Coal variance question.

[Crawfish1]

Hi everyone,

I have a question about a shifting over all length of my reloads. I am frustrated because I don't understand what is causing it to change. I am loading .40 with 180 GRN Xtreme plated rnfp. My press is a Hornady LNL AP using RCBS carbide dies.

Basically I will be loading rounds with no problems then I will feel more resistance on a certain case while seating the bullet. I then take the freshly seated round and notice there is a little bunching of the plating near the mouth of the case mostly on one side and the over all length is out of spec. I cull the bad round and I then continue to reload and might not have a issue for 75 cases then it might happen with two cases in succession. It's seems completely random. Sometimes it will be five in a row of rejects then no issues for two hundred rounds. The cases that are problematic all have different head stamps.

This is only happening with .40 as I just reloaded 3k 9mm without any trouble. I have never had problems like this and I have gone through a metric ton of .40s.



Thanks for reading.

 

[hdwhit]

It sounds like you are occasionally getting a bullet that is either starting out crooked or is just a little bit larger than the others and the case mouth is shaving the plating off the bullet.

• Are you expanding the case mouth adequately to allow the occasional outlier to comfortably seat? I've used a lot of Xtreme's 115 gr 9mm hollow points and really like them, but in my experience they were more "comfortable" with a tiny bit more case mouth expansion.
• Do your RCBS dies have more than one seater stem? If so, have you tried the other one? It may not seem intuitive, but the seater stem for the round nose bullets might work better since the curvature might allows the bullet to center more easily than an angled surface.

 

[LiveLife]

loading .40 with 180 GRN Xtreme plated rnfp. My press is a Hornady LNL AP using RCBS carbide dies

I will be loading rounds with no problems then I will feel more resistance on a certain case while seating the bullet. I then take the freshly seated round and notice there is a little bunching of the plating near the mouth of the case mostly on one side and the over all length is out of spec.

This is only happening with .40 as I just reloaded 3k 9mm without any trouble. I have never had problems like this and I have gone through a metric ton of .40s.

How much taper crimp are you using?

If you are using too much, longer case mouth may be digging into the plating causing the bunching up of plating.

Since case wall thickness average .011", I usually add .022" to the diameter of the bullet to determine the amount of taper crimp. So for .400" sized bullets, I will use .422" taper crimp. Measure some resized brass length and use longer cases to adjust your taper crimp die.

If you are still getting significant OAL variation (more than .005") after addressing the taper crimp, try resizing in separate step as shell plate deflection can add to bullet nose profile variation and increase OAL variance. Walkalong resizes his brass separatly on his LNL AP.

 

[higgite]

I agree with bds that it could be that longer cases are crimping earlier in the seating process, before the bullet is completely seated. Another possibility is that some cases are shorter than others so while most cases are getting expanded enough, the shorter ones aren’t. I have that happen occasionally when loading mixed headstamps, but not as often as you are experiencing.

 

[bersaguy]

I've had the exact same thing happen loading .45 on my lee turret. IIRC the issue was the (forgive me if I get the terminology wrong) stem inside the seating die that contacts the nose of the bullet was stuck in the full upward position. It is supposed to drop down and guide the bullet as it travels upward into the die. Mine had been in storage for a while and was stuck all the way at the top, so unless the bullet was placed nearly perfect on the case, it would end up shaving plating off. Once I took the die apart, wiped off the surfaces with a light(very light) coat of oil, that issue went away

 

[Walkalong]

Try hdwit's& bds's suggestions. Make sure the shortest cases are getting enough "flare". Make sure there is not too much "crimp" going on, it should be be just enough to remove the flare/belling on the shortest cases, which means the longest cases will get .001, maybe .002 of inward movement of the case mouth. Starting the bullet fairly straight always helps the whole seating process. You should be able to taper "crimp" .40 in the same step as seating. There will always be some variance in OAL, it all depends on what processes are going on, how well the seater stem fits the bullet, case wall variances, etc. A .005 spread is a good goal. Sometimes it will be more though.

A Post on Crimping

.40 S&W with a plated bullet.