3 PPC length

[COLT45SA]

My custom built 6MM-PPC was built in the early 80s and was delivered to me with 50 SAKO .262 necked cartridges loaded with 62.5 gr Watsons over H322. I won't bore you with details of the build or just how incredibly accurate the rifle performed. This was well before there were any published material on specs for the 6PPC cartridge. Watson sold out to Bart and the formula for H322 has changed.
I found a figure for dimension on the internet showing a .2618" necked cartidge that measured 1.5032" in cartridge length, but I don't remember where I found it.
My question is about cartridge length. I found the originals from the builder measured between 1.510" and 1.518" (quite a range~!). I bought some supposed once-fired Lapua brass which measures 1.485" and bought some new neck sized cartridges from Brunos that measure1.495". What should be my target length~? If I use those cartridges, how seriously will this affect my accuracy potential~??

 

[Tim Singleton]

A lot of folks with 1510 length reamers aim for 1490 trim length.
1485 won’t hurt a thing but the 1495 needs to be trimmed back to 1490

 

[JEFFPPC]

A lot of folks with 1510 length reamers aim for 1490 trim length.
1485 won’t hurt a thing but the 1495 needs to be trimmed back to 1490

And the reason is?

 

[Tim Singleton]

For me 1490 gives me 020 clearance to the end of my chamber and works well
If I let mine get past 1495 and approaching 1500 I start to see bullet spit out of the group.
IMO the brass is expanding out when firing hitting the end of the chamber and pinching into the bullet
Operating between 1490 and 1495 works for me

 

[COLT45SA]

A lot of folks with 1510 length reamers aim for 1490 trim length.
1485 won’t hurt a thing but the 1495 needs to be trimmed back to 1490

There*in lies a problem. James dies quite a while back and I have no idea what he used for a reamer. I kinda guess that since he used SAKO cartridges he might have used a reamer for the SAKO cartridge and modified for the .262" neck diameter. The word guess should be modified to read "swag" (Sophisticated-Wild-Ass-Guess) because I have nothing else to go on.
Thank you Tim for your response~!
After writing this I did a deep search for 6MM-PPC cartridge dimensions and came up with the following:
1.490 Hollister
1.503
1.520
1.503
1.505 Hornady
1.520
I think I'll go with Tim Singleton's response which I just printed out.








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[Tim Singleton]

There*in lies a problem. James dies quite a while back and I have no idea what he used for a reamer. I kinda guess that since he used SAKO cartridges he might have used a reamer for the SAKO cartridge amd modified for the .262" neck diameter. The word guess should be modified to read "swag" (Sophisticated-Wild-Ass-Guess) because I have nothing else to go on.
Thank you for your response~!








`1

Make a cast of the chamber

 

[R.Morehouse]

1.486 here, for oal.....Being anal about the oal matters on my targets and between my ears.....

Regards
Rick

 

[TonyinKY]

Here you go:

SINCLAIR INTERNATIONAL Chamber Length Gauge, Tight Neck, 6mm SKU: 749000751

Check out SINCLAIR INTERNATIONAL Chamber Length Gauge, Tight Neck, 6mm SKU: 749000751 available Online at Brownells Today and many more Case Length Gauges products are available in our Reloading Department.

www.brownells.com

 

[Jonnyofalltrades]

Here's what I do.
Measure a case, record the length.
Chamber the case, and insert a borescope from the muzzle to inspect the gap between the end of the case and the end of the chamber.

This only works if you have a borescope as long as your barrel.
The Sinclair tool looks effective and economical.

 

[COLT45SA]

1.486 here, for oal.....Being anal about the oal matters on my targets and between my ears.....

Regards
Rick

In purely logical terms that makes a lot of sense. The single difference in loaded rounds would be the amount of the bullet that would be inside the neck of the loaded round which would create more or less friction on the bullet as the bullet left the case.
I like the thought about importance of OAL~!

 

[gunsandgunsmithing]

Here you go:

SINCLAIR INTERNATIONAL Chamber Length Gauge, Tight Neck, 6mm SKU: 749000751

Check out SINCLAIR INTERNATIONAL Chamber Length Gauge, Tight Neck, 6mm SKU: 749000751 available Online at Brownells Today and many more Case Length Gauges products are available in our Reloading Department.

www.brownells.com

^^^THIS^^^. You really should get this. It gives you just what you're looking for. There are simply different ppc lengths because it's a wildcat so there is no "standard".

 

[JEFFPPC]

Here's what I do.
Measure a case, record the length.
Chamber the case, and insert a borescope from the muzzle to inspect the gap between the end of the case and the end of the chamber.

This only works if you have a borescope as long as your barrel.
The Sinclair tool looks effective and economical.

I drill out a case and inspect the neck clearance from the rear with my borescope.

 

[JEFFPPC]

For me 1490 gives me 020 clearance to the end of my chamber and works well
If I let mine get past 1495 and approaching 1500 I start to see bullet spit out of the group.
IMO the brass is expanding out when firing hitting the end of the chamber and pinching into the bullet
Operating between 1490 and 1495 works for me

Your splitting a hair I never chased. Just so I could see clearance with the borescope is good for me.

 

[JEFFPPC]

^^^THIS^^^. You really should get this. It gives you just what you're looking for. There are simply different ppc lengths because it's a wildcat so there is no "standard".

I never trusted that system. Just me.

 

[Tim Singleton]

Your splitting a hair I never chased. Just so I could see clearance with the borescope is good for me.

So, share with us your trim length

 

[JEFFPPC]

1.495

 

[21PHX]

I never trusted that system. Just me.

Why?

 

[Shooter13]

For me 1490 gives me 020 clearance to the end of my chamber and works well
If I let mine get past 1495 and approaching 1500 I start to see bullet spit out of the group.
IMO the brass is expanding out when firing hitting the end of the chamber and pinching into the bullet
Operating between 1490 and 1495 works for me

I think this is what Jack Neary said too, been doing it for a while now.