Problem with Canik TP9 SFX and cast.

[marek313]

After Doug put his magic touch I can now chamber Lee 356-125-2R @ .357-1.120 which i wasnt able to do before. With 4.2 gr of HP38 this gun finally shoots lead as well as FMJs. I'm not a bullseye shooters but i was all over paper before and now I'm putting fist size groups at 7yrds and can pretty consistently shoot 8" plate at 20yards. I miss but its because of me this time. I can tell gun shoots great now. Thank you again Doug.

On the other hand I did order Lee 356-120-TC which drops undersized for me at around .355-.356 and even after PC sized to .357 still didnt shoot as well as 125-2R which I prefer. Bottom line is if your gun doesnt have a proper throat it will never shoot lead accurately. Stop chasing different molds and have Doug throat ream your barrel. Fixed it for me in this Canik.

[Landshark9025]

Ok, Marek and Doug, help me out here. What advantage does having the throat cut vs seating the bullet .020 deeper? I'm able to seat both of the bullets I referenced earlier deep enough to pass the plunk test and still have what I would consider the leading edge of the driving band outside of the case mouth.

Now, if the 356-125-2R has a profile that won't allow that because of the blunt nose, that may be fine, but I wouldn't think it's any more blunt than this one: MP Mold 9mm Round Nose 147-grain Competition

I'm truly interested.

[DougGuy]

If you look at a SAAMI drawing for a 9mm Luger chamber, it shows freebore on a taper between the case mouth and the leade ins to the rifling. This is commonly called the throat. Manufacturers more times than not don't bother with reaming a barrel to have sufficient freebore as it is just another costly machine operation to them. If they put just enough angle on the rifling to make room to chamber a factory produced round, that's all they feel they need to provide the consumer. They take NO consideration for anyone using handloads or reloaded ammo.

Throating a barrel with freebore allows for a smooth section of the bore to hold the boolit in perfect alignment with the centerline of the bore as it exits the expanded case mouth and transitions into the rifling. The freebore serves not only as an area of relief that is machined away in order to chamber a boolit, it also serves as an alignment tool that guides the boolit and holds it square and on center with the bore as it travels into the rifling.

As an added benefit, a gun with a properly throated barrel can use ammo seated out to the length that the magazine will accept, which often greatly improves feeding because the longer the cartridge, the less likely it will experience the common "3 point jam" which creates a stoppage and a failure to feed.

Furthermore, I have not found a point at which the length of the freebore -OR- the angle of the freebore, becomes detrimental to accuracy. It doesn't seem to have a negative effect to have caliber length or a longer than caliber diameter section of freebore in the throat.

If you look at the cylinder of a Ruger 45 ACP revolver, you will see that it has easily 2.5x the caliber diameter of smooth cylinder throat (this is also freebore) in front of the chamber and they shoot plenty accurately when honed to .0005" greater than boolit diameter.

If you look down the bore of a Mossberg 12ga slug barrel, you will notice that the barrel is smoothbore inside for roughly 16" and is only rifled the last 8" or so of the length of the barrel. 16" of freebore before the slug or wadding engages rifling? Yep. Is this accurate? Yep. Mine will cloverleaf a playing card at 100yds with $3 a box Walmart slugs.

[marek313]

Ok, Marek and Doug, help me out here. What advantage does having the throat cut vs seating the bullet .020 deeper? I'm able to seat both of the bullets I referenced earlier deep enough to pass the plunk test and still have what I would consider the leading edge of the driving band outside of the case mouth.

Now, if the 356-125-2R has a profile that won't allow that because of the blunt nose, that may be fine, but I wouldn't think it's any more blunt than this one: MP Mold 9mm Round Nose 147-grain Competition

I'm truly interested.

For one thing your spiking pressure a lot higher by doing that. If your barrel doesnt have properly cut throat and your seating deep in order to pass plunk test your still seating that boolet right against rifling when chambered. That throat helps reduce pressure and allow bullet to align before it hits rifling. That also helps with accuracy from my understanding.

In my case I couldnt even chamber .357 at all no matter how deep bullet was seated. There was no doubt in my mind after shooting .356 that It needed throat reaming. No accuracy at all at .356.

More often i think this affects inexpensive guns as manufacturers like to save a buck any way they can as Doug pointed out. I dont have this problem with Sig, FNH or CZ but Canik definitely needed help in that department.

[whisler]

Had to have Doug sweeten up my CZ-75 so they can have a problem too.

[joebaja]

That is fantastic to hear marek. Of course seating deeper like I do with my TP9SF means backing off the powder charge to take some of the spike out of the pressure. I know Doug does good work based on what he has done for me before. Looks like I should send him my barrel. The only hard part is finding a few days when I can have my pistol down. I shoot USPSA or steel most weekends. Maybe it is time to give the K2-45 a workout in L10.