45 ACP COL Variation

[octalman]

Have been reloading 9mm, 38 Spl, 357, and 45 ACP for a couple years. Ran into a new problem recently with 45 ACP, 185 g SWC. Set up the die for COL of 1.23" with a no powder or primer case. When started seating bullets for real immediately noticed the COL varied widely. First 5 ranged from 1.15" to 1.28". Tried adjusting the die to zero in. Could not get COL consistent. Made sure die is not moving, everything was tight. RCBS press bought new. Primers all seated property. Good quality mechanical calipers. Even if the flatness of the bullet nose varied it should not affect COL? Would only affect seating depth, Right? What am I missing?

 

[Cat-Herder]

if you're using LLA, it could be buildup in the seater. otherwise, IDK...

 

[XtremeVel]

Depending on where your seating plug contacts the bullet nose, varying bullet profiles can throw your COL off. I can't imagine it throwing off nearly as what you are getting though...

Are these Cast bullets with lube ? If so, lube can build up on your seating plug, but when this happens, you would be seeing a gradual decrease in your COL.

You state you have good quality calipers, but have you checked them to make sure they return to zero everytime ?

 

[octalman]

The bullet nose is flat. The seating plug is for SWC and is clean. Bullet holder is clean. Bullets are jacketed. Calipers are zeroed and return to zero.

The only other thing I can think of is something with the press. Even though practically brand new, maybe something in the mechanism not making the same stroke length each time. Strange that COL comes out short, long, or right on.

 

[XtremeVel]

The bullet nose is flat. The seating plug is for SWC and is clean. Bullet holder is clean. Bullets are jacketed. Calipers are zeroed and return to zero.

The only other thing I can think of is something with the press. Even though practically brand new, maybe something in the mechanism not making the same stroke length each time. Strange that COL comes out short, long, or right on.

Did you state the correct extremes ? .130 ? That is over 1/8 inch !


While varying differences in your bullet profile can cause variances in COL, that is too much.... I have seen bullets vary enough that would explain maybe .010, but not .130....

Look closely at your bullet and where it contacts the seater plug... Do some of the bullets have a large radius where the flat transitions into the angles where some are sharp corners ?

Take a decent scale and measure the distance from top of your shell holder to the bottom of your die when you are fully upward stroke. See if this repeats... If anything is wrong with your press, you'll see it quickly since you are talking over an 1/8 inch.

Lastly, are these plated by chance, or jacketed ? If plated, are they so soft and are being deformed ? 185gr are light and might deform pretty easily, but again, .130 would still be too excessive for that also.

 

[BGDave]

Did you state the correct extremes ? .130 ? That is over 1/8 inch !


While varying differences in your bullet profile can cause variances in COL, that is too much.... I have seen bullets vary enough that would explain maybe .010, but not .130....

Look closely at your bullet and where it contacts the seater plug... Do some of the bullets have a large radius where the flat transitions into the angles where some are sharp corners ?

Take a decent scale and measure the distance from top of your shell holder to the bottom of your die when you are fully upward stroke. See if this repeats... If anything is wrong with your press, you'll see it quickly since you are talking over an 1/8 inch.

Lastly, are these plated by chance, or jacketed ? If plated, are they so soft and are being deformed ? 185gr are light and might deform pretty easily, but again, .130 would still be too excessive for that also.

What he said. 100%

 

[octalman]

The shortest COL was 1.15, longest 1.28. Yes, that is too much variation. Bullets are jacketed, no deformation. Profile looks consistent from bullet to bullet. Seating plug is flat and square. Good idea to measure from top of shell holder to bottom of die several times to check for variation. There has to be a reason.

 

[octalman]

OMG! Forehead Slap Learning Moment. Checked distance from top of shell holder to bottom of die per XtremeVel. Light bulb came on. Went back to RCBS die adjustment instructions and repeated the procedure. After installing Lock-n-Load quick change bushings on my dies a couple months ago did not readjust for the proper cam-over at top of the stroke. Shame on me. Thanks for the input.

 

[Fullmag]

Not a FSLM, just an opportunity to learn and troubleshoot. Everybody makes mistakes but if it makes you feel better go ahead and slap your forehead again for good measure.

 

[octalman]

Update! Discovered the real problem. Using IMI bullets with a prominent groove. If the bullet seated just a tiny fraction too deep, the crimp will grab the groove and pull the bullet deeper resulting in a short COL. Reloading manual 1.23 COL puts the groove in a bad location. A little less crimp and seating for 1.25 COL working so far. Next test is will they feed properly.