45 ACP Bullet Seating Depth in a 1911 questions


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chbrow10
July 19, 2008, 09:50 AM
I am trying to seat the bullet at the correct depth for MY gun, a Rock Island Armory Tactical Model 1911 in 45 ACP.

I am currently loading Berry's 185 grain round nose bullet above a charge of 4.7 grains of Clay's with a OAL of 1.2-1.22". I'm reasonably happy with that load. However, in the spirit of constant improvement that is inherent to handloading, I'd like to see if I can make it better.

I did some internet reseach and read that if you seat the bullet such that the rim of the case is level with the hood on the barrel, you are seating THAT bullet at the correct/optimum depth for THAT gun. So I tried this. It turns out that even with the bullet ridiculously long (1.3"), the bullet still isn't level with the hood. So then I tried an empty, sized case, and the case fits at the same spot.

Is this what they refer to has "headspacing on the case mouth"? If all this is correct, perhaps the method that I read about with regard to the barrel hood is incorrect?

What are others doing to get the bullet seating optimal, besides trial and error loading?

Thanks in advance, Chris

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The Bushmaster
July 19, 2008, 11:39 AM
Yup...You are seeing the case seat on the case mouth inside the chamber. I would almost bet that when you drop the cartridge into the chamber you hear a "clunk" sound. I seat my 185 grain JHPs at 1.250" and unlike others try to maintain .890 in case length as my Colt .45 ACP seems to prefer that case length. You can adjust the bullet out to where it no longer fits or feeds from the magazine. Which, by the way, doesn't leave much bullet seated in the case. But I would play with the powder and primers first to see if you can improve that way. Incidently I use W-231 with good results.

rcmodel
July 19, 2008, 12:26 PM
If all this is correct, perhaps the method that I read about with regard to the barrel hood is incorrect? What you heard about bullet seating depth controlling headspace is completely wrong.

It has nothing to do with headspace on any firearm.

(Although it can be used to fire-form cases for wildcat calibers, and to correct excess headspace in old mil-sup rifles, etc.)

If it does, you need to seat the bullet deeper, so it isn't contacting the rifling before the case is fully seated in the chamber.

If your .45 ACP cases are the correct length, the head should be even with the end of the barrel hood as that is what controls the headspace. In actuality, it is not real critical in straight-wall pistol cases.

Better to be slightly too short then slightly too long, as the slide won't close if they are too long.

rcmodel

NuJudge
July 19, 2008, 12:37 PM
Headspacing on the case mouth for a straight case is describing a situation where the mouth of the case positions the cartridge in the chamber. There is usually an allowable maximum and minimum length from the boltface to a shoulder at the front of the chamber, and a slightly smaller maximum and minimum allowable case length. The rifling gradually begins ahead of the shoulder in the chamber where the case mouth abutts.

When you seat the bullet out such that the back of the rim is level with the top of the barrel hood, you are probably headspacing on the bullet, not on the case mouth.

One of the odd things about rimless pistol cases is that they actually shorten with repeated firing, not lengthen like rifle cartridges.

Years ago, Dean Grinnell (sp?) did a test where he got some cases that were longer than normal and trimmed them to precisely fit his barrel, loaded them and fired them, and reported better accuracy.

With normal cases (which are too short), if you seat the bullet out enough the bullet will be touching or actually jammed into the rifling. If you seat the bullet out the precisely right amount,the back of the rim should be even with the top of the barrel hood. You may get the same effect Dean Grinnel was trying for.

Be aware that seating a particular bullet design out that far may result in bad feeding, or cartridges that will not fit in your magazines. For the .45 acp, I've only tried this technique with H&G 68 type SWC bullets.

CDD

Ol` Joe
July 19, 2008, 12:38 PM
Also keep in mind the farther out you seat the bullet the less the case wall grips it. The taper crimp on a 45acp does little to hold the bullet, most is accomplished with case tension. Short bullets seated out can tend to move under stress from recoil and feeding. The pressures can also be affected by enlarging or compressing the chamber volume. You are best to keep the COL close to the manufactures/datas recommendation as possible.
JMO..........

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