Forcing cone question. Updated with pics.

[Sailormilan2]

Does an oversized barrel throat cause accuracy problems?
I have a 6" 629 that I have never been impressed with the accuracy of. Recently I discovered that while I've been sizing my cast bullets to .430, the cylinder throats measure .431/.432".
I have been considering changing the barrel to a 4", and just got a brand new barrel and all the tools to do the change. Just to check things out, I put a Brownells .429 18* throat plug in the 6" barrel, and it drops in about 3/32" - 1/8". If I do the same to the brand new 4" barrel, it drops in even more. But I realize that's because it will need to be cut to the proper length to set the cylinder gap. But it looks that it is also oversized.
If I insert a Lyman SWC sized .430" into the throats of both, the bullet goes in up to the grease groove.
It appears that if I want to get a tighter cut throat I'm going to have to set both both barrels back at least 1 turn, possibly 2.
So, the question is, how much, If any, does an over sized throat contribute to inaccuracies?



New, unfired replacement barrel.

 

[StakeOut]

It depends on how large the oversize cylinder throats are and the size/type of bullets fired.

Some wners of 45cal Model 25s with .454" throats state jacketed .452" bullets fire more accurately than hard cast lead.

If you have .431" throats cast or buy .431 bullets

Oregon Trail Laser-Cast Bullets 44 Cal (431 Diameter) 240 Grain Lead

I use 240gr .430" bullets in all my 44 caliber revolvers with excellent results.
.44 240gr, 500 ct. box, hard cast lead bullet, Summers Enterprises LLC

 

[Protocall_Design]

Apparently you are referring to the forcing cone. It's been my experience that the exact diameter is not as important as it being concentric to the bore, fairly smooth and round. Often times a factory forcing cone is less than desirable. In terms of accuracy, the factory muzzle crown is often off center or otherwise poorly done. The rifling is usually fine. If you create a quality forcing cone and muzzle crown, that is usually as good as that particular barrel will shoot. This is assuming that all other factors such as bullet size, cylinder to barrel alignment and other mechanics are also correct.

 

[Sailormilan2]

Toolguy, you are correct. I am referring to the "forcing cone". My bad, I had a brain freeze when typing and couldn't think of the correct term.
I just checked and the entire front driving band of a .452 SWC KT bullet will drop into the forcing cone. I didn't know if that was considered normal or not.
I did notice that the forcing cones are very rough, but am hesitant to try to clean them up and make the forcing cone even bigger.

 

[StakeOut]

I just checked and the entire front driving band of a .452 SWC KT bullet will drop into the forcing cone.

Now I'm confused since post number one is about a Model 29 and 44 caliber bullets.

 

[Protocall_Design]

Different bullet profiles will drop in to different depths. That doesn't really matter much. You can get by with a rough forcing cone shooting jacketed bullets, but the roughness may scrape some lead off. I would do the absolute minimum to smooth off the worst of it and call it good.

 

[mike campbell]

I have a 6" 629 that I have never been impressed with the accuracy of.

And what would that be?

Rhetorically....what precision are you capable of?

I'd say, if you can only accomplish groups of about double what you can routinely do with your another favorite gun/ammo combo, then you may have an accuracy issue with this gun.
Generally speaking, that 6" 29 should equal whatever you can do with another combo.

IME, the vast majority of "accuracy" issues lie with the shooter.
Before I dug into the minutiae of bullet diameters, chamber throats and barrel swaps, I'd want to be sure this particular gun is not up to my established standards.

 

[Sailormilan2]

Now I'm confused since post number one is about a Model 29 and 44 caliber bullets.

It is about a 629 and 44 caliber bullets. However my last post was about me using a .452 SWC bullet to see how far it would go into the .44 forcing cone. What I was trying to show, if poorly, that the forcing cone is loose enough (large enough) that the entire front driving band of a .452 sized bullet can drop into the forcing cone.

 

[Sailormilan2]

Original post is updated with pics.

 

[Protocall_Design]

Normally, an oversize forcing cone doesn't affect accuracy. There are limits, though. The first thing I would do is get or make bullets that fit the throats of the cylinder. The throat is the part between the cartridge and the barrel. If the bullets are a good fit to the throat, you will usually have good accuracy. This is assuming the bullets don't lead the barrel, usually due to wrong bullet lube. If the barrel is leading, you will have no accuracy.