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Old February 20, 2010, 05:13 PM   #1
Walkalong
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Using an auto pistol barrel find a MAX O.A.L with your bullet

This topic comes up a lot, or should I say this question.
Quote:
Why won't my reloads chamber?
A short throat is sometimes the culprit. Too long an O.A.L. is sometimes the problem, even with barrels with average throats.

This pic is often used to help explain correct headspacing and how O.A.L. can affect chambering and headspace.

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Last edited by Walkalong; February 21, 2010 at 11:53 AM. Reason: Title
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Old February 20, 2010, 05:16 PM   #2
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I decided to do a little testing (with pics of course) with a couple of .45 ACP barrels and Precision 200 Gr SWC's.

The first barrel is a Fire Dragon barrel. A .894 long case dropped around .013 below flush. I started way long on the O.A.L. and went from there. The second is a Wilson. The .894 case dropped .008 below flush in it.
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Old February 20, 2010, 05:19 PM   #3
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.45 ACP Fire Dragon barrel









So far so good. This O.A.L. would probably work.
.
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Last edited by Walkalong; February 21, 2010 at 08:29 AM. Reason: Added another note to pics
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Old February 20, 2010, 05:24 PM   #4
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Notice how another .014 shorter O.A.L. did not go any further below flush. Still .007



Notice how just a light taper crimp on the 1.239 O.A.L. round dropped the round another .004 deeper.






Note: - Fire Dragon Barrel

A case .894 long and sized around .466 to .468 at the case mouth was .014 below flush.

A case loaded with a bullet that was now .470- at the case mouth would only go .011 below flush.

.
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"Oh bother" said Pooh, as he chambered another round. Author unknown.

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Old February 20, 2010, 05:27 PM   #5
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.45 ACP Wilson barrel









This O.A.L. would probably work. It may need to be a hair shorter. Should give good accuracy
.
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Old February 20, 2010, 05:35 PM   #6
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Notice how this time a crimp was no help in getting the round deeper in the chamber





Note: - Wilson Barrel

A case .894 long and sized around .466 to .468 at the case mouth was .008 below flush.

A case loaded with a bullet that was now .470- at the case mouth would only go .003 below flush.

.
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"Oh bother" said Pooh, as he chambered another round. Author unknown.

Last edited by Walkalong; February 21, 2010 at 08:44 AM. Reason: Added another note to pics
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Old February 20, 2010, 05:46 PM   #7
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Now that we have our MAX O.A.L. with a bullet and a barrel, we can tweak it for feeding.

If you have several .45 (or whatever) barrels and want an O.A.L. that feeds and chambers in all of them, you will need to find the shortest max, and see if it works in all your barrels. Chances are it will.
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Old February 20, 2010, 05:53 PM   #8
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Great sticky worthy write up!

But may I suggest you edit your title to reflect this is for a Pistol

While the principal is the same for a rifle the method of determining is completely different
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Old February 20, 2010, 06:04 PM   #9
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Thanks very much for the illustrated information, this is just what I needed.
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Old February 20, 2010, 06:09 PM   #10
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Quote:
But may I suggest you edit your title to reflect this is for a Pistol

While the principal is the same for a rifle the method of determining is completely different
You are right. I will do just that.

That better? Any more suggestions?
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Old February 20, 2010, 08:44 PM   #11
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This should be a sticky. Come on mods
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Old February 20, 2010, 08:48 PM   #12
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Great camera work and labelling.

Thank you....again.
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Old February 20, 2010, 09:12 PM   #13
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Good job Walkalong, adding the light taper crimp on the fire dragon barrel dropped the below flush* down another .004" Right above the photo is posted
Quote:
Notice how just a light taper crimp on the 1.239 O.A.L. round dropped the round another .004 deeper.
But the photo below has a type O i think?? on the measurement. (1.239" - 1.329") I would like to know the measurement from the head to the shoulder of the bullet on the fire dragon with a oal of 1.239" Thank you. Mine measures .947" [IMG][/IMG]

Last edited by 243winxb; February 20, 2010 at 09:30 PM. Reason: change oal to below flush * added photo
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Old February 20, 2010, 10:13 PM   #14
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Hi Walkalong,
What effect will this have on pressures with all things being the same with very light crimp.Should starting load be used or below that?The reason I ask is I had my Fire Dragon barrel break at the locking lug today after only 100rnds using the method in this thread.By the way it is a 40 cal XD.175grn,5.5 grn of AA#5.but seated below lee specs.
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Old February 20, 2010, 10:56 PM   #15
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Quote:
But the photo below has a type O i think?? on the measurement. I would like to know the measurement from the head to the shoulder of the bullet on the fire dragon with a oal of 1.239" (1.239" - 1.329")
Both rounds are 1.239 O.A.L.. The only difference was the crimp narrowing the case mouth and allowing it to drop a bit deeper. I don't know the measurement to the shoulder. I have already seated it deeper so I cannot check it without doing up another round. It isn't important to this exercise.

