Reduced load when shortening COL?

I use 3.8 and it does cycle my pistol but I use a dust cover mount to mount my Ultra Dot. With a 200 grn LSWC from Zero they chrono at 725 and with a 185 they chrono 680 so it is was up to me I would not go lower

What's measurement from bottom of case to the bullet shoulder? 0.920" is a good seating depth.
Jon

Jon Eulette wrote:What's measurement from bottom of case to the bullet shoulder? 0.920" is a good seating depth.
Jon

The bullet shoulder is flush with case.
The time bullet shoulder is above case the plonk test fails.

That seems like a pretty short chamber.  I'd inspect the chamber to make sure it's clean.
- Dave

Run a caliper on one of your home-made home-powder-coated bullets that has not been previously loaded.  My guess is that you might be dealing with an oversized projectile.  When you push it all the way into the case, that resizes the bullet.

How does factory ammo plunk into your barrel?

Please also confirm that the barrel has been thoroughly cleaned.

Thanks! 
Will do a proper clean tomorrow to see if that's the case. However, when i do the plunk test i hear a clear distinct metal sound.
Bullet size is .452 measured with digital caliper.
It's not me myself that casts the bullet, but it is a private on-the-side business.

Does a longer COL feed and chamber in your gun? As stated, if you are shooting a SWC, then all SWC bullets will feed and chamber at the SAME shoulder-to-case head distance. With a 1911, I like the case head to be flush with the barrel hood to minimize head space gap.
When you reduce the COL, it is a good idea to either drop the charge back to the start load or, if below a manual's start load, to drop by about 5% of the charge weight. You aren't worried about pressure of the round as much as getting back to the accuracy point.

Hi,
Can you measure from front edge of chamber to the hood (rear of barrel)?
I've seen some SA pistols that were short chambered.
Jon

Jon Eulette wrote:Hi,
Can you measure from front edge of chamber to the hood (rear of barrel)?
I've seen some SA pistols that were short chambered.
Jon

It's 0.897ish from the edge of chamber to the end of the hood.
0.739ish from edge of chamber to end of barrel (beginning of the hood.)

Looked at page 57 and .898 seems to be minimum lenght (i guess mine is .898, near enogh for human failure when measure)

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.3-CFP-and-R-Approved-2015-12-14-Posting-Copy.pdf

Have you tried a factory round . Are you crimping in a separate operation? If not, often a small ring of lead will extrude creating a false cartridge edge.

I've shot Sellior&Belliot 230 RN, it worked.
Didn't check then because i wasn't aware of this situation.

It was when i was started reloading this swc that i realized there might be some problem.
Separate crimp (Dillon dies), checks every round with my fingers to spot any lead shavings. Good flare.

I can't understand what's going on. If i don't remember all wrong i think i reloaded some copper plated 230 RN with no problem (flush with hood, ok plunk test), but now with SWC it's a no-go.
The bullets is sized .452 after powder coating, and when measuring it's correct.

Edit*
Measured the copper plated RN that i reloaded, and it measures .450 at the bottom and .448 at the top (that would be the part seen of bullet when seated).

Hasn't slugged my barrel. Beginning to think my barrel is .451 or less. Thoughts?

Update!
All seem fine now.
Did a good cleaning and now the plonk test is fine with a col of 1.224.
Note to self... Clean gun more often.

Thanks for all input on the subject.