Need help with 6mmPPC

cdoc42 · February 21, 2015, 03:01 PM

I have a Rem M700 action used to make a 6mmPPC with a Hart barrel. It shoots Berger 68gr Match and Hornady 65gr V-max bullets sub- 0.5" at 100 yards.

But my reloads are giving me a headache. After 39 years I just ran into a situation that I cannot figure out. Some the rounds simply will not chamber; others I may have to force the bolt to close; others close without a problem.

I'm using Norma cases. An unfired, new case measures 1.127" from base to a point on the shoulder. My fired cases, which extract w/o a problem, measure 1.137." I have resized these to 1.132." Empty, they chamber without a problem.

I've determined the overall size from the base to the ogive of the Berger bullet is 1.639" if seated 0.015" off the rifling. These rounds chamber without difficulty most times, but among them are the troublesome ones that are hard to chamber, or won't chamber.

A troubling round:
1) overall case measures 1.502"; maximum is 1.515"- so the case is not too long
2) Base to shoulder, resized to as low as 1.125" (fired = 1.137.") -so the shoulder is not out too far
3) The bullet seated to the rifling gives an overall cartridge measurement to the ogive of 1.654." As said above, a 0.015" seat = 1.639. I have seated them down to 1.625" - 0.029" from the rifling, and they still won't chamber.
4) The bullets measure 6.17mm (2.42.5") at the base (flat base)

What am I missing here?

Compounding this issue is a future reload using Berger bullets. My original box had a BC of .293 and these, as I said, were 0.015" away from the rifling with a measurement of 1.639."

A new box has a BC of .280 and when seated in the die that made the 1.639" rounds, they measure 1.645." Obviously the new rounds have a difference ogive position, even though they are "the same" 68gr, 6mm Berger bullets. I have not loaded these yet so they are not the culprit above.

Clark · February 21, 2015, 03:08 PM

10 years ago I got some 6mmPPC Krieger, hart, Shilen, and Lilja benchrest take off barrels from ebay.
I wanted to make 243s with premium barrels, but then I found out what a 1 in 14" twist, short, fat barrel is good for... maybe 65 gr Vmax.

Anyway the necks are so tight that brass must be turned for it to fit in the chamber.

If you have pin gauges from 0.251 to 0.500, you might measure the chamber neck. Many of these barrels have 0.262" necks.

Those benchrest guys get a piece of barrel reamed with the same reamer, and then turn necks that just fit in the hole with a seated bullet. They are chasing precision down to 0.0001" in neck turning.

Snyper · February 21, 2015, 05:13 PM

Color one of the problem rounds with a black marker and chamber it carefully to see if you can tell where it's binding

I think Clark may have gotten it with the neck diameters

I'd also look closely at the neck to make sure those longest cases aren't being crimped and causing a bulge

**Unclenick** · February 21, 2015, 06:50 PM

If you have any old cases that worked well, size and seat a bullet in one and measure the neck OD over the bullet and do the same with the Norma. I, too, suspect Clark may be onto it and you'll find the Norma a couple thousands wider.

Longshot4 · February 21, 2015, 06:53 PM

To trouble shoot make one change at a time so you can pin point the problem. I had a similar problem with my 222 when I neck sized for several rounds. When the bolt got tight to close I used a FL S type sleeve die and just bumped the shoulder approx. .002". The problem went away. Also I had purchased a Wilson case gage so I can see the problem the nest time before they get to tight. Good luck

cdoc42 · February 22, 2015, 09:21 AM

That sounds like a plan; thanks to all for your help!

jdscholer · February 22, 2015, 10:39 AM

I was having some of these problems with my 22BR, and finally got some Cerrosafe chamber casting alloy. With an easy to measure chamber casting, I was able to determine what I was up against. I now turn necks, AND use a small base die.

jd

cdoc42 · February 22, 2015, 05:46 PM

I just finished playing around with the cases. A new Norma case measures 0.263" at the neck where it meets the mouth. A resized case measures 0.264and a loaded round measures 0.265 to 0.266. These won't chamber. The stats on the order for building the rifle note the neck is 0.264.

So it looks like the neck is the problem. I'll have to buy a mandrel for the neck turner that I have and finish this experiment.

Thanks again.

