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Tight-Neck Tragedies

opening actino72The 6mm PPC has garnered an impressive reputation for accuracy and is often at the top of the list when people talk about “THE MOST ACCURATE CARTRIDGE IN THE WORLD.”  That makes it attractive to novice shooters who are often novice handloaders as well.  Back in the dark days while I was still building rifles for a living, it was surprisingly common for a person who was interested in shooting, and prone to doing their due diligence by studying everything shooting related, to decide on one of our PPC models. In my mind, this choice is like giving your 16-year-old new driver the keys to an Indy 500 car.  Performance requires practice and skills, in both auto racing and shooting.

There is no doubting that the PPC is accurate, but they are a technically demanding cartridge when it comes to wringing out match-winning performance.  If you load it like casually using the same level of care you might for your .30-06 deer rifle, it typically shoots about like your .30-06 deer rifle.  There is no magic, just the potential for accuracy in the hands of a skilled loader and shooter.  Compounding problems with this potentially befuddling cartridge is the likelihood of tight-necked custom chambers.  It was this combination of the 6mm PPC’s attractive reputation for accuracy and the presence of a tight neck chambering that brought a rifle into Keith’s Gunsmithing shop the other day.   It’s a sad story of a beautiful now ruined rifle and man who now may have an incurable flinch.

action72The story starts like a lot of tight-neck tragedies, with a good deal on a used benchrest rifle.  Because this problem is surprising common with used match rifles and the fact that it happened to a very nice person, we will use a pseudonym to protect the innocent.   We will call him Shaky Flinch.

Shaky was offered a 6mm PPC built on a Rampro action.  After looking at the rifle, I would have purchased it too, as long as my wife was at least one state away on business.  It was beautifully built and the Rampro actions certainly deserved their place in the sun when it came to benchrest competition.  Shaky purchased it and later got dies and brass to go with his new rifle.  What he missed was the subtle number next to the caliber stamp.  Etched in fine silver print with no explanation was the number .262.

BarrelstampAOn custom guns, the second number after the caliber stamp is a dead give-away that something is different in Denmark.  Benchrest rifles, especially older benchrest rifles commonly used neck dimensions that required the necks to be turned down using a neck-turning tool.  This practice is drying up, thankfully, but it is still very common to find tight necks on competition rifles.  The second number, in this case .262″ is the true neck dimension.  The loaded cartridge case neck needs to be between .002 and .003 smaller than that diameter to allow clean release of the bullet.  So, if Shaky had made turned his cases to have a loaded dimension of .259 he would have been fine and the accurate little benchrest rifle probably would have continued to shoot tight little groups.  If, on the other hand, the case neck is too tight to allow the bullet free release, it becomes the plug in a high pressure bomb.

In Shaky’s case, his non-neck turned brass measured something closer to .265″ and bad things were about to happen.  It isn’t hard to imagine that closing the bolt took a bit of force as he swagged the neck down to .262″.  A moment later a well-crafted benchrest rifle was ruined.  Shaky broke two cardinal rules of handloading.  He didn’t know enough about his rifle to produce safe loads and he ignored the warning signs that come with a difficult to close bolt.  If something feels wrong: STOP and figure out why.

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Recovered brass from the case head.

Recovered brass from the case head.

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View of chamber.

View of chamber.

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Any used benchrest rifle should be treated as if it has a tight neck, even if there is no neck dimension printed on the side of the barrel.  The easiest answer is to take it to a competent gunsmith who will make a Cerrosafe casting of the chamber.  You can also make the casting yourself for the cost of block of Cerrosafe and some shipping.  It is quick and easy.  Here is a link to Midway:  https://www.midwayusa.com/product/462291/baker-chamber-casting-alloy-1-2-lb

If you happen to have gotten a tight-neck chamber, turning brass isn’t as horrible as a root canal.  There are actually just a few steps and little elbow grease required.  Here is a link that explains the process.

http://blog.westernpowders.com/wp-admin/post.php?post=1521&action=edit

Another option would be to have a gunsmith open the neck to a standard non-turn dimension.  Once the barrel is removed the process only take a few minutes and removes very little metal from the chamber.  Your hands will thank you.

Check Before You Shoot
All used rifles should treated with healthy skepticism, especially if they show signs of custom manufacture.  Typical competition calibers like PPC’s and BR’s should have their chambers checked before they are fired to confirm the actual chamber dimensions.  Odd calibers, wildcats, or rifles that are clearly built-up for competition should also get a once over to confirm their chamber dimensions.  Once you get a block of Cerrosafe (it’s reusable), there is no cost other than a few minutes of time. Not checking can cost you a rifle.  Or a finger.  Or an eye.