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Posted: 5/12/2009 10:50:43 AM EDT
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I am new to the subject of reloading and have a question about case lengths. I have looked in this and other forums and have not gotten and answer to what is most likely a very obvious question. In looking through the various manuals and various cartridges I find a max case length and a case trim length. I suspect that anything that is in between is good to go. For the .223 in an AR the Hornady manual shows 1.760 and 1.750 respectively. I suspect that the 1.760 is the absolute maximum and the 1.750 the absolute minimum. Or in my case, with the first cartridge I am looking to do the initial reloading with, the 45 Colt shows 1.285 and 1.275. Am I correct in this assumption, or have I missed something somewhere? Thanks in advance.
jb |
and you'll be fine
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Any dimension between the maximum and trim to lengths has to be acceptable. Think about this problem a little.
There are some exceptions both ways. For a new reloader, it's better to stick with the recommended numbers and do not let brass for bottleneck cases exceed the maximum length. It's potentially dangerous, and I don't have time to expand on that right now, but someone else will fill in the details for you shortly. |
AeroE is correct. As a matter of fact I can't ever think of a time when he was wrong!
One other measurement you will find is COAL (cartridge over all length). This is the measurement with the bullet seated. This is usually listed as the minimum to avoid over pressure. The max length depends on things like if it will fit in a mag ect. |
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Quoted:
AeroE is correct. As a matter of fact I can't ever think of a time when he was wrong!
One other measurement you will find is COAL (cartridge over all length). This is the measurement with the bullet seated. This is usually listed as the minimum to avoid over pressure. The max length depends on things like if it will fit in a mag ect. Keep watching, you probably won't have to look hard. |
If a bottleneck case gets too long it could allow the case mouth to run into the end of the chamber. Take a look at the diagram I've attached (from Ammo Oracle):
The end of the chamber (at the ".040" or .073" points) is the absolute maximum length point for the neck of the chamber. If the case gets too long, it will put the neck past this point. The chamber is cut with a bevel here; if a round with an overly long case neck is chambered, the force of chambering the round could make that ledge bend the case mouth into the bullet effectively creating one hellacious crimp and thus increasing chamber pressure VERY dangerously. Bottleneck rifle cartridges are far more likely to "grow" in firing than pistol cartridges. I've never seen a .38 SPL, 9mm or .45ACP case change length through multiple firings, but a 5.56mm case could grow from "minimum" to "maximum." with just a couple of hot loadings. ALWAYS check the length of bottleneck rifle cases EVERY loading. Check AFTER sizing, because part of the "growing" process is created by the expander ball pulling out of the case mouth. Have I missed any important details here? |
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Thanks guys. Like I posted, I have never seen any information written about (ABCs, NRA, Hornady, Nosler, Lyman...etc.) this particular issue. I began to wonder if I was going to have to get a trimmer to prep the new cases because they measure somewhere between max and trim length. I understand about the problems trying to chamber a case that exceeds the max length and the other problems associated with chambering a round that exceeds the OAL. As I said it is such an obvious answer, but... I know just enough about chemistry and physics and mechanical engineering to be extremely dangerous. With this I don't want to push my luck. I will start with a couple of hundred rounds of .45 Colt and when I get comfortable with the process will move to the bottlenecks (.223 &.308). Again, thanks for the replies. My reading is almost done to the point of putting it into action.
jb |
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Quoted:
the force of chambering the round could make that ledge bend the case mouth into the bullet effectively creating one hellacious crimp and thus increasing chamber pressure VERY dangerously. I agree in theory. But Black Hills Blue box ammo debunks this every day. That friggin brass is goofy long/out of spec, and there's never a exessive pressure issue ever reported. Check AFTER sizing, because part of the "growing" process is created by the expander ball pulling out of the case mouth.
I'd recommend ditching the expander ball completely. I did so and went with an RCBS neck expander die that sizes on the downstroke. My bullet runout is excellent too... 0.003" on a handfull that I checked. |
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I've never seen a published "absolute minimum" length for a .223 case, only "trim to" lengths. The old Accurate Arms loading book says the trim to length for .223 is 1.740" while every one else says it's 1.750". Anything below 1.740" is too short for me personally. |
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