I am working with a new-to-me 1954 Marlin 336 in 35 Rem. It has a 7 groove barrel and because of the odd number I can’t drive a slug thru the bore and measure it. What is the best way to find the sizing diameter for best accuracy?
I have sizing dies in .356, .357, and .358. The only thing that I can think of is to try them all, which could be a lengthy (and component consuming) test.
Any thoughts on the best approach?
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shoot as big of a bullet as the throat will accept.
"if it was easy we'd let women do it" don't tell my wife I said that!
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Bump a slug in the throat. It's round, and what you need to know anyway.
Glenn
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I had best luck with hard linotype in my microgroove 35 Rem when running about 1600.i was able to shoot .360 diameter
"if it was easy we'd let women do it" don't tell my wife I said that!
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My experience with with the Marlin 1895 .45-70, two with the 12-groove Modified Micro-groove. This rifling requires a bullet fully fitting the leade and seated as far out as reliable feeding will allow. I'm shooting used linotype with Javelina NRA lube at 1500 feet-per-second. The bullet dropping at .459+ and sized in a .460 die just to lube.
This give less than two-inch groups. (I hate to scope and test loads as these two rifles are hard on scopes.)
There are those who disparage Micro-groove rifling while not knowing or forgetting that Pope barrels are shallow groove. Pope barrels are renowned for accuracy.
Farm boy from Illinois, living in the magical Pacific Northwest
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A friend has a Marlin 336A in .35 Rem, I think 1950 so same rifling as yours. We measured it at .361", so big bullets definitely the go. And don't rule out paper patching to get there.
Loading oversize is no sin. At the very least "fill the throat". I had a Mannlicher Schonauer 9x56 carbine with .353" groove diameter and .359" start of throat (and a long throat). It shot poorly with .354" bullets (#350447HP and 358009HP sized .354"). When I ran the #358009HP unsized at .360" it was suddenly producing 1.25" groups at 50 yds. Load was 40 gn 3031, velocity a little over 1900 fps, and the load shot to the sights.
Some older cartridges do not have a throat - the bullet just collides with a fairly abrupt rifling origin. This definitely applies to .30-30, with which I am familiar. I'm not sure about the .35 Rem, but I suspect it might also be throatless.
In the absence of a throat, I get good results from .30-30 by filling the neck with a .312" bullet. The neck takes on the guidance function that would be performed by the throat in a more modern cartridge. Put another way, in these throatless cartridges, use the biggest bullet that will chamber freely. That may require keeping a lookout for over thick necks, ensuring that everything has clearance.
One way of determining the biggest bullet you can use is to measure the O.D. of necks on your fired cartridges, then measure again when they are loaded with bullets of a known diameter. The difference is how much you can add to that "known diameter". Springback after firing will ensure neck clearance in this calculation.
Another method is to see how big a bullet you can get into a fired case without expanding it any further. Again watch for the odd thick neck that could give you tight chambering - or do a really gentle outside neck turn to touch just the high spots and to find the rogue cases.
You are only as good as your library.
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Wilderness: You are correct, it has no throat.
Bill: Interesting question. The mold was given to me by a friend who shot handgun silhouette. It looks like an RCBS block, but it is set up for a Magma machine. It has no markings at all. The bullet weighs 206 gr in scrap lead. It looks similar the Lyman 358315 with a flattened nose. When seated to the crimp groove, it engraves in the rifling and requires a little extra squeeze to lock it up. (No throat.). When seated to the crimp groove in a .357 mag case, it is just short enough to fit in a Blackhawk cylinder. I have wondered if it was intended for Contenders in .357 mag / max and 35 Rem.
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I have a Marlin 336 Sporting Carbine in .35 Rem with the same 7 groove barrel. I've never slugged the barrel. I just started with .361" sized bullets. They chamber easily and shoot great at full power.
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Admiral:
If you are sizing .361, I should be able to shoot mine powder coated and un-sized.
Two questioms:
What bullet are you using?
When was your 336 made? The letter in the serial number is a date code.
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Wayne I might be wrong but it sounds like you’re trying to measure bullet bearing surface. The sizing die affects the bullet base and has more to do with the freebore dimension than the lands.
“ What is the best way to find the sizing diameter for best accuracy?”
It sounds like your mold is a spitzer design?
A fast way to see how much contact you have with the lands is to cut the nose off a bullet, finger lube/grease it, then tap it down the barrel. A brass rod with some electrician tape to keep it centered will let you see how much contact you have with the lands and you’ll be able to feel for loose spots in the barrel. Not a dead’s on hard number but you’ll know if the nose is making solid contact which helps accuracy. Same practice is used to pound cast which is a good idea and easy to do.
Another way is to run a tight neck bushing, using an unsized bullet, seat the bullet long and look for land and freebore impressions after chambering.
Doing that 2 or 3 times will give you the freebore diameter (if the cast bullet base is larger than the freebore diameter), lands engagement (assuming a spitzer the nose which is designed to engage the lands its entire length other than north of the olgive). And if you watch closely and catch both the freebore and the lands with the same bullet you’ll be able to rough measure the freebore length. Let me know if that makes sense. Bill C.
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Boschloper,
Date code is "H" which on a chart I found says 1951. The bullet is from an Accurate mold 35-210B.
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Bill:
What I am after is the diameter to size bullets to for the best accuracy in my particular gun. I can’t just drive a bullet thru the bore and measure it because of the odd number of grooves.
The bullet that I am using “looks” more like a pistol bullet than a rifle bullet. There is a short driving band in front of the crimp groove and the ogive starts just in front of the driving band. There is no bore riding section.
The barrel has almost no throat, the rifling starts right in front of the chamber.
When the bullet is seated in the crimp groove, the ogive is engraved into the rifling as the cartridge is chambered.
Wayne
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size bullet as big as will chamber is the simple answer.
"if it was easy we'd let women do it" don't tell my wife I said that!
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Aaron
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