- March 7, 2016 at 2:14 pm #25590uber7mmParticipant
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I cut trimmed 50 pieces of brass .001″ over specified trim length. I load these cases with a gallery load (13.6 grains Red Dot) to fire form the cases. From there, the plan was to neck size and reload a near max load for jacketed bullets. I’ve shot off 30 of these and have noticed that the length of empty cases are now shorter and on average .008″ under trim.
I read years ago that near max loads increases brass length, thus the necessity to trim cases, and reduced loads tend to shrink brass. I’ve experienced reduced load shrinkage over the years and retire brass as necessary, but .008″ on the first loading?!!! Does anyone have any insight or advice on this subject? Please advise.
- March 7, 2016 at 5:28 pm #25602JPHollaParticipant
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Fire-formed/trimmed from what to what? Did you trim according to something written in a book or to the chamber for which they are intended? Why shoot a gallery load before a full-power load? Is this a dramatic case change? If the brass is expanding a lot, it will shrink a lot. My problem is most chambers being too long in the neck. I don’t ever recall brass stretching enough to require trimming. If loaded hot, I generally wear out the web first. I also try to work up loads that do not require a crimp. If the neck is not crimped enough to fit inside the throat, you don’t have to worry about over-pressure due to long brass. One thing I always keep in mind is the story of when Quigly Down Under came out and everyone had to have a 45-120. Many people were having brass fail after just two or three loadings. It turns out, they were trimming the brass to minimum length after every shot. That massive bullet inside the brass expanded upon firing and pulled the brass with it as it left, until the case mouth reached the front of the chamber and bottomed out. When they trimmed it back, it would do it again the next shot. If they just let the brass fit the chamber, everything works out fine. I’ve learned it is not always prudent to do things exactly as the loading manuals say (gasp!).
With jacketed bullets, I’ve found that your .008″ too short brass will not hurt anything. If you crimp, you may have issues depending on your crimp die.
What gets me is when you take a loaded cartridge with brass fitted to one gun and fire it in a gun with a slightly smaller chamber. The bolt may take some force to close, but after firing the brass case fits almost like it had been full-length re-sized.
- March 7, 2016 at 7:03 pm #25607
If the cases had not been fire in the chamber before they would have to expand to fill the chamber – as the brass pulled back from the shoulder and expanded back towards the bolt the case would appear to shrink. That’s why I trim after first firing.
- March 7, 2016 at 8:41 pm #25616ScharfschuetzeParticipant
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Artful;n4002 wrote: If the cases had not been fire in the chamber before they would have to expand to fill the chamber – as the brass pulled back from the shoulder and expanded back towards the bolt the case would appear to shrink. That’s why I trim after first firing.
Another cause for shrinking cases when using squib or reduced loads (like your load of Red Dot) is that the pressure in the primer pocket is greater than the pressure in the chamber or case. This will force the case forward and shrink your case slightly. It is most apparent in your case’s base to datum line measurement or headspace. To preclude this, many shooters of light loads will drill out the flash hole in their segregated squib load cases to reduce the pressure in the primer pocket and thus preclude shrinkage.
- March 7, 2016 at 11:10 pm #25632
True, but usually you get the complaint that the primer is sticking out or showing pressure signs with the light load.
- March 9, 2016 at 2:21 am #25689uber7mmParticipant
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I think I’ll neck size the cases in question and load them stiff with jackets and see if they don’t grow a bit. I have nothing to loose as far as these cases are concerned.
Again thank you for your input.
- March 13, 2016 at 9:11 pm #25834MilkmanParticipant
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I had the symptoms described by Artful in post #5, in a 35 Whelen hunting load where the pressure was in the low 20K’s. I couldn’t believe that pushing a 280g bullet to 1700 fps could still be called low pressure. I argued for days and refused to believe what I was told. No way a primer could move the shoulder back. Then I changed to a pistol primer with that load and have had no more problems. I guess it was some kind of magic, there is no way I could have been wrong.
- March 13, 2016 at 10:42 pm #25836
Milkman;n4266 wrote: Then I changed to a pistol primer with that load and have had no more problems. I guess it was some kind of magic, there is no way I could have been wrong.
What not married yet 😉
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