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Discussion Starter #1
Been reloading for well over 45 years. I always slug my bore and size accordingly.

Here's my question for my fellow casters and reloaders. My Marlin Guide Gun (mfg. 2009) mikes out at .456". I keep hearing how so many have to use .460" rounds etc. and how Marlin 45-70's are known to be overbored and need large size rounds. Most everyone repeats that the Marlin likes fat rounds.

I cast both with Lee and Ideal moulds and size to .457 with a VERY soft mix of lead. I have no problem accruacy wise, and no leading either. I do not drive my rounds at hyper speed, as I just don't enjoy beating myself up with my weapon.

So if ya'll could advise what your bore sized out to be it will give me an idea if I got one of the few that are either undersized or what...hope that made sense...

Thanks, Wade
 

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I thought it was just the 44's were over sized. Honestly I never slugged my 45/70. Tried .459 bullets & they worked so I never bothered.
 

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The bore in my 1895 isn't over sized...its .457", I think its the throat thats over sized and makes oversize boolits necessary. That helps to get everything aligned and pointed the right direction.

I cast and shoot .460", hard alloy, gas checked boolits...because I push them as hard as I can push them...I like recoil! :)
 

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My guide gun runs about .4563, like you I size to .457 and it works great. 8)
 

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piguy said:
My guide gun runs about .4563, like you I size to .457 and it works great. 8)
Just my opinion but I think a .457 is a little small for a 45.70 especially in a lead bullet. I think RidgeRunner is closer by sizing his to .460. A lead bullet should be a little larger than the bore slugs out to be.
 

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Slugged my 1895SBL that I bought new in Jan 2010, and it's .457. I get poor accuracy with Oregon Trail 350's that everyone seems to get good results from, and thought I might have an oversized bore but that appears not to be the case. Guess I'll have to play around with powder levels.
 

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Great question Wade. No I have not slugged my 45/70’s bores.

This is a area that causes great confusion… So maybe we can help clear up this and bury a few other cast bullet myths… :)

Slugging the bore – this is done to “get a feel” of the bore condition and check for constrictions… The actual bore diameter is not what we need to calculate proper bullet fit.

Groove dia. – This is the number that will get us close to the best bullet fit…If we shoot a bullet .001-.002” (over) groove dia. we will usually be close to best bullet fit…

Slugging the throat, or leade – This will give the best results in selecting the proper size cast bullet…It is in this area that’s the hardest on the bullet; if the bullet doesn’t fill and seal the throat, the hot gasses will cut the bullet before getting into the rifling…
Ever clean a rifle with a lot of leading just out of the chamber?? – That’s the cause…

Bullet obturation – is only needed by those who are shooting a bullet too small in diameter to begin with…

Rowdy Tip of the Day – 8)
The easy way to find the correct bullet fit without going thru that entire BS.
Take a fired but unresized case from the rifle and put a slight bell on it.
With a handful of bullets, all different sizes, slip them into the neck by hand – which ever one fits tightest, but still moves without binding – That’s your bullet…. :)
 

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Discussion Starter #9
Well, this is interesting. From what those who have slugged your bores, the average is right around .4567". Sorry, old time crime analyst is comming out here :)

So if I understand correctly the throat at the breach is oversized. One must question why? To allow a multitude of non standard cartridges to fit in a lever action firearm? Due to the camming action being less than that of a bolt gun? Or is it a result of manufacturing of the barrel itself? As a former gunsmith and armourer for uncle sam, I'm puzzled.... ???

The other 45-70's I had in the past were all old original. A '78 TD carbine. An '84 TD rifle. And a '79 or so Sharps rifle....saddly they were sold for a down payment on a house :'( But they were all slugged and if memory serves correct, the TD's ran about .457 and the Sharps was just a tad larger. I shot mostly ,458 sized lubed bullets in them without any problems. I did, and still do, load a lot of paper patched rounds. My lead mix has always been on the soft side probably around 30:1 or better.

Oh well, I guess since I have a bore that measures .456" and the lubed rounds are .457" and I have no leading or bad shooting rounds issues, I'll just go back to what I was doing and not worry about it then.


