BFR in 357 Magnum, throat and bore/groove measurements taken today

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  • Last Post 23 February 2021
corerf posted this 16 February 2021

I procured about 2 months ago a new BFR in 357, the 6 shooter released about 6 mo ago. I am a fan of the BFR, I just liquidated a Dan Wesson Pistol Pack (1980's) in such confidence that the 357 BFR would shoot as well as the other BFRs I own and bettre than Danny Boy did with a tensioned barrel system and a tight set gap and lightened trigger. My DW's have been the tightest shooting handguns I have ever touched, hopefully until now.

Then, I bought a second one (funding has been good lately) and received it Saturday, 7.5 inch in 357. So I have twins. Since the second one is on the kitchen table, I decided to measure the throat(s) and bore/groove to see if it would be like my 30-30 or like my 44M (5 shot frame, not the new 6). I have been itching to shoot the first 357 but time is never on my side. I collect more than I shoot by an order of magnitude.

The 30-30 has perfect throat/bore/groove dimensions that would make any cast bullet shooter happy.

The 44 mag, I have procured a 432 throater from PTG with custom pilots to cure its ails. Throats severley mismatched and too small. One is good enough, 4 are a crap shoot way undersized. Well they would be ok if the barrel wasnt Fubared and OVERSIZE. Nonetheless, its always a crapshoot on a revolver, when can you truly rely on finding perfect throat/bore/groove that suits CB's? You can't unless you drop the coin for an FA.

Ruger set a standard of ruining the ratio making it a matter of fact, and then you horse around with dimensions to make things right or your shoot 25000 rounds to fix the forcing cone.... right?? Or dump money into a sows ear to make a silk purse. I respect the BH and its GREAT but it has some permanent unresolved issues with assembly that all owners have to deal with at some point. I dont like problems designed into systems.... I prefer things to be right from the factory, a car, a piano, a piece of furniture, a GUN???!!!

Smiths are good from the factory, or were..... but weak (ish), no offense. Pricey too, have funny locks now and shake loose in severe duty use.

I have yet to ream the 44 cylinder on the BFR but I did shoot it once to verify the compromised measurements and its good/reasonable accuracy and room for improvement with throating.

Maybe tomorrow Ill fix it, snow days all week forcast so no work for the week. Its a 30 minute job.

 

But........ MRI has built at least one masterpiece recently, I am hoping for the twins to both measure excellently. I will slug the #1 I received and see if it measures similarly.

 

Here we go:

Groove on barrel, .3555 and I mean dead nuts .3555, all grooves with no bind at the forcing cone (or a swolen spot in barrel either!) It took taps from the mallet to move it through the barrel, No tight/loose spots. Just a smooth traverse to the forcing cone. No tighting at cone exit either, it slipped into my hands didnt drop out. It sat there perfectly held in the forcing cove waiting for me to remove it from the frame window with my fingers. Impressive!

Throat (measured only one, and thats enough for me): .3570 dead nuts.

I can deal with mismatched throats as long as they are LARGE enough.

I am in shock! This is the first time in my life I need to ensure I didnt sell off an unused .357 lyman H&I die to size/lube. Ill should have one...... I would only ever use that die for 9mm work. Its TOO SMALL for anything I have ever owned and that is quite a few revolvers!

Its a 9mm barrel stock, not a .357/358 handgun barrel stock. I could not be happier.  I suppose this lends some credence to Winchester using 9mm groove barrels for the 350 legend (aside from their proprietary crap and their financials). That was upsetting as the cast bullet shooter is so accustomed to the use of .358 or better as cast stock to load, usually nearing .360 to get a good fit- doesnt play t all in the 350 Legend.

I guess its not so bad to have to size a .358+ to .3575-.3570. Cant run as cast on most molds but I conventional lube almost exclusively and a sizer gets employed anyway.

I will not be fussing with finding fat enough molds or customs. Just cast ANYTHING in any 35 cal pistol mold and it will drop with nearly any alloy soft or hard or HT, above .3570. All of my pet 35 cal molds up to 210 gr will be dimensioned correct for reduction to .357

That is just a WOW for me.

I have owned FA, Ruger, Smith, Colt, still own IHMSA Seville, 1970-80 Smiths and BFRs now in 3 cartridges. I like the FA, it walks on water but is offensive to shoot in the hand although dimesnioned perfectly. Ruger: cheap, sloppy, needs refinement and dimensioned poorly. Smith dimensions beautiful but not as robust as an SA for stout service. Colt: dimensions perfect but collectible and unworthy of severe duty. Seville....well Sig is dead and thats that, I cant afford or find any more-- Absolute Perfection but also a crown jewel.

That leaves the BFR, a poor mans Freedom Arms, now with perfect dimensions (almost all the time), build strength at FA standards, better than Ruger fitment and in SA. Almost a Seville..... almost.... not quite an FA but not as painful either.

