Pardini SPBE .32 ACP Chambering Oddity?

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Pardini SPBE .32 ACP Chambering Oddity?

Post by beeser on Mon May 25, 2015 7:40 pm

While chambering a couple of rounds in my Pardini SPBE .32 ACP conversion I noticed that the factory Hornady 60 gr XTPs went in further than the rounds I reloaded using T&Bs 60 gr LSWC bullets by about .030.  The inside edge of the rim on the factory rounds were flush with the end of the barrel while there was a .030 gap with the reloaded rounds.  I think it hangs up on the lead bullet shoulder.  Or it may hang up on the casing itself after being expanded by the bullet.  The T&B bullet OD is .314 while the Hornady XTP is .311 - .312.  Regardless, will the T&B round not perform as well because it doesn't chamber as deep.  Sorry in advance if my terminology is off.

beeser

Posts : 920
Join date : 2014-06-19

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Re: Pardini SPBE .32 ACP Chambering Oddity?

Post by noylj on Mon May 25, 2015 10:40 pm

Not clear what you mean:
1) One round chambers and the slide closes just fine and the other round doesn't chamber properly and the slide can't close completely
or 
2) One round chambers properly, as far as you can tell, and the other drops too far into the chamber and the round isn't struck by the firing pin
Which is it.
For rounds not feeding and chambering properly:
The SWC has a bore sized shoulder that means the shoulder can not extend too far from the case without contacting the lede/rifling. If you just take the barrel out of the gun and drop a round in, you can see the problem. You need to develop the COL based on each bullet and not assume that there is some generic COL that works for all bullets. One old "rule of thumb" is that the shoulder of a SWC should not exceed 1/32" from the case mouth, unless you have a sufficiently long lede.
Per Ramshot:
"SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as
1) magazine length (space),
2) freebore-lead dimensions of
the barrel,
3) ogive or profile of the projectile and
4) position of cannelure or crimp groove.
• Always begin loading at the minimum "Start Load".
• Increase in 2% increments towards the Maximum Load.
• Watch for signs of excessive pressure.
• Never exceed the Maximum Load."
 
Your COL (OAL) is determined by your barrel (chamber and throat dimensions) and your gun (feed ramp) and your magazine (COL that fits magazine and when the magazine lips release the round for feeding) and the PARTICULAR bullet you are using. What worked in a pressure barrel or the lab's gun or in my gun has very little to do with what will work best in your gun.
Take the barrel out of the gun. Create two inert dummy rounds (no powder or primer) at max COL and remove enough case mouth flare for rounds to chamber (you can achieve this by using a sized case—expand-and-flare it, and remove the flare just until the case "plunks" in the barrel).
Drop the inert rounds in and decrease the COL until they chamber completely. This will be your "max" effective COL. I prefer to have the case head flush with the barrel hood. After this, place the inert rounds in the magazine and be sure they fit the magazine and feed and chamber.
You can also do this for any chambering problems you have. Remove the barrel and drop rounds in until you find one that won't chamber. Take that round and "paint" the bullet and case black with Magic Marker or other marker. Drop round in barrel (or gage) and rotate it back-and-forth.
Remove and inspect the round:
1) scratches on bullet--COL is too long
2) scratches on edge of the case mouth--insufficient crimp
3) scratches just below the case mouth--too much crimp, you're crushing the case
4) scratches on case at base of bullet--bullet seated crooked due to insufficient case expansion (not case mouth flare) or improper seating stem fit

5) scratches on case just above extractor groove--case bulge not removed during sizing. May need a bulge buster.
For a round that chambers too deep, the COL is way too short and the extractor is not grabbing the extractor groove on the case.
I am sure that I am still missing exactly what the problem is, but that is the best I can do.

noylj

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Re: Pardini SPBE .32 ACP Chambering Oddity?

Post by beeser on Tue May 26, 2015 12:07 am

I thought my bad terminology and description was going to be misleading.  Starting over again armed with the information provided by noylj ...

All of my observations were done with the barrel removed.  I was just dropping the rounds in the chamber.  The factory Hornady rounds as well as empty cases would go in or chamber up to the full thickness of the case rim.  In other words, the full width of the case rim would stick out past the barrel hood.  They (factory rounds and empty case) both would not chamber flush with the barrel hood.  The reloaded rounds using the cast lead bullets would chamber shy of the above rounds by .030".  In other words, there was a .030" gap between the barrel hood and inside (toward the bullet) rim of the case.  After further thinking about it I'm sure the lead bullet is bottoming out on the shoulder.  It sounds like to me the .314" bullet is too large for the chamber.

Edit:  After reading noylj's instructions a multiple of times it may be that an insufficient crimp is the reason why the rounds are not chambering deep enough.  I'll go back and check that.

Edit 2:  Nope, no amount of crimp will allow the cartridge to chamber further.  The base diameter of the bullet is definitely too large and is headspacing on the shoulder of it.  Again, I think the bullet needs to be smaller in diameter.

beeser

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Join date : 2014-06-19

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Re: Pardini SPBE .32 ACP Chambering Oddity?

Post by pistol champ on Wed May 27, 2015 12:08 am

Beeser,
My Pardini does the exact same thing as yours with those same bullets and I get great results from the lead bullets in my gun.

pistol champ

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Join date : 2013-02-27

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Re: Pardini SPBE .32 ACP Chambering Oddity?

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