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Old August 18, 2017, 05:40 PM   #1
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6mm PPC question

I have a custom Hart manufactured target rifle in 6mm PPC with a Remington model 700 action as the basis. I do not shoot in competition, I do shoot just for fun. I'm using 65gr Hornady Vmax and Berger 68gr HP bullets and although both are impressive, Berger has produced 5-shot, 100yd groups of 0.195", 0.288" and 0.382."

However, every now and then, perhaps 5 out of 50 hand-loaded rounds won't chamber. If I knock the bullets out, those cases chamber with just slight resistance. With the bullet seated, the bolt won't lock up at all but I also have had to use a mallet to help open the bolt.

Fired cases are larger than resized, and all resized cases have the same measurements found in the 50th Edition of the Lyman Reloading book.

So the problem seems to be confined to the presence of the bullet, yet when I measure the outside mouth diameter of a seated bullet in one cartridge that DOES chamber with one that does not, there is no difference in that measurement. The heads of the cartridge cases also have the same measurement, as does the point where the shoulder drops to meet the neck as well as the measurement of shoulder set-back after resizing (from the base to the datum line).

The overall length of the cases is within accepted range between 1.505 - 1.515. Difficult to chamber cases with a measurement of 1.504" have occurred.

I suspect the chamber tolerances are very tight in this rifle but I'm stuck or a reason to explain why some finished cartridges chamber while others won't. All cases are Norma. Any suggestions will be appreciated.
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Old August 19, 2017, 12:18 PM   #2
T. O'Heir
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"...had to use a mallet..." Indicates excessive pressure or bad headspace.
"...why some finished..." Usually about excessive OAL. Maybe the sizer die is coming a tick loose in the press.
Rummage around here. There's a whole site about the PPC linked.
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Old August 19, 2017, 02:37 PM   #3
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Thanks for the link, T. Just to clarify, use of the mallet to open the bolt was after chambering an UNfired, primed and loaded round. It would not chamber completely and the bolt wouldn't close. But neither could I then get it open.

I was just monkeying around with this in the reloading room and struck upon an idea. I had to trim a few resized cases and in the past I noticed, in other calibers, how thick the mouth of the case was after trimming. So I measured and trimmed 2 of the 6PPC's:

Case #1: mouth diameter before trimming= 6.17mm
mouth diameter after trimming= 6.36mm
mouth diameter after chamfering and deburring: 6.17mm

This empty case chambered in the rifle. Then I seated a dummy bullet and the mouth diameter was 6.22mm (from 6.17mm) and it chambered.

Case #2: Mouth diameter before trimming = 6.18mm
Mouth diameter after rimming= 6.39mm
Mouth diameter after chamfering and deburring= 6.22mm

I seated a bullet and the mouth diameter = 6.28mm. It would not chamber.

So it appears my problem is with some of the Norma brass after I trim! In these instances, more brass than usual must be pushed to the case mouth during resizing.

I'll have to see if I take those live rounds that wold not chamber and turn the necks a few millimeters. If they chamber............that was the problem.

Looked at another way: The 6mm is a .243 caliber. .243 = 6.17mm My second dummy round was 6.28mm = 0.247"
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Old August 19, 2017, 08:46 PM   #4
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Sounds like maybe your necks are too thick.
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Old August 19, 2017, 09:47 PM   #5
old roper
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I pulled up one of your old post about that 6ppc.

Have you turned any necks since 2015.
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Old August 20, 2017, 04:25 PM   #6
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From a few cases I inspected, I must have turned a few then had no problems that I recall. This experience may in fact be a repeat of whatever was posted in 2015; I have less control with memory these days. But I just ordered a new .243 mandrel for my hand-held neck trimmer that I dug out of the box in storage.
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