Removing the gas check step from a mold

[Centaur 1]

Hi everyone, new to bullet casting so please be patient with my questions. I have just enough knowledge to be dangerous. :D

Here's my deal, some of you might have seem my other posts so I'll try to keep this short. I need a bullet to plink with out of a Marlin 336ss that is chambered for 30-30. I don't want to use a bullet that weighs any heavier than it needs to be as long as it's accurate enough for plinking, and maybe a squirrel or two. Logic tells me that the less a bullet weighs, the more bullets that I can mold from my finite supply of lead. Using that criteria my first choice is the Lee C309-113-F, but other options are the Lee C309-150-F, and the Lee C309-170-F. Correct me if I'm wrong, but I'm under the assumption that a flat based bullet will shoot better than a gas check style bullet without a gass check installed. And since I'm on a budget I don't want to use gas checks.

Back to the title of this thread. I own a reamer that cuts a hole at .3115. Is there anything wrong with clamping the mold together and floating the reamer into the mold to remove the gas check step. I could stop the reamer just shy of connecting with the rear dring band, which will leave me a small lube groove. Also since the mold has an advertised diameter of .309 which is exactly .001 over my bore diameter, my last driving band would be slightly larger at .3115. It seems that quite a few Marlin owners are recomending a bullet between .311 and .312.

So, will my idea work? I'm sure that someone has tried it. To top it all off. I have a buddy that runs an indoor pistol range, so most of my shooting will be at 50 feet. I just hang picture targets of animals on regular printer paper, I figure if I can hit the small target at 50 feet offhand, that it'll be good practice for hunting

[longbow]

Do a search and you will find several posts on the same idea. Ben did a nice job on a mould not to long ago (search Ben).

I have made a D reamer and am about to modify a Lyman 314299 to make it plain base. I have an NOE 316299 gc so thought I would modify the old Lyman. I generally shoot without gas check anyway.

If you set up in a drill press or milling machine you should have no trouble. Free hand may work if you are careful.

A couple of people have managed to do a nice job just using a drill bit so a reamer should do just fine.

Personally, I find gas checks a pain and prefer plain base boolits. If I want to go faster I will paper patch.

No personal experience with the boolits you are suggesting but I am thinking the 113 gr. might be a little short so unless it fits the throat well, accuracy may not be great. Something a little longer might do better. Just my thought but maybe someone here has some hands on experience.

Longbow

[quack1]

It'll work. I reamed out the gas check shank on a sc 311291. It added about 2 grains of weight and they shoot as good as any other bullet i have tried. I set the mold up in a mill and centered the cavity, but I don't see any reason a drill press wouldn't work if done carefully.

[RKJ]

Centaur 1, I'm not trying to hijack your thread but I also have a question: Could you use a GC bullet w/o a gas check? I'm thinking handgun but I'd still want accuracy. How would this degrade accuracy and bullet deformation? Thank you for letting me piggy back onto your thread.

[RayinNH]

RKJ, this should answer your questions...Ray

http://castboolits.gunloads.com/showthread.php?t=65035

[3006guns]

I "plain based" a Lyman 8mm mold because it had the WORST machining I'd ever seen, so basically the mold was a clunker (machining marks on the nose).

I chucked it in my 4 jaw lathe chuck and carefully bored out the gas check step, watching until the cut blended with the main diameter......here's where I got into trouble. After about five tender cuts, I finally measured the diameter while it was still in the chuck and found that I'd bored it to .331! Way too big, so I thought I'd really screwed up......until I sized and lubed it. It makes a perfect non GC 200 grain boolit that really performs with 9 grains of Trail Boss.....very accurate and the only mold I use now for 8mm Mauser.


My point is that I have the necessary tools and experience.....yet despite my screw up the boolit works very well. I'm sure careful hand work would produce the same result.

[Centaur 1]

Thanx 3006guns, I was thinking that an over-sized band at the base of the bullet would work.

[JIMinPHX]

I've had great results using the 150-grain Lee flat point in a Marlin 30-30. I size to .310". I tried some shorter boolits & got bad accuracy.

Some folks have removed gas check shanks, the way that you are suggesting, with good results. Others have wrecked molds trying. A guy with a lathe or milling machine should be able to do a reliable job of it. A guy with less rigid equipment may be taking a risk, but with good craftsmanship may prevail. It's a $20 mold. Availability seems to be getting better these days. It's up to you.

[theperfessor]

For a less rigid (drill press vs milling machine) to keep the chatter down and have better control of the reamer you can turn it by hand with a tap wrench or pair of locking pliers after you chuck it up and align mold under spindle. If you're careful you won't go too deep this way. And a drop of cutting oil helps.

[MT Gianni]

A sizing die takes a lot of the oversize out if need be.

[frankenfab]

You could definitely eyeball it and do a good job, but it would be best if you could clamp the mold in a vice and indicate it in with a coax or other indicator before reaming. If you know any machinists, they could get you fixed up in a snap!

[RKJ]

RKJ, this should answer your questions...Ray

http://castboolits.gunloads.com/showthread.php?t=65035

Ray, Thank You. That did answer my question.

[Centaur 1]

Unfortunately I don't have a lathe or a mill at home (yet), but I've worked as a toolmaker/machinist for over 30 years before I took a medical retirement. I'm not afraid to use my drill press, it'll take a little finess but I'll indicate its location and float the reamer in. The drill press doesn't have a power feed, but I bet I could even use a boring head if I go slow. If I ever fall into a little money, I'm going to buy one of those $5,000 milling machines from Harbor Freight.

[JIMinPHX]

If you were to drill & ream a hole in a small piece of flat bar & then indicate it to to be concentric with the gas check shank hole in the mold blocks & C-clamp the reamed flat bar in place on top of the blocks, I'll bet that, with a little oil, it would make a dandy guide to keep everything where it needs to be when you run the reamer down into the blocks.

that's just off the top of my head, but I think that it should work well.

[Elkins45]

I wouldn't do home surgery on the mold until I had tried to shoot the bullets as-cast.

No sense taking the chance of ruining the mold when there's a pretty good possibility you don't need to modify it at all.

[runfiverun]

finite supply of lead and buddy that owns an indoor range is an oxymoron.....

[beemer]

I have a single cavity 309-113 that poured close to .313. I found a drill bit that was close and clamped the blocks in a small vise on my drill press and floated it in by hand. It cut very easy so the chuck was turned by hand. It shot good in my 32 S&W Long but was heavier than I wanted.

Next I scribed a line around the blocks about even to where the gas check shank would have been and started filing. I cleaned it up and squared it up the best I could by hand. I now have a nice flat nose 100 gr mould for my 32.

The bullet also shoots very well in my 91/30, about 1 in. groups at 25 yds with a small charge of Trail Boss. I haven't tried it in my Marlin but I suspect it would do well.

Dave