.44 special cylinder throat vs bore diameter question

[BeMan]

I have tried several things to get my Blackhawk .44 special to group without success. I checked some measurements today and found that my cylinder throats actually average .4285 ( .4282-.4287). I slugged the bore again to recheck my earlier measurements and confirmed .4295. Is it probable that the smaller cylinder opening is down sizing the bullet before entering the bore and therefore robbing accuracy and consistency? And, shouldn't a .431 cast work fine for the bore? Thanks for any advise you guys may have.

[WALLNUTT]

You are correct.

[DougGuy]

If your boolit won't go into the cylinder from the front, then it is definitely downsizing them upon firing through the undersize throats. I do several Ruger cylinders per week for shooters just like yourself. If you'd like to see some finished work click on the link to the Facebook page in my signature, there are photos there of cylinders that I have done. Cylindersmith closed up shop, so I am now doing cylinders for anyone who needs this service done. There are four on the bench today to be done..

I do have a .431" reamer that will finish slightly over that diameter, if you'd like to send the cylinder you can send one or two of the boolits you want to shoot in it and I can make sure the throats are all sized evenly for those boolits. Send me a PM or msg me off the Cylinderhone.net facebook page if you are interested..

Doug

[376Steyr]

Conventional wisdom is that diameters should taper down from bullet to cylinder throat to bore. Before cutting on the throats, you could try using a softer alloy and see what happens. I spent years getting poor accuracy from my .44 Specials and a big part of the problem was I was using rock hard commercial cast SWC's with Crayon lube over 7.5 grs of Unique. Something like half pure lead and half wheel weights should be plenty hard enough for a Special.

[DougGuy]

Conventional wisdom is that diameters should taper down from bullet to cylinder throat to bore.

This is exactly correct. 2 things about the softer alloy comment, one, if you know you have throats smaller than bore diameter, why would you try to make up for that with soft alloy when the prudent and practical thing to do is to correct the throats? The other thing, there really isn't enough gas pressure to obturate an undersized boolit in the bore to seal with the .44 Special. .44 magnum, totally different animal and yes they will fire an undersize boolit and still swage it up to seal the bore because of the immense pressure behind the boolit. *IF* it is soft enough alloy!

I have found my Rugers take a distinct liking to 50/50+2% ww/pure lead + 2% tin. It is a really good alloy hardness for the twist rate of the Ruger big bore barrels. I totally agree on the hard as a rock cast boolit and hard lube not being the best thing you could feed a Ruger with, my experience was much the same until I came on this forum and learned about alloys, gas checks, and Felix lube. Now, I have .44s and .45 Colts that shoot cloverleafs for groups (WHEN my old eyes can do their part! LOL) and don't lead the barrels.

[Larry Gibson]

BeMan

How did you measure the throats?

Larry Gibson

[BeMan]

measured with my calipers. Is there another way?

[35 Whelen]

Probably a better way would be to knock soft lead slugs through the cylinder throats then measure them with a micrometer. It's somewhat difficult to get accurate measurements from a caliper.

Totally agree about a softer alloy. Over the last couple of years and over 5000 cast bullets through various .44 Specials and one 45 Colt, I simply cannot find any advantage to hard bullets up to and including 1200 fps. As far as lube goes, again, doesn't seem to matter much. My Star lubrisizer, with which I size all my .44 bullets, has hard-ish lube that requires a little heat, in it, while a home-made wanna-be-a-Star lubrisizer has no heat required lube in it.

35W

[DougGuy]

35 have you ever tried Felix lube?? WELL worth the effort to make it, and you can see the difference in group sizes..

[35 Whelen]

I've made some home-made lube, but not Felix lube. Maybe I'll try it some day!

[Larry Gibson]

measured with my calipers. Is there another way?

35 Whelen is correct, push a lead slug through the throats and measure with calibrated micrometer or caliper. Inside measuring of throats often gives a smaller diameter. Also I've checked numerous calipers over the last few years with certified pins and found the to be as much as .001 -.003" +/- off in the .35 - .45 range. Best way to measure the throats is with pin gauges.

Lastly I suggest, if you still have it, take that slug from the barrel and see if it is at least a slip fit through the throats. If it is you then know the throats are larger than groove diameter and do not need reaming.

Larry Gibson

[stu1ritter]

measured with my calipers. Is there another way?

