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Excessive "extreme spread"


kamikaze1a

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I have been reloading for years but I am baffled by the results I got with a new brand of bullets. I have been happy with my coated practice bullets and plated match bullets but just couldn't pass on an offer by a new to me plated bullet manufacturer. They gave 20% off to first time buyers and free shipping so bought 2500 bullets.

I loaded a few loads with my 650 and shot 20 rounds each over the chrono with puzzling results. The extreme spread was over 100 with some near 150. Additionally, the first shot from a couple of strings were extremely slow, low enough to "feel/hear" the difference.

Loaded a few more but this time I started the chrono session with a string of my practice rounds just to verify that the chrono was functioning properly...and it was. The test loads with the new bullets once again were high extreme spread and the first shot on a couple of strings were once again low.

This time, at the loading bench, I sorted the brass, weighed each bullet and measured it's diameter. Also weighted each powder throw and trickled to the mark before loading them up.

At the range I got the same wide extreme spread and slower first shot on several of the strings.

They shot pretty accurately even with the varied velocity. To solve the low velocity first shot I shot a few rounds of practice ammo before the new loads to "warm up the barrel" but that didn't change anything. My usual match plated bullets chrono'd properly as did my coated practice ammo so I am really at a loss to understand my results with these new bullets.

Any ideas what to try next?

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The following are guesses, and might not be very good ones :)

Your OAL has the bullet very near / touching the rifling.

The bullet OAL varies enough to effect pressure (seems pretty unlikely).

Bullet has a residue that's effecting grip.

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What powder are you using, and how much? What happened when you used your "match" load with the new bullets? Did you set the chrono up ANY differently than previously?

Here are some things I've learned. Small doses of dense powders generally give high SDs. You can "improve" on this somewhat by tilting the muzzle straight up to settle the powder over the primer, then carefully lower to firing position. This doesn't help you in real life, but it will tell you if you have a too little powder in a large case problem.

Checking OAL was a very good suggestion.

You've sorted cases, weighed powder charges and measured bullet diameter. Did you weigh the bullets to see if there is a significant difference? I once had a brand and type of bullet that varied over a 5gr range.

Check your taper crimp. It may be that the brand of bullets you are now using has a very thin copper plate and you are cutting into at least some of them with your crimp.

Take a file and gently file off the plating on a number of bullets to see if the plating is uniform. It may be the plating is not consistent and that will cause velocity variations.

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Right now loading major with HP38. Coated practice bullets gets 4.9gr, plated match 5.3 but this new plated bullet needs 5.4 and also tried 5.5gr, all 180gr out of an Infinity. With the new bullet, the slow rounds clock at lower/mid 800 to high 800fps with the majority at 950 to 970 and a few going just over 1k... I was going for 175pf.

The coated and match bullets are TC while the new is round nose/flat point. My coated and plated match are seated 1.2" while the rnfp with it's slightly different profile, using the same seating dies setup is 1.18.

Acceptable extreme spread with coated and match plated, just not this hew bullet. Planning to try a few loads with WST next.

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The following are guesses, and might not be very good ones :)

Your OAL has the bullet very near / touching the rifling.

The bullet OAL varies enough to effect pressure (seems pretty unlikely).

Bullet has a residue that's effecting grip.

The new bullet's profile is rnfp while the others are tc so I can see that the rounded ogive of the rnfp probably getting deeper into the throat so possibility getting closer to the rifling but I didn't check for that. I am using a .020" shorter OAL with the new bullet but that is definitely worth looking into.

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Here are some things I've learned. Small doses of dense powders generally give high SDs. You can "improve" on this somewhat by tilting the muzzle straight up to settle the powder over the primer, then carefully lower to firing position. This doesn't help you in real life, but it will tell you if you have a too little powder in a large case problem.

You've sorted cases, weighed powder charges and measured bullet diameter. Did you weigh the bullets to see if there is a significant difference? I once had a brand and type of bullet that varied over a 5gr range.

After the two sessions with high ES I did weigh each bullet. They did vary by a few grains so I sorted those out and only loaded bullet that were 180 +/- 0.1grain but that did not resolve the problem...

