125 gr SWC not plunking

[Wobbly]

The bullet diameter is a bit too much to rotate freely in the leade (maybe due to the coating) and I don't want to build too much pressure.

This is the problem you get into with lead and the "push test" we outlined in the Stickies. So you need to sand off 0.001 or 0.002" on that portion of the bullet that contacts the freebore (leade). That's the only way you'll be able to tell freebore resistance from rifling resistance.

When you finish testing and load up your batches of the same projectiles, the freebore resistance on unmodified bullets won't add up to anything.

 

[charlus]

Made some measurements today to find the best setting. Made a internal molding of the first 2 inches of the barrel to have exact dimensions. Chamber is 16.25 mm, freebore 3.5mm. I verified that 4.5gn of silhouette powder are 0.35 cc (Anytime there are two systems used:metric and SAE I prefer to check. NASA sent a robot crashing on Mars because they messed between meters and feet on the radio altimeter)
By setting the 124 gn SWC 6.5mm into the case (leaving 2.5mm between base of bullet and powder) I have an OAL of 27.8 mm (1.094") and a jump of 1.25 mm for the bullet to start. The shoulder is engaged a little more than 2mm into the freebore but less tight than I initially thought.
Going into production and test next week. Will send updates.

[Wobbly]

Sounds like progress !

[IDescribe]

By setting the 124 gn SWC 6.5mm into the case (leaving 2.5mm between base of bullet and powder) I have an OAL of 27.8 mm (1.094") and a jump of 1.25 mm for the bullet to start. The shoulder is engaged a little more than 2mm into the freebore but less tight than I initially thought.

Sweet!     Now you're in better shape than I typically am, which is where most people are. 

You're using a great bullet at a more forgiving OAL with a fantastic, forgiving, accurate powder.  You are in good shape, sir.

[charlus]

OK, let me give you some updates and results:

CZ S2 with OEM #15 recoil spring, light CGW hammer, firing pin & trigger springs. CGW adjustable sear. CZC hammer.
Trigger pull 1100 grams (38.8 oz)
Brass from Starline, Winchester SP primer, Powder RS Silhouette, Bullet: Missouri 125 gn SWC set at 27.8mm OAL
Each load hand weighted.
The published starting load for the 125 gn lead RN for that powder is 4.5 gn (Nothing published for the SWC)

4.5gn: 10 rounds. perfect cycling. No sign of over pressure. Bullet seemed pretty fast (felt by the recoil as I could not use the chronograph) some dispersion and one flyer (Me?)
4.4 gn down to 4.0 gn by 0.1 gn increments: five rounds of each. Perfect cycling with no need to change the recoil spring weight. As the load decreased, the dispersion went down to a very good 1? inch group at 15 yds with 3 bullets practically in the same hole. Very soft recoil. Nice to see the neat and crisp holes made by the SWC.

What's next: A 30 rounds sequence at 4.0 gn load to verify the consistency of the results and I will test 3.9 and 3.8 gn loads (Maybe, at the end of the testing period, only the primer will be needed

All of this thanks to everybody's help on the forum.

[Sidecar2]

I was having plunk-test problems until I installed a Lee Factory Crimp die in Position 4 of my Dillon 550.

The Lee has an additional carbide sizer ring and a crimper. Forcing the reloaded round through a final resizing die brings the round into conformity MOST of the time now.

I believe part of the problem is the wall thickness of the brass. If the original brass was holding a 115gr bullet, the bottom of the bullet would stop a bit higher than heavier rounds.

I was trying to load 124gr and 147gr bullets into a variety of brass with mixed results. I could see the bulge from the larger bullets pushing the case wall out just a bit.

Now with the Lee sizer/crimper, almost all my rounds fit.

However, that said, determining the actual OAL for a given bullet (especially if it's non-standard and not specifically referenced in your reloading manuals) is the most reliable way to guarantee the gun going into battery. Wobbly's treatise on OAL at http://www.czfirearms.us/index.php?topic=34225.0 is very helpful, and I end up shortening the OAL even more that his recommended 0.015-inch.

[charlus]

Forgot to acknowledge: the reloads are made using a Lee 4 dies carbide set.

[Wobbly]

Both of you need to insure that the Lee FCD is not diminishing the diameter if the lead bullet ANY. If not set correctly the FCD can swage your perfect 0.357" bullet right down to a perfect 0.355".

[1SOW]

What Wobbly said above is precisely true.
I load 9mm on a Lee press with those same dies. For oversized (.3565" or more) I strongly recommend setting the taper crimp with the powder thru die or a dedicated taper crimp die.
My coated lead .356" diameter bullet loads would go through the FCD with only a tiny bit of compression,  but I decided to just use the powder though die set specifically for that bullet's taper crimp and skip the FCD.
.
A relatively minor consideration when using  mixed brass:  SOME of your loads will be crimped slightly more than others.  Compare an FC or CCI cartridge  case with a PPU or Win Nato.  A little allowance in your TC for the thickest cases may be a good idea... Or not.

[IDescribe]

I was having plunk-test problems until I installed a Lee Factory Crimp die in Position 4 of my Dillon 550.

Don't use the FCD with lead or coated lead. You'll sewage the bullet and reduce accuracy, if not induce tumbling.

[charlus]

I checked the bullet diameter before and after running the FCD: Size is unchanged at:0.3575".
The case O.D after running through the FCD is 0.380" at the mouth and the thickness of the case is .012. This leaves an I.D of 0.356" for an original 0.357 bullet. Do you think it is too tight?

[IDescribe]

To measure the relevant part of the bullet, you need to pull the bullet.

But yes,. 356 ID is too narrow for a. 357 bullet. Seriously, just buy a regular taper crimp die.

[SoCal]

^^^^

And the LEE Taper crimp is very reasonably priced at $14. 

https://ads.midwayusa.com/product/469800/lee-taper-crimp-die?utm_medium=shopping&utm_source=google&utm_campaign=Reloading%20-%20Dies%20%26%20Shellholders&utm_content=469800&cm_mmc=pf_ci_google-_-Reloading%20-%20Dies%20%26%20Shellholders-_-Lee-_-469800&gclid=Cj0KCQjwqPDaBRC6ARIsACAf4hCRf9Zhztz8bRdam8fobTDkODyuaS_Fz4hzvd7QqHelkve6hxQpY0waAt7dEALw_wcB

[charlus]

When pulled out from the case, the bullet's base measurements are +/- .3565 (+/- = the caliper's accuracy)

[IDescribe]

It doesn't measure to the ten thousandth.  That fourth number is either a 5 or a 0, so it measures to the the 2000th, and since calipers aren't particularly precise, I'd call it .356.

Either way, you'd be best off not to use an FCD with lead or coated lead.