So I'm looking at buying a Marlin lever action 45-70 and thinking that I would like to reload for it. Checking out the Lee molds, I see that the only gas check mold they have is in the 500 gr. model.
Seems that a GC would be needed for a stout 300 gr lead bullet to get a good trajectory.
Wondering if some seasoned reloaders can shed some light on this for me.
Thanks.

Unless you intend to severely nerf your loadings for target practice or cowboy stuff, then gas check your loads. Use a different mold for fast moving bullets.

A 300 grain bullet doesn't need a gas check to tip over steel. It does need some checking when you apply ballistic/hunter scrutiny.

Thanks Dan. That is along the lines I was thinking.
I'm looking at Lee dies because the cost is affordable. It just doesn't make since to me that they don't make them in GC model. It seems they would sell more if they did.

I don't shoot cast in 45-70 but I do in several other calibers. As long as you are sized properly and using the correct alloy/hardness of bullet and a good lube, you should be able to run up to about 1500-1600 fps before needing to use a gas checked bullet (though I have heard of those with success at faster speeds).

For the 45-70, I don't know that I'd call that a "nerf" load but it certainly limits you to roughly trapdoor loads or the very lower end of lever-action loads at best. Given that many folks want the extra punch of the loadings available to Marlin lever-action and more modern firearm designs it is odd that Lee doesn't offer a gas checked version of its 300 and 400 grain 45-70 bullet molds. But then, I don't even see a proper 300 grain bullet mold, just their 340 grain mold...

Unfortunately, that means you'll need to look elsewhere for the mold. Look around for used molds and hopefully you can find a good one without having to spend too much. On the other hand, by spending the extra you can get a much better mold that will last much longer than the Lee aluminum molds. They are fine for beginners to find out if casting is for them, but they don't hold up well.

Looking at other companies, there doesn't seem to be many 45-70 in GC.
I called Lee just to confirm since they used to make molds for Ranch Dog with GC (now out of business). The guy said it was a lot of trouble to cut the GC groove into the mold.
Anyway I just found a site that now sales the Ranch Dog molds. They are aluminum and pretty sure they are made by Lee.
The lightest weight is 350 gr. would be okay. They run from $79 to $133.

You can try to contact stephen45-70 He is into casting and reloading the 45-70. He had a couple molds for sale but I don't remember the caliber.

Good idea so I looked it up Turns out it was for 38.
Thanks anyway.
Maybe He'll chime in when he gets a chance with some advice.

Google "custom bullet molds". There are several companies that will make any mold you like. Accurate Molds has several gas check molds already in their catalog. The 45-255S is my design for muzzle loading with a sabot. If you have a good design that isn't in the catalog they will add it.

To gas check or to not gas check

I do have a couple questions .. the marlin you are looking at. Is it a micro groove barrel
Or ballard or conentional rifling .
The micro groove barrels need a good bit more work to get cast to shoot well in them at times
They are also fairly slow as to twist rate .

Lets assume it ballard or conventional rifling .

First consideration with lever guns is bullet lenght ..it does have to work threw the action
And that usualy leaves bullets over 400 grains out of the picture without seating bullets realy deep
Twist rates are generaly to slow for heavier bullets anyway

So that leaves most lever gun shooters looking at 350 grain bullets like you are
Like you a lot of fellows look at launching them at warp speed to improve ballistics ..this line of thinking usualy doesnt last long once you get tired of the rifle beating the snot out of you
And a 350 grain bullet in a light marlin @2200 fps is going to be painful to a fair percemtage f shooters .


Bit i got off track .. gas checks
Ive found that as bore dia gets bigger the faster you can push bullets without a gas check
A 350 grain bullet cast in wheel weight is very easy to get 1800 fps without any need for a check
2000 fps is obtainable as well if you work with a toughr alloy .. ( not harder tougher)
I
A gas check can make things easier on you as to developing a load and avoiding any potentiol leading issues you mayrun into .
But as you see most molds are plain base for a reason ... the gas check isnt needed for almost all normal shooters needs

Thanks Stephen, that's really encouraging.The Winchester ammo I was looking at is 300 gr. at around 1850 fps out of the muzzle and the leverevolution ammo 325 gr. I think was 2050.
So that may be doable without a GC.
I'm not real recoil sensitive but probably won't be shooting it as much as if it were a 22 anyway.
Oh and it is a new rifle. Pretty sure it is not micro grooved. I believe I read somewhere that they only did that for a while.

Some nice simple advice ... dont get wrapped up in velocity
Let the rifle tell you what it wants .. ie .. find the load that shoots best and stick wiiith it
In the real world the ballistic gains of a few hundred fps is very little .. an accurate load will bring home more meat then a fast load every time . ... and a deer isnt going to tell any differance between a bullet goin 1600 fps.or one going 1900 fps

Oh and if you can find ranch dog molds they are a good choice .. made by lee to his specification
And generaly a step or three better in quality then normal lee molds .. not that i dont like lee mold because i do ... and most of the ranch dog designs are specificaly for lever rifles .

I also recomend staying away from the hornaday lever revolution amm ... it is good ammo but if you want cases to reload after shooting it you will fimd the hornaday cases are 3/10 or so short

That's a good firearm.I bought one at New Carlisle Shooters supply,(now closed) 10-11 yrs back,I've run 300 gr hollows and 400 semi jacketed thru it.Shot real well with the 400s.Have given serious thought on mounting a scope on it.The fish bitin at Adams Lake.I used to live in Adams co.Used to fish the Brush creek over by Marble Furnace.Down below the Old Mail Pouch barn.

Eyes not being what they used to be a scope is a definite.
I live close to Adams Lake and Brush Creek but I don't fish. Maybe if I ever get to retire I will have time for another hobby.