30BR barrel length

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  • Last Post 03 June 2010
delmarskid1 posted this 16 May 2010

  A friend and I are putting together an inexpensive cast bench rifle on the 30 BR case. I have brass, neck die, and chamber type seater. My barrel is a stainless, 1/12” twist, 292” bore, .308” groove depth. It is a 30” blank with a #8 taper.  My main question Is how long do we make this thing? I like the idea of a 20: barrel as it will balance well on the bags. It should be alright for weight with a 24” barrel but who needs the velocity gain? Nobody in my club shoots cast bench rifles so I don't get to try any on for size. Any thoughts? How bad am I messing up with the small hole down the middle? I was going for a tight nose ride and a little more rifling depth. We have the Rabenet reamer. So far the only part that has been inexpensive is the Stevens action. On that note what are my stock options? Thanks guys. I hope to see some faces some day to go with all the astute information that I have been blessed with since I've joined this group.

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billwnr posted this 17 May 2010

I'll be interested in the results of your rifle. There's a bunch of things that go into an accurate .30BR. I've shot barrel lengths of 22 inches up to 27 inches. The quality of the barrel is more important than short or long barrels.

29.2 grains of Vitavouri N135 and a 180-208 grain bullet would be a good starter for a .300 bore barrel. Not sure what .008 smaller would do, but it will increase chamber pressure.

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Vassal posted this 17 May 2010

IF you plan on shooting PB I have heard it said that shorter is better. But I have no direct experience with such a terrific project.

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JetMech posted this 17 May 2010

Shorter barrels tend to be stiffer: less harmonic vibration. The question is what powder do you intend to use? You need sufficient barrel length tp allow 100% powder burn plus a couple inches to allow pressure to decrease so that as the bullet leaves the barrel, the escaping gasses have less tendency to disrupt the flight path, to my way of thinking.

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delmarskid1 posted this 17 May 2010

Those are all good points. I will probably go with the medium fast or fast medium powders to start with. The .292” is a typo. I meant .298"

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JSH posted this 17 May 2010

Powder burn in short barrels is a wives tale/myth 99% of the time. Maybe an issue with a belted mag case and a bunch of slow burning powder. The BR case was pushed as much by IHMSA as any of the shooting communities. Max barrel length for that was 15". I have shot enough CB's in full length rifle calibers in 15” barrels to put the old thoughts of “in complete burn” to bed. Actually a good powder bullet combo in a rifle length barrel will show good promise in a pistol as well. Blasty, yes. Inaccurate, nope. I have a 30BR project that needs finished up on an XP 100 that has a 15” Hart barrel. jeff

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billwnr posted this 17 May 2010

More important than barrel length is the angle and length of the throat and.... how deep to seat the bullets in the cases.

Tight necks are a plus!!!

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Tom Acheson posted this 17 May 2010

Ditto with what Bill said on the throat detail. I have a 15” XP-100 using a 30 PPC round that likes either 28.6-grains of Varget or 28.0-grains of N-133 with a 180-185-grain bullet. For some reason the set-up likes muzzle velocities between 1980 and 2100 fps. make it fun to hang onto over the bench!

I always thought that best acuuracy for CB's was to have the bullet in contact with the lands at ignition and maybe even a slight resiatnce on the bolt as an over-length round is chambered. But my Savage in .308 Winch.seems to have at least one flyer in 5-rounds groups under that condition while rounds loaded shorter and not in contact with the rifling, have fewer “flyers” (couldn't be the shooter could it?).

Tom

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delmarskid1 posted this 17 May 2010

  I'm still listening. Keep up the good work fellas. I'd like to hear more about this throat angle business. Seating depth I can change easily. Moving throat metal around is a lot more permanent. I did cough up for a cut rifled barrel from Brux Barrels.

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Tom Acheson posted this 18 May 2010

The throat angle some of our local guns are cut at is 1 1/2 included degrees or 45-min. per side. Then they use the reamer they used to chmaber the barrel to make a bump die. The bump die imparts a taper to the bullet that matches the taper of the chamber throat. Coinciding tapers is a good accurcay combination. They also use tight necks (no less than 0.005” clearnace per side), thurned necks and then just experiment with seating depth and neck sizing bushing. I have XP-100 in 30 PPC that didn't shoot well the first year I was using it until I extended the seating depth AND tightened up the neck bushing to get a slightly firmer grip on the bullet. Just tight enough so that when a loaded round (about 0.015” overlength) is chambered, the bullet isn't so loose in the case that it gets pushed back too far into the case when closing the bolt. Just feel a small amount of resistance as the bolt is closed.

FWIW.

Tom

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delmarskid1 posted this 03 June 2010

Well we got the thing together and I'm nearly ready to shoot it. My friend got tired of waiting for me to make up my mind about the barrel length and cut the barrel to 23". He figured an odd number would suite my personality I guess. It looks good  anyway. .80” at the muzzle with a straight taper to 1.20". With the 1.20” running about 3” to the receiver. I'll be needing a smallish bushing to keep the bullets from going in the case what with the smaller than standard bore size but they show a nice set of engraving marks on the bore riding portion. I'm pretty fired about shooting this thing and would love to skip work and shoot it in but I need to pay off Mr. Mastercard too.  Thanks to you all for the words of advice. We get better by shooting with people who shoot better than us, right?

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