When you load to power factor do you...?

[LeviSS]

Shoot 10 or 20 rounds over a chrono and then average the fps for power factor or make sure EVERY round is above PF?

I'm getting ready to shoot my first match above the local level. When I worked up my load I averaged it and came out to 130pf.

I just want to make sure everything is in line for this match. Thanks.

[Gooldylocks]

I average the velocity and then see what that pf is. I have been going with about 171 in the open gun, I would think that a bit above 130 would probably be ideal for production because of the serious penalty for going subminor (shooting for no score). I would probably aim for the average velocity to give you a 135 or something, but maybe I'm more cautious then the production shooters on here.

[Flatland Shooter]

For major I target 170+ PF. For minor I shoot right at 135 PF. When I chrono, all rounds must exceed the minimum or I bump it up a bit.

If you travel very far to matches, don't be surprised if the match chronodgraph does not agree with yours. Lots of factors come into play besides the chrono itself.

Several years ago I took ammo loaded and tested here in the Texas Gulf Coast region to the Area 4 match in Fort Smith, AR.

There my loads came in at exactly 165.0.

[Hi-Power Jack]

all rounds must exceed the minimum or I bump it up a bit.

+1 For local matches, it really doesn't matter.

For all other matches, I like it when ALL rounds equal or exceed the minimum.

I was at a major match and the first two rounds were BELOW minimum - I lost

an hour's sleep until the third shot was over enough to get my 3-round average

above minimum...

I don't like that feeling, at all.

So, Every Round Equal to Minimum, for me.

Now, I sleep like a baby (71 year old baby).

[Rob1125]

I make sure all rounds exceed the PF I need. Back when the PF for major was 175, I would target 180. I had a bullet come up almost a full grain light at the Nationals one year, but was still easily able to make PF because of this.

[SV650Squid]

My Shadow has been most accurate around 133-135 pf. I just average my most accurate load, and ~9-10 pf cushion is way more than enough when my SD is 7.

[jwhittin]

Here we go again! How close to the min PF should you get? The answer is no less than a minimum of 2 times your standard deviation (STD) (measured using 8 rounds). In other words add at least 2*STD to the minimum PF for your bullet weight. Use 2.25, 2.5 or 3 times your STD depending on the unknowns. It is a waste of time and money to use 10 or 20 rounds as suggested.

LeviSS see this post for clarification and examples.

http://www.brianenos.com/forums/index.php?showtopic=229005&hl=

[kitsapshooter]

Averages suck.

I chorno 12 rounds, I pick the lowest number (MV). If it comes out 128 or above i am happy and now my loads are good.

[fishsticks]

Here we go again! How close to the min PF should you get? The answer is no less than a minimum of 2 times your standard deviation (STD) (measured using 8 rounds). In other words add at least 2*STD to the minimum PF for your bullet weight. Use 2.25, 2.5 or 3 times your STD depending on the unknowns. It is a waste of time and money to use 10 or 20 rounds as suggested.

LeviSS see this post for clarification and examples.

http://www.brianenos.com/forums/index.php?showtopic=229005&hl=

How do you account for the inevitable variability in bullet weight? Velocity variability could be coming from either powder charge or bullet weight (among other things of course).

I ask as I shoot coated lead which varies more than plated or jacketed.

My current load has a relatively low standard deviation.

[fishsticks]

Here we go again! How close to the min PF should you get? The answer is no less than a minimum of 2 times your standard deviation (STD) (measured using 8 rounds). In other words add at least 2*STD to the minimum PF for your bullet weight. Use 2.25, 2.5 or 3 times your STD depending on the unknowns. It is a waste of time and money to use 10 or 20 rounds as suggested.

LeviSS see this post for clarification and examples.

http://www.brianenos.com/forums/index.php?showtopic=229005&hl=

How do you account for the inevitable variability in bullet weight? Velocity variability could be coming from either powder charge or bullet weight (among other things of course).

I ask as I shoot coated lead which varies more than plated or jacketed.

My current load has a relatively low standard deviation.

[motosapiens]

if you are averaging over 130, but some of your loads are slow enough to be less than 125, I would call that excessive SD.

Personally I don't really stress about. I only chrono 5 or 6 rounds at a time, but I do it once or twice before every match that might have a chrono, just to make sure nothing has changed.

The variance in the weight of the bullet shouldn't be enough to matter unless you are cutting it too close for comfort anyway.

Since you only need to have the highest 3 out of 7 shots average above pf, you really have to screw up to go subminor.

[GrumpyOne]

all rounds must exceed the minimum or I bump it up a bit.

+1 For local matches, it really doesn't matter.

For all other matches, I like it when ALL rounds equal or exceed the minimum.

I was at a major match and the first two rounds were BELOW minimum - I lost

an hour's sleep until the third shot was over enough to get my 3-round average

above minimum...

I don't like that feeling, at all.

So, Every Round Equal to Minimum, for me.

Now, I sleep like a baby (71 year old baby).

You wake up crying every two hours?

