S&W 629 - 44 rem magnum......is this possible?

[mozeppa]

when it comes to cast boolits, fit is king....right?

so today i cast cerro-bend into 6 hand guns....wasn't too surprised at the outcome.

.380---------mic'd out at .3565
9mm--------mic'd out at .357
.38/357-----mic'd out at .3585
.45----------mic'd out at .453
.45 colt-----mic'd out at .453

BUT

The S&W 44 rem magnum it mic'd out at .4365 from the beginning of the lands and grooves AND,
3/4" beyond the start of the lands and grooves!

is this possible?/ normal?

thought these were to be 430 +/- .001
measured several times both ways.

does the barrel get narrower further down?

check out the pix!

[geargnasher]

S&W has a funny way of doing things. Mine measures about the same the way you did it, and I believe that is a product of the grooves being curved on a much longer radius than their radius length would dictate. IOW the bottom of the grooves are almost flat, and the center of the grooves tend to come out right on spec when measured in a vee block compared to catching the corners of the slug with a mic. The corners are deeper than the middle of the groove. I would be a lot more interested in the cylinder throat diameter and consistency than the barrel at this point.

Gear

[leftiye]

Cerro bend is only the true size of the thing cast about 1/2 half hour after casting. I may have the exact time wrong, but it expands after that - eventually getting to be several thous oversize. Cerro Safe is somewhat better (doesn't expand as much, but still ends up oversize. For most things it is good enough, but you should check with slugging the bore to be exact. And don't use anything but pure lead. Alloy slugs tend to be oversize.

[44man]

I have never been able to get a good measurement with Cerro-Safe no matter the time. Only thing I use it for now is to get a visual of a chamber.
A pure slug is far more accurate.

[Tatume]

According to the Brownells:

Cerrosafe shrinks during the first 30 minutes of cooling and then at the end of an hour, is EXACTLY chamber size. At the end of 200 hours it will have expanded approximately .0025".

Cerrobend (now called "CS Alloys Bend 158) was never intended for chamber casting. According to the manufacturer:

It can be used to make filler material for tube bending (specifically tubes up to 1-3/4"), drill jig bushings, internal and external support of delicate machining components, cores for spinning, filament wound mandrel, for fiberglass lamination; embossing and stamping dies.

[kevmc]

I'd slug the barrel and also the cyl. throats with pure lead slug (.440 muzzleloader ball!) , then see if the barrel slug will fit cyl throats.
If you start the slug at the muzzle, you'll feel if it gets loose at the other end of the barrel.
The cyl. throat slug will be easy to measure, and u can compare the barrel slug to the throats.

[Larry Gibson]

The S&W obviously has a 5 land & groove barrel. The method of measuring you are using is incorrect which is why the measurements seems large. A V anvil micrometer is needed for precise measurement of odd numbered land and groove slugs. Or you can wrap a strip of .004 - .006 shim stock tightly around the slug, measure that diameter and then subtract twice the thickness of the shim for very close to the actual groove diameter which is close enough for what is needed to figure "fit" with cast bullets.

Larry Gibson

[frnkeore]

Measuring a 5 groove barrel with a regular mic can only result in a smaller measurement than actual size. It can result in actual size if the lands and grooves are the same width and the grooves have sharp conners.

The way I do it is to use a gage pin for the bore diameter and a blade mic to measure the height of one groove (or all). Double that measurement and then add the pin gage size.

Frank

[John Allen]

The S&W obviously has a 5 land & groove barrel. The method of measuring you are using is incorrect which is why the measurements seems large. A V anvil micrometer is needed for precise measurement of odd numbered land and groove slugs. Or you can wrap a strip of .004 - .006 shim stock tightly around the slug, measure that diameter and then subtract twice the thickness of the shim for very close to the actual groove diameter which is close enough for what is needed to figure "fit" with cast bullets.

Larry Gibson

Larry,I never thought about doing it this way I am going to try this on a couple of odd balls I have.

[Larry Gibson]

Just pinch the shim tight on one side of the slug with the thumb and trigger finger of one hand and mic with the other hand. With smaller caliber slugs I've clamp and held the shim with Vice-Grips. A shim (4" x 1/2") of aluminum pop/beer can works fine.

Larry Gibson

[geargnasher]

Measuring a 5 groove barrel with a regular mic can only result in a smaller measurement than actual size. It can result in actual size if the lands and grooves are the same width and the grooves have sharp conners.

The way I do it is to use a gage pin for the bore diameter and a blade mic to measure the height of one groove (or all). Double that measurement and then add the pin gage size.

Frank

Most of the .357 Magnum Ruger and Smith revolvers have pretty close to equal-width grooves and I have had no issues measuring accurately with a micrometer across the corners of the slug per the op's illustration. One Smith .38 had square-bottom grooves and was overly large across the corners, and two examples of Model 29s both have squarish grooves. The mean minimum is about .430" for both, but the maximum, as one would measure by drawing a circle around the largest diameter of the slug, was more like what the op was getting. The bottom of the grooves are not always cut on a radius equal to half the groove diameter.

Gear