AmericanLongRifles Forums
General discussion => Gun Building => Topic started by: grabenkater on August 03, 2011, 03:39:50 PM
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A friend of mine is wanting to convert a CVA Hawkens from percussion to flint. In order to do this properly, he is needing a touch hole liner in 10mm x 1.25 mm per thread. Can anyone point me in the right direction for a supplier or someone who could make one?
Thanks!
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In order to do this properly
The only way to do it properly is to obtain a flint barrel and lock. Just removing the drum and screwing in a touch hole liner won't do it. There are too many variables involved. Just a word to the wise....nuff said!
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I just did a conversion on a heavy bench gun its in the tutorial section.
Dan
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Actually you can do it properly just not optimally like a blank barrel and new breech would provide . But it depends on what CVA you have .
If you have an early one with the normally /common type drum bolster then all you need is a liner . But if you have the more common CVA drum bolster then you have issues that have to be dealt with
The problem you have to deal with is that CVA uses a very long 80% threaded bolster . As such you cant just thread in a liner without leavening a very large amount of threads exposed inside the breech plug.
If you do , these will build with fouling and begin to corrode with carbonized fouling . Eventually this will start to effect the area of the liner .
So what to do ?
Well as was motioned , Optimally and for best possible performance a new barel is the answer .
The other option is to pull the drum bolster .
Check the outlet to the main powder charge . In some case CVA only made a slit in this area , not a hole that’s the same size as the flash channel . If you find that slit , drill the neck to have a hole .
. Now re thread the drum bolster to the breech .
Cut the drum section off so as to leave the neck in the breech .
Now you can drill and tap the neck so as to apply a 1/4,28 flash hole liner .
But only drill and tap the neck no deeper then what’s needed for the liner
You now have solved the issue with the threads. You have 5/8 of threading holding the sleeve into the barrel . The exact same amount as originally provided for the percussion system and you have a flash hole liner that’s faced to the inside shoulder as well as the outer shoulder .
the sleve will be no more prone to coming out then the original drum bolster was .
the thing you dont want to do is use such a big liner that you get to thin of a wall thickness where you seat the liner to the original neck .
So why is this less the optimal .
sometimes the inside of the original boster is just to corroded to be able to safly apply a liner to . thus wall thickness becomes a concern .
Also since what you have is a patent breech with a large anti chamber it can be troublesome to keep clean .
vs a true patent breech with a smaller flash channel that goes to a larger antichamber .
If the chamber also doesn’t fill with powder , you have a long distance for the flint ignition to reach the main charge . IE a slow ignition.
VS a new barrel and breech that will provide a much closer distance to the main charge , faster ignition and less issues with fouling
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This is the first thing I ever considered doing to ML firearms and is what sparked my interest in wanting to build them from start to finish. I was going to try a CVA conversion and I'm glad I researched it first and asked more knowledgeable folks a thousand questions. What I arrived at is that if I wanted a flintlock weapon, I needed to change the lock and the barrel together.
CVA has a special breechplug/drum assembly and as far as I understand it is intentionally designed NOT to be messed with. Safety first ... spend the money for another barrel and lock and match those 2 pieces together. That way when you want to swap back and forth you have a lock and barrel perfectly matched of both ignition sources and you don't have to worry about your safety being compromised.
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There is only 2 safety concern to deal with concerning this conversion.
The first is really ones personal opinion concerning the use of a liner .
The 2nd concern is as to if there is enough material left in the old bolster neck wall to allow the liner to be threaded in and hold properly .
If the existing bolster is in good condition then there is enough material , of proper quality to hold the liner in place . Unless one uses a liner that way to large
No internal modifications to the breech or the way the original bolster is threaded to the breech , have been or need to be changed .
Here is alittle knowledge for those with little Jukar/ Adesa experience .
The parts for these guns are fitted by friction machines.
Basically what this does is the machine spins the part into place . Think of it kinda like holding the palm of your hand to a jar lid and trying to turn it , without gripping it .
But the machine uses a lot more force while at the same time using a stall so as to limit the torque applied . This is why you see no notches on the bolster or for that mater the breeches"which also have a mm laper prior to setting " which allow you to apply a wrench to tighten . The machine doesn’t need them .
