Last spring I had a bad experience with Butch's Bore Shine, some rain water, and a patch left in the shoulder area of a stainless MRC barrel. Now I've got a perfectly useable barrel (I hope) except for the fact that there are approximately .010" deep pits in the steel of the shoulder and neck area of the .450 Ack chamber.

The barrel is a #5 contour, 416R steel. The chamber parrallel is 1.200" dia x 2.75" long. The next 2.5" tapers to 0.935".

If the $&#@% pits hadn't occured at the neck, a .458RUM would clean up the chamber with no setback needed. As it is, the pits are at the rear of the neck, leaving approximately 0.250" of the front of the neck usable. So a RUM would only need a 1/4" setback - should be safe right?

Trouble with that is what action can I put a RUM case in and still use the 1x16 MRC threads?

A standard Ruger 77, which is the cat's meow for the .458AR, AND has the 1x16 thread, would require setting the barrel back another 0.300" (2.85" Ack coal vs. 2.55" AR coal).

Question is then: Is 0.600" too much to set back a barrel of this contour/material for a chamber cleanup from .450 Ackley to .458AR?

No problem with that much parallel Knoxform and such a fat taper ahead of that.
It would be best to whack off the threads completely and start fresh, square and true as possible. You have plenty of shank for that.

I had a Win M70 .375 H&H take-off barrel cut off a full 1" at the breech end, and did a .375 RUM with it. 23" barrel resulted with excellent results.

How long is your barrel?

Use a Ruger!

Thanks RIP ,

Barrel is 22" long as it is so it already like Francis Macomber's PH's .505. Another 0.5-0.6" won't hurt the aesthetics any and nothing can be done about the velocity potential.

BTW, it has a 1-10 twist and as an Ackley, was very accurate with jacketed loads both full power and reduced but SUCKED with lead practice loads. Nothing over about 1100fps shot without leading and accuracy.

Next questions: Anybody have a stainless Ruger in a standard magnum that they want to get rid of?

PWS,

Does the rifle no longer feed, chamber, shoot, or extract the .450 Ackley rounds?

If it does, why worry about the pitting?

George

George,

The rifle would feed, chamber and shoot with the pitting but NOT extract. Long story...

From what I gathered in my investigations, I guess the pits were the result of having lead fouling in the bore in addition to some rain water that caused severe electrolysis with the addition of Butch's Bore Shine. I was stunned at the severity of the pitting as I'd shot some lead practice loads on Sunday (in the rain) and did my normal cleaning procedure of swabbing the bore with BBS until the powder fouling was clear, then left the rifle standing muzzle down with a wet bore and patch in throat to prevent it from drying out. On Tuesday, I swabbed the bore clean and took it out to fire some full power loads. First shot went off fine but extracted with noticable difficulty. I initially thought I'd messed up the powder charge but after beating the bolt handle up and back with my hand, the case ejected. A quick look revealed the pits at the shoulder/neck area. Hoping in desperation that they weren't so deep that further shots would be affected, I fired two more rounds with the same result.

I talked to Sinclair about cleaning compounds, Butch's, and MRC and pretty much had to eat this one. MRC did rebarrel the rifle in-kind with at slight discount though. The barrel in question has been sitting in the corner in the meantime. I tried to duplicate the pitting by exposing it to water, lead and BBS but naturally wasn't able to replicate the problem. It has less than 200 rounds through it and other than the pits and a solder patch for the front sight, it's in fine shape.

You can see the imprint of the pits on the cases and I fished the plug patch out of the trash. The red scabs on the patch are iron oxide!

Having shot a lot of rifles using both cast and jacketed bullets, I'd suggest trying a different cast bullet. Find a person who casts bullets HARD and or uses gaschecks. Had a Marlin .45/70 with microgroove rifling. Tried four different bullets before I found one that shot well.

