marlin SBL & rcbs 45-500 boolit

[bigted]

my SBL 45-70 shoots like a dream with j bullets but have had problems with the cast leading the first 6 to 8 inches of my barrel. bought this rifle for shooting the big rcbs 530 gr boolit with the gas check as it just seems to be the rite on medicine for an angry bar in tha thick stuff.

shooting them at around 1400 to 1600 fps seems like a good rpm to run em and i cast from WW's and also have the fine lead from Steve Morris here on c/b site. problem that i get is a kinda surprise with the leading as these are cast with the gas check [hornaday] and the diameter is .460 inch as poured.

ive shined the barrel with valve grinding compound to take the rough edges off and lapped it for a final with toothpaste [ crest] but have yet to go shoot it to see if this treatment will or has worked for it.

just wondering if someone else has tried this combo of rifle/boolit and what is your load/outcome?

thanks for the answers in advance. ill prolly shoot bp thru it as well but want the bore shined up very well first as it has a bunch of tool marks still left on the swirly things in there....:groner:

[btroj]

I would not use valve grinding compound- could be too course.

With a Marlin and .460 bullet you should not be getting leading with a reasonable load. Makes me wonder about your lube and alloy. I also would want to know what your bullets actually measure- are they really .460? Does running them thru a .460 sizer to crimp on the checks show signs of sizing all the way around the bullets?

What powder? Sometimes a heavier charge of a slower burning powder can stop leading.

We need more specific info here to help you.

Brad

[mroliver77]

And whenever this shows up we want to know what seating and crimping die is used. Pull a loaded round apart and measure to see if boolit remained .460 after loading.
J

[W.R.Buchanan]

I doubt the bullet is big enough. These moulds were all designed around the shrink rate of Linotype and wheel weight material will make a boolit that is smaller.

Send the mould to Eric at hollow point moulds and he can open up the driving bands a couple of thousandths which will produce a boolit that is .461-462 that can be sized to .460, then it will shoot. What I have layed out is a problem with this entire series of RCBS bullets. IE .45-300FN, 45.-405FN and .45-500FN.

The other point is that 500 gr boolit is going to kick the krap out of you.. Better off with 400gr Ranch Dog running around 1600 fps as something you'll actually be able to shoot more than once. Same bullet just shorter. A bear won't know the difference as both will make a 1/2" hole clear thru the critter.

Randy

[flinter62]

I shoot mine sized .458 about 1300fps very accruate alittle ruff on the shoulder.Couldn't imagine pushin to 1600fps. It'll still shoot thru 10" poplar tree at 1300fps

[Jailer]

Definitely pull one apart and check the diameter, I bet they are getting swaged down when your seating them. With the leading in the first few inches of the rifling it sounds like the boolit is undersized. Maybe try running your expander down a bit more?

I'm running a 385gr air cooled WW boolit at .460 in my SBL. I've pushed them to a bit over 1400 FPS with no leading at all. They were panned lubed with equal parts beeswax paraffin and vaseline so nothing special in the lube department either.

[bigted]

more info...

2 loads;
42 grains imr3031 in r/p cases sparked with fed large rifle = 1450 fps

25 grains 4227 in same cases sparked the same and equals= 1250 fps

these boolits lubed with equal parts bee wax/Crisco/peanut oil.


as for measurements they are as follows

sized case od = .475
flared case od = .477
flared case id = .456

sized boolit od = .460

loaded case od = .480

pulled boolit od = .460

all od measurements taken at 1/4 inch down on neck of case
id taken rite at mouth of flaired case.

the marlin SBL barrel measures... with a .530 pure lead ball pounded thru a greased barrel comes out at .4515 and .458

the lead used is some of muddy's fine boolit lead. poured at 750 degrees from a lyman dipper.

the loading dies are rcbs 45-70 gubberment. the flair/expander is a .456 inch

[longbow]

Can't speak on that gun but I was having a lot of leading trouble with my 1894 in .44.

I found out on the Marlin owners site that Marlins seem to have tight spots under dovetails so slugged my barrel and sure enough I found 3 or 4 tight spots under dovetails.

A little hand lapping, and I do mean a little as I have microgroove rifling, to get rid of the tight spots along with a few full length strokes and leading disappeared.

I used a .440 round ball drilled for a rod then swaged into the barrel to push through and feel for tight spots.

Find yourself a round ball or even a boolit, though a boolit may be hard to swage into the rifling then push through, and feel for tight spots. If there are any then lap them out.

Fire lapping may work but I wanted to work directly on tight spots so went the hand lapping route and it worked for me.

FWIW

Longbow

[btroj]

What did you use to measure? A caliper isn't accurate enough, you have to use a micrometer.

If all you measurements are dead on then I would say you have either too soft an alloy or a lube problem. A .460 bullet thru a .458 bore is about ideal. With a gas check at the velocities Lu listed there should be no leading at all.
Search this site for info on fire lapping and maybe give it a try. Don't use anything coarser than a 320 grit. You want to shoot my enough to polish things up a little. Try maybe 20 rounds to start. You can always take more off, ou can't put any back!

[longbow]

If there is a 0.457" tight spot in that 0.458" bore then the boolit is 0.457" after the tight spot.