If I wanted to seat the bullet to just touch the lands, I would put the final crimp on before I got to flush, and then slowly work my O.A.L. down until I was happy with the relationship of the bullet and case to the lands/chamber. I would not try to measure the distance to the shoulder as a reference for other bullets. I would repeat the procedure with other bullets. That is how I would do it anyway.

I don't load to touch the lands in any of my auto calibers by the way. They already out shoot me anyway. I load for 100% feeding, and take what I get. I'm not shootin' Bullseye, just playing around.
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Old February 20, 2010, 11:01 PM   #16
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Quote:
What effect will this have on pressures with all things being the same with very light crimp.Should starting load be used or below that?The reason I ask is I had my Fire Dragon barrel break at the locking lug today after only 100rnds using the method in this thread.
Obviously the pressure goes up a little as the O.A.L. gets shorter. How much is a job for a lab. When you get the O.A.L. you want to use, then yes, begin with a start load and work up.

Too bad about that barrel, but I bet it was not pressure but a mechanical problem, assuming the loaded rounds headspaced OK, as in not too long, and were not really jamming into the lands.

With only 5.5 Grs of AA #5, a 175 .40 Gr S&W bullet would have to be seated excessively deep to be over pressure IMHO.
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Old February 21, 2010, 07:23 PM   #17
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Walkalong, I always like your Pics

Not to steal your thread, I want to offer another method I have used.

An easy method to determine OAL can be done using a Digital or Dial Caliper and a new pencil cut about a 1/2 inch longer than the barrel.

With the barrel removed, put just a bullet into the chamber until it stops and hold it there.
Now put the cut pencil into the muzzle until it touches the bullet nose and measure the amount of pencil sticking out of the barrel.
Use the step feature on the BACK of the caliper and note the measurement.

Remove the bullet and re-assemble the barrel/gun.
Now put that same pencil into the muzzle until it touches the breech face and again measure the amount of pencil sticking out of the barrel.

The difference between the two measurements is the MAXIMUM overall length that will CHAMBER in THIS barrel/gun/bullet combination.(Fixed it, hows that)

Walkalong, feel free to reduce all these words to 2 pictures!

Note: The cut pencil must be square cut on both ends, not sharpened.
This works for rifle too...with a really long pencil though.
For my critics: If using a DIGITAL caliper, zero it on the 1st measurement and it will read the OAL on the 2nd measurement, no math required...or a micrometer

Last edited by Tilos; February 22, 2010 at 02:07 AM.
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Old February 21, 2010, 10:37 PM   #18
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Quote:
The difference between the two measurements is the MAXIMUM overall length for THIS barrel/gun/bullet combination.
Actually, as Walkalong brought up, this isn't the MAX "USABLE" oal. This measurement would be touching the leade/lands and would give high pressure spikes.

As taught to me by an old knowledgeable reloader (yea, I am thinking of you) you need to subtract your "max 'press' seating deviation" and a reasonable jump to the lands.
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Old February 22, 2010, 12:33 AM   #19
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A picture is worth a thousand words ... and you posted a lot of pictures!

Keep up the great work!
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Old February 22, 2010, 02:25 AM   #20
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Hi Walkalong,


What a nice, well done presentation.

Very good info, anyone Loading for Automatic Pistols will do well to look over.
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Old February 22, 2010, 10:25 AM   #21
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Walkalong...Can I have your autograph?? (Before you get too famous)
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Old February 22, 2010, 02:57 PM   #22
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Thanks Walkalong, I will have to give this a go. I appreciate you taking the time with the pics and sharing this information.
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Old February 22, 2010, 09:49 PM   #23
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Nice job Walkalong, So what camera did you get
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Old February 23, 2010, 09:02 PM   #24
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Walkalong - this is manna from heaven for a newb like myself, but I'm still a little confused. I'm loading 9mm right now (115 grain Missouri Bullet LRN with 3.0 grains of Clays) and the Hodgdon site says OAL is 1.100 inches. I have four pistols in this caliber so. taking your advise, I'm loading to the shortest max. which turns out to be 1.069" for my SIG P6. My EDC is a SIG P239 and it worked out to be 1.095". My P226 can handle 1.108". What's really confusing is that my H&K P7 doesn't have a barrel hood and the 1.069" load protrudes way out the breech; but being a polygonal barrel I probably won't shoot lead in it. So, do I load to 1.069" which is way below Hodgdon COL for the other three guns?
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Old February 23, 2010, 10:16 PM   #25
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I don't see how you can get into trouble with 3.0 Grs Clays, even at that shorter O.A.L. Maybe one of the folks with Quickload can run it for you - Hint Hint. Clays is very fast, and is not real forgiving once it gets up there a bit in pressure.

While 700X is often by Clays in the burn rate charts, it is much more forgiving, and has worked well for me in 9MM, even with plated bullets as long as I don't push it real hard. W-231 would be another good one.

I think you will be fine though.

Hodgdon shows:

115 GR. LRN / Hodgdon Clays / .356" / 1.100" / 3.0 / 954 / 25,300 CUP / 3.4 / 1039 / 31,000 CUP

If you have a chrono, as long as you don't exceed 1039ish FPS, I would say your pressure is fine.

Clays is definitely not a good choice for speed in 9MM, as I am sure you are aware. AC
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