I would first square the action, then simply face the threads off .300 inches,move the shoulder foreward .300 and groove the shank below the shoulder just enough for clearance of the threads.Re-clock the barrel by lightly cutting the shoulder until everything lines up. That distance should be almost exactly the same as the original shank to shoulder measurement. Then go back in with your original Ackley chamber reamer about .025 per pass cleaning everything carefully with solvent before going in again. Use a real good floating chamber reamer holder too. Polish to 400 grit. You'll still have to probably re-glass bed the action.
I'll bet you that works just fine. It would be best to cut off the original threads but your barrel shank will never fit your stock again.
I'm not a fan of trying to rechamber to a RUM case because of all that unsupported reamer length you'll have. You could wind up with a non-concentric chamber or rings which will be just as bad as what you have now.
BTW- Did you try and polish your chamber first with 150 grit-400 grit emery cloth using a long dowel and electric drill? Sometimes you can polish out those pits enough so extraction will work. Don't get too carried away here oryou'll wind up with a new wildcat. I have seen some very nasty chambers fixed adequately this way. In particular its an Ackley and headspaces off the belt so you can polish the hell out of the shoulder and neck without hurting a thing. Thats the easiest thing to try before its Gunsmith time.-Rob

So either option: a .458RUM case or moving the Ackley forward is safe and not problem to loose about 1/2" off the rear. That was my biggest concern.

The barrel is alone and in need of an action. Standard magnums are cheaper and easier to find than H&H lengthed. I'll start looking around.

Prof, I didn't try too many cast loads. Had the pitting problem early in the life of the barrel and figured the fast twist was why the ones I tried didn't fly true. Maybe I'll revisit it if I get the barrel going again.

A RCBS 405FN over 65gr H4895 in my Lott is my favorite cast load - 425grains@2000fps and 2moa.

Thanks all for the input!

I have always questioned how much thread is really needed. I'll bet 2-3 turns is probably enough as long as the barrel shank locks up tight on the action face. Actions differ all over the place in shank length and I dobut any definative study has ever been done. Your good to go except as I said watch out for a non-concentric chamber.
BTW I clean the bore of my SS.50BMG 1000yrd gun ( now with 1500 rds through it) with a 1:5 mix of 30% Conc ammonium Hydroxide and Ivory soap followed Butches Bore shine, water and then acetone. I never ever leave the bore wet with anything. small amounts of halogenated solvents, like chloroform or methylene chloride will corrode SS unbelievably fast( hours). Wonder if you got a bad batch of Butch. -Rob

If anyone is interested in this barrel for a .458AR on a Ruger, or an Ackley on a MRC, or whatever... I posted it in the classifieds for $50 shipped&insured.

Too many projects on the stove already...

Mike

If the pits are not too deep, wouldn't a re-bore and rechamber to 470 Capstick work?

again, I would concur with RGB's assessment. I would prefer about six-threads minimum myself; but I think the primary reason we see so many is to keep the rifle length a bit shorter.

Rich
DRSS
Knowledge not shared is knowledge lost...

CASII,

For the cost of a rebore, you could buy a fresh barrel and have some change left over. The .450 Ackley is 0.503" at the shoulder and the Capstick is 0.499" (according to Any Shot You Want). I don't recall the height of the imprints on the cartridge but I want to say they were in excess of 0.010". This coupled with the light for caliber #5 contour, there wouldn't be much barrel left by the time you moved everything forward and recut the tube. Seems to me you may as well start over.

RIP's and Rob's idea of lopping off the threads and moving the Ackley forward is a good option but if you have a standard mag action lying around and really wanted a .458 AR, you could lop the threads, carefully clean up the chamber, and you're good to go!

.............PWS,..,I had a 338 Ruger in classifieds last week ,., perhaps I was too steep on the price but I would have thot about trades ect......It,s gone now .....Is the barrel stainless ???????Does it have any holes in it from sights ect............

Gummy, I saw that .338 and thought about it. AlanC had a similar setup but with a Houge stock about two weeks ago for about the same $$. Thought about that one too... Got too many other diversions in the meantime.

Olcrip posted "I'll take it" on my ad in the classifieds so unless he backs out, barrel is on the way south.