Testing loads - Need a check list

[mpmo]

Hey y'all. Got my second batch of test rounds loaded up. Took the recommendations here and started with the min power spec in the manual. I am testing 2 pistols so I made 4 rounds at 4 powder levels. (0.2gr step up each time, and still well below the max spec in the manual.)

I'm looking to achieve min power factor for IDPA. Got a few questions about what I should be looking for when I go test these rounds. I have a Competition Electronics Chrono that I will be using. Here is what seems obvious to me.
-Does it feed well?
-Does it cycle the gun?
-Does it slightly exceed a 125 power factor?
-Does it do anything strange? (Squib, smoke)

So my questions are:
-What else should I be checking? Especially for safety.
-How do I know it is 'safe' to go to the next hotter load that I created?
-What distance or other considerations do I need to take into account for setting up the chrono?

It will be my first time clocking rounds. I plan to run a bit of Blazer CCI 9mm 115 to test it out and make sure I get how it works.

Thanks!

[mpmo]

One other note. Thought about shooting the CCI factory stuff first to warm up the barrel. Does the heat of the barrel have a decent affect on velocity?

[ghbucky]

-How do I know it is 'safe' to go to the next hotter load that I created?

Familiarize yourself with the signs of overpressure

There is a good guide here

You also might have a manual that covers it (Lyman's manual doesn't really have much to say about it)

Inspect each ejected case as you move your way up to the higher charges and look for those signs.

I don't have a chrono, so I can't help you much on how to use except to say... don't shoot it!

[Aguila Blanca]

Yes, "Don't shoot the chrono" (says the guy who has done so more than once).

Years ago, in doing a series of chonograph testing, I noticed that with some [commercial] rounds but not others, as I progressed to guns with shorter barrels I began getting more errors -- that being shots for which the chrono (a CED Millennium) registered "ERR." What I realized was that there was enough still-burning powder being ejected from the shorter barrels that the hot ejecta were messing up the chronograph's detector.

I had it set up at 12 feet. I moved it to 15 feet and that solved the problem. That said, I read a lot of gun tests in which the author states that the chrono was set up 10 feet from the muzzle. The IDPA rule on conducting the chrono test is 8.3.2:

8.3.2
Official Chronograph Procedure
Chronograph is conducted with the competitor present. Ammunition is pulled and/or bagged prior to arriving at the chronograph stage. The chronograph official will use the competitor-supplied firearm, and the following procedure will be used:

A.

If two of the three rounds meet or exceed the required power factor, the ammunition is in compliance. Prior to each shot, the muzzle of the firearm will be elevated to vertical (if range rules permit) to move the powder charge to the rear of the case, thus giving the competitor every chance to achieve maximum velocity.

B.

A bullet will be pulled and weighed using a powder scale. If two rounds exceed the highest velocity for the caliber and power factor, pulling the bullet and weighing is optionally waived.

C.

A competitor whose ammunition fails to make power factor will be allowed to shoot the match, but their total score will be a disqualification.

What this rule does not tell us is what distance to set the chronograph. I have never shot in a big match where they actually checked competitors' ammo so I have no first-hand experience. I've reached out to a friend who is a long-time SO and match director to ask for his input. I'll report what he says if/when he gets back to me. For starters, try using ten feet. If you get errors, move it to twelve feet. If you still get errors, move it to fifteen feet.

Or just start at fifteen feet, to be safe. If you make power factor at fifteen feet, you'll make power factor at ten or twelve feet.

I will also suggest that you might need a few more rounds at each level. The IDPA standard is that two out of three rounds, chosen at random, must make the power factor. I have always used five rounds as my standard, allowing me to get some sense of how much variation I have between/among rounds at a given charge. For most purposes I'm looking at the average velocity but, for IDPA, ideally you want to be sure that NONE of your rounds are below the minimum power factor. If you only have two rounds of each charge weight, you only know that two rounds produce 'X' velocity. If both are well above the required power factor, that's not a problem. You are seeking to just make minimum, so a sample size of two rounds, IMHO, isn't large enough.

Also note that the IDPA procedure calls for tipping the muzzle up (if allowed by the range rules) to settle the powder at the rear of the case. This helps to maximize velocity. If you can't tip the muzzle up, consider dropping the magazine between shots, tapping the spine of the magazine on the bench to shift the powder back, and then reinserting the magazine into the pistol as gently as possible in order to keep the powder at the rear of the case.