Thanks, Wade
 

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Wade505 said:
Well, this is interesting. From what those who have slugged your bores, the average is right around .4567". Sorry, old time crime analyst is comming out here :)

So if I understand correctly the throat at the breach is oversized. One must question why? To allow a multitude of non standard cartridges to fit in a lever action firearm? Due to the camming action being less than that of a bolt gun? Or is it a result of manufacturing of the barrel itself? As a former gunsmith and armourer for uncle sam, I'm puzzled.... ???

Thanks, Wade
Wade - It is interesting and I’m not going to downplay anyone’s results. :)

Let’s look at how a rifle barrel is manufactured and how that plays into correct cast bullet fit in general.

Bore the hole.
Rifling - Pull a button through the bore for MG or push a broach through for Ballard.
Rough ream the chamber.
The finish reamer will take the chamber to final spec – and will clean the throat/leade of any machine marks left from the rifling process…Leaving the leade a slightly larger diameter than the grooves…

;D
 

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Rowdy, sounds like a great idea to me. Could I use a micrometer to measure the inside diameter of the once fired brass and use that measurement as the proper bullet size?
 

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findrichard said:
Rowdy, sounds like a great idea to me. Could I use a micrometer to measure the inside diameter of the once fired brass and use that measurement as the proper bullet size?
You may be able to - but I'm not that good with an inside measurement. ::)I go be feel ;D
 

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Discussion Starter #14
Rowdy,

Thanks for the info. My time spent in gunsmithing was about 90% working and building up 1911's and S&W DA revolvers. I was a cop for 25 years and thus a majority of my customers were cops and I was a busy lad working on their weapons. Can't remember how many 1911's I set up all tricked out in the '80's when that was THE WEAPON for cops. Now they're all shooting those .40 S&W's and such in pistols that I think look funny!

My rifle time was mostly spent on muzzle loaders and older military rifles that my customers had. I had built up my first rifle for distance shooting in 1969 at a little firebase out in the jungle. Was a 1957 mfg. Win M70 in .30'06. That was a real shooter and as a sniper, it was my prime piece. After that when not in the field, I was in the armoury working on weapons. So, my time with leverguns is limited, as most of my work was always with boltguns and ML boomers! Oh yeah, and tons of Rem. 870 conversions for cops as well.

So I'll study the Marlin some more and will learn it's little secrets as time permits.


Wade
 
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I've slugged my brothers two Marlin 45-70's, My 2 Marlin 45-70's, and my Ruger 45-70 and my H&R Buffalo.

All the Marlins and the H&R were in the .4585 range. My Ruger was right at .458. They all work best with the .460 boolit, and may even do with .461 or more, but i've not tried it.
 

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I bought the largest sizing die Lyman makes for the 450 = .459"

Loaded up a bunch and they make one hole groups at 50 yards & no leading.

Working out well so far.
 

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I slugged mine and it was at .457" If I shoot plain cast I cast and size at .459" or .460" if making paper patchd bullets I cast smaller and size to .457" and do a double wrap of paper and then lube and run trrough a .461" sizer and load.
 

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I size at .459 with my XLR and GS and both shoot real good with AC WW.No leading unless I push my BRP 420GC hard with lots of H-322.48 grains starts to lead a little but ragged hole groups at 60yards.Get a few lead streaks coming out when cleaning rifle but nothing to worry about.Recoil gets pretty stiff at 48 grains anyway.I shoot the rcbs 300and 405GC and saeco 350GC and Mtn moldPB a lot also,they work fine sized at .459 and the PB bullets shoot real good over 28.5 grains 5744.That loads works real good with the 420GC bullets also.Lots easier on the shoulder.If I don't want to mess with GC's and shoot ragged hole groups,the PB bullets shoot very good with 4759 and a dacron tuft.It's more time consuming than using 5744 but gives a little better groups.
 

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Discussion Starter #20
Well it just seems strange that with a bore that mikes an true .4561" grove to grove, that I get no leading, and super tight groups with my little GG with sized .457 rounds. This is in spite the large leade in the barrel and all. I was just really wondering what the deal was with everyone saying Marlins needed big oversized bullets and such. Guess I've got a fluke huh? What can I say?

Thanks for the replys folks,
Wade
 
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