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You need more powder to get a plated bullet going than a lead bullet - you may have

too little powder.

Try another .2 or .4 grains of powder - might just straighten it all out. :)

If I weeded out the extreme velocities I got 175pf with 5.4gr and slightly higher pf with 5.5 grains. I could try higher I guess but the median velocity would be higher than I was hoping for but it's worth a try.

I'm thinking that perhaps this new plated bullet just doesn't like HP38 while my coated and match plated bullets give ES of less than 50fps. By the way, I am intentionally not mentioning the brand but it is well known and even listed in USPSA Nationals equipment poll. If you want to know the brand I can provide that info via pm...

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Strange. I use plated bullets almost exclusively (various manufacturers) and generally load them with HP-38. I've hit PFs of 165 or so with 5.0 grains but I'm also seeing SDs in the 10 - 12 range with these loads. Curious why your speed differences are so large. Clearly, HP-38 can work well with plated so I'm really curious on what your problem turns out to be.

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And even with the weighed and mic'd bullets with sorted brass and individually weighed powder charge I got a few low velocities that were low enough to "feel/hear"...I am really at a loss to understand what the cause is.

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The only thing I can think of (and should have mentioned in my earlier post) is to repeat what someone said before. Check your OAL with the new bullet. Do a plunk test in your barrel and be sure you can spin the round without hanging up on the rifling. You have probably already done that but I didn't see it mentioned. As you know, progressive presses don't deliver all rounds at exactly the same length and if your longer rounds are hanging up on rifling and the others are falling just short, it may be a consideration. Measure a batch of your loaded ammo and choose the longest for this test.

Good luck.

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Are you using hornady 1 shot on your brass? If so try loading a few without it. See if your results are better. I had same thing happen & when I quit the 1 shot, problem went away. I am not saying its a bad product but I am saying I had bad results with it.

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Are you using hornady 1 shot on your brass? If so try loading a few without it. See if your results are better. I had same thing happen & when I quit the 1 shot, problem went away. I am not saying its a bad product but I am saying I had bad results with it.

Not using any lube but that made me wonder about varying brass length and change in crimp...

As for overall, practice and match ammo is consistently at 1.2" while the new plated 1.18".

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You still need to plunk and rotate test the longest plated rounds you have loaded up. Just because the COAL seems shorter, the ogive is probably different and MAY touch the rifling in spite of the COAL being shorter. It is probably not an issue but for the ease in checking it, well worth the time to eliminate this potential variable.

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Kamikaze, one of the things that affects SD is light reflecting of the bullet nose directly into the sensors. The sensors are supposed to be looking at a stably lit background, then record the bullet as more or less a shadow crossing overhead in front of that background. Light reflecting off the bullet into the sensors can confuse the sensors. The duller your bullet, the less the effect. The shinier the bullet, the greater the effect. Shiny plated bullets will produce higher SD and ES ranges than their duller counterparts. XTreme Plated, for example, is especially shiny, and back before I figured out that plated bullets were a waste of time and money, in general, and shot a lot of them, I got my worst SDs with Xtreme plated. Next worse was Berry's. Then Montana Gold. Then bare lead. Then coated, with BBI being the best of the bunch. Nothing better than black coated lead to improve your SD and ES. My worst numbers of all time came with the XTreme HP, which I basically couldn't chrono at all -- I had extreme spreads of ~400 feet/sec, so it was worthless. And a lot of this has to do with angle of sunlight, so some people might have no problems at all based on how their range is oriented. Because of how my club's pistol ranges are oriented, I have to fight the sun.

I shoot with a target stand next to my chrono now that casts a shadow across the entire chrono. No direct light at all. Works great. I have a buddy who shoots at the same range who went out and bought a shade, basically a tarp mounted overhead on tent poles. And he puts the chrono underneath.

If you want to see if your problem is super shiny copper plating, take a black sharpy and color the bullets in black from the nose down to the case mouth. AND set up something to cast a solid shadow across the chrono, if possible, but if not, the black-nosed bullets should show results if the problem is the shiny plating.

Do this trouble-shooting step first. Shiny plating and a bad sun angle is the most likely culprit for wild SD and ES numbers.