-----

Preliminary response from my IDPA SO friend -- he doesn't know, either. He wrote that he is reaching out to other officials whom he knows. I'll post back if there's anything useful that comes back.

[ghbucky]

I actually didn't believe you that the rules didn't specify, but you are correct.

I checked the rules, the addendum and the match admin rules and nothing is stated about range.

I did find a quote from someone on Brian Enos forums stating 10ft, but there was no link to back that up.

How can the IDPA have uniform PF when the range to shoot at isn't specified? seems like a crazy oversight.

[Unclenick]

My understanding is that at the Nationals, they used to run two CED Millenniums in line with each other with IR screens and sensors inside a wood tunnel painted black inside. This eliminated skylight variation from the readings. The two chrono's had to agree within a few feet per second for the reading to be considered valid.

The firing distance, I don't know, but figure 9's will be losing around a foot per second per foot of travel and the 45's about half that. Compare that to your shot-to-shot velocity variation to see how much difference it makes.

[hounddawg]

I honestly don't think a difference of 5 or 10 ft would make that much difference. I have done range officer duty at USPSA, IDPA, and USPSA Steel Challenge matches but never manned the chrono station. Near as I can remember the chrono box is pretty close at maybe five to ten feet. I would go run some chrono tests myself just out of curiosity but it will be another month before I can do so

If anyone really wants to know email the IDPA here

https://www.idpa.com/about-idpa/contact-idpa/

or USPSA at 1 (360) 855- 2245

[Aguila Blanca]

Got an answer from my SO friend:

Reply is from the HCSC IDPA MD.

“USPSA used 10 feet from muzzle, but they used CED infra red chronos. I worked 4 years at Classic Nationals. The best is to use the recommended distance for the brand of chronograph used.”

Tom Skuse

[ghbucky]

for OP:

I don't think you really need to sweat PF unless you are thinking you are going to be going deep into the rankings and shooting very competitively.

I've shot a handful of IDPA matches, and I never saw a chrono. For myself, I stepped up loads until I found one that consistently ran the gun, then went up one more step and if it was safe, that was my load.

[Aguila Blanca]

Originally Posted by hounddawg

I honestly don't think a difference of 5 or 10 ft would make that much difference.

It only makes a difference if it means making power factor or not making power factor. For someone shooting one of the division that uses 125 as the minimum, if you load to juuuuust make 125 ... how much higher should you go to ensure that two out of any three rounds the match officials pull out of your box of ammo will make the threshold?

How close can you be? Out of curiosity, I pulled up a review of a 9mm 1911 Commander from a few years ago. Several of the loads run through it were handloads, but to illustrate I chose the commercial loads. First up was 115-grain Winchester white box. The low velocity the test reported was 1084 fps, the high was 1129 fps. That's an extreme spread of 45. The power factor for the minimum calculates to 124.7. For me, that's too close for comfort.

The other commercial round was a Remington 124-grain. Low velocity was 1004 fps, maximum was 1056. Extreme spread was 52. The power factor for the minimum round works out to 124.5. That's MUCH too close for comfort. Make it an even 1000 fps and the power factor would be an even 124, which would mean an automatic disqualification.

The OP is looking for a load that just makes a power factor of 125. There is always going to be some variation; the goal is to minimize the extreme spread but, even then, you have to load to an average velocity that's high enough so any three rounds they pull from your supply will be at or above the minimum power factor. How much higher you need to go will depend on how consistent your ammo is. If you want a 5% cushion, you'll be looking for ammo that (on average) is actually 131 power factor. If you want a 10% cushion, you'll load for an average of 138 power factor.

[hounddawg]

If you want a 5% cushion, you'll be looking for ammo that (on average) is actually 131 power factor.

Wife was the pistol competitor in our family before she messed her back up. When I loaded for her plus 5% avg is what I loaded for.

[Nathan]

I would add accuracy.

[mpmo]

That over-pressure article was great! Anything else I should have on my checklist?

[Unclenick]

For competition, the rules say they fire 3 rounds and two out of the three have to match or exceed the power factor threshold. This makes "how much extra" question statistical in nature. If your mean velocity is 0.43 standard deviations above the power factor velocity for your bullet weight, then only one out of three rounds will fall below the power factor. The problem with relying on that is, some individual sets of three will randomly all be above the power factor, and some will randomly have two or occasionally even all three below the power factor. It will only be adequate on average, and the chances of one three-shot set having that average of two above and one below is only about two out of three tries. That's uncomfortably risky. So the question is, how much will you risk failing the test? Here is how many SD's above the PF velocity (vPF) you need to average for different chances of passing the test:

Approximate  Required
Passing        Mean
Chance       Velocity

67%        vPF+0.43 SD
75%        vPF+0.67 SD
80%        vPF+0.84 SD
85%        vPF+1.03 SD
90%        vPF+1.28 SD
95%        vPF+1.64 SD     
98%        vPF+2.05 SD
99%        vPF+2.33 SD
99.9%      vPF+3.09 SD
99.99%     vPF+3.72 SD

I would add another 10 fps to the above to cover myself for differences in shooting distance and accuracy variation among chronographs and minor test condition differences.