Calipers are notoriously inaccurate when trying to measure a cylinder throat. Much better would be to use a pin gauge in the minus configuration, so that a .430 is actually .4298 or .0002 smaller. You would need 3 or 4 of them and they are only about $4 each and sometimes $2.50 each depending on size at Amazon. Just search for Vermont pin gauge and go to the sizes you require. It is the most accurate method of measuring a cylinder throat and you can also check your calipers against them to see how accurate the caliper is at that size. They act as go/no go gauges.
Stu

[Airman Basic]

If your boolit of choice won't slip through the chamber throats with a little finger pressure, doesn't that tell you some throat enlargement is called for?

[9.3X62AL]

If your boolit of choice won't slip through the chamber throats with a little finger pressure, doesn't that tell you some throat enlargement is called for?

Not always. This bullet/throat relationship in a revolver is also viewed in the context of the barrel's groove diameter. I don't routinely ream revolver throats, in fact have only done so with one example to date. Even in that instance, I ran the revolver for close to 3 years to absolutely confirm that there was no other path to accuracy and lead-free barrels. Ruger's idiocy with (primarily) 44-40 WCF and 45 Colt throats as undersized relative to the barrels they fed led up to folks like Doug Guy developing cottage industries to finish building revolvers. My only caveat is that a shooter should be certain that throat surgery is necessary before conducting it.......it's not a first move, more of a last step after trying other less drastic measures to obtain good performance, which to my mind is accuracy without leading in conventional revolver calibers.

[DougGuy]

To my mind is accuracy without leading in conventional revolver calibers. That's what I'm talking about!

To do this with restrictions either in cylinder throats or thread constricted barrels is a daunting task that can ONLY be accomplished with softer boolits and enough gas pressure behind them to obturate and seal the bore after they pass through the tight places. Soft booilts and j-word boolits are soft enough to do this with magnum pressures forcing them through those places and then sealing them in the bore by expanding from the pressure behind them. Won't happen in a .44 Special, or a .45 Colt loaded to tier 1 (14,000psi) specs.

Not shooting softer alloys or j-words? Once those hard cast boolits pass through a constricted place, be it a too tight/too small cylinder throat or a thread constricted barrel, they stay sized down. No amount of pressure from burning powder is enough to slug them back up to seal the bore. Now you have gas cutting up the sides of the boolit, skidding in the rifling from being under diameter of the bore, leading in the barrel, and terrible groups.

It's not rocked science, it's 3rd grade math really, there is no "magic workaround" or "perfect load" that will compensate for undersized chamber throats. They are just that, undersized. THAT.... Is the part that needs fixing, not having to come up with some magic formula at the loading bench that will make up for it.

Cylindersmith closed up his operation (I think) because of his health. I started mine, because of my health. I had undergone all summer of radiation and chemo last summer, and I am still not able to return to pipefitting in chemical plants and operating construction cranes which I am licensed for and often employed as an operator, so I am doing things that I can do in my own shop on my own time, and helping others at the same time to improve their firearms and their shooting. Why Ruger doesn't address the issue is beyond me. The cylinders in the medium frame guns are GORGEOUS! Almost all of the .45 caliber cylinders I have worked on have taken a .451" pilot very snugly. They are as consistent as they are pretty. They are just .0015" too small for us cast boolit shooters. Until they fix their end of the problem, I will continue to offer to help shooters fix it on this end..

[WALLNUTT]

DougGuy, I hope I don't need your services when my new revolver arrives but if I do you'll be the first to know. Ruger Vaquero 45ACP

[MtGun44]

Listen to Al - he is dead on - although maybe you can be sure in less than
three years. :-) Al is thorough!

Larry is giving you the straight scoop, too. Measuring anything with most calipers is +/- .001
territory and you need .0001 reading mic for this work, and actually the gage pins (minus set)
are the real way to get this right. As long as the throat is a bit larger than the groove diam and
you are sizing to throat diam you should be on the best and shortest path to small groups.

HOWEVER - every gun is a thing unto itself and you should spend some substantial time working
with the thing before just running out and doing the irreversible step of reaming. I have reamed
exactly one of my many revolvers, and it was a particularly egregious case.

Ulimately, Mr. Target knows the real answers and all of our suggestions, while they are the best
wisdom known for revolvers (much better than is known by most and especially 20-30 yrs ago!) but
this is not a guarantee that yours will act exactly the same way. MOST do, but not 100%.

Bill

[BeMan]

Fired the revolver this morning for first time after having the throats opened. I noticed a huge improvement in groups. Still working on most accurate load, but right now 10.4 gr AA#7 shoots to point of aim and casings are not blackened. Thanks for helping me solve this problem.