This is also why concerning the breech on factory breeched barrels , why the can be such a bugger to get out and often times even after pulling the bluster the plug threads get buggered up either in the barrel or on the plug . The pressure fitting expands the breech slightly . Then the bolster hole is drilled and threaded which complicates removal even more as that process can create a burr
This has been the standard of assembly for CVA , Jukar and Traditions thought their manufacturing .
Thus in the early models with the short necked drum bolsters , commonly used today by custom builders . The bolster was prone to backing out becouse its not fitted to the barrel by the same process
As such Jukar /Adesa went to a longer threaded neck . This did not solve the problem . Its seen every time you see an old CVA with vice grip or pipe wrench marks around the drum..
The early bolsters again commonly used still today even in the full custom rifles do NOT tighten down to an internal face . They tighten to the side of the barrel flat the very same way as tightening a bolt that’s threaded into a steel plate without a nut .
As such the design was changed so as to provide an eternally mating surface and not rely barrel flat alone . Thus you see the longer necked bolster with a mating face that are used in these guns today ..
Also for a time Jukar was using a mill process to expose the bolster flash channel with a slot . We have to remember that these guns were being made as cheaply as possible .The thought was that this would allow more threads and increase the integrity of the bolster neck while at the same time serving the purpose of allowing the flash to reach the main charge . But it also was troublesome because it more easily fouled . So they went to a milled hole .
Chances are if you pull the bolster on a CVA your going to find a hole in the bolster neck that’s aligned with the main charge NOT a slit . But there are still guns out there with that slit . Just as there are still guns out there with the short and medium necked bolsters .
Anyway . I submit this .
By cutting the drum section off and utilizing the neck , have we changed the way the system has/was designed to seat . Nope because it seats eternally and your still providing that seat .
Have we changed the amount of threads the design uses , nope .
Have we made the design weaker , nope
In fact what we have done is marginally reduce the amount of pressure that the design may encounter because now its vented .
So again the only concern is IF one has enough meat left ion the bolster wall to thread a liner to .
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I do custom guns and I seat parts to a shoulder in almost every case.
The mass produced stuff, no matter who makes it is assembled so the parts will screw together with no fitting. "Tolerance" and a high torque capability is all that is needed.
Even the big name stuff has a significant fouling/oil trap in the breech.
Like this one sold by a big and old name in international gun making.
(https://americanlongrifles.org/forum/proxy.php?request=http%3A%2F%2Fi72.photobucket.com%2Falbums%2Fi199%2FDPhariss%2FMore%2520ML%2520guns%2FBrowningBreech4.jpg&hash=6c33e63fe57e7afc2b6a94c5b2b551de53661783)
This was the upper end of the mass produced ML market. But still sloppily assmbled.
Another not so old but still big name in firearms machine installs breech plugs, or did, so tight they would often break off if removal was attempted. This was a result of the torque applied and the high torque stretching the rebate (short cut in manufacturing) behind the threads so that it was already stressed near the breaking point in some cases. The breech pictured at least has no rebate behind the threads.
But they don't have the time or a workforce that can do the work and still sell the gun for what the usual Wally World gun buyer will pay.
Given the properties of some of the propellants used in MLs today I am constantly amazed that there have not been some corrosion related catastrophic failures of these things.
I won't have a mass produced gun in the shop.
I am rebarreling a custom built sometime back (Douglas barrel) by a well known name in MLing that had a very poor job of breeching and drum installation. Sure it worked and did not fail but that is not the point. The point is it should have been done right to begin with.
Far too many people just screw things together and let it go at that with no worry about fouling traps, fouling penetrating into the threads , gases leaking around the threads (these last two due to modern "tolerance" built into the taps and dies etc etc. Many don't even understand "fouling trap" which can result simply from tapping the hole for the drum so deep that threads are cut in the bore making a fouling trap. Relatively minor but still a fouling trap.
In some cases this is little more than an annoyance. But in other cases its a safety problem especially with the use of propellants with far more aggressive fouling than BP produces.
But fitting a breech, counterboring for shoulder seal, cutting a proper nipple seat on a percussion breech etc takes time and the purchase of tools that that are not available at the local hardware store. So many just put the parts together as they get them and figure thats how its supposed to be not realizing the parts are just that and need to be properly modified and/or fit for any given application.
Dan
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cant disagree with you there dan