes through the measurement points, it changes the distance between the points thus changing the calculations. Next, measuring such minute amounts of time lends itself to a high error rate, again translating to incorrect calculations. Most of the chronographs on the market have a +/- 0.5% accuracy. Hypethetically, two bullets traveling the exact same path through the measurement zone at the exact same real velocity, could produce very different results. Example: real velocity of each of these bullets is 2600 fps. The chronograph may give a reading of 2613 fps ( + 0.5 % ) or a reading of 2587 fps ( - 0.5 % ). The difference here is 26 fps. That is the possible acceptable error in the chronograph alone, not accounting for any other external factors. Using a chronograph with this error rate will drive you absolutely insane.


For decades, the chronograph designed and build by Dr. Oehler was the industry standard. The model 35 Proof chronograph was used by every ammunition manufacturer because it was the most accurate. It had an accuracy rate of about +/-0.25 %. It was actually two chronographs stacked together. The bullet would pass through the two measurement zones and the readings would automatically be compared. If they did not fall within a specified limit, the shot was discounted from the results.

Today, the LAB RADAR chronograph is king. It uses dopplar radar to measure actual velocities, and has an error rate in the area of 0.1 % @ 1000 m/s. This system has a few drawbacks of it's own, but is far superior to any other on the market.

You can drive yourself crazy trying to make sense of numbers that are nearly meaningless.


Also keep in mind that temperature and barometric pressure can have a dramatic effect on ballistic measurements. A load that chronographed 2875 fps on a 75° day may drop to 2825 fps on a 50° day.

Its not a high end chronograph. Its a basic Caldwell unit. But I was pretty careful with the setup, the bullets trajectory was consistent going through the sensors.

My velocity results are in the ballpark of where they should be, based upon published load data, and loads I've seen floating around the forums.

The only result that had me confused were when I ran a few rounds of Federal .308 Match round through my Howa. The velocities I was seeing were right around 2390, when the velocities advertised on the box where 2600ish. A big difference, but who knows what kind of setup Federal uses for there tests.

I even ran some Surplus M2 ball I have. That stuff is HOT. 150 grain averaging 2800-2900fps.

So I dont think the Chronograph is too far off. Especially considering the low(er) S/D numbers (I know the sample sizes aren't very big. Next range trip I'll load 50 rounds or so of one load to get a better sample size.)

Also forget to mention, the chronograph was setup 15' downrange of the muzzle.

 

[dsdmmat]

When you are doing load development, I suggest you clean your barrel with a good carbon and copper remover after every 10 rounds. Otherwise you are going to see a lot of variations from carbon and copper build up.

 

[Tisto]

Advertised velocities of factory ammunition are NEVER what you can reliably expect to see in the real world. Factory ammo measurements are taken as the ammo is fired from special barrels using a universal receiver. The barrels almost always have minimum sized chambers. Barrel length affects velocity as well.