Gas checks???
- Thread starter bogie
- Start date
Gas checks are little "Buttons" that are pressed to the base of cast bullets. Since lead is so soft and has a low melting point, the gases will melt and gas cut past the bullet and deform it, thus causing accuracy issues and speed up fouling. The gas checks are a harder material and provide a barrier to help protect the lead bullet. They are not required, but are strongly recommended.
The 38/55 was a very accurate target rifle with cast bullets before gas checks were invented. If you are trying for higher velocities, say over 1500 fps. you might want to consider a bullet/mold cut for the gas check. More important however is to slug barrel to determine the exact size of bullet you need. M.T. Chambers makes cast bullets for the 38/55 in sizes .376", .377",.378", .379",.380" and .382" for this reason. I'd try a plain base .378" 250 gr. flat pt., it is the traditional std. in this cal. If you buy cast bullets, the maker should have installed a gas check on the bullet if the design calls for it.
- Location
- The Conservative part of Ontario
You're walking the line IMO. But, it depends. Bullet design, the powder you use, lead hardness, bore condition all play a part.
You can also use a filler wad, which can accomplish much the same thing if done right, just a PIA to put them in with a bunch of cases.
My 44-40 will lead if I go much past 1300fps with no gas check, but, my 45-70 will let me go to nearly 1800 without leading with a plain base bullet.
One of the 38-55 sites I was rooting around in said that I should not load the Winnie any higher than 1700fps as it was originally a BP round. If it was a Marlin then it would be a lot different as it is a much more robust system than the Winnie. There was actually a rumor that Marlin was going to release a rifle in that cal and would allow much higher pressures but from what I hear the brass is too thin and will not tolerate that too much. Marc at Oma seems to think slugging should not be necessary for cast bullets.
Oh really, usually when I hear such asinine thought patterns I just smile, and says thanks and leave. Only one I can think of that does not need to be slugged would be a black powder rifle. Ask me how I know shooting a .312 cast bullet out of an old .303 Brit rifle is not a good idea when it actually slugged out at .317, go ahead ask me. That was 25 years ago when I first got into casting and didn't know better. After what seemed like for ever cleaning that .303 to point where I could at least see that it had rifling in the barrel, I decided not to take advise from so called experts in the gun store and bought the Lyman Cast Bullet book and it hasn't failed me yet. First thing I do when I get a new Pistol/Revolver/Rifle is slug the barrel, new or used. How do you know what to size to otherwise? Such a simple 5 minute job to ensure you get the best accuracy, most fps and little effort in clean up after-wards. I have a slugged barrel bullet for each of my rifles and pistols clearly labeled and kept in a box to be referred to if necessary, on my revolvers I have not only a barrel one but all cylinders also.
Finger Toes
Regular
- Location
- Yellowhead County
Just a question or two. When bbls are slugged for cast bullets do you record the dimensions at different areas in the bbl with different slugs? I read the Lyman manuals and they seem quite adamant that bullets that are sized to the dimension 2" ahead of the throat generally give the best accuracy and least fouling. I'm going to start casting some 348 bullets and I want to slug the bbl before I decide on a sizer. I have a .350" sizer hopefully it will work. The real problem I think I'll run into is the bbl is a 5 groove and I'm not sure if a standard 1" mic will be able to measure groove to groove dia. Any ideas? Can I use as cast bullets to slug the bbl?
Think about something for a second. The barrel is contoured on the outside and the rifling etc has all been completed on the inside. Then it gets the 2nd amendment inscribed on the outside of the barrel. Take a look at some of the Ruger revolvers, goodness , 4 lines that take up most of the side of the barrel. Well you will find that when you drive the slug into the barrel, obviously the size that will be the smallest is usually right where the lettering is. I was anal one day and took slug measurements one inch at a time in my savage 30/06 from the muzzle to the breach. Sure enough the most constriction was where the lettering was. You would never know shooting jacketed bullets because they don't lead, switch to lead bullets and if it is bad you will find out soon enough. So lets say at the throat it is .308 then the lettering comes along in the middle of the barrel and it is .306 then back to .308. Using a jacketed bullet the bullet will be swagged down to .306 and kind of rattle down the end of the barrel and out, using a lead bullet the same thing only that 2 thou that is now missing in the diameter after it passes the lettering is a recipe for disaster. Now in most cases I exaggerated a bit there but I had a 30-30 that was 2.5 thou out and leaded badly till I discovered it. The next step is called fire lapping and google for the proper steps, basically you are trying to get rid of the bulge so to speak in the barrel where the lettering is. You put a polishing compound in where the lube grooves go on the cast bullet and with a small bit of gun powder you shoot the bullet down the barrel. Usually it takes about 30 rounds or so and each time the bullet goes down the barrel, anywhere the constriction is will be slowly removed by the polishing compound until the barrel is the exact same dimension from the throat to the muzzle.
As far as being able to mic a 5 groove barrel, yes it is hard and sometimes near impossible. I cheat, I have a few H&I sizer dies that I use for measuring. If the the barrel of a .38 spl is slugged, I take out my .356 size and see if it fits. If it doesn't then I go to the next size up and so forth until I find the proper size and then size one thou over that. Sometimes the only way to measure it is to set the micrometer at the best guess of what you think it should be and with the bullet you slowly turn it between the opening and see if it just moves barely or if you can see daylight in between.
You can use a cast bullet to slug your barrel, it should be slightly oversize and soft, either pure lead or 30-1, this is the same hardness as most would use in the .38/55 despite someones' recommendation here to use BHN 25 bullets!!!!! What ever you do, don't use them to slug a barrel!!!!
Finger Toes
Regular
- Location
- Yellowhead County
Ya, the tightest point in the bore should be at the crown as far as I understand it. I'm under the impression that if the bbl is turned to dimension after it has been rifled the bore opens slightly more where material is removed. I've also heard that factory hammer forged bbls have made improvements over the years by trying to keep the muzzle end tighter than the breech before they are contoured. Kriegers are supposedly rifled after contouring to solve the problem. I agree a tight spot in the bore anywhere but the crown will kill accuracy to a certain degree.
Ok so I have had the rifle slugged by Shane at Reliable Gun here in Vancouver. Barrel slugs at 0.378. Should I be using bullets sized to .378 or go a tiny bit larger? I will provide that info but seems I misinterpreted Marcs remarks and he is much happier now that the barrel has been slugged. FYI shoots Winchester Super X factory jacketed rounds happily with excellent accuracy.
