Question about boolit to barrel fit for .38-55

[BCRider]

OK, so I'm finally getting prep'ed to load up some test rounds for accuracy for my rolling block/Shiloh Sharps barrel combo gun. As part of the prep I knocked a soft round ball into the end of the barrel to slug the bore and get an idea of what I've got. And that's where things ground to a halt and I've come with hat in hand for some help.

You see the bore slugs out as if it's intended more for a .375 than a .38. Groove diameter is .373 to .374 and the lands/bore diameter checks at .362 to .363.

My boolits that I've used so far are spot on .379. So any way you cut it that's a lot of lead to shape or shave off, right?

It also explains what happened during the initial test and sighting in rounds. In that case I found that the sizing die and stock brass is WAY undersize for the .379 boolits and the brass was bulged. No problem I thought. The ones I shot with lead were fireformed now and the rest I fire formed with Unique behind a COW filler. Worked great. BUT those first 50 rounds actually had bits of lead desposited onto the OUTSIDE of the casing due to the poor fit. Hopefully the fire forming and annealing I'm going to do will fix this issue.

But it brings us to the topic of what boolit diameter should I be using? Clearly the .379 seems rather fat for this bore. But the next size down that I can get is a 265gn .376 diameter gas check.

Now that all sounds fine. But it's a helluva long way to neck down the brass. Especially since the chamber would appear to be a trifle generous in size and has left the brass fireformed to a fairly easly slip fit on the .379 boolits. If I form the brass down to have some tension on the .376 then it'll be REAL sloppy in there.

Thoughts on which way I should go with this? Or is pushing a .379 boolit into a .374 hole actually OK from an accuracy point? And what about all the lead that seems to be getting sheared off and left behind?

Edited to add- I went ahead and did a chamber casting. Not pretty because I didn't warm the reciever. But it came out well enough to confirm the groove and lands and I found that the portion where the mouth of the casing sits is .405. That's pretty generous a clearance it would seem to me. But would this be due to the need to have some play to allow for fouling when shooting with BP?

[bigted]

what you describe sounds like a proper .375...[on the tight side]...barrel. this is what is generally cut for the modern 38-55 barrels. ...[a shiloh barrel???]...[on a roller action???]...so anyway the inside meassurements dont sound that far off to me. the chamber however is what my early marlin 38-55 chamber is in meassurement...my shot brass accepts a .380 boolit with ease and chambers this combo very well for my .3815 bore barrel...this leaves you with the generous chamber and a tight bore...not the best combo for my thinking. with such a combo im bettin that it will be hard to get it to settle down without setting the barrel back to allow a re-chamber in part or whole

so if i may ask...how did the marriage come about for a shiloh barrel and a roller action? did shiloh mount and chamber the barrel...orrrrr...has someone found a shiloh barrel and arctic engineered it with a too large a chamber? just curious

[Bad Ass Wallace]

My custom 38/55 has a .375 bore and I shoot .376 through it. The Pedersoli Hiwall is .379 and I shoot .380 through it. Both accept the long Starline 2.125"brass.

[John Boy]

Groove diameter is .373 to .374 and the lands/bore diameter checks at .362 to .363.
Please explain ... "rolling block/Shiloh Sharps barrel combo"? Two rifles or one and who made them?

Never heard of a 38-55 caliber barrel with your land/groove dimensions. The lands on a 38-55 normally are 371 (tight) or 375 and the grooves are 377 to 379

With a land diameter of 362-363, that's not even close for shooting a 375 Winchester smokeless jacketed bullet. So there's no sense about talking of a lead bullet for your bore

[BCRider]

The rifle is something that was made up by a local gunsmith team that took a number of surplus Swedish rolling block rifles and fitted them with Shiloh barrels at the time along with new wood stocks. The fellow that I bought my rifle from at a gun swap meet last year was one of the team and the one I got was the last of the batch that had been sold for a while and came back. The work on this batch of rifles was done back in the 90's. Pictures of my toy are shown below. The receiver is actually stamped 1869 on the side opposite the serial number.

The thing is that this is a properley stamped Shiloh barrel so I'm assuming that the chamber was cut by the Shiloh company. But it seems odd to me that the chamber would be so generously cut. Unless the intent was to allow for fouling that you'd get with black powder? Seems like being cut so large that it would become a self fulfilling prophecy though....

After I posted this question last night I was looking around for information on .38-55 chamber fit and found the references to .375Win and how one needs to be careful to not stick any into the old guns. But along with all this it would appear that the brass used in .375Win ammo is a little thicker all around. I'm thinking that if I'm lucky and find a box of factory ammo in .375Win I might just pull the bullets and dump the powder and use it as a way to better allow using the .376 cast boolits with the fairly sloppy chamber fit. Being a single shot I'm not too worried about the slightly shorter length as I can just let the boolit sit a little proud of the case mouth as I'm planning on using a light amount of neck tension with no crimp at all.