Edited by IDescribe
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Having any direct sunlight hit the sensors or the bullets is a recipe for bad chrono results. The best way to chrono is in the shade using IR emitting screens.

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That could be the issue and coloring the bullet with a marker is easy enough to try. I do recall reading about this issue and that coloring the bullet solved their issues. I'll definitely give that a "shot".

The only other question would be that why do I often get a lower reading on the first shot. It's usually extremely low enough and low enough that I can feel/hear the reduced recoil. zzt mentioned that the position of the powder in the case could be a factor which also makes sense as it's usually the first shot that is low. The recoil then affects the position of the powder so the follow up shots are more consistent.

Now I wonder if the shot moves the powder forward or to the rear? I would imagine that the recoil probably moves the powder charge forward but does the slide returning to battery redistribute the powder to the rear?

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Finally had a chance to try the plunk test and bullets colored with a marker but got mixed results and raised additional questions.

40 S&W, 180gr, HP38. With new brand of plated bullets, individually weighed each bullet and powder charge (5.4gr) and sorted my brass, blackened exposed portion of bullets with marker.

Passed plunk test.

Raised muzzle before each shot, velocity was more consistent but consistently lower (upper 800fps to just over major) than strings without raising muzzle before shot. String shot (same load) without raising muzzle before each shot were less consistent but all were major and within my 170pf goal. It appears that raising the muzzle caused the velocity to drop by approx 50+fps. I never tried raising the muzzle before each shot but I thought others have said that this practice raised their velocity? I wonder if this relates to my low velocity first shot?

Coloring the new bullets black did not seem to resolve the inconsistent velocity but I will try additional rounds just to make sure. I will also be trying this with my usual match bullets, plated Berry.

Working with HP38 right now as I have good supply but load WST for match ammo so will try the new bullet with WST too.

The results makes me wonder the position of the powder charge after each shot/recoil/cycle. I'm thinking that the charge is carried forward against the base of the bullet when the slide goes to battery? May try a string of lowering the muzzle before each shot.

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  • 3 weeks later...

I finally had a chance to do additional load testing with the new plated bullets and my two go to powders. Loading for 40 major, 180gr bullet, 1.18" OAL with an Infinity. Powder charges dispensed with Dillon measure (not individually weighed) and bullets chosen at random (not weighed).

First load; 5.4gr HP38;

910, 903, 931, 869, 908, 935, 908, 942, 949, 889 - 914 average, 80 extreme spread, 24 standard deviation

muzzle dipped DOWN before each shot

Second load, 5.4gr HP38;

981, 973, 970, 981, 977, 973, 975, 953, 995, 997 - 977 average, 44 extreme spread, 12 standard deviation

muzzle raised UP before each shot

Third load, 5.4gr HP38;

911, 942, 944, 985, 920, 931, 965, 955, 946, 867

932, 910, 945, 987, 947, 981, 963, 994, 968, 919 - 945 average, 127 extreme spread, 25 standard deviation

shot normal

WST same bullet

First load 5.3gr WST;

903, 903, 927, 881, 957, 920, 859, 908, 854, 796 - 890 average, 161 extreme spread, 45 standard deviation

muzzle dipped DOWN before each shot

Second load 5.3gr WST

954, 966, 950, 908, 944, 946, 942, 951, 933, 889 - 938 average, 77 extreme spread, 23 standard deviation

muzzle raised UP before each shot

Third load 5.3gr WST;

915, 923, 900 912, 946, 938, 966, 897, 915, 953

936, 951, 934, 948, 959, 957, 941, 946, 965, 915 - 935 average, 69 extreme spread, 21 standard deviation

shot normal

These are not compressed loads but by my estimate there would be little space between bottom of the bullet and the powder charge so I am amazed at the amount of change in velocity by dropping the muzzle before the shot.

Tried WST because my other go to powder, HP38 with the new plated bullet gave me high extreme spread and standard deviation but it appears that it was not only with HP38. Shot 20 additional rounds for accuracy and both loads in spite of high ES/SD gave good accuracy. Plan to bump the WST charge up 0.1gr for additional velocity tests but I think I am going back to my previous brand of plated bullets.

Edited by kamikaze1a
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