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Old January 21, 2000, 08:59 AM   #1
JKnight
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I haven't reloaded in 5 years and have just got setup again with a dillon 550. I'm reloading 9mm for a glock 19. I'm using Speer 115gr. FMJ. Hornady recommends 1.105 for OAL and Sierra recommends 1.090 for OAL, which is right? I went ahead and setup for 1.105 OAL but the length of my seated rounds vary from 1.1040 to 1.1075. Why does the length vary? When I checked OAL of my factory ammo UMC varies from 1.0955 to 1.1220 and Winchester varies from 1.1565 to 1.1585.

I also have a question about the crimp, the manuals recommend .380 at the case mouth. When I check my factory ammo UMC is .3780 and Winchester is .3750. Which is right?
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Old January 21, 2000, 10:33 AM   #2
Mal H
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Both Hornady and Sierra are right. The OAL is not a fixed length for any particular caliber. It varies with the type and shape of the bullet. For example, a JHP will most likely have a shorter OAL than a FMJ. The important dimension is the length from the base of the bullet to the inside bottom of the case. You should find that dimension mre of a constant than the outside OAL.

So the answer is to use the OAL specified for the particular bullet you are reloading, not the OAL of a factory round unless the bullets are similar in shape.

The variations you noticed in factory rounds is not unusual. That is one reason why handloading can yield more accurate rounds.

If you are crimping correctly (a short taper crimp for the 9mm), then the crimp measurement will take care of itself. No need to worry about it. The differences are most likely due to slight differences in case thickness.
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Old January 21, 2000, 11:05 AM   #3
JKnight
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The OAL I quoted from both manuals was for a 115gr. FMJ-RN bullet. Which manual's measurement should I go with? Also should'nt the OAL be the same from round to round when I load them since the distance is fixed from the bottom of the shellplate to the inside tip of the seating die? If I have the die locked down why would I see a different OAL in the rounds I load?

[This message has been edited by JKnight (edited January 21, 2000).]
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Old January 21, 2000, 11:31 AM   #4
labgrade
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First of all, blow off that .0001" when dealing with COAL. A human hair is about .003" & trying to be so precise in your measuring in this area will just drive you crazy.

Sounds like you're using a micrometer (X.0001" resolution - I hope you're not expecting this type res out of a caliper). Unless a speciality type micrometer, the spindle rotates which can cause measuring errors well within what you've reported - just due to techinique. Unless everything is positioned the exact same way everytime, you're gonna get variations. Your cartridges may all be the same size.

OAL variations in your 1st post is about .003" is well within anything you can expect unless using custom equipment.
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Old January 21, 2000, 12:33 PM   #5
Mal H
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I fully agree with labgrade. I hadn't even noticed that you were using measurements to the ten-thousandth of an inch. I guess my brain is geared to ignoring any reloading measurements less than .001" even though I work with measurements in the sub micron area at work. I assume you aren't using a "lab grade" scale to measure your powder to the nearest microgram. Please don't be too anal or you will soon tire of the hobby as it will become too much of a chore.

As labgrade said, the differences you see can be from the measurement itself or they can be real. One bullet may have an unnoticeable dent on the top or the case may be uneven on the bottom or the bullet press may not hit the top of the bullet the same way each time. IOW, there will be some variations, but don't worry too much about them.

(added)
We both failed to answer your actual question as to which manual to believe. The answer is to use the one that applies to the actual bullet you are using if you have that manual. If you have a bullet that isn't included in a manual, and there are a lot of them, use the measurement from the manual that most closely matches the weight and shape of the bullet. In the case you are talking about, you can safely go with either manual's OAL for a FMJ.

[This message has been edited by Mal H (edited January 21, 2000).]
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Old January 22, 2000, 11:14 PM   #6
JKnight
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Thanks for the help Mal H, and labgrade.
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