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Pressure goes up in a straightwall case as COL goes down. Most companies like to TEST at the low end of COL for this reason.
Your COL (Cartridge Overall Length) is determined by;
your barrel (chamber and throat dimensions, particularly the head space dimension of the barrel)
and
your gun (feed ramp)
and
your magazine (COL that fits magazine and when the magazine lips release the round for feeding)
and
the PARTICULAR bullet you are using.
What worked in a pressure barrel or the lab's gun or in my gun has very little to do with what will work best in your gun.
Take the barrel out of the gun. Create two inert dummy rounds (no powder or primer) at max COL and remove enough case mouth flare for rounds to chamber (you can achieve this by using a sized case—expand-and-flare it, and remove the flare just until the case "plunks" in the barrel and lock the die body down temporarily).
Drop the inert rounds in and decrease the COL until they chamber completely. This will be your "max" effective COL. I prefer to have the case head flush with the barrel hood (or a few mils higher than where the head of an empty case aligns with the barrel, as all cases are too short and I prefer to minimize head space). After this, place the inert rounds in the magazine and be sure they fit the magazine and feed and chamber.
You can also do this for any chambering problems you have. Remove the barrel and drop rounds in until you find one that won't chamber. Take that round and "paint" the bullet and case black with Magic Marker or other marker. Drop this round in the barrel and rotate it back-and-forth.
Remove and inspect the round:
1) Scratches on bullet--COL is too long
2) Scratches on edge of the case mouth--insufficient crimp
3) Scratches just below the case mouth--too much crimp, you're crushing the case
4) Scratches on case at base of bullet--bullet seated crooked due to insufficient case expansion (not case mouth flare) or improper seating stem fit
5) Scratches on case just above extractor groove--case bulge not removed during sizing. May need a bulge buster.
If you have ANY data showing 1500 fps for 9x19, you have BAD data.
Check two sources of data and start at the lowest start load and work up.
"Snap" is entirely a qualitative feeling and lowest actual recoil is with the fastest powder powering the lightest bullet at a velocity/pressure that just cycles the slide.
Plated bullets traditionally use LEAD bullet data or jacketed date from start to mid-range.
I would start at 4.4gn N350 and work up: 4.4, 4.7, 5.0, 5.2gn (the first MAX load in my manuals).
The start load is set such that ANY reasonable COL will not produce an overload, as any load/gun max charge is dependent on the powder lot number and the exact bullets, cases, and primers used that vary from what was used by the test lab.
Your COL (Cartridge Overall Length) is determined by;
your barrel (chamber and throat dimensions, particularly the head space dimension of the barrel)
and
your gun (feed ramp)
and
your magazine (COL that fits magazine and when the magazine lips release the round for feeding)
and
the PARTICULAR bullet you are using.
What worked in a pressure barrel or the lab's gun or in my gun has very little to do with what will work best in your gun.
Take the barrel out of the gun. Create two inert dummy rounds (no powder or primer) at max COL and remove enough case mouth flare for rounds to chamber (you can achieve this by using a sized case—expand-and-flare it, and remove the flare just until the case "plunks" in the barrel and lock the die body down temporarily).
Drop the inert rounds in and decrease the COL until they chamber completely. This will be your "max" effective COL. I prefer to have the case head flush with the barrel hood (or a few mils higher than where the head of an empty case aligns with the barrel, as all cases are too short and I prefer to minimize head space). After this, place the inert rounds in the magazine and be sure they fit the magazine and feed and chamber.
You can also do this for any chambering problems you have. Remove the barrel and drop rounds in until you find one that won't chamber. Take that round and "paint" the bullet and case black with Magic Marker or other marker. Drop this round in the barrel and rotate it back-and-forth.
Remove and inspect the round:
1) Scratches on bullet--COL is too long
2) Scratches on edge of the case mouth--insufficient crimp
3) Scratches just below the case mouth--too much crimp, you're crushing the case
4) Scratches on case at base of bullet--bullet seated crooked due to insufficient case expansion (not case mouth flare) or improper seating stem fit
5) Scratches on case just above extractor groove--case bulge not removed during sizing. May need a bulge buster.
If you have ANY data showing 1500 fps for 9x19, you have BAD data.
Check two sources of data and start at the lowest start load and work up.
"Snap" is entirely a qualitative feeling and lowest actual recoil is with the fastest powder powering the lightest bullet at a velocity/pressure that just cycles the slide.
Plated bullets traditionally use LEAD bullet data or jacketed date from start to mid-range.
I would start at 4.4gn N350 and work up: 4.4, 4.7, 5.0, 5.2gn (the first MAX load in my manuals).
The start load is set such that ANY reasonable COL will not produce an overload, as any load/gun max charge is dependent on the powder lot number and the exact bullets, cases, and primers used that vary from what was used by the test lab.
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