No more throat length worries

[charger 1]

$66 from Pacific tool and gauge will get you a throating reamer. I used to fuss and fart trying to get mold design and throats just perfect in my 458's. Now I'll order the mold whatever weight and contact area front of the crimp I like. Then load a dummy round and keep trying it till I've reamed the throat till it just fits. Cant miss.......I FIGURE

[kywoodwrkr]

Did the same thing for 30 cal.
Got one with removeable pilot.
Got standard 30 pilot and pilot for Swiss K-31.
Some folks with Contenders have used it for changing throats in some barrels with success.
FWIW
DaveP kywoodwrkr

[762cavalier]

How does it work. do you just open up the throat till it accepts whatever boolit you're trying to use? kywoodwrkr- what were your results with the .30 cal and what boolit molds were you using?

[charger 1]

How does it work. do you just open up the throat till it accepts whatever boolit you're trying to use? kywoodwrkr- what were your results with the .30 cal and what boolit molds were you using?

I can't comment on the other gentlemans 30 cal, but your concept is exactly right. If you find a boolit that your in love with, and you know it will fill all your requirements,ie bore dia,weight,length ,contact,etc. Except in my case my throat was .459 and very short. So I ordered the .460 reamer and will take it out to that diameter. Plus with a loaded dummy round (which I know is to long due to the contact area ahead of the crimp groove) I will cut a little out of throat length,then try round,and back and forth like that till I get the round in and just kissing the rifleing

[Bass Ackward]

I can't comment on the other gentlemans 30 cal, but your concept is exactly right. If you find a boolit that your in love with, and you know it will fill all your requirements,ie bore dia,weight,length ,contact,etc. Except in my case my throat was .459 and very short. So I ordered the .460 reamer and will take it out to that diameter. Plus with a loaded dummy round (which I know is to long due to the contact area ahead of the crimp groove) I will cut a little out of throat length,then try round,and back and forth like that till I get the round in and just kissing the rifleing


Charger,

Maybe this is going to be a little difficult to write or visualize, but unless you got a throater with less than a 2 degree angle, your throat is going to walk on out with you from your ideal if you cut it that way. For one you will lose the reamer marks, then since you can't size to .460, when the angle changes, you could pick up more length. Just so you know.

[charger 1]

Charger,

Maybe this is going to be a little difficult to write or visualize, but unless you got a throater with less than a 2 degree angle, your throat is going to walk on out with you from your ideal if you cut it that way. For one you will lose the reamer marks, then since you can't size to .460, when the angle changes, you could pick up more length. Just so you know.


Certainly difficult for me to understand
>2 degree,get it made straighter
>Throatis going to walk out?
>Lose reamer marks?
>can't size to .460?
>more throat length to accomodate bullet with longer contact was the idea

[Bass Ackward]

Charger,

Yea. I was worried about that. If you shoot cast like cast, minimal movement will likely be seen. If you want to shoot cast like jacketed, there will be "more throat wear" than jacketed. Virtually all wear comes from powder impact and hot gases. Lead will continue to polish these rough areas as the softer than jacketed bullet obturates under pressure to larger and larger dimensions, thus wearing the throat.

This may be wasted time / stress. After your ideal throat is cut, would you be negatively affected if your seating depth got .100 longer? If not, then no worries. But as the marks leave from the rotational cutting and the angle on the end of the rifling decreases from wear, you will have to seat out farther and maybe size larger to hit the lands. Even your throat diameter will open about .0015 as those marks on the ball seat are worn away. Just expect it.

If these dimensional changes will affect your "ideal throat", then short change your dummy cartridge length and let it wear in to the point you want it.

[charger 1]

http://i7.photobucket.com/albums/y259/Chargerdive/throat.jpg

This is what I meant by deepening throat. Bass are you saying that the powder will erode the throat? I would have to think that on a very shallow degree climb to bore size that errosion would be some kinda SSLLOOWW. Or do I dream

[Bass Ackward]

[QUOTE=charger 1;121473This is what I meant by deepening throat. Bass are you saying that the powder will erode the throat? I would have to think that on a very shallow degree climb to bore size that errosion would be some kinda SSLLOOWW. Or do I dream[/QUOTE]


Sure. Powder impact roughs up the throat. It's called erosion. And as little as 6 lead bullets will polish that back to smooth. As an example, I was cleaning up a revolver cone and using 600 grit on a wire nut to rough up the surface a few weeks back. Now even though 600 grit is very fine, the roughed up surface was visibly rougher than the polished shine of the lead bore. In as little as 6 shots, the roughed up finish in the cone could not be distinguished from the rest of the bore. Thats at 22,000 psi and 1100 fps using ACWW. Imagine the polishing force generated by pressure at say 2400 fps. Especially if you add more antimony.

It's just like sanding wood. Any grade of paper cuts fast until that surface takes on the best finish that that paper is capable of producing and then cutting slows dramatically. Lead quits polishing once the surface is smooth, but it will polish agressively until that surface is achieved. For this reason, I have seen faster lengthening of a throat with cast than with jacketed. But jacketed will correct dimensional problems farther down the bore when obturating pressure on the base no longer creates base expanding pressure. So barrel break in is best achieved with jacketed in my mind for this reason. Plus, the heat and friction of jacketed will harden rifling and make a stronger bore finish.

