.44 Mag Cylinder Throat Dia.

[scruffy]

New to me, 629-6 .44 Magnum with 6.5" barrel and Power Port manufactured 2005. Gun has been fired very little prior to my purchase and I recently put 50 rounds of Winchester 240 gr. JSP .44 Magnum through it. Gun shot fine and did it's part when I did mine. Two issues:

1) Cylinder throat size looking for it to be .429" to .432". I measured all cylinders with digital inside calipers (not ball) and was getting .4275"- 4285" but not repeatable and varied with how I placed to caliper. I did mic the OD of the Winchester bullet just above the case mouth and it was a consistent .429". I put the bullet in the cylinder throat from the front (see pic below) and this is what it looks like. My concern is if this is causing high pressure in the chambers. Unfired cartridges drop right in, fire and extract easily with no issue. The fired cases are not bulged and spent primers are seated normally. Is this an issue or not?

2) Two adjacent cylinders have slightly slow timing. Only if I check by cocking very slowly with slight finger drag can I detect it. If I cock normally it in S/A or D/A the cylinder locks up fine. No endplay and B/C gap is an even .005" on all chambers. Ejection rod and yoke appear to be straight. Gunsmith looked at it and said he noticed some burrs on the extractor star that appeared to be from the factory and also commented the the gun appeared as new.

Gunsmith whose work backlog has him busy for the next month said he could hone the cylinder chambers and correct the timing for $150 if I brought it back in a few weeks. In the meantime, is there any reason I should not shoot the gun while waiting, particularly because of the tight cylinder throats. Thanks for any input or advice.

 

[steelslaver]

Probably not much pressure rise, because the soft lead bullet is very quickly and easily squeezed to the throat size when it is fired. But, accuracy probably suffers as you are then sending a .4275 bullet down a .429 groove dia barrel. 4DRreamer rental has cylinder throat reamers , a little light oil and brake cleaner and you can fix that part yourself.

Cylinder Throater Archives - 4D Reamer Rentals

I had a newer 44 mag cylinder with the odd end extractor arms and when I went to ream it to 45 colt discovered most of the throats were under. 429 some .428 and I used pin gauges to measure them.

It cracks me up when people are worried by the idea of running a 22lr finish reamer down a tight 22 cylinder because they believe that S&W has precision chambers. LOL

 

[6string]

A caliper, digital or dial, won't get you reliable measurements of your chamber throats. You need pin gauges of an adjustable ball gauge.
Your undersized throats won't help accuracy and will likely give you a bad leading problem.
Fortunately, you're actually in a great situation!!
You can have your cylinder throats reamed or lapped to the exact size you want!!
I know a guy in NC who specializes in this work. PM me if you like and I'd be happy to pass on his info and refer you to his extensive list of satisfied customers, most of whom are very particular handloaders.

 

[BLUEDOT37]

I measured all cylinders with digital inside calipers (not ball) and was getting .4275"- 4285" but not repeatable...
I did mic the OD of the Winchester bullet just above the case mouth and it was a consistent .429".
.
I put the bullet in the cylinder throat from the front (see pic below) and this is what it looks like.

Neither are the most accurate way to make those measurements.

That cartridge in the front of the cylinder looks like a handload?

You need to accurately know the diameter of the bullets before trying to determine the throat's diameter.

As mentioned, you need to use a set of pin gages to verify the throat diameters & as well as a micrometer to measure the diameter of any bullet that's not already seated in the case.

A digital caliper just won't cut it here.

.

 

[steelslaver]

Another method besides pin gauge is to drive a lead slug through each throat and measure them on several axis with good calipers. If an unloaded jacketed .429 bullet that has been verified as that dia needs more than thumb pressure to go through the throat it is to tight.

There have been numerous reports of tight throats in the .428 area on recent 44 cylinders. Earlier ones were known to run .430-.432