[Airman Basic]

DougGuy, I hope I don't need your services when my new revolver arrives but if I do you'll be the first to know. Ruger Vaquero 45ACP
Received my two 45s, acp and long colt, from DougGuy yesterday. At an unwanted "continuing education" conference this week, but by the weekend I'll be trying them out and I'll let y'all know.

[9.3X62AL]

Fired the revolver this morning for first time after having the throats opened. I noticed a huge improvement in groups. Still working on most accurate load, but right now 10.4 gr AA#7 shoots to point of aim and casings are not blackened. Thanks for helping me solve this problem.

Good news to read, and I'm glad the modifications worked out well for your rollerpistol.

Bill/Mtn Gun--don't necessarily assign to "thoroughness" that which is better explained by serial disappointment, serial disgust, and/or serial distractions. I did go through A LOT of bullet designs during the chase, only one of which worked worth a hoot--#454490, with gas check, made of 92/6/2, run at 900-1000 FPS. A revolver steps up to the plate 0-2 when it's a One Bullet Wonder needing gas checks and a narrow velocity slot to behave itself at 900 FPS. Oh, H--L NO.

[35remington]

Asking even a soft lead bullet to obturate beyond the forcing cone is asking a lot at 44 Special pressures. Since it is well beyond the case mouth and pressures are plummeting it likely won't happen.

since that's in agreement with what's been said before I'd fix the revolver too.

just a comment.....we say "bore" when we really mean barrel diameter way too often around this place.

[MtGun44]

Al -
I had a pretty good idea that distractions and disgust would be major
players in that mini-drama. Been there, done that. I wish I could
run as linear and thorough a testing plan in my private life as I could
when I was doing if professionally. Too many distractions and competing
required things that must be done, and no doubt the irritation factor
isn't there when it is somebody else's "stuff" and time and money.

Bill

[daleraby]

I have a Ruger/Lipsey Flattop .44 Special. Chamber throats measure .432 (using a .440 round ball driven through the throat with a punch, then a Lyman dial caliper to measure the slug). Groove diameter at the forcing cone was bad enough that I could feel the threading constriction with a patch and fitted jag while cleaning it. When I first got the gun I did not have the dial caliper, but knowing that Rugers in .45 & .44 have a tendency to crush down the barrels at the forcing cone, I ordered a Wheeler Bore Lapping Kit (https://www.wheelertools.com/gunsmithing-tools/bore-lapping/bore-lapping-kit/299849.html) The bore lapping procedure made me nervous, but I managed to enlarge the forcing cone enough to where I could barely notice it. I still experienced leading though.

This morning I did a bit more lapping, this time cleaning the bore and using a measured slug. After firing two .430 255 grain cast bullets over 4 grains of Trail Boss (using the 600 grit abrasive compound), I could no longer feel any constriction. Slugging the bore produced a diameter of .430... the same diameter as the bullets I am shooting. I haven't determined a procedure to measure the bore diameter beyond the forcing cone, but I'm pretty sure there is a way to do that. Accuracy with my old eyes is questionable, but good enough for my purposes, though I may order the next batch of bullets sized a bit larger.

As to the aforementioned Wheeler Bore Lapping Kit, their procedure is to apply the abrasive to the bullets before using and then loading them into the case. This is a messy procedure that will leave residue in your dies that will require removal before using the dies again. This morning, I just put the compound on the exposed band of a the Keith bullet with a bit more compound forward of it, figuring that upon firing the gunk would be driven back toward the bullet. I would think that a better option might be to use a cut-down cartridge or maybe a .44 Russian cartridge, load it light, seat the bullet with most of the driving bands exposed and then apply the compound to the loaded shell. You should not expect any level of accuracy with bullets used in the lapping procedure. This would keep the grit out of your dies.

[35 Whelen]

Several years ago I bought a forcing cone cutting kit that cuts forcing cones to 11°. Now every revolver I buy gets the treatment. My Uberti Frisco had a minor flaw in the forcing cone so I recut it-

https://i.imgur.com/Ze9YpsHl.jpg https://i.imgur.com/bvKZK2Ql.jpg

With one of my Uberti Hombre's I took it one step further, I cleaned up the forcing cone then did a little fire-lapping-

Before- https://i.imgur.com/REowldKl.jpg

After- https://i.imgur.com/b33Ht3Gl.jpg

This revolver is now smoking accurate and leading was greatly reduced.

35W