Burr
06-19-2015, 02:10 AM
My first foray into resizing cartridge mouth from .224 caliber to .257 caliber - the case is 22-250, resizing to 250 Savage AI - next step will be to fire form.
Would it be expected, advised to resize to 6mm before going up to .257? I've done the first dozen cases - most all of them have collapsed the shoulder at least a little. I plan to jamb the bullet into the lands for fire-forming, and all my cases will chamber, the bolt closes without any extra effort. But I'm sure I now have what is essentially a headspace issue since the shoulders are set back by the collapsed amount.
I swapped the button for one made for resizing. I lubed inside the case neck with a q-tip.
What I did - new Lapua Brass in 22.250
Took baseline measure of case mouth thickness prior to any resizing - measurements were .014-.0152 - very rare to fall below .014 - just a couple of the 10 I measured dropped into .0138. Consistent thickness.
Weight sorted cases, I ended up with 4 - 1/2 grain groups qty 5-161 Gr; @44-161.5 Gr; @44-162 G; 7-162.5 Gr. So I took the 5 lighter cases and 7 heavier cases to continue case prep, leaving the 2 larger weight-sorted groups for later.
lubed cases - full length and inside case mouths with Imperial Sizing die wax
resize with aftermarket button in 250 AI FL die. Noticed most shoulder collapse at this stage of case prep.
measured case mouth thickness again, determined to trim case necks to .01275
Lube inside case mouth with q-tip
Expand case mouth for neck Trimming - may have increased shoulder collapse a little on this step - surprising at the pressure in this step to expand the case mouth for trimming?
Trimmed case neck to .0128
Steel wool inside and out.
cleaned/brush lube from inside case neck
run through FL die again - backed off die a bit to just pull the button through the neck.
measured for length, all short, no trim for length.
Cleaned cases
loaded fire forming load - CCI 200, 35.5 gr H380 with 120 Gr Nos BT. I found a seating depth that is a moderate jamb, by closing bolt on loaded round. Moderate powder charge, heavy bullet, fast(er) powder. 11 case necks measured .282, 1 was .281. Had to get through above steps to determine what size bushings to order - I've ordered 279, 280, and 281 busings - so I'll be able to neck size with bushing in the future - but the FL die with button is the tool I have now to resize the necks for a fire-form load.
I do plan to clean my chamber with alcohol prior to fire forming, assure I don't have any lube in the chamber prior to fire forming. Moderate jamb should hold the case against the bolt for fire-forming - if the firing pin pushes it forward maybe the dry chamber will prevent mid case stretching, we'll see. Plan to fire-form these 12 rounds 2-3 times taking measurements between each firing to get good data points.
Would like to get some advise before I start resizing the next 88 of my 100 cases. I'll shoot these first to see how fire forming goes, and I'm thinking I'll be OK as long as I have the bullet jamb into the lands for the fire form load - but a bit concerned the firing pin will push the case forward since the shoulder collapse has created some headspace. I'll take whatever advise I can get on how to resize case neck/mouths to a larger diameter before I get into the larger brass lots.
These 12 cases are destined to become modified cases and get sent out for a custom dies. Since they are the light and heavy cases - they'll be out circulation once barrel break in is completed. Would like to get on track to prevent the shoulders from collapsing before I get into the larger lots. I'm out of ideas.
Would it be expected, advised to resize to 6mm before going up to .257? I've done the first dozen cases - most all of them have collapsed the shoulder at least a little. I plan to jamb the bullet into the lands for fire-forming, and all my cases will chamber, the bolt closes without any extra effort. But I'm sure I now have what is essentially a headspace issue since the shoulders are set back by the collapsed amount.
I swapped the button for one made for resizing. I lubed inside the case neck with a q-tip.
What I did - new Lapua Brass in 22.250
Took baseline measure of case mouth thickness prior to any resizing - measurements were .014-.0152 - very rare to fall below .014 - just a couple of the 10 I measured dropped into .0138. Consistent thickness.
Weight sorted cases, I ended up with 4 - 1/2 grain groups qty 5-161 Gr; @44-161.5 Gr; @44-162 G; 7-162.5 Gr. So I took the 5 lighter cases and 7 heavier cases to continue case prep, leaving the 2 larger weight-sorted groups for later.
lubed cases - full length and inside case mouths with Imperial Sizing die wax
resize with aftermarket button in 250 AI FL die. Noticed most shoulder collapse at this stage of case prep.
measured case mouth thickness again, determined to trim case necks to .01275
Lube inside case mouth with q-tip
Expand case mouth for neck Trimming - may have increased shoulder collapse a little on this step - surprising at the pressure in this step to expand the case mouth for trimming?
Trimmed case neck to .0128
Steel wool inside and out.
cleaned/brush lube from inside case neck
run through FL die again - backed off die a bit to just pull the button through the neck.
measured for length, all short, no trim for length.
Cleaned cases
loaded fire forming load - CCI 200, 35.5 gr H380 with 120 Gr Nos BT. I found a seating depth that is a moderate jamb, by closing bolt on loaded round. Moderate powder charge, heavy bullet, fast(er) powder. 11 case necks measured .282, 1 was .281. Had to get through above steps to determine what size bushings to order - I've ordered 279, 280, and 281 busings - so I'll be able to neck size with bushing in the future - but the FL die with button is the tool I have now to resize the necks for a fire-form load.
I do plan to clean my chamber with alcohol prior to fire forming, assure I don't have any lube in the chamber prior to fire forming. Moderate jamb should hold the case against the bolt for fire-forming - if the firing pin pushes it forward maybe the dry chamber will prevent mid case stretching, we'll see. Plan to fire-form these 12 rounds 2-3 times taking measurements between each firing to get good data points.
Would like to get some advise before I start resizing the next 88 of my 100 cases. I'll shoot these first to see how fire forming goes, and I'm thinking I'll be OK as long as I have the bullet jamb into the lands for the fire form load - but a bit concerned the firing pin will push the case forward since the shoulder collapse has created some headspace. I'll take whatever advise I can get on how to resize case neck/mouths to a larger diameter before I get into the larger brass lots.
These 12 cases are destined to become modified cases and get sent out for a custom dies. Since they are the light and heavy cases - they'll be out circulation once barrel break in is completed. Would like to get on track to prevent the shoulders from collapsing before I get into the larger lots. I'm out of ideas.