Understand throaters can be anywhere and all over the map. .5 degree is great. Up to 2 degrees is OK. Over that and you will see enough change to make a difference. Cut slow, clean often, and use what appears to be WAY TO MUCH oil.

And you can use that reamer over and over and over as long as the throat of what you want to cut has a ball seat not over .460 diameter. If the throat you are attempting to cut does, then it will leave a .... sort of ledge somewhere in that throat depending on the shape of the origional. And if you choke to fill the old ball seat, your bullet will encounter that ledge. Tapers will cut fine. Larger ball seats is where you will have the problem.

[kywoodwrkr]

762,
I haven't used the reamer on any of my K31s yet.
Did manage to PO some of the Swiss purists who think the rifle left the arsenal perfect and that its a sacrilege to modify anything about the rifle. Than goodness I paid for the rifles I have so I can do what I want to them!:-?
I've loaned it to some folks who had contenders which as I understand it have throats all over the place.
Only feed back I can remember is one 30-30 barrel where the owner said it did a good job for him.
I'm currently waiting for a retirement date so I can start playing with my assembled toys.
FWIW
DaveP kywoodwrkr

[leftiye]

BA In my mind, the real question is, "Can it be done any other way?" Is this not just living in the real world? Don't we first ream a chamber and then shoot the gun until either the barrel wears out, or we rechamber to a longer cartridge or change the barrel itself. As the barrel wears, the throat elongates, and opens up. Oh well,

[charger 1]

Plus, the heat and friction of jacketed will harden rifling and make a stronger bore finish.


I'm not sure that I see enough heat being produced to get the parent metal hot enough, nor enough metal quench to cool it fast enough. Is there enough force perpendicular to the bore for work hardening of any amount??????

[Bass Ackward]

BA In my mind, the real question is, "Can it be done any other way?" Is this not just living in the real world? Don't we first ream a chamber and then shoot the gun until either the barrel wears out, or we rechamber to a longer cartridge or change the barrel itself. As the barrel wears, the throat elongates, and opens up. Oh well,


Leftie,

Not with cast. You can have your throat elongate to the point that the barrel is basically useless and still have the origional tool marks in the rest of the bore. Most cast wear (under high pressure only) occurs in the throat area as far as the powder roughs up and the pressure obturates. So the wear eventually stabilizes. It's just that you never know just where that point is going to be.

Another reason choking works. When you fill what's space is there, you never have to keep enlarging to stay with the wear. But if you go back and slug every so often, or if you continue to seat out to the lands, then you see it.


Charger,

The hardening is surface or flash. It remains unless the lead polishes this away. Which is why I alternate bullet materials in my guns so that this is always present. It does seem to slow the wear, but in the end, there is no free lunch. You either shoot cast with fast powders like cast at cast pressure and velocities .... or chase the throat.

[felix]

Best to have a long neck case, seat the boolit to the bottom of the neck, and now throat the gun for that overall length. You can now shoot the gun for 10K plus rounds as hot as you like, moving the boolit ever so slightly out of the case every 100 rounds or so. BA's attitude of switching between condoms and cast every so often will reinforce your thought of making the barrel the best it can be. ... felix

[charger 1]

Best to have a long neck case, seat the boolit to the bottom of the neck, and now throat the gun for that overall length. You can now shoot the gun for 10K plus rounds as hot as you like, moving the boolit ever so slightly out of the case every 100 rounds or so. BA's attitude of switching between condoms and cast every so often will reinforce your thought of making the barrel the best it can be. ... felix

Every 100 rounds the throats gonna move noticeably? Then I say the throat was way to steep from the get go.And that rather than using large quantities of slow burn powder,rocket fuel has been used. I dare say nobodies got things crankin outta nothin as crazy as I got em crankin outta that lott. And I got way more rounds than that threw it and still as tight as a nuns woogy in a sand storm

[felix]

I just said 100 rounds for lack of any other number for real. I changed my seating stem for the BR gun every 500 rounds using the same boolit. Doubt I could notice how much to change in less than that. Like you say, it depends on angles, how hot is hot, etc. ... felix

[Char-Gar]

Throating the barrel for one specific bullet might help the performance of that bullet a mite. However, unless you are willing to dedicate that rifle to that bullet for all time and everywere, it might prove to be less than a sterling idea

Once you remove that rifling, you can't put it back. I consider the downside of throating greater than the upside. yes, I speak from experience and not theory.

[leftiye]

Charger1 In high power rifles the flame temp. is around 4000 degrees at chamber pressures. This is about twice the melting temp of steel. This and the nitrogen in the powder (reads something like explosives= nitrates) melts and nitrides thesurface of the leade and throat of the barrel , making the surface brittle, and microscopic pieces come loose from the parent metal as it flexes under pressure. Obviously pistol, and cast boolit pressures are lower. but a match burns at 1400 degrees, and it's not hard to imagine these lower pressure loads having enough heat to do a proportionately lessened version or that aforementioned nitriding.