Throating or modifying lever chambers?

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  • Last Post 06 July 2017
Canuck Bob posted this 12 May 2017

http://www.castbulletassoc.org/thread/6375-best-chance-for-a-tack-driving-32-20-rifle-load/

This link is to a 2010 thread I started.  Ed Harris answered my question and I recommend folks revisit it if the 32-20 is a caliber that interests you.  He discussed the throat many lever actions are saddled with.

This thread is to discuss throating lever chambers. I'm considering Ed's advice for a 32 Special Win 94 and a 32-20 Winoku 92.  Has anyone done this to a lever action or throatless chamber? Results?

 

One thing I'm considering is to cut a tapered leade at 1 to 2 degrees per side and dispense with the cylindrical throat portion (freebore).  The idea is to seat with rifling contact to centralize the bullets nose.  What do you guys and gals think?

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onondaga posted this 12 May 2017

The 15 degree basic taper opened up to 3 degrees necessitates increasing your ammo LOA for the bullet to engage the taper Your bullet shape determines the amount but it may be substantial depending on your ogive.

Engagement of the 3 or the 15 degree taper both stabilize and center bullets. The difference for cast bullets engaging either angle doesn't effect accuracy if both engage. You would would only be changing the needed LOA for the taper. Stable is stable with either angle.

The RD design bullets have a big diameter flat nose and only a slight ogive so either taper can be engaged without huge difference in LOA.  Bore riding bullets offer no advantage as the under diameter section will exacerbate LOA problems in either taper if engagement is achieved. You get really long ammo because the riding nose doesn't contact till it hits land to land contact . Those kind of bullets need to be set out till the first bearing band engages.

Yes, I am saying that good bullet selection is better than throating 3 degrees and stay with the standard cut.

 There is certainly arguments the other way giving 3 degrees a more gentile start for jacketed bullets but the same is same with cast bullets. A cast bullet that slides in the chamber and when fully chambered engages the taper is the best fit for either taper.

Gary

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Ed Harris posted this 12 May 2017

If you go back and read the original article in American Rifleman, the AMU style 3-degree throat improved accuracy in .357 and .44 Magnum Marlins firing factory ammunition and no attempt was made to change bullet shape or cartridge OAL to contact the throat.  Shooting .38 Special 148-grain wadcutters in the rethroated .357 Magnum chamber produces wonderful grouping despite the long free bullet travel.  The reamer used had no ball seat at all, but was a long gradual taper from the .379" diameter case mouth.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Canuck Bob posted this 26 May 2017

Thank you both.  Gary this rifle is my tinkering gun.  I appreciate your advice but that chamber irritates me.  The plan is to form the leade just from the groove diameter.  

Ed thanks for the info. I googled it and was amazed and educated by what I found.  I don't have access to the article but your description is concise.  I can't see any problem with a leade starting at groove diameter, can you?

I'm seriously considering fire lapping in a careful manner.  In a sense shooting in a gentler rifling transition as a start.  One nice thing about this chamber is there is no throat to enlarge or erode.  A tight patch indicates minor tight spots at the stamp and rear sight dovetail.

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Ken Campbell Iowa posted this 26 May 2017

hi ... i have a ppg throater for 308 with a 3 degree angle ... just for the purpose of this modification .  the taper is max at 0.313 and tapers down to under bore dia.  the 0.313 is in case some of the older " worn "  throats  needed to clean up, but if infeed is less it will cut smaller.   if interested pm me ; maybe we can further your project .

ken

 

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Canuck Bob posted this 05 July 2017

Thanks Ken, I'll ask for a rain check please.  I'm undergoing chemo and had my first cataract removed last wed. and the next cataract in 2 weeks.  Everything is on hold until I know the outcome of my new vision.  It's a little early but my right eye is capable of iron sight use already!  I'm a lefty so the next eye is the shooting eye.  Easy peep sight use would be a dream, the silver lining in a rather cloudy life right now.

 

Your reamer is a perfect fit.  I'll PM when things settle a bit, probably early aug..

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Bud Hyett posted this 06 July 2017

This can be done, it takes a lot of time. Marlin 1895 .45-70 rebarreled with a 28 inch heavier barrel, chose a reamer with 3 degree lead, no ball seat, and gave sample bullets to the gunsmith. The goal was a long-range lever action rifle with heavier barrel for competition.

I helped the gunsmith chamber the barrel, this was tedious work. There were many times of putting the action on and off while trying sample loads and slowly advancing the reamer. Marlin headspace is the relief for the rim thickness and the tightness of the locking bolt when closed. This requires assembly to assure complete lockup after each cut - time consuming. 

The chamber was cut for seat the bullet into the leade with a slight marking.Bullet choices for single-loading were the SAECO 645. 745. 1881 and a custom Hoch 480 grain mold. The RCBS 300, 405 and 500 grain gas-check molds were set at an overall length to operate through the action and a snug fit when closing the action. . 

Everything shot well, nothing shot exceptional. The best load was the RCBS  45-300-FN with 49.0 grains Reloder #7 that made this a varmint rifle in a way. 

In the end, I bought a Sharps and put this rifle away. I still have the original barrel and will return it to the rifle sometime this Fall.

 

Farm boy from Illinois, living in the magical Pacific Northwest

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