Effects of COW fireforming on a new chamber throat.

[tooter]

Here's a topic for all you "wise guys" (no pun intended) to help educate me on any detrimental effects of COW FF on a new chamber throat.

I've been using the COW forming process for 6 Dasher and 223AI brass on a new switch barrel BAT with great results. I've only FFd 50 pieces of brass for each. There's been no evidence of copper fouling during barrel break-in or during subsequent load development on either of these Krieger barrels; but I'm just getting started. I've not yet made the investment in a borescope, so I have no practical means of visually determining if I'm inflicting harm or benefit. Does COW act as a mild polishing abrasive, or is there something evil going on?

With a new 6.5x47AI Bartlein on the way, I'd appreciate a reading from you experienced and wiser gents before I begin the same FF process on some new Lapua brass.

I've read much banter here on Accurate Shooter about the merits of COW vs. hard jam and fire (to each his own); but nothing specifically about the comparative physical effects on the chamber throat life.

Side note --- COW FF does allow me to load and shoot from my walk-out basement door during dreary winter months, plus, the birds, chipmunks and squirrls seem to like it for morning breakfast as well!

Thanks in advance,

Tooter

 

[alf]

I did a 22-250 Ackley this winter using 700X and butt wipe.

I did it in three sessions, cleaned after each, and monitored with my borescope, as I always wondered myself. I didn't see any negative effect. The barrel still gets warm, so I shot and loaded one at a time.

 

[tooter]

Alf,

This is good news!

I've been swabing the chamber and bore after every five shots to keep any debris from collecting, especially that fine cake ring that sometime forms between the clearance area from the end of the case neck and the end of the chamber neck.

I use TiteWad powder and small pieces torn off a cotton ball jammed into the neck to keep everything from falling out, and like yourself, shoot slow paying real close attention to barrel heat.

Thanks for the input,

Tooter

 

[TonyR]

I used the COW method to fire form and expand the necks of some new 6.5X284 Lapua brass to 284 Shehane. I was very pleased with the results. I only lost 2 cases out of 75 to split necks but it did save me a long trip to the range and a bunch of bullets and powder. I ended up using about 8 grains of Bulls-eye caped with a quarter sheet of toilet paper then COW then sealed it with bullet lube. The usual start low and work up advice applies. I started with something like 10% of my normal rifle powder charge and worked up carefully. These fast pistol powders can generate excessively high peak pressures. Also, read the label on the COW carefully. Some varieties have a lot of salt in them and I think that could do more damage to the barrel than anything else. I also ran a cleaning rod through the bore about every 10 rounds or so. The higher powder charges left less gunk on the barrel. It's hard to imagine how 8 grains of Bulls-eye could do as much damage to a barrel as 54 grains of IMR7828SSC and a 180 grain bullet.