Measuring the throat

[fatelvis]

Do you make chamber castings to measure the actual throat and lead of your rifles? If not, what is the best way to do it? Thanks-

[montana_charlie]

In my opinion, that is the most important part of the information provided by a chamber cast.
CM

[243winxb]

Cerrosafe Chamber Casting Alloy http://www.midwayusa.com/viewProduct/?productNumber=462291

[Eutectic]

Do you make chamber castings to measure the actual throat and lead of your rifles? If not, what is the best way to do it? Thanks-

You could...... I would want to know if chamber cast material had any expansion/shrinkage upon solidification though...

I use either small hole gauges or telescoping gauges. Sometimes i will "push" a pure lead ball (oversize) if throat is both small and deep. I have used precision tools so long now I'm confident measuring to 10,000ths. using my technique.

Eutectic

[StarMetal]

To tell you the truth I don't think we have to get down to the tenth of thousandths of an inch. I doubt that would have any effect on accuracy one iota.

Another material that doesn't shrink when it cools, but rather expands, is sulfur. It would be somewhat little difficult to push out as it's rather brittle.

Joe

[fredj338]

In a rifle or semiauto, chamber cast. In a revolver, pin gages.

[badgeredd]

Another alternative (prefered by 45 2.1) is a pounded slug. One fills a fired case with a hard lead alloy leaving just a little of the neck empty, and then drives a soft lead slug into the lead/case/throad area. Using a brass rod of near bore dimensions if the best driving road. There are other ways to get the same pounded slug, but this is the way that worked best for me. Lube the bore and outside of the case and use a heavy hammer to pound the slug into shape. there is no shrinkage doing it this way.

Edd

[captaint]

I've been using small hole gages. Along with a decent set of mic's, they work well. Only for revolver throats though. Might be a good trick to feel your way into a rifle throat and get that right.... enjoy Mike

[JeffinNZ]

I use sulphur (sulfur) and a touch of graphite powder with in. Gently (and I mean GENTLY) melt the sulphur in a WELL ventilated area and pour into the chamber after plugging the barrel with a piece of cleaning patch or such. The sulphur sets in a minute or less. Push out with a cleaning rod and measure immediate prior to shrinkage.

You can buy sulphur at your gardening/hardware store for next to nothing.

[geargnasher]

Another alternative (prefered by 45 2.1) is a pounded slug. One fills a fired case with a hard lead alloy leaving just a little of the neck empty, and then drives a soft lead slug into the lead/case/throad area. Using a brass rod of near bore dimensions if the best driving road. There are other ways to get the same pounded slug, but this is the way that worked best for me. Lube the bore and outside of the case and use a heavy hammer to pound the slug into shape. there is no shrinkage doing it this way.

Edd

I've used sulfur and cerrosafe, both a royal pita and I was never convinced of the accuracy.

Then I tried the impact slug method recently and THAT is the way to go. Safe, convenient, accurate, inexpensive.

I did exactly what you mentioned, based upon an older thread where 45 2.1 gives the instructions in detail: Hard alloy in the fired case up to the base of the neck, then PURE soft lead boolit. Ten or so smart raps to a brass rod and voila, perfect chamber neck and throat impression, even the lube grooves on the slug completely disappeared!

Gear

[Eutectic]

I've been using small hole gages. Along with a decent set of mic's, they work well. Only for revolver throats though. Might be a good trick to feel your way into a rifle throat and get that right.... enjoy Mike

I prefer this tool & die approach with small hole gauges as well. A lot of my rifle throat work is on single shots where you can get in closer. (yes, I usually don't like what I find and change them) I use colleted extensions if need be. Something like a .375 H&H bolt gun is a challenge! Like my other post states I may tap a .40 caliber pure lead ball into a .375 to a measured length and mic it for a throat diameter. I have used longer pure lead slugs as already mentioned in this thread as well and this is probably the best for throat configuration check when diameter, length, any taper dimensions are all needed... Chamber neck length as well. Some of these lengths are quite generous! If I'm going to cut one of my long encapsulating throats for my boolit there is a good change I'll slug the shoulder, neck, throat all with soft lead first before I remove metal.

The throat configuration is the heart of accuracy; I've proven it many times in many calibers. And yes, I go to four figures after the decimal most times. I don't have doubt.... I've tested and tested throat configuration to find what works! Some think the .22 Hornet isn't quite as accurate as some of the rimless .22's. Try one with a good throat!. Of course those long gentle case tapers march to the beat of their own drum too.... Another story for another time!

Eutectic

[StarMetal]

I've used sulfur and cerrosafe, both a royal pita and I was never convinced of the accuracy.

Then I tried the impact slug method recently and THAT is the way to go. Safe, convenient, accurate, inexpensive.

I did exactly what you mentioned, based upon an older thread where 45 2.1 gives the instructions in detail: Hard alloy in the fired case up to the base of the neck, then PURE soft lead boolit. Ten or so smart raps to a brass rod and voila, perfect chamber neck and throat impression, even the lube grooves on the slug completely disappeared!

Gear

I make a small steel rod to fit inside the case leaving just enough room for my pure lead slug. It's more solid then the harder alloy and don't waste the alloy either. Did he mention to just put a light, very light, very light coat of oil on the lead slug?

Joe

[357maximum]

Chalk another vote up for the pounded slug method. Fast and easy...and it works. I bought several brass rods from the hobby shop just for this application.

[mpmarty]

Melted sulfer with a wire core works fine.