February 21, 2015, 03:01 PM	#1
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	Need help with 6mmPPC I have a Rem M700 action used to make a 6mmPPC with a Hart barrel. It shoots Berger 68gr Match and Hornady 65gr V-max bullets sub- 0.5" at 100 yards. But my reloads are giving me a headache. After 39 years I just ran into a situation that I cannot figure out. Some the rounds simply will not chamber; others I may have to force the bolt to close; others close without a problem. I'm using Norma cases. An unfired, new case measures 1.127" from base to a point on the shoulder. My fired cases, which extract w/o a problem, measure 1.137." I have resized these to 1.132." Empty, they chamber without a problem. I've determined the overall size from the base to the ogive of the Berger bullet is 1.639" if seated 0.015" off the rifling. These rounds chamber without difficulty most times, but among them are the troublesome ones that are hard to chamber, or won't chamber. A troubling round: 1) overall case measures 1.502"; maximum is 1.515"- so the case is not too long 2) Base to shoulder, resized to as low as 1.125" (fired = 1.137.") -so the shoulder is not out too far 3) The bullet seated to the rifling gives an overall cartridge measurement to the ogive of 1.654." As said above, a 0.015" seat = 1.639. I have seated them down to 1.625" - 0.029" from the rifling, and they still won't chamber. 4) The bullets measure 6.17mm (2.42.5") at the base (flat base) What am I missing here? Compounding this issue is a future reload using Berger bullets. My original box had a BC of .293 and these, as I said, were 0.015" away from the rifling with a measurement of 1.639." A new box has a BC of .280 and when seated in the die that made the 1.639" rounds, they measure 1.645." Obviously the new rounds have a difference ogive position, even though they are "the same" 68gr, 6mm Berger bullets. I have not loaded these yet so they are not the culprit above.

February 21, 2015, 03:08 PM	#2
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	10 years ago I got some 6mmPPC Krieger, hart, Shilen, and Lilja benchrest take off barrels from ebay. I wanted to make 243s with premium barrels, but then I found out what a 1 in 14" twist, short, fat barrel is good for... maybe 65 gr Vmax. Anyway the necks are so tight that brass must be turned for it to fit in the chamber. If you have pin gauges from 0.251 to 0.500, you might measure the chamber neck. Many of these barrels have 0.262" necks. Those benchrest guys get a piece of barrel reamed with the same reamer, and then turn necks that just fit in the hole with a seated bullet. They are chasing precision down to 0.0001" in neck turning. __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?

February 21, 2015, 05:13 PM	#3
Snyper Senior Member Join Date: December 16, 2013 Location: Eastern NC Posts: 3,047	Color one of the problem rounds with a black marker and chamber it carefully to see if you can tell where it's binding I think Clark may have gotten it with the neck diameters I'd also look closely at the neck to make sure those longest cases aren't being crimped and causing a bulge __________________ One shot, one kill

February 21, 2015, 06:50 PM	#4
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	If you have any old cases that worked well, size and seat a bullet in one and measure the neck OD over the bullet and do the same with the Norma. I, too, suspect Clark may be onto it and you'll find the Norma a couple thousands wider. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

February 22, 2015, 10:39 AM	#7
jdscholer Senior Member Join Date: March 23, 2008 Location: Jefferson State Posts: 1,197	I was having some of these problems with my 22BR, and finally got some Cerrosafe chamber casting alloy. With an easy to measure chamber casting, I was able to determine what I was up against. I now turn necks, AND use a small base die. jd __________________ "We're all dummies, just in different ways." Old Okie Philosopher

February 21, 2015, 06:53 PM	#5
Longshot4 Senior Member Join Date: February 22, 2014 Posts: 868	To trouble shoot make one change at a time so you can pin point the problem. I had a similar problem with my 222 when I neck sized for several rounds. When the bolt got tight to close I used a FL S type sleeve die and just bumped the shoulder approx. .002". The problem went away. Also I had purchased a Wilson case gage so I can see the problem the nest time before they get to tight. Good luck

February 22, 2015, 09:21 AM	#6
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	That sounds like a plan; thanks to all for your help!

February 22, 2015, 05:46 PM	#8
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	I just finished playing around with the cases. A new Norma case measures 0.263" at the neck where it meets the mouth. A resized case measures 0.264and a loaded round measures 0.265 to 0.266. These won't chamber. The stats on the order for building the rifle note the neck is 0.264. So it looks like the neck is the problem. I'll have to buy a mandrel for the neck turner that I have and finish this experiment. Thanks again.