This is the most excited about a revolver I have been in over a decade. If your on the fence about a solid workhorse revolver for stout cast bullet service, Id think twice about just going after the Ruger NMBH..... Its more expensive but out of the box it speaks quality, refinement, heavy duty service and precision in assembly and machining-- not to mention accuracy!! Bank vault PLUS tight at lockup and cylinder spins for a year on the base pin if you give it a whirl.

I wish Ruger would correct the dimensions issue, its the sole reason I don't own Ruger revolvers anymore.

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corerf posted this 23 February 2021

I almost sold my first 357 BFR unfired due to a preliminary measurement error!

I dont want a pair of revolvers that have differing requirements (significant differences).

I have spoken quite highly of MRI and their attention to dimensions prior. I procured two BFRs about 4 weeks apart form separate vendors, vastly differing Serials but same production year. They are both unfired.

As menitoned prior, the first slugfest performed was stunning. .357 throats with .3550 groove on barrel, all throats +/- .0001 at worst.

I performed a pin gage test without removing the cylinder on the former BFR. Using same Minus gages... I found one cylinder too tight for .357- and 5 that with friction fit. I became concerned. I dont want another gunsmith excursion where I have to invest in a throater and multiple pilots to get the cylinder right. But I also failed to slug the bore at that time.

fast forward--- I had decided to sell the BFR unfired simply based on the measurements with pin gages. A friend (who you might want to look up on Ebay, he has hundreds of molds and reamers that just arrived, old lyman/ideal, lots of Winchester hand tools, etc) had tonight, a 357 Manson throater available for me. When he ofered to loan it to me it forced me to do my "due diligence" in measurements, Im not going to jerk his chain when not needed.

The bore slugs at a groove of .3555 with one groove pair shallow at .3552

Great, that is close enough to be considered a twin to the former revolver measured.

Pulled cylinder and attempted to get the .357- pin into the chamber 6, the odd duck. It took some work to get it into the other 5 and I mention that as a sign of how close to .3569 it is (the actual pin gage dimension). I say, 4 of 6 are dead nuts .3568, one an extra .0001 and then #6-- problem child. 

A burr was left at cylinder face on #6, that was the issue. Not visible, couldnt feel it but sure enough the burr rolled off and the pin entered repeatedly with the same friction/fitment as the prior 4, tight but in the machine shop, it would be "dead nuts" and we would have to measure below a ten-thousandth to see the fitment.

I used a jacketed bullet as a slip fit gage from the mouth of each chamber. Remington bulk 158 JHPs, selected one at .3568 and very concentric. It dropped in and stopped hard, used a probe to press through and it slipped through with some friction from the reamer marks in each throat when manufactured. The PROBLEM child was tighter. But more force actually rolled the burr completely off. So there was a fine invisible burr at the exit and it simply needs to be "SHOT OFF".

This leaves me with having two revolvers of nearly identical throat dimensions, .357/+.0001-2 and .3569/+.0001-2

Again this will be the first time I have ever had to size a 38/357 bullet to anything less than .358 (and upwards of .360!)

I shal shoot 2 cylinders of Jacketed heavy loads through each gun, then proceed to feed them with only cast. It seems the throats may like having some abrasive burnishing to normalize them before cast only shooting.

I believe in my 44 BFR (throated by me) I should do the same. I dont want to ever put jacketed bullets through any of these revolvers but it appears there is a use for a few in the early stages of break in.

Shooting reports STILL forthcoming, now on 3 revolvers.

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corerf posted this 18 February 2021

I finally reamed the 44 MAG BFR.

It appears my pin gage set has a nice .431 slip fit with a .432 No go.

I havent slugged the throats again, I dont see a point.

I use almost exclusively the Lee 310FP-GC and run them through a .431 H&I.

They come out fully sized at .431+

I have never been able to make the whole PENCIL PUSH deal work on a revolver.

I dropped one in and its stopped in the throat as it did before.  I took a pencil and with the most gentle push it slid forward and stopped when I did. Pushed further and to the point where only the gas check was still in throat. The bullet stayed put. Pushed again and it came out. Performed same on ALL 5 throats. Each throat uses the same effort and are literally an interference fit, but lubricated in feel. I do believe maybe I have .0002 over the bullet diameter. The point, it fit so well it that at any time it maintained continuous contact while staying completely mobile and no force used to propel.

Two holes piloted at .4296, three at .4290 during ream.

I polished the throats for about 20 seconds at 400 rpm with a 3/8 split dowel and 1000 grit Alum Ox flapper and cutting oil. Almost no change in surface finish detected after. There was at least one annular chatter mark in two throats but cant feel them and Im sure they will disappear after a few rounds.

There was about 1/8 inch of leading at exit of forcing cone from the 20 rounds tested prior. It brushed out with one pass of a brush, I could eat of the bore. No leading in throats. That confirms the throat undersize issue prior.

 

I do believe that is now perfection following the ream.

I am pleased. Shooting report with 310 FPGC loaded stout forthcoming.

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OU812 posted this 16 February 2021

Powder coat your soft or hard cast bullets to eliminate forcing cone and cylinder face leading. You may find the Ruger shoots best.

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