44 Mag BFR questionable dimensions

  • Last Post 03 January 2019
corerftech posted this 02 January 2019

I procured 2 BFR revolvers over the last 6 years, one in 30-30/10in and one in 44/5in.

I have finally gotten around to “planning” shooting them!

Checked dimensions on both, 30-30 has a .306/307 groove and a 310 throat (bore slug and pin gaged) Great.

The 44- .431 groove, nasty construction at muzzle and frame, .429- (pin gages are minus not plus) throat.

Now for me that is not a good recipe for a cast bullet or even a jacketed bullet.

The spec groove from MRI is .430. I called and was offered a conversation with THE Gunsmith who assembles but I decided to shoot before I cry wolf.

I pushed .4292 240 gr Keith’s through the throats and they slide through with moderate to heavy force but a pencil will slide one through. You are putting significant force on pencil but there is no sizing so the throats really are .429

Additionally my go to bullet is the 310 Lee fpgc. Having them sized to .430, I have to set max oal to 1.625, at 1.630 that is the end of the road. Bullet can’t extend further forward. That is the highest crimp groove plus .025 (groove is set my LEE to give 1.600 at last groove).

So I can’t seat the bullet long to decrease pressure nor can I likely load a longer 335 or heavier bullet with a RNFP or WFN.

Reaching out as I’m looking for any other owners who have experience with the BFR dimensions.

Not crying wolf, like support said, never gotten that complaint for the 44 mag yet. I actually tend to believe him. But I have seen some reports of barrels too large to small and questionable throat sizing.

Caveat: I did some reading and if I understand correct, Elmer Keith set S&W dimensions initially to bullet .0005 under throat, and throat .001 under groove. That goes against all contemporary wisdom of progressive reduction to groove diameter. He was using soft alloy and stout loads. Maybe there is a pearl of wisdom to take from his designs that may apply to BFR. My alloy is about 14.5 bhn and checked (used for my 445 SM Encore) lubed with Carnuba Red 2700.

Any feedback would be appreciated. Hoping to shoot by Saturday and capture some live data.

Running Alliant 2400 ladder at loads listed in Lee #2 from IIRC 14-15.8 grains (and .3 gr over max)

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Ken Campbell Iowa posted this 02 January 2019

 ...   guessing for the very best results, you will need to polish the cylinder throats to at least 0.431  ... and then correct the forcing cone at the frame if it is tight ...   i would at least ask their service dept if they would like to do that for you ...  likely " in spec " though ...  sigh ...

if you get it done right, the cylinders will match and you can " write it off " over about 10 years of great shooting to ease the pain  ... guessing $250 of smithy time ...  but you will wind up with a $2500 custom revolver !! ...

yep, the lee 310 was also my favorite for the 44 mag ...   with h110 ....   my oh my ...


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corerftech posted this 03 January 2019

After work today I intended to go shoot it. Didn’t happen, rain, time, an appt, etc.

got it sterilized of copper from factory test firing with some sweets 7.62 which was only used for 3 mins and very lightly. Factory hoop removed, base pin now allows smooth action. Ready to shoot tomorrow, magnetospeed fitted up and on a 5 inch SA barrel it’s awful tight space.

i have some Keith’s with some NRA lube or what have you on them and some 2400 up to 21 gr in a ladder, from an FA 10 inch I parted with a few years ago. And also my lee 310s over 2400 in ladder to a low dose but at Lee’s manual max. I also have about 20 J bullets, factory federal and Winchester 240s.

Ken I agree, it’s not right. I spent an hour measuring again. I dropped a pin gage from muzzle to breach. Bore is .425 and the perceived frame constriction is not there. Must have been a product of my slugging. Therefore I slugged (poundcasted PROPER) THROAT, 1/2 inch past MUZZLE, and 1/2 inch forward of forcing cone face. 


Breach: .425/.4312

Muzzle: .425/.4312

Throat: .429x (x is .0002/.0003 depending on axis measured)

There is no denial available, it’s a bad deal. But, open minded I will shoot it with the 310s to start and bore light it, and photo/cut/save all targets and holes as closeup. Concerned about keyholing. Concerned about leading. Concerned about accuracy. I’ll have 50 foot to work with. 

I shall find out (potentially) what MRIs service department will be like shortly. I’m crossing fingers that magic happens. The barrel is waaaay oversized, that’s a 444 marlin gorge for a rifle barrel. The only fixes avail are, replace barrel AND open throats minor, or leave barrel and MAJOR open throats. Big throats make dies and bullets a problem, big enough to accommodate a 432 throat. I’m not paying for the fix. 

If it’s got issues I’ll try to clean it at range which is frowned upon as I have found and shoot the j bullets as a test so that the question they will have - did you try factory Ammo? Can be answered honestly.


more to come.

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Ken Campbell Iowa posted this 03 January 2019

from out here, it sounds as though you are not too far from getting it right.   

although i often get myself in deep trouble by being wildly optimistic, " all " you have to do is get the cylinder throat up to 0.431/+

and then produce bullets at 0.431/+ ...   

somewhere in the united states there is a pistolsmith that has the tooling to do those cylinders  in an hour or so ...  we used a small sunnen hone to do thousands of 0.4 inch valve bodies within a tenth or so ... i still have that hone but it also takes experience with that exact work to get the first piece ( your cylinder! ) right ...  no practicing allowed !!    also you could polish these out yourself, just allot for one chamber a day and proceed very slowly and gauge constantly ... 800-1200 grit cuts faster than you might think ...

as far as 431+ bullets, my first thought would be that a lot of molds cast that big in the first place ... if smaller, how about a simple bumping/swaging die to uniform/size/square base/seat a gas check ....  it would be easy to make a bumper die for the flat nose lee 310 bullet .. ..... keith types more difficult .......... oh, not good on rock-hard alloys however ...

keep us informed, improving things is always interesting ..  come to think of it, my guns that shoot the best are the ones that i shoot least ... more fun to try to get a cripple working better ....   


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LIMPINGJ posted this 03 January 2019

Check with DougGuy on Castboolits he can make your cylinder right. 

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John Alexander posted this 03 January 2019

Additional thoughts on making larger bullets to fit throats.  You could also lap out the mold to get the size needed which should be easy on big easy to work on cavities.

The easiest and fastest solution is to simply beagle the mold a layer of aluminum foil at a time until the desired diameter is reached. Yes the bullet will be slightly less round but will shoot just fine in your BFR.  Up to at least .002" out of round I know from direct experience will shoot under 1 MOA in rifles.

Worry of the roundness of cast bullets is a waste of time and not supported by any experimental evidence I have ever seen.




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corerftech posted this 03 January 2019

The issue isn’t fat bullets, most of my molds are custom and drop .432 and if not, have been lapped to drop 432. It’s MRI and the throat issue. This is more of an awareness thread to MRI slacking. This is precisely why they go head to head against Ruger. And they have joined the Ruger club. They tout cast bullet performance yet I’m not alone with small throats and oversized groove. Me paying to fix this is absurd. Not in custom molds, not in smith work. It’s an unfired Gun NIB and assembled poorly. I believe others who shoot cast and shoot revolvers should be aware of the situation and how it is resolved. Of course there is a cast bullet involved, exclusively at that rate, and thus worthy of mention. Appreciate the advise on fixing, was more reaching out to the community to get “experience” from other BFR owners who shoot cast bullets.

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