I do, and there are makeshift methods. And yes, the reamer could be wrong somehow. - dan
Case separation on first firing
- Thread starter propliner
- Start date
I do, and there are makeshift methods. And yes, the reamer could be wrong somehow. - dan
- Location
- Western Manitoba
Materials to cast a chamber? Some years ago I added a pound bar of "Cerrosafe" to an order from Brownells - I have used that over and over, for various projects. Just follow the directions that come with it. I think Rusty Wood in Canada stocks it, among others. I also read of people using sulphur, or candle wax - all have their limitations and problems to use, but eventually one can get a casting done. I like Cerrosafe because it shrinks when it hardens - so can get it out if you have no mechanical locks, then it starts to swell - as per the instructions, it is back to the casting chamber dimensions, exactly, an hour after it goes solid from liquid - a day or two later it is larger than what you casted - so, an hour after casting, is a "correct" time to measure it, to get accurate numbers.
Go here - Post #28 for picture of a chamber cast that I did - to find out where the end of that chamber neck area was, in that chamber -
https://www.canadiangunnutz.com/forum/showthread.php/2166654-9-3x57-sloppy-chamber?highlight=9.3x57
It also showed me the relationship between the cast bullets that I intended to use, when they hit the rifling - compared to the brass cases that I had formed.
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Chamber cast?????
People really need to start thinking out of the box.
As stated, most people aren't set up with "accepted" chamber casting materials, there are more options than Cerrosafe.
If you happen to have a one off issue, such as the OP, go and pick up a slab of plastercine from the Dollar Store, then go back home, oil up the chamber really well, then warm up the plastercene and force it into the chamber so that it's proud and close the bolt on it. Put it in a cold or cool place (freezer?) and open the bolt after letting it cool off for an hour or so. If you're lucky, the casting will come out with the bolt. If not, give it a nudge with a cleaning rod.
Measure or compare the casting against a factory cartridge. You can't stop for a smoke or whatever between extraction and measuring You've got about ten minutes before the plastercine warms up and becomes to soft.
The other cheap option, which I don't really like, is to oil up the chamber, plug the throat and fill with plaster of paris and let harden
I saw one fellow that oiled the chamber and filled the chamber with calking compound and left it overnight to harden. Worked well enough to get a measurement from.
People really need to start thinking out of the box.
As stated, most people aren't set up with "accepted" chamber casting materials, there are more options than Cerrosafe.
If you happen to have a one off issue, such as the OP, go and pick up a slab of plastercine from the Dollar Store, then go back home, oil up the chamber really well, then warm up the plastercene and force it into the chamber so that it's proud and close the bolt on it. Put it in a cold or cool place (freezer?) and open the bolt after letting it cool off for an hour or so. If you're lucky, the casting will come out with the bolt. If not, give it a nudge with a cleaning rod.
Measure or compare the casting against a factory cartridge. You can't stop for a smoke or whatever between extraction and measuring You've got about ten minutes before the plastercine warms up and becomes to soft.
The other cheap option, which I don't really like, is to oil up the chamber, plug the throat and fill with plaster of paris and let harden
I saw one fellow that oiled the chamber and filled the chamber with calking compound and left it overnight to harden. Worked well enough to get a measurement from.
Jonnyofalltrades
Regular
- Location
- North-central Saskatchewan
Dennis, do you think that a rough chamber could cause a false reading with the empty case/primer method?
No... because there is no chamber pressure... nothing to make the case stick to the chamber... the case just gets driven ahead as far as it goes and the primer pops back as far as it can... the primer creates a quick burst of pressure that has to go through the flash hole... this pressure is what pops the primer back.
Not really a suggestion, just part of the conversation.
- high temperature wax.... the stuff they use for investment casting. does not shrink
- epoxy (with a ton of filler!) - most of the bedding compounds are engineered to not shrink. but also ... eeek!
- there are tons of resin casting kits out there for things like miniatures, dice, jewellery. Get em at arts/crafts supply (Michael's, Currys)
- does pewter shrink? low melting temp and reusable.
I've used the wax method, just have to make sure to block the barrel really well, and make sure the chamber is well oiled, and cold when poured.
Epoxies and resins can be a very nasty thing to clean out if they aren't used properly and extreme care isn't taken to make sure the chamber is adequately coated with release agent. Not something I would suggest to a newbie under any circumstances. Fine if you know what you're doing though.
Good on you for walking him through it.
Lots of people that have been shooting for decades, using factory ammo only, don't know what is really going on inside that chamber when a cartridge is fired.
Good explanation.
Which is the point. Buggered reamer, how do you check? Chamber cast is the easiest. And as pointed out, there are various ways to do this. If you're not comfortable with the process, take it to a gunsmith. - dan
6.5 shooter
CGN Regular
- Location
- Medicine Hat
I took the necessary precautions and fired a single round of different ammo. Here is the result:
This barrel is garbage.
FWIW, the case stretch from base to shoulder using a comparator is .050"
Soooo just a thought. The brass separated right at the belt web junction (correct?) If this is correct then the body of the brass actually gripped the sides of the chamber just as it should have. Causing the base of the case to expand backwards and cause the separation? If this is true I would have to ask the question. Do you have a "soft" bolt? which is "squishing" back and allowing the brass to flow backwards into the action of the rifle and creating the separation problem? Reasoning: 1) The bolt face has the signs of high pressure, the markings on the bolt face with the brand and make of the brass imprinted on it. 2) The case being belted, head spaces off the belt but this allows the brass to flow forward towards the muzzle (assuming the chamber is cut properly) hence creating a false shoulder of sorts. BUT if the case grips the side of the chamber and the head of the brass can be pushed back hard enough the case will split behind the belt or at the front of the belt which yours seems to have. Something to think about, especially if you or someone else has swapped bolts or it has been overheated in some fashion.
I'm using a Blaser magnum bolt head which is the one required for Blaser's .300 Weatherby barrel. This barrel I have here is an aftermarket one chambered in 6.5-300, a chambering that Blaser doesn't offer. I don't think that should make any difference as they're the same dimensions at the rear of the case.
This bolt head works fine for the .375 H&H barrel that I have, with no headspace issues.
I've inspected the bolt and action. Everything looks perfect and it locks up as it should. I've also considered buying a different bolt head but I'd probably be throwing good money after bad.
Also, several cases split halfway up and in a perfect ring so I don't know what's going on.
This bolt head works fine for the .375 H&H barrel that I have, with no headspace issues.
I've inspected the bolt and action. Everything looks perfect and it locks up as it should. I've also considered buying a different bolt head but I'd probably be throwing good money after bad.
Also, several cases split halfway up and in a perfect ring so I don't know what's going on.
This is what I'm thinking. The locking recess is not machined far enough forward, therefore the belt of the case is nowhere near the shelf in the chamber that it is supposed to headspace on.
I'm going to try sticking on a bit of modeling clay just forward of the belt on the cartridge. I'll chamber one and eject it and have a look.
Cases splitting halfway up are usually faulty brass.
"Normal" case separations usually occur close ahead of the belt. This occurs because the case is driven forward as far as it will move when the firing pin hits the primer... then as the pressure build up the case expands and sticks to the chamber walls.. and as the pressure gets higher the brass stretches at the rear of the case and the thicker portion of the case head moves back against the bolt face.
