case head expansion

[truckboss]

hi guys,got my first marlin guide gun,45/70.i want to work up some loads and want to know what an acceptable amount would be?

[crabo]

What boolit are you using? plinking or hunting?

[Bret4207]

I strongly suggest you get a copy of Ken Waters "Pet Loads" and read his articles on judging pressure. Excellent advice from a genius in this line.

Beyond that, with cast you usually find our loads running lower pressure than similar weight jacketed. It would be unusual to find one that ran higher. Measuring case head expansion of a factory load fired in your gun will at least give you a standard to work from. Just remember to take a reading of what the brass measures after being run through your dies to see what they leave it at compared to unfired. IOW, if the unfired factory load is, say, .475 (I have no idea what 45-70 brass measures of the top of my head) and it expands with the factory load to .479 and it measures .476 after being sized in your dies you need to account for that missing thou and set your goal as no more than .003 expansion, not .004.

Hope that helps rather than confuses you.

[btroj]

I don't measure case head expansion, I just go with known loading manual data. I also don't use max loads in my Marlin.
I don't think the extra pressure and recoil a few grains of ppwder makes a difference in the ability of the 45-70 as a hunting round. A 405 gr bullet at around 1700 gives much lower pressure than the same bullet at 1900 but will kill just as well. Much easier on the shoulder too!

Bret gave good advice on measuring head expansion. This is a guide but I would not use it as the entire basis for your load levels. Much data exists for the 45-70 so you should be able to find loads that fit your needs.

Brad

[truckboss]

thanks for the replies.the bullet will be a 350 grn. wfngc,i was trying to get bout 2000fps.just trying to shoot a little flatter,not really trying to make it something it's not.what kind of powder does this gg like? re#7,h322,h4895,varget etc.thanks.

[MtGun44]

Case head expansion is maginal at best, has been bypassed and is a reason that some
modern reloading data is a good bit slower than older data done with this method.
Case head expansion said the load was OK - actually measuring the pressure with a
piezoelectric transducer showed that the old method was off, so the data had to be
corrected.

I recommend a chronograph and matching the velocities that are quoted in reloading
manuals as a max pressure indicator. If the book says you can get 2000 fps from a particular
bullet and barrel length in .45-70 with a particular powder, expect less with a shorter barrel
(altho not much with a straight case like .45-70) and if you are getting more velocity, you
can count on the fact that you are generating more pressure - not some magic chamber or
super bore or whatever is commonly imagined. Guns will shoot faster with tighter chambers,
but that is because they produce more pressure.

Bill

[Baron von Trollwhack]

If you get a really sloppy Marlin chamber you will get a lot of case head expansion. The real question is how you deal with that in reloading. BvT

[btroj]

Well, if you get 1900 fps it will shoot about as flat as 2000 fps. Flat is not a word to use when describing a 45-70.
I have spent lots of time with a ballistics program trying to see if the 45-70 can be sighted for 200 yards dead on and still work with a dead on hold for closer in. Nope.
Of you want to hunt past 100 yards with a 45-70 either get a range finder or learn to estimate range yourself. Then learn how to hold over the correct amount.

RE7 or 322 will work well to give you the velocity you want. Just realize that you will also be getting some hefty recoil. I would suggest you work up to it.

Brad

[truckboss]

i think i found one of my answers.my shoulder will run out of room be fore my load does.i fired some 425grn. with 50 grn of h322,ouch.this load expanded the case bout .004 more than this load,45grn imr4895 with a 350.this load leaves the case just about the way it was before i fired it.i can't measure my chamber but the case is real close to .483, this seems loose to me?

[btroj]

Ignore the expansion measuring. Follow known load data and you will be fine. Hodgdons website has lots of data. I also use data from Handloader magazine a lot.
As for a generous chamber, it might be. I cant say I have measured mine. I just shootem and size em. No measuring other than case length every so often. As long as you follow good data and don't try to push thing you will have no problems.
Your shoulder will be the likely limiting factor. Pushing a 425 past 1700 fps is not at all fun. Uless you need that much horsepower I would suggest going to a more reasonable load.
Try that 425, or the 350, with 24 gr of 2400. Should go about 1350 to 1400 fps and shoot well. Won't beat you to death either.

Brad