Bore slugging question

[wvfarrier]

So, I went to slug the bore of my Winchester 1892 in 45 colt. I was using the Hornady 50 cal (.490) lead balls. However, once I got the ball started past the muzzle the ball essentially pushed down the barrel with almost no resistance. Ive never had that happen before and am a little perplexed. Thoughts?

[4t5]

Did the slug show it filled the grooves completely?

[wvfarrier]

The marks were pretty shallow

[wvfarrier]

Here is what I ended up with. I guess its not as bad as I thought.

[Sixgun]

Your measuring it wrong....you want to measure the groove which will be the higher point......turn the bullet the other way and get your caliper on the high point and stay away from the ends......should be .450-.454....

Yes, when you are first pushing the round ball in the muzzle you are actually "forming" it so there will be resistance and once it's formed it will usually slide down the rest of the way.......muzzles tend to be a tad tighter than the rest of the bore hence another reason for resistance followed by easiness.

I like to add a bit of grease to the round ball and slowly tap it with a brass or hard wooden dowel that's near groove diameter but not enough to hit the sides of the barrel.....slowly so it completely fills in the grooves.......

I personally like to shoot an oversized bullet into a pile of towels but if your not familiar with the process do it the way you just did it.....----006

[wvfarrier]

Good info. Thank you. The outer measure .451

[marlinman93]

I also check mine perpendicular to the grooves, not with the grooves as you are showing. But dial calipers also aren't very accurate, and I only use a micrometer to check them.
I slug my bores from each end, as once you've slugged past the tightest constriction it wont tell you what the largest part of the bore is. Normally the rifling process causes a barrel to be tighter at the muzzle, so slugging from the muzzle end wont tell you how large your groove diameter really is.
I slug in from the muzzle, and also from the chamber end. Then compare the two, and size my bullets to the larger of the two. On some guns this means disassembling the bolt to get it out of the way. But it needs to be done to get an accurate reading.

[Tycer]

Sometimes a fast tapered barrel will be tighter at the breech end as the hoop stress on the muzzle end expands the thinner metal.

[Nate Kiowa Jones]

Using a round ball you can get some wobble.
Here's how I like to slug a bore. I like to use a slug of soft lead that is at least 1 1/2 times long than the bore dia that's being slugged. This extra length assures that the slug doesn't wobble or try to turn in the bore as it's hammered through. This can be verified with short slugs. Measurements will vary depending on where you measure it. The longer slug yields more consistent results. Make sure the bore is clean lead free and lightly oiled, as in an oiled patch pushed through it.
You can drive the slug in from the muzzle if you use a leather or rubber mallet so as not to damage the crown. I like to drive it all the way through to feel any high spots or bulges. I like to use a brass or hardwood dowel that is close to bore size. A rod that is too small can deform the soft lead. Next if it's a levergun I use two wooden dowels just smaller than the bore and cut to the cartridge OAL. These are inserted into the chamber end and the action closed. Next the slug is re inserted in the muzzle end and driven to the wood dowel then bumped up so it's now tight. Now, open the action, remove the dowels and gently tap the slug on out. This will give you a really true picture of the bore just in front of the chamber or farther out depending on how many dowels are used.
To measure I like to use a zero-ed Starret micrometer. Most dial calipers aren’t accurate enough.