12 gauge; What accurate mold?

[gvanzeggelaar]

Can I pour molten lead into the muzzle of my shotgun with a stop about 2" in and use that as a reference for bore diameter?

[gvanzeggelaar]

Anyone

[GT27]

I wouldn't, you have no lubrication other than the lead on the steel! Find a lead ball(as close to pure lead as you can find) just big enough to expand in the bore,coat the bore with a good lubricant(Kroil),(CLP).I use a brass sectioned rod just below the bore size,and pound it through the bore being careful with the crown as not to damage anything,has worked for me for 35 years now! Smoothbore, or is it rifled???? A lot of folks might disagree but on a smoothbore I would find a brass shell casing,cut it off,fit it on a strong wooden sectioned dowel,lube the bore and then go at it!Rifling in a barrel makes a lot of difference in resistance! GT27

[longbow]

Short answer is yes but it will shrink several thou as it cools. Cerrosafe would be better if you are going to cast.

It would be easier to use an inside mic or calipers if the barrel is cylinder bore.

If the barrel is choked then you will want both maximum bore diameter and minimum choke diameter so will have to check muzzle and mid bore diameters.

An oversize ball or slug would be better (I think anyway). Push it in from the breech and run it through the barrel (with a film of lubrication) then you will feel any constrictions and it will measure to exactly what the bore diameter is.

Longbow

[GBertolet]

You didn't mention if your shotgun was a smoothbore or rifled barrel, but I would still suggest you not do what you proposed. I guess it wouldn't hurt anything, but rather I would prefer driving a slug through the bore and measuring it instead. If you have no suitable slugs on hand, I would suggest dissecting a factory forster type slug shell, and drive that slug through the barrel with a wooden dowel, and measure it. Be sure to lube the slug with some oil before you drive it through. I have a dissected Remington slugger slug on my bench and it measures .730 at the base, which should work well with any barrel.

[gvanzeggelaar]

Ok thanks guys. I ordered some Cerosafe and will do it that way. Btw my shotgun is a savage bolt action, so it is rifled.

[Harmon_Greer]

its big enough bore you can measure across the lands and in the grooves with a set of calipers. the only time this cannot work is if you have a odd number of lands and grooves.

its not that difficult.

[Shooter6br]

Lyman 12 ga Sabot is a great projectile

[gvanzeggelaar]

So I slugged the bore with cerrosafe. After an hour the slug came out at 0.7325. Would a 0.734 mold diameter be a good choice?

[excess650]

yeah, .002" over should seal up

[longbow]

What slug mould are you thinking about?

If a full bore solid slug I am thinking groove diameter is good. You will have wads under to seal and much over groove diameter may result in high bore friction and raise pressures.

Just my opinion.

The mould maker may be able to advise on best fit if you are getting a custom mould.

Longbow

[gvanzeggelaar]

I am getting a slug by accurate molds

The 770gr one

[longbow]

Unless some can advise as to what they have and works (which I can't) then I suggest asking Tom what he recommends for fit to groove.

[white eagle]

Tom and I made the mold you are talking about
I went .001-.0015 over I have a heavy rifled barrel
ask Tom is good advice