keyholed bullets 2

[bigotto]

Here is a pic of the chamber cast and a loaded cartridge

http://s1080.photobucket.com/albums/j333/bigotto1/


http://<a href="http://s1080.photobucket.com/albums/j333/bigotto1/?action=view&amp;current=shortchamber.jpg" target="_blank"><img src="http://i1080.photobucket.com/albums/j333/bigotto1/shortchamber.jpg" border="0" alt="Photobucket"></a>

[303Guy]

It looks as though the boolit is quite loose in the throat. That's a lot of taper leaving a lot of jump before it reaches the leade. You might try actually slugging the throat to get a more accurate dimensional idea then getting a boolit that closely fits the throat. It is actually hard to see the throat shape from the cast but there is a hint of it.

A trick is to drop a boolit into the throat and measure its depth from base to chamber face then seeing how that relates to seating depth.

This the shape boolit I am using.
http://i388.photobucket.com/albums/oo327/303Guy/TAILLESSPATCH005.jpg

Ok, it is paper patched but the shape is what counts. Note how short the nose actually is. That's to maximise the bearing length.

Here it is without the patch.
http://i388.photobucket.com/albums/oo327/303Guy/205grPigGunMkXXI004.jpg

[Wayne Smith]

Chamber cast is a little rough. I'd suggest doing it agin, plugging the barrel above the throat. Heat the chamber/barrel with a hair dryer before casting and you will get a much smoother and accurate cast.

[10x]

Have you checked that the muzzle is square with the bore and that the crown is good?
I just acquired a savage 99 that keyholed. The barrel was shortened by a home gunsmith and he cut the muzzle off square. I trued up the muzzle and crown and keyholing stopped.

[Larry Gibson]

As mentioned on the other thread it appears to me that your assumption "So I was seating my brass into the rifling and basically extruding the lead bullet into the barrel" was correct.

Are your cases trimed to suggested length?

You could trim a couple cases back to where the throat taper begins and shoot those. That would tell you quickly whether it was a bad bullet or the case mouth in the thraot was sizing the bullets down.

Larry Gibson

[bigotto]

I have decided that I will rent a chamber reamer and make the repair myself. I know the pics are not clear but the rifling meats with the end of the cartridge area of the chamber with no throat at all. So even if I were to trim the brass back the bullet would be seated directly into the rifling of the barrel. Thank you all for your advise but the chamber is short and can be repaired with the correct reamer.

[ss40_70]

something isnt adding up to me here , before you go reaming on things take wayne's advice and do a good chamber cast first .. things just dont sound right to me , let me get this right .. you have a short cut chamber that has no throat , and .459-460 dia bullets ok all this in a trapdoor sprinfield grn mt barrel ... how did you get the action closed ? .. i kinda think it would go beyond a little tight to darn near having to beat it closed .. im not tryin to pick a fight or start an arguement but my gut says stop what your doing and take a very deep breath ... if im wrong feel free to remind me i'm an idiot

[303Guy]

That cast is not that bad.

http://i1080.photobucket.com/albums/j333/bigotto1/shortchamber.jpg

That boolit worries me. Do the fired cases have an obvious 'crimp' appearance of the mouth? I'm with ss40_70 when he says "something isn't adding up to me here".

Having another look, it seems there is no room for the crimp to open up. Is there a need for a crimp in a single shot rifle?

[ss40_70]

no sir theres no need for a crimp in a single shot , i was trying to get to sleep when something else cropped up in my mind , i'd like to see a pic of one of the fired cases i kinda think it will tell a big part of the tale here , im with .303 guy here i dont see any room for the crimp to open up and if things are as bigotto says i would kinda expect to see rifling marks on the case mouth as well ,.. and for the amount of time it takes i'd still do a second chamber cast and make sure of my measurments

[Tom Myers]

Here is a pic of the chamber cast and a loaded cartridge

http://i1080.photobucket.com/albums/j333/bigotto1/shortchamber.jpg



Bigoto

I do quite a lot of scaling of images when designing or imaging bullet designs.

I scaled out the cartridge and then used the scaling ratio to measure the chamber cast. It appears that your chamber has been cut to a depth of approximately 2.00 inches whereas a SAMMI SPEC 45-70 Govt chamber should be cut to a depth of 2.1099 inches.

You will need to either trim your cartridges back to where they will just chamber (approx 2.00 inches) or have the chamber reamed out to SAMMI specs (2.100 inches),

If you perform an impact impression of your chamber you can obtain a very accurate measurement on the depth of the chamber and the Neck-Step-Freebore-Leade-Groove-Bore dimensions.
If you are interested I can give step by step how-to directions on how to make an accurate chamber impact impression.

Hope this helps