Question about Having a barrel re-bored ?

[Silvertp]

Thinking ahead...

I am shooting a 22 caliber based on a .284 case, 30 inch pac nor barrel with a 1 - 7 twist.  In anticipation of the day the throat goes south I am considering my options. 

My question concerns the internal dimensions of the lands and groves.  I am thinking about re-boring to 6.5 / 284 to gain some barrel life and larger projectiles.  Am I stuck with a 7 twist, or is the .264 enough larger that a new twist can be cut in?

How about just having the barrel set back and re-chambering to 22/284 ?  Pros and Cons? 

Silvertp

[Catfish]

I would have it set back and rechambered. I did that with a 22-6mm barrel and it`s shooting good again. I`m not sure how long it will last, but the first throught was gone in 1,000 rounds.

[Silvertp]

Catfish

Im thinking the smart answer has to be rechambering.  What are you using your 22/6mm for & and what bullets are you using to hold  together?

I built my rifle for wolf hunting and am still looking for a load that works for me.  Future decisions on caliber  really dependens on what kind of performance I get out of the 22/284.  If the caliber / rifle lives up to my expectations I likely want to extend my shooting of that caliber.

Given the wealth of loading data and popularity of the 6.5 x 284 it would be a little traditional to work up loads and enjoy for a wider range of shooting experience.  The key there is if the .264 bbl is enough larger than the .224 bore that I could select a new twist rate when re-boring?

I tried finding the internal dimensions needed for lands and groves for the 2 respective calibers, but no luck yet.


Silvertp

[tacklebury]

Why not just do a barrel re-line?  Liner's aren't nearly as expensive and it'd let you keep your previous performance...  I know several people who have had 22-250's relined here locally.

[mattl]

  Why not just do a barrel re-line?  Liner's aren't nearly as expensive and it'd let you keep your previous performance...  I know several people who have had 22-250's relined here locally.

Who relines 22-250's?  If your thinking about Barel Liners like the ones form Redmans...
 
http://www.brownells.com/.aspx/pid=10976/Product/CENTERFIRE-BARREL-LINER
 
They are only soldered or epoxyed in and are designed for low pressured pistol and rimfire cartridges.  22-250 does not fit in that category.  I would not think that the solder or epoxy would hold up to the high pressure of a 22-250. 

[Silvertp]

Mattl...Well I learn something every day.  I had always thought of re-lineing a bore as a   process used for .22 rimfires.  I didn't know the process could be used for centerfire barrels.

Tacklebury...What  process are these folks using to deal with the pressures of a 22 / 250?/

Silvertp

[tacklebury]

There are various levels of re-lining.  The guy I know that does it doesn't use the thin walled rimfire ones, there are thicker walled.  He basically uses an oversized counterbore bit, I believe about .30 cal and then bores back to the chamber just past the throat.  Once the liner is prepped and fitted to it with his lathe, he does something to it on his milling machine to etch thin lines full length.  Not sure about what epoxy he used, but that's all he used to affix it.  The lines in the liner don't extend all the way to the tip, so you are hard pressed to see it where he seams it to the crown cut.  15,000 pound epoxy full length on a .32 tube is going to take a crap load of pressure and won't be driven back out.  Anyway last step is to run the throater back into the chamber and make sure the throat is picked up with the bevel.  He was shooting one when I arrived one afternoon, but he's in his late 70's and does smithing for his own stuff or friends only nowadays.  Green mountain also sells gunsmith blanks in some calibers which can be turned down to a specific diameter if you don't think .30" is enough. 
 

[mattl]

This is very interesting to say the least.  I have heard of stories at a gunsmith school that I went to where a student test fired a ruger 10/22 that was originally 22LR but was lined for 17Mach2.  Apparently he test fired with a 22 stinger and the result destroyed the action and broke the liner loose.  I am not sure how much pressure was produced by that little 22, but I would have thought that the 65,000 PSI Chamber Pressure of a 22-250 would be enough to break loose even the strongest epoxy.  Guess I learned something new too.

[tacklebury]

You are talking in the case of that 10-22 of the equivalent of using a 22 to hammer into a hole too small for it to fit, thus the pressure had no where to go.  Chamber pressure is mainly against the walls of the chamber as long as there's not a restriction in the bore to stop the bullet, it's going to go the path of least resistence.  There is no way that the small bite that the rifling exerts on the jacketed or lead bullet would be enough to overcome several inches of 15000 lb epoxy.  The one thing I'd be leery of would be temperature sensitivity as even thermoset plastics will weaken as heat increases, so if you are shooting a great many bullets in single settings, it'd probably be smart not to go this route.  I suppose there may be a way to do this with a solder joint at the end where you weep silver solder in also.  This would be higher temperature, but it'd be a lot harder to get everything to flow evenly.

[Silvertp]

Interesting discussion guys, but at least for now Im leaning heavily toward just sitting the bbl back and rechambering.  That will allow me to take advantage of the Pac Nor bbl and load development to a large extent. 

Thanks everyone for your feedback.

Silvertp

[Catfish]

That would be by far the cheapest way to go. You will loose abt. 50 to maybe 100 fps., but that`s not to big a deal. Besiaes, if you can get it done with the same reamer you can use the ammo you have loaded for the old chamber. you will probly have to seat your bullets a little deeper as you will have to set them out as your throught burns out to keep accuracy, again, no big deal. I`m looking for a 22-284 reamer right now. I have 96 lbs. of very slow burning powder and it`s way to slow for the 22-6mm so I`m going for a larger case.

[Graybeard]

If you like what you have then I'd chop a bit and rechamber.

But I have a .25-20 that was once a .22 Hornet and was rebored and chambered so yes a 6.5 will easily be doable in your .224" barrel.