Fouled base pin

[mhblaw]

At the range yesterday with my Bowen OMBH 25-20. After 50 rounds I could hardly turn the cylinder to load/eject. Got home and could only remove the base pin with difficulty. All cruded up with powder fouling. Have not had this problem with other Rugers or other calibers. Cleaned the base pin and all is fine. Thoughts?

 

[WIL TERRY]

THINK ABOUT THIS...That basepin in that custom 25-20 pistol must be to damned small to allow all that crap to blow back along the basepin and into the basepin hole in THAT custom cylinder...
I always ALWAYS use grease on the basepin and in the cylinders basepin hole, ALWAYS !!
And so it goes...

 

[z1r]

Often the opposite is true. Cylinder pins fitted tightly may increase accuracy but are also more prone to locking up if subjected to debris.

 

[JLarsson]

And they may NOT increase accuracy as they do not allow for the bullet to "self-align" to the barrel and correct minor misalignment between cylinder and barrel.

 

[Chuck 100 yd]

And they may NOT increase accuracy as they do not allow for the bullet to "self-align" to the barrel and correct minor misalignment between cylinder and bxarrel.

I doubt that a cylinder is going to self align with the forcing cone when the bullet passes through the cylinder gap at a speed of several thousand + inches per second. A 40 gr. Bullet would have to move a cylinder that weighs several ounces in a micro second to accomplish that. It's a cute theory but thats about all.

A very close fitting base pin with a barrier of lube will do a better job of keeping the fouling from tying up the cylinder. Any misalignment of chamber to barrel (there should be very little in a properly fitted revolver) is the reason for a forcing cone in the first place.

 

[Hondo44]

And they may NOT increase accuracy as they do not allow for the bullet to "self-align" to the barrel and correct minor misalignment between cylinder and bxarrel.

I doubt that a cylinder is going to self align with the forcing cone when the bullet passes through the cylinder gap at a speed of several thousand + inches per second. A 40 gr. Bullet would have to move a cylinder that weighs several ounces in a micro second to accomplish that. It's a cute theory but thats about all.

A very close fitting base pin with a barrier of lube will do a better job of keeping the fouling from tying up the cylinder. Any misalignment of chamber to barrel (there should be very little in a properly fitted revolver) is the reason for a forcing cone in the first place.

And what do you think does the correcting of the "misalignment of chamber to barrel" by using "the reason for the forcing cone in the first place"?? Yep, what JLarsson posted.

 

[Chuck 100 yd]

We will just have to agree to dissagree on this one.
The bullet , being the soft fall guy,will take a beating every time if there is any missalignment. Unless the base pin is super sloppy in the cylinder there is less than a thousandth or so movement possible anyway.

If the cylinder could self align, why would gun builders go to all the trouble to line bore cylinders with the bore!? They could just run a loose base pin and let the cylinder take care of alignment by it's self.

 

[Hondo44]

Chuck,

Since the forcing cone principle of bullet/chamber alignment, hence the name "forcing" cone, is such an established fact we don't have to agree to disagree. We can politely discuss it, though.

You're right, the cylinder chamber cannot and does not "self align", because only the bullet can do that. The only thing moving when the cartridge is fired is the bullet, there's nothing else going down the bore. So when the bullet hits the forcing cone and makes a slight movement to align to the bore with it's base still tightly fitted in the chamber throat, that chamber is going to move with it, period. And that's by design.

Guns didn't always have forcing cones in the old days of hand craftsmanship. S&W for example didn't introduce them until 1920. Line boring is a preferred and very precision method for custom revolvers. But prohibitively expensive for production revolvers. So manufacturers have successfully dealt with slight cyl/bore misalignment by the use of the forcing cone principle.

Therefore revolvers are made with a certain amount of tolerance (play) in cylinder fitting including base pin tolerances, and forcing cones. No the tolerance is not much but the cyl must have some play for the bullet and forcing cone to do their job of aligning the chamber to the bore. That's also why when oversize or extra tight cyl pins are used in an otherwise mass produced revolver, very often accuracy falls off. Because the ability of the bullet to align the chamber and itself with the bore is inhibited.

Another benefit of parts tolerances is exactly the issue of the OPs complaint. The precision parts fitting of the OP's custom built Bowen revolver is superior but from a practical standpoint can have the downside he reports. They are more subject to fouling. But a small price to pay for a super accurate revolver; just takes a little more care than a mass produced product.

 

[Chuck 100 yd]

I think we are just picking nits (sp.?). Guys are pleased to find a revolver that
" locks up like a bank vault "with little to no play at all. The self alignment theory,
if correct , suggests one should look for guns that rattle a little, yes/no?
I still believe the bullet will upset/ bend / deform and find it's way out the barrel
and of course that is not conducive to good accuracy.

Have you seen the pictures of bullets Dr. Mann fired from a revolver with no barrel at all screwed into the frame, cylinder only? They expanded at the base and looked like a Badmitten birdie (sp?).
I wish there was a real study done on this subject with hi-speed photos. That would be very interesting for sure. Every gun nut has his own theory's on just what really goes on inside of his favorite six shooter. Until then I think I will just let it rest.
It does make for an interesting discussion though.

mhblaw , sorry for the thread drift. I will try to stay on subject in the future , as hard to do as it is sometimes.

 

[Hondo44]

You're right, guys are always looking for "tight" revolvers but it's misplaced priority for all the reasons above. They often are not the most accurate guns, again for all the reasons above, much to their chagrin. One tight part or tight parts w/o precision fit, like just a tight cyl pin or cylinder, does not equate to something good. Again unless custom built and designed that way.

No don't look for a gun that rattles, that's the opposite extreme, equally bad, and another wrong approach.

There are high-speed stop action photo studies but I couldn't find one right off. Google can be helpful.

Another truism you bring up: "Every gun nut has his own theor[ie]s on just what really goes on inside of his favorite six shooter." Forums can be good places to validate and invalidate those theories, but mostly the writings of the pros. I admittedly am not one so I read the writings of the pros and I keep my opinions to myself or don't form any.

 

[mhblaw]

Thanks for the interesting comments/observations. The gun in question is reasonably accurate and I am going to take Wil Terry's suggestion of greasing up the base pin, a Belt Mountain by the way.

 

[98Redline]

I have found the same thing, even on my double action guns, grease on the base pin or the neck of the crane keeps the crud out of the bearing surface and allows the gun to shoot longer without starting to get bound up.

 

[PriseDeFer]

Still got your stock base pin? Maybe that can get you passed the 50 round barrier.