Anyone with .375Win brass that can confirm the wall thickness at the mouth for me?

[Gunlaker]

BCRider that's definitely a big diameter at the case mouth. I have a .38-55 and we used a reamer that was .396" at the case mouth which is pretty good for slip fitting .377" diameter bullets usig Startline long brass which is pretty thin. Around 0.007" if I remember correctly. Sounds to me like someone used a reamer designed for original .38-55 diameter bullets but with a modern spec barrel.

Chris.

[rbertalotto]

Sounds to me like someone used a reamer designed for original .38-55 diameter bullets but with a modern spec barrel.

I agree........That bore seems quite tight even for a modern 375 Winchester barrel.

[BCRider]

I'm going to cast around on some forums for information about the wall thickness for .375Win brass and see what comes from that.

In the meantime I picked up some .376 165gn RPFN GC bullets from the local outlet to try. I've just sat down from partial sizing the casings to allow a light but firm neck tension on the Starline short .38-55 brass and see how it works out.

One thing I can see is that the brass will not center well. I just checked the outer diameter of the sized and flared case mouths and they are only out to .392 to .394. That leaves me with the potential for the bullet to be sitting below the bore axis by a good 5 to 7 thou. Not the best starting point for a clean entry into the rifling.

I might just try a few with a heavier flare to bump the edge of the mouth up to .400 to .402 so it centers better.


The FINAL solution might be to set back the barrel and extend the chamber with one of the smaller reamers. But I'm going to mess with these other options first.

If nothing else what you guys are showing me is that the present setup is not an optimum one. If I can't fudge a solution to the slopiness issue I'll have to get more serious.

[EDG]

>>>I'm going to cast around<<< Interesting pun.

My .375 Win. brass measures .011 to .013 with a micrometer.

[BCRider]

THANKYOU EDG ! ! ! ! !

I'm going to start the hunt for some .375 brass with a little more seriousness. The Starline brass is .0075 to .008. So going over to .375 brass gives me a 3 to 5 thou head start with the radius on centering the rounds more accurately. And thats just about all it needs.

PS; No charge for the bad pun either.... :D

[Jon K]

BCRider,

How long is the chamber? Measure your chamber cast.
Which end did you slug...sounds like you slugged the muzzle end, which is smaller.
Most new single shot rifles(USA barrels) are of the .376-.377 groove diameter.
If you use the Winchester brass which is thicker, and a .377 boolit, you should have .002-.003 clearance when fired.

Jon

[BCRider]

The rather spotty looking chamber casting that I did supports the muzzle slug as for sizing. At least it does to within a thou. And that's close enough to call it a match. Once pushed past the muzzle the slug moved with a light hand pressure on the rod. But it was not the sort of loose fit that a .376 sort of bore would suggest. AND it got snug as it got to the chamber end. I suspect a burr or two from the reamer on the start of the rifling that hasn't been burnished away yet.

Not sure what you consider "new" but this batch of conversions done by the folks I got this one from were done back in the mid 90's according to the talk I had with the guy I bought the rifle from.

[McLintock]

I'd try it with the bigger bullets and see how it shoots; start with lighter loads and work up. I had a Browning 1885 in 38-55 that slugged at .376" and during load development I tried everything from .376 up to .381". It shot the best with a .381 gas checked Lyman type 375449 and 31 grs of 3031 and 2nd best with a .380" plain base and 18 grs of 4227. Always consistent and very accurate, out to 500 yards, 300 for the lighter load, and no problems. Lead bullets swage down pretty easy, as Mike Venturino has pointed out on numerous occasions when writing about loading for mismatched bore's and cylinder throats in Colts. That'd solve your oversized chamber problem if it does shoot good; but it's your gun, your choice.
McLintock

[BCRider]

That may be an option. But if I go that route and use the remaining 140'sh .379's I'm likely going to want to give the beginning of the rifling a bit of a taper and smoothening job. The chamber cast revieled that the start is rather abrupt and sharp edged. Which is likely why I had a lot of sheared off lead particles stuck to the outside of the brass from the initial 60 rounds that I loaded up and shot already. A smoother entry would swage the oversize bullets down and into the bore rather than shear off the excess..... at least that would be my thinking on it. Your thoughts? In any case thanks for the option and your own results. It's well worth adding to the list of options at this point.

[leftiye]

Compromise. Size boolits about .375 or .376. Use a bore rider boolit so boolit is lined up with bore when fired. Seat against lands/lead. Use .375 brass, and open up the neck of the sizer so as not to size too much more than necessary.

[BCRider]

I'm already on the way towards trying that. I got me some cast .375Winchester boolits that are sized to .376. For now I don't have any heavy wall brass so I'll load with a moderate neck tension and generous flare to let the flared mouth of the brass aid in centering the mouth in the chamber to guide the boolit on it's entry to the bore. It may or may not prove to be workable but it's the plan for now. I'll load up a few with various powders I've got and try them for grouping.