For Aquila Blanca's example of Winchester White Box 115-grain bullets, if the number of shot velocities measured was 10, then the standard deviation will be about 15 fps. If AB wanted 95% certainty the ammo would pass chronograph testing at a match, the mean velocity of the Whitebox would have to be:

vPF + 1.64 SD = 1087 fps + 1.64×15 fps = 1112 fps

That is so close to the maximum measured velocity that unless the lowest velocity measured was a bit of an outlier, Whitebox would fail the 95% test in the test gun.

We can also work it backward. Suppose the mean velocity was 1105 fps.

1105 - vPF = 1105 - 1087 = 18 fps

18 fps / SD = 18 fps / 15 fps = 1.2 SD

From the table you can see the odds are a little less than 90% (works out to 88.5%) that the round will pass a chronograph check at the match, assuming it measures velocities exactly the same as his chronograph does. AB could then decide whether to take that much risk or not. I would be more comfortable having an extra 10 fps for the reasons I mentioned after my table.

[mpmo]

Are the rounds fired though your gun or a random test gun in competition?

[Unclenick]

They would be through your gun. They want to know how much momentum you are putting on the target. If it were based on standard velocity test barrels you would find that the SAAMI standard is 5" for 45 Auto and 4" for 9 mm, giving the 4" 45 owners an advantage by having to control less momentum than 4" 9 mm owners.

[Aguila Blanca]

Originally Posted by mpmo

Are the rounds fired though your gun or a random test gun in competition?

Your gun. I quoted the rule in post #4.

[Aguila Blanca]

After reading Unclenick's post, I tried to dredge up the review I took those numbers from. I couldn't find it again, but I came across a review of a 9mm 1911 that used only factory ammo, and which tabulates not only the velocities but also the extreme spread and the standard deviation. here it is. Remember, these are all factory loads. You can calculate the power factor for each -- power factor is simply bullet weight x muzzle velocity divided by 1,000.



The pistol being tested in this review was a 9mm STI Guardian.

[rclark]

I would add accuracy.

That would be my thought too. But maybe this competition IDPA, accuracy isn't a concern. Just how fast you can go and hit somewhere on the target....

[ghbucky]

I wouldn't worry much about accuracy, OP is not shooting bullseye or for scoring rings, he just needs to be able to hit the center mass on the B1.

[Aguila Blanca]

I spoke (wrote) too soon. Here's the table for the velocity numbers I reported earlier and to which Unclenick referred. Note that the STI Guardian is a 5" 1911. The pistol in this test is a 4-1/4", Commander-size 1911. That helps explain why the same ammo has such different velocity in the two tests.

[Unclenick]

Does it say how many shots per test?

Since the table is at 15 feet, for the 9 mm you can add 5 fps for what you would measure at 10 feet, assuming absolute accuracy from the chronograph.

[Aguila Blanca]

Originally Posted by Unclenick

Does it say how many shots per test?

No, it doesn't.

[hounddawg]

It only makes a difference if it means making power factor or not making power factor. For someone shooting one of the division that uses 125 as the minimum, if you load to juuuuust make 125 ... how much higher should you go to ensure that two out of any three rounds the match officials pull out of your box of ammo will make the threshold?

what I was referring to is how many FPS would a bullet lose between five ft from the muzzle and ten Ft from the muzzle. I doubt it would lose even one FPS.

edit - well I was dead wrong on that one. I found some BC numbers from Hornady and plugged them into JBL. A 125 gn hollow point loses appx six FPS every five feet for the first fifteen feet

[Unclenick]

Any ballistics program will tell you the answer. It depends on the velocity and BC of the bullet. In 9 mm firing in the 1100-1200 fps range, near the muzzle, a 115-grain HP bullet will lose about 1 fps for each foot of travel at near muzzle velocity. That's why I threw 5 fps in for chronograph distance differences (and another 5 fps for chronograph precision disagreements).