Should I be worried? 358 won't fit through cylinder.

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Matt 357

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I got my shipment of 1000 MBC 357 Action (.358 diameter) bullets 18 BHN.

Should I be worried that I can't push them through the chambers of my GP100? Is this normal?

My Remington SJHP 357 (.357 diameter) slide through the cylinder pretty easily.

I know cast bullets should typically be .001 more than jacketed.

Just need a little reassurance before I start loading them up...
 
They should go through at .358. You can always have the throats reamed to .358 or .359, depending on the bore (groove) size.

You may have leading problems if the throats are .357, but maybe not. If the bore is over .357, and the throats are .357, you will almost surely get leading unless you ream the throats.
 
Measure dem bullets !!!

I have cast many & run em through my .3585 sizer then miced em at .359 & almost .360 a week later !!!!


& measure em all da way round !

A member on the Ruger Forum.com CAS will ream it for ya & ya only send the cyl & very reasonable !!!
 
I have a Ruger Sec Six I sluged the cylinder throats at .3575", .358" cast lead shoots well in it.
I your throats measure .358" a .358" bullet will not pass through without some persuasion.
 
If your throats measure .358" a .358" bullet will not pass through without some persuasion
Click to expand...
Very true. Getting the bullet lined up square to the throad is hard to do. Also, sized bullets are not always round. Load and shot a few before you do anything.
 
I had a feeling I would end up just giving it a try.

If you ream out the cylinder to .358 for lead, how does it affect the use of .357 dia jacketed ammo? Would I be making a commitment to shooting lead from now on?
 
I know you won't have a pressure problem (and that IS your concern, is it not?) and it may actually help a tad with accuracy.
 
You are groping around in the dark until you slug your barrel. THEN you will know if those .358 throats will be okay.

Now, slugging the barrel of a GP-100 is not all that easy. Since it has a 5 groove barrel, it's not as simple as driving a soft ball through the barrel, then measuring with a micrometer. You have to have a precision hole gauge to slip the slug through to get a measurement. I have been unable to find such a thing, if anybody knows where-to-get-one, let me know1:uhoh::confused:

How do I know this? 'cause I just got a GP-100 from Ruger, and I want to shoot mostly lead from it. The slug from the barrel is a tight fit in ALL the cylinder throats, and the cylinder throats slug at .3575. So boolits sized @ .358 or .3585 will work quite well.

I'll find out if this damn winter ever quits, 2' of snow and more coming with a high today of maybe 15F. Maybe by May second when I retire, I'll be able to find out.
 
Load up a few and see how they work...When you put them in the case and crimp tight should be ok...
All this about reaming your revolver chamber/cylinder is :confused: me:scrutiny:
Regards
 
You are groping around in the dark until you slug your barrel. THEN you will know if those .358 throats will be okay.
Click to expand...

Guess I wasn't clear in my original post. The cast bullets are .358. My chambers pass .357 SJHP with no effort. I tried pushing a few .358 bullets through the chamber with a pencil and and the bullets got stuck 1/2 way out. It seemed like a tap of a hammer on a wood dowel would push it through.

I was wondering of those who shoot lead in revolvers, do the cast .358s slide right through the chamber or does it take some effort. From what I've read, snug is better than loose so you avoid hot gas blowing past the bullet.

BTW Snuffy, I'm in FL and it is about 80°F today. Probably hit the outdoor range this weekend. Sorry...
 
I was wondering of those who shoot lead in revolvers, do the cast .358s slide right through the chamber or does it take some effort. From what I've read, snug is better than loose so you avoid hot gas blowing past the bullet.
Click to expand...

It depends. Not all revolvers have .358" throats. Some have .357" throats and some have .359" or .360" throats.

From your description, your bullet to throat fit is just right, although the lube could be interfering with the fit. Remove all the lube from the bullet and pass it through all six chambers.
 
Yep, as long as your barrels groove diameter is not more than .358, you will probably be OK. We would prefer a hair less, or better yet .357, but as long as the bore isn't larger than the throats you will be OK.

Preferably the throats would be .001 to .0015 over the groove diameter.
 
Quote:
You are groping around in the dark until you slug your barrel. THEN you will know if those .358 throats will be okay.
-------------------------------------
Guess I wasn't clear in my original post. The cast bullets are .358. My chambers pass .357 SJHP with no effort. I tried pushing a few .358 bullets through the chamber with a pencil and and the bullets got stuck 1/2 way out. It seemed like a tap of a hammer on a wood dowel would push it through.
Click to expand...

You WERE quite clear, but the important part is what is the groove diameter of your barrel. Ideally, it should be smaller than the throats. This allows the bullet to seal the throat, then pass into the barrel tapered leade to be swaged down to the smaller size. This is THE most important element in controlling leading with bare lead bullets, (lubed of course).

On another thread here on THR, there's the question of how to mic a slug from a 5 groove barrel. The best method is a "V" anvil micrometer. However they are very expensive and hard to find. Another method is a precise hole in thick steel plate, should be in even .001 increments. I have NOT been able to find such a gauge.

What I did was take the slug I drove through the barrel of my GP-100, try to slip it through the cylinder throats. it passed with some pressure, since I already know the diameter of the throats, I then know the barrel diameter.
 
So far so good. Only some minor leading.

As some have suggested I loaded some up and tried out the MBC 158 Action! in my GP100

I loaded up 25 rds with 5.5 grains of SR4756 and 25 with 6 grains.
The 5.5 grain load was way too low (mouse fart 38s). I thought I'd try the low end incase there were any pressure issues with the tight fit in the throats. Lots of unburnt powder typical of low loaded SR4756. The 6 gr was better. No high pressure signs (primer or ejecting). Seemed pretty accurate off hand. I'd like to use a rest sometime.

When I got home and cleaned it, didn't notice much leading. Did my usual cleaning (brass brush and Hoppe's 9) After cleaning, there are still some streaks in the cylinder throats. Nothing that can be felt. Looks like somebody drew some lines with a pencil. Barrel looks clean except for some slight stuff just past the forcing cone.

If it doesn't hurt the gun, I'd rather not go nuts cleaning every last bit of lead. I'd rather save the chore boy scrub and brush in electric drill until it gets bad.

Am I wrong in assuming it is okay to leave a little lead until accuracy is affected?

I'll try a heavier load next time and work my way up. Current IMR max data for LSWC .357 diameter 158 grain is 7.0.
 
If there is any leading from previous loads, clean it out before trying a different load. The heavier load may not lead where the lighter one did.
 
I was going to be lazy, but it makes sense to give it a good cleaning before the next round of testing.

Two things I forgot to mention:

I had some copper streaks in the barrel. I heard that copper build up in the barrel can make leading a bit worse. I finally picked up some Hoppe's Copper cleaner. The local gun shop closed up and WM doesn't carry it so I have to shlep up to the Bass pro shop an hour away. I'll give it a good cleaning with that before further testing.

Also, I noticed some leading on the cylinder face. No biggy. Came right off with my regular cleaning. Guess that is normal?

So far I like the 158gr Missouri Bullet Action! for the 357. Ordering, shipping, and packaging were good. Easy to load. Hands were pretty clean after loading. No lead or lube mess. Nice to be able to shoot a box of 50 357s for less than $7!
 
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