Bought 50 pcs of 6.5x284 Lapua brass. Sized them down to 6x284 in a Redding type "C"series FL sizing die. Fired the ammo some brass ejected with resistance others didn't. Measuring the case necks Most were .278 and a bullet easily slips into fired case. Other cases measured .271 and a bullet didn't fit at all. What's up with this ? I purchased a K&M neck turner tool . The cases that measured .271 don't fit the K&M mandrel .I have a K&M expander for those. The cases that measure .278 fits loosely over the K&M mandrel. So do I run the .271 cases over the expander and then neck turn them and then neck size them ? What about the cases that measure .278 ? Do I neck size those,run them in the expander neck turn them and then neck size then again ? When I fired them at the range ( Before I new of this discrepancy) the accuracy was poor. When I fired these same loads out of Norma brass accuracy was best ever.
Neck diameter variations
- Thread starter Ironworker
- Start date
You are on the right track.
I have ran into similar situations when manipulating brass demensions.
After fireforming, some of your brass ended up with thick necks. When this happens to me,,,,,I measure and compare the neck thickness between the brass that performed ok and the 'tightnecked' brass. I expand the neck enuf to accept the neck turn mandrel,,,,,then remove just enuf material so that the neck thicknesses are pretty much the same as the the 'ok' brass. I then resize those neck turned pieces of brass,
load em all up, along with the 'ok' brass. After that firing, I neck turn them all,,,just enuf to take off the highspots. This should uniform all your brass. Then it's happy shooting after that. FWIW: I have found that uniform neck thickness, translates into uniform neck tension, then translates into accuracy. For my target guns,, I am always very aware of neck tension and may neck turn the brass several times over the course of their life. It works for me. I get superb accuracy and get many loadings from my brass.
I have ran into similar situations when manipulating brass demensions.
After fireforming, some of your brass ended up with thick necks. When this happens to me,,,,,I measure and compare the neck thickness between the brass that performed ok and the 'tightnecked' brass. I expand the neck enuf to accept the neck turn mandrel,,,,,then remove just enuf material so that the neck thicknesses are pretty much the same as the the 'ok' brass. I then resize those neck turned pieces of brass,
load em all up, along with the 'ok' brass. After that firing, I neck turn them all,,,just enuf to take off the highspots. This should uniform all your brass. Then it's happy shooting after that. FWIW: I have found that uniform neck thickness, translates into uniform neck tension, then translates into accuracy. For my target guns,, I am always very aware of neck tension and may neck turn the brass several times over the course of their life. It works for me. I get superb accuracy and get many loadings from my brass.
A variation of 0.278" to 0.271" in a fired case is a huge difference. Something is not right. Perhaps someone with some more experience can comment on the cause. I don't think this is something that needs to be addressed with a neck turner.
My only guess would be that you may have a load that is too light. I ran into this once with a hunting cartridge. The load did not generate enough pressure to open the neck up to fit the chamber. What is your load?
My only guess would be that you may have a load that is too light. I ran into this once with a hunting cartridge. The load did not generate enough pressure to open the neck up to fit the chamber. What is your load?
Oh my loads are hot. The brass case that measure .271 were 56.9grs of Re#17 behind a Nosler 70 gr BT just touching the lands.( Also I'm having to chase after the lands barrel is reaching end of BBL life) loads that measured .278 were 52.9grs of Re#17 behind 90gr Nosler BT also seated to touching the lands. Its the loads with Nosler 70 gr gave me resistance in extraction. Perhaps that is where the answer lies ?
My bad. 
I turned the necks on the troubling cases ,then necked sized them. Then to see the difference if any? In the extraction of a empty neck sized case. Same thing it extracted with resistance ! So I decided to start back at square #1 I full length sized the case,but discovered I didn't have my FL die adjusted right :
So I adjusted it right and sized that case and now it fits my chamber perfectly. :-[ I've been loading for decades. This was a "rookies' mistake.
I turned the necks on the troubling cases ,then necked sized them. Then to see the difference if any? In the extraction of a empty neck sized case. Same thing it extracted with resistance ! So I decided to start back at square #1 I full length sized the case,but discovered I didn't have my FL die adjusted right : So I adjusted it right and sized that case and now it fits my chamber perfectly. :-[ I've been loading for decades. This was a "rookies' mistake.
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