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.

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.

 

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.

 

.45 ACP Fire .45 ACP Fire Dragon barrel.




So far so good. This O.A.L. would probably work.

 

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.
.

 

.45 ACP Wilson barrel









This O.A.L. would probably work. It may need to be a hair shorter. Should give good accuracy
.

 

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.
.

 

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.

 

You are right. I will do just that.

That better? Any more suggestions?

 

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.

 

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.

 

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