Charter Arms Pit Bull .40 issue with ammo

Went to try out my new Charter Arms Pit Bull 40S&W revolver today.
Had a little more kick than I anticipated, and grouped ok, but a little low and left.
The low can be corrected filing the front sight down a little, a common thing I've read with CA revolvers. I can live with that, filing down is easier than building up.

BUT- I had an issue chambering Federal American Eagle FMJ. Most of them simply would not go in far enough to close the cylinder. They would sit proud of the cylinder rear about .015-.020. There were two chambers they would fit in, a little looser apparently than the other 3. Interestingly they are adjacent.
Gold Dots, Corbon DPX and Winchester WB 40S&W chambered fine in all chambers. All 4 types shot well in my Walther P99, PPS and a Keltec Sub2000.

I notice most 40S&W bullets are straight just above the case mouth for a bit then taper in. The Federal bullet profile is more rounded like a 9mm but it does have the flat tip.

Using my inexpensive Harbor Freight caliper, measuring the bullet right at the case mouth the Win WB and Gold Dot were at .395, the DPX was at .396 and the Federal was .399.
The SAMMI spec here for the bullet is .4005-.003, so anything smaller than .4005 should chamber it seems to me.

Two puzzles here-
First - why are the Gold Dot and Win WB smaller than the "allowed" minimum of .3975?
Second- It appears the chambers are undersized in the PitBull since it won't admit .399 past the step in the cylinder.

The SAMMI chamber dimension drawings show a 3 step drop in size from .401 to .395 to .390. The CA certainly isn't machined this way, nor is the P99 barrel I just checked.

Any insight?

Any insight?Mmmmmm?

Because it's a Charter Arms??

The chambers are improperly reamed to accept all factory ammo.

Send it back and let them fix it.

rc

Well yeah:rolleyes: that answers the second part but what about the "undersized" ammo part?:scrutiny:

You can't measure a seated bullets true diameter right at the case mouth.

Some have full dia bullet shanks outside the case to the point where the ogive starts.

Others are undersize outside the case mouth, but full .400" inside the case where the bullet bearing surface resides.

Nobodys .40 S&W bullets are smaller then .400" inside the case.

The only way you can accurately measure them is to pull the unfired bullets and measure them.

rc

Consider me "schooled" thank you!
Guess I'll be giving Charter a call in any case....:D

That CA 40 is supposed to have some spring innovation that extracts the cases. I would be interested if that had anything to do with it. I would be interested in how that works.

I like to measure chambers with pin gauges. .250 to .500" I keep a set in the reloading room, and a wider range in the machine shop. I don't use Cerosafe much.

The 40sw head spaces on the case mouth, and that is a tiny round ledge that could have dirt on it.

I would like to say that no company would ship a revolver with errors in the chambers, but my Taurus 650 357 mag 5 shot over sized and rough chambers show otherwise.

FIXED IT!


Very careful inspection tonight when I had more time revealed a very slight ridge where the case mouth step transitioned to the bore in the cylinder.
Being an affirmed tinkerer who can't leave well enough alone I dove in-:D

Took a rubber abrasive tip just under .4" on a shank and chucked it into my Dremel...tried my best to keep it in the transition area to sand down the very slight ridge. Since the abrasive rubber bit was a little small I had to "wallow" it around a bit to get the ridge out.
After frequent inspection revealed the ridge was removed in the 3 bores that were defective I chucked a .410 mop in a regular drill put some Flitz on it and lightly honed the bores.
Cleaned it up real well in an ultrasonic bath with Dawn and hot water. Air nozzled it dry, rinsed it well in WD40, air nozzled it again and did a test fit.

All is well! The Federal fits fine now.
Hard to believe that little ridge I could barely see or feel with a pick was stopping full insertion of the Federal.
Doesn't leave me real confident in Charter Arms but I'm glad I was able to fix it without sending it back:)

Speaking of rubber polishing points. I've been using Dedeco rubber polishing points since the 1990s. They make LOTS of different polishing and abrasive and cutting points that are a Dremel owner's dream.