Gas check question [Archive]

Rockchucker

11-19-2009, 09:51 AM

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I bought a Marlin 1894 in 357 with micro groove rifling and was reading more about the rifling and it is recommended to use gas checks for better accuracy. Well since I'm wanting to hunt some with this gun it looks like the way to go but not knowing or ever using the checks I'm kinda lost. I'm looking at some RCBS and Lyman gas checked molds in swc designs in 158 grain. Now are there different size checks for each size of the boolits? I'm sizing all my boolits to .357 and getting a shinny clean bore and using Carnauba Red lube. I do have a Lyman 4500 with the seater (don't know how to use the seater yet though) I guess my main question is what size gas checks do I get? Any help would be greatly appreciated, Thanks.

jlchucker

11-19-2009, 10:14 AM

Get the 35 cal gaschecks that Hornaday sells, or some other brand. They should fit every bullet you cast for your 357, and the same gascheck works for 35 Remington. Whatever mold you buy though needs to be a gascheck design if you want to make gascheck bullets. The bottom part of the cast bullet, where the gascheck fits on, should be the same dimension for all gascheck bullet molds-assuming good quality control by mold makers. That lyman seater is easy to use. It's purpose, when installed below the H & I die, is to keep the bullet from going down into the sizing die when seating the gascheck as a separate operation. You'll have to remove that gascheck seater and size/lube your bullets as a separate operation. The seater goes UNDER the sizing die and is nothing more than a spacer. Your manual should show you a sketch to go by--describing it verbally seems kind of vague and I apologize, and defer to others for a better description.

BABore

11-19-2009, 10:22 AM

You need either Hornady or Gator 357 gas checks. They are both crimp on style and only come in one size unless the check maker screws up. Which they do on occasion. Lyman also has a GC and is supposed to be a slip on. At least they used to be from what I've read. I've never used them and never plan to. What can slip on can also slip off, and not necessarily in the same place.

I don't own a Marlin, MicroGroove 357 Mag, but I do know MG rifling. I would highly suggest you slug your bore and also measure the inside diameter of a fired case, with crimp removed. MG rifling like BIG boolits. It not really that the rifling is shallower than the current Ballard rifled bbls, cause it's not. Both run around 0.0035 deep. MG rifling has many more lands and grooves than conventional rifling. It tends to not hold a good grip on a cast boolit that is just little bit over groove diameter. Personally, I would size boolits to what will safely slip fit into a fired case, regardless of groove diameter. Even if your groove is 0.357, if a 0.360 boolit slips into a fired case, use it. Your bbl is a very effective sizing die. A boolit with very limited clearance in the chamber and throat will be more likely to drive straight into the rifling over one with a few thousandths clearance.

You need to also look at boolit nose profile before you gt a mold. Nose length and profile are critical feed and function in the Marlin. The is an OAL that can't be exceeded unless the shell carrier is modified. Imashooter has a good post on that, so you should do a search for it. While SWC's will feed, you sometimes have to seat them deeper and crimp over the front band. Sometimes it's due to OAL, sometimes it's the front band being too long for the throat. The RNFP, LBT-style or 640 nose style is a better boolit IMO.

Wally

11-19-2009, 10:23 AM

Rockchucker

I have a 1894C and have used it for over 25 years. It works beautifully with almost any bullet with the exception of those over 160 grains. It works well with any .38 Special round that I have used as well, inclusing wadcutters. . This year I used for the first time aluminum home made gas checks with it and they worked superbly. I used the Lyman 358156 with 8.0 grains of Unique to obtain 1,500 FPS MV. Using Blue Dot I can get up to 1,800 FPS, but I have found that the Unque load serves me very nicely. I size my bullet to .359" using an old Lyman 45 sizer/lube tool.

It is an accurate and handy carbine; a lot of fun to shoot.

Rockchucker

11-19-2009, 03:24 PM

I just ordered a set of Skinner sights for this gun hoping to get better accuracy. Using a 358-158 RN boolit I shooting 4 inches left of dead center of the bullseye, and with no windage adjustment on this rifle I'm not very happy with the sights, but love the gun. I appreciate all the help and going to order some Hornady gas checks and a new mold.

BABore

11-19-2009, 04:16 PM

Rockchucker

11-19-2009, 05:51 PM

You should be able to drift the dovetail mounted, rear, buckhorn sight to to the right to correct your POI.

I called Marlin up and that's also what they said, So I took a small dowel and tapped it over some until I can sight it in some more. I like the peep sights too, the Skinner sight had some great reviews so I ordered a set today. Our hunting season starts in one week from today (Thanksgiving), so after giving thanks and chowing down I'm hitting the lease with my brother and see what this little gun will do.

Blammer

11-19-2009, 06:28 PM

ah, another convert. :D It won't be long, you'll be shooting 180gr boolits and tipping over deer too. :)

the gator checks are labled as 35 caliber.

Rockchucker

11-19-2009, 07:01 PM

Thanks Blammer, something about cowboy guns That I love, This is my first lever gun but have several single action Rugers I load for. The 38 40 win. is a gun I'm real interested in and can only find the high end ones going for 1600/1800.00. Guess I'll hold off til after Christmas and hit a few gun shows. Ain't nothin but an addiction we all seem to have.