[jwhittin]

Fishsticks, your measured STD does includes the bullet weight variance. If you are concerned, you can measure the variance of your bullet weight and calculate what the impact would be on PF. Weigh bullets from various boxes and use the worst case variance. It shouldn't have a big impact. If the variance in bullet weight is abnormally high you could switch bullets. I would think most bullets should be within +/- 1 grain may be +/- 1.5 grains.

If you want more margin, you can simply bump up your load to say 2.25, 2.5, or even 3*STD.

[jwhittin]

if you are averaging over 130, but some of your loads are slow enough to be less than 125, I would call that excessive SD.

I agree. If you see bullet variances that cause this, its time to switch to a different bullet maker.

Edited April 28, 2016 by jwhittin

[LeviSS]

I got around to checking them today. The lowest PF was 127, my average was 128 something. So, it looks like I'm fine. Thanks guys.

Edited April 29, 2016 by LeviSS

[GrumpyOne]

I got around to checking them today. The lowest PF was 127, my average was 128 something. So, it looks like I'm fine. Thanks guys.

Until it warms up or cools down.... some powders get slower as the temps get hotter, and vice versa. While you may be fine now, in 2 months with the summer heat, you may find yourself shooting for no score. Better safe than sorry...bump it up to 135PF.

[jwhittin]

Levi - Well it seems you didn't get what I was saying. Forget the PF, what is your bullet weight and STD. Reread the link in my earlier post.

[LeviSS]

I get it. I was just shooting ammo I already had and calculating PF.

So, you're saying that I need 851fps (rounding up from 850.34) with a 147gr bullet to make minor PF (125).

My chrono showed I had a STD of 6 today. So I should load to at least (2*6)+851=863.

It just so happens that my slowest shot of the day (20 shots) was 863.

It appears by your logic that I'm in the clear, with a 10% or less chance of failing, correct? Or should I go 3*STD to be extra safe? All my shots were above 125PF. So where do you say enough is enough?

Edited April 30, 2016 by LeviSS

[gixxerjunky]

I would call it good. If you slowest shot was above PF your good.

Sent from my iPhone using Tapatalk

[warpspeed]

Just in case you are interested in what TGO thinks about it http://www.brianenos.com/forums/index.php?showtopic=194797&p=2182387

Gotta forget about power factors guys and focus on velocities. If you shoot a light bullet, you will have a greater margin for error on the chrono when loaded to the same power factor as a heavier bullet. 170 power factor is only 22 fps higher than 165 with a 230. 200 grain bullet, 25 fps. 180 grain bullet, 28 fps. However that's only 6 fps different between 180 and 230.

I chronograph a lot here in az. I never go by power factor, but by the velocities needed to make the factor. intentionally loading or accepting a load that only makes major is not safe. Different days with different temps on 2 identical chronographs for each shot at the same time routinely show 6-8 fps differences in speed between the two identical chronos, and averages of 10 to 15 fps from. This is an average. The high and low extremes are more like 20-30 fps. That is easily the difference between making 170 pf and not making 165. Kids, you can't feel a 5 pf difference with a 230 grain bullet. Or a 200 or 180. You can notice going minor very easily.

I use this system; I shoot 10 shots, discount any single super high or low shot and take that average. If I still have a large extreme spread, I go back and work on the load until es is no more than 20-30 fps Max. I then load up until my slowest of the accepted average, and never remove a shot unless it is obviously a bad round, makes the needed average by 20 fps minimum. this is repeated many times until I never have a low shot less than 20 fps over the lowest speed needed. My averages usually then run around 35-40 fps minimum, over the slowest speed. If I am having wild speed variations, It's nearly always a powder issue, either too slow a powder or inconsistent metering on the press.

Using this system you will probably never have an average under 172 pf. If you then chose to lighten that to lower the pf, you will occasionally, when the odds stack against you, not make 165.

[LeviSS]

If I read that right, according to TGO, i should bump it up a little because my average fps is at least 20fps over the needed 851fps needed to make minor, but I still have a low shot that is only 12fps over the 851fps floor?

I averaged 874fps, with an ES of 20, and a SD of 6. Low 863fps and high 883fps.

Edited April 30, 2016 by LeviSS

[jwhittin]

TGO's way is far too complicated. You shouldn't throw out data. As I said, velocity is random and the best way to understand and mange it is using the STD.

Levi - how did you measure your STD? You should shoot 8 rounds and record the STD. Repeat the same process a few times to see if the results are consistent. It will change as the gun heats up.

As long as your 8 round average velocity is above 863 (assuming your STD is correct) you should be good. But with a small STD, some unknowns and your concern, just use 3*STD and don't sweat it. Doubt you can feel the increase and you will have piece of mind.

Edited April 30, 2016 by jwhittin

[LeviSS]

My chronograph tells me the SD of the string of shots.

[jwhittin]

Yes but use 8 shots and measure SD 3 or 4 different times to see if it is consistent. Use the highest SD.

[LeviSS]

Ok. Will do. I appreciate the help.