Starting Position of Front Driving Band in Cylinder

[ejcrist]

When a loaded cartridge is placed in a wheel gun cylinder chamber, is it beneficial if the boolit front driving band is started in the throat? Intuitively I'd think it would be so it starts out as straight as possible but I have some revolvers where it doesn't, like in a Ruger Single Six 32 H&R using 32-098-SWC. Group sizes are still good at ~ 1.5" at 25 yards off a rest but I often wondered if group sizes would improve if the first boolit band started out in the throat.

[MtGun44]

In most guns it is impossible to be actually "in the throat" with the front driving band because there is
a significant length conical transition from the front of the chamber (case diam) to the throat. You would
like the front driving band to be as close to this transition cone as possible to get the front band actually
into the throat during launch while the rear of the boolit is still supported by the case, keeping it straight
into the throat.

Seating farther out is a problem because recoil is likely to move the bullets out too far if not seated
and crimped in the crimp groove. Also many designs of boolits are fairly close to the end of the cylinder,
so cannot be seated much farther out without projecting out of the front.

If you can seat farther out - you should try it and see if accuracy improves. Making ammo that
is specifically adapted to your particular gun and purpose is one of the main reasons for
handloading.

Bill

[Tatume]

Bill is correct. Some guns lack the conical transition though, and they benefit from having the bullet seated so the front driving band is in the throat. My 41 Rem Mag revolvers all allow this. Bullets must be sized so they will just barely enter, and sometimes they are difficult to extract if unfired. Accuracy is great though.

The RCBS 45-270-SAA is a bullet that works well this way in 45 Colt and 454 Casull revolvers. The front driving band is elongated, and enters the throat in many guns. If not sized to throat diameter they will not chamber. When correctly sized they shoot very well indeed.

Take care, Tom

[DougGuy]

In .44 Magnum and .45 Colt revolvers, it helps a LOT if the front of the boolit is in the throat, be it a driving band or the bearing surface behind the ojive as in the RF boolits. To this extent, many cylinders won't chamber a boolit of chosen diameter until they are reamed larger to accommodate the boolit diameter. The .357 is the same, lots of shooters want to shoot .358" - .360" boolits and have to seat short until the chamber throats are enlarged to accommodate the boolit. In every instance, the gun will shoot better when the boolit is in the throat, and the throat is just a tad over boolit diameter.

If you want to seat out into the throats, and they are too tight, ream the throats so they don't impede boolit diameter OR seating depth. The throat is not the important part, the boolit is, and the throats should be made to fit the boolit, NOT THE OTHER WAY AROUND!

[ejcrist]

Roger that. I have a Ruger Bisley 45 Colt that I reamed the throats to .4525 with a Manson Reamer and the 45-270-SAA sized .452 gives me excellent accuracy since it's seated in the throat. I also have a Ruger 32 H&R and I'm using 32-098-SWC but the front driving band doesn't go into the throat. I know this because the throats are .311 and the bullets I sized for another 32 H&R are .312. These cartridges go all the way in the chambers but when you try to insert only the front driving band through the front of the cylinder (into the throat) it won't fit. I also have pin gauges and the .311+ fits in the throat but not the .312+. I wish that boolit reached into the throat. I haven't shot this particular revolver yet but I'm contemplating getting a mold with a long enough front driving band or perhaps designing a custom SWC mold and ordering. Another mold I was looking at was the Saeco 30254 118 grain bullet. That one is a RNFP but the diameter extends a fair distance further than the RCBS mold.

[9.3X62AL]

IIRC, Elmer Keith recommended that his SWC bullets have a front drive band of a length and diameter to provide a very slight "interference" fit within the throats. This is from one of his books or articles, I can't recall which one right now. Many of my Keith-design castings enable this ideal to be realized; some of the other SWCs do not, but still shoot pretty well.

I think there is more than one way to skin this cat, however. Shoulderless RN designs seem able to "self-center" within the bore, and I recall reading in Waters' "Pet Loads" that his recommendation for a wheelgun with a bit of clocking slop can reap an accuracy benefit from use of those Old School designs. We should also not lose sight of how well flat-fronted wadcutters continue to perform in both autopistols and revolvers chambered in 38 Special.

[EdS]

Two comments: first, I think 1-1/2" hand held groups at 25 yards approaches the best most people can hold, sight and press the trigger of a non-target revolver. That is, how much better could you expect? Second, I grew up reading Elmer Keith and tried to follow everything he wrote about the .44 Magnum. If I recall correctly, he was consistent in recommending sizing his design SWCs at .429". That's the sizing die I bought and used for many years, until other, more modern writers explained about matching the cylinder throat diameter. I'll welcome other recollections of Keith. Best Regards, Ed

[DougGuy]

Couple things.. Concerning alloy hardness and cylinder throats. With a softer alloy, couple different things happen in the cylinder throats. First off, if the alloy is soft enough, BHN 10 - 12, soft enough to dig a thumbnail in, and you are using this in Tier3 loads, this would be a Ruger Only load in .45 Colt, and a standard full house load in .44 or .357 or any of the magnums that generate upwards of 30k+ pressures, the boolit you fired will swage and completely fill the throat upon firing. This can help accuracy rather than hurt it.

Also, if you are sized .001" or .002" greater than throat diameter, when you fire the gun, pressures will increase noticeably over firing smaller boolits, or the same boolits through larger cylinder throats.

If you use a hard alloy, pressures can increase dramatically on firing through a tight throat that is smaller than boolit diameter, and if the throats are larger than boolit diameter, the hard alloy is not likely to swage to the size of the throats like the softer alloy will.

[Char-Gar]

If the front driving band will indeed enter the charge hole throat, it will need to be somewhat smaller than the throat for a drop in fit. When you add up the slop of the fit of the round in the charge hole and the fact that most bullets are seldom truly round, a bullet that is the same size as the throat might require a bit of jiggling to get it in the throat.

Keith accomplished allot of thing, but he put some really dumb stuff in print as well. I recall him waxing eloquent on the proper size for a 45 cast bullet in the 1917 Colt and Smith and Wesson. He said that .451 proved the most accurate in his testing. Really...a .451 bullet in a .456-.457 throat being the most accurate?

[9.3X62AL]

As always, I reserve the right to be wrong--and this goes double when I'm operating from very dated memory.

There are very good reasons that most modern factory revolver ammunition uses an ogival form for its bullets--such forms do away with the entire throat fit question, and plunk right into chambers with a slight gravity assist.

I don't recall having read Mr. Keith's sizing recommendations for the 44 or 45 calibers, but both of those values listed above are indeed the Usual SAAMI Spec (c). Just speculating here, but bullets so sized would certainly not cause issues with chamber fit. Also, given Keith's usual binary revolver bullet alloy of 16:1 lead/tin, I imagine there was some "bump-up" possible with smokeless powders.

[ejcrist]

Thanks for the info gentlemen. I generally don't cast any boolits with anything harder than straight wheel weights with maybe a dash of tin and haven't had any leading issues even with the 44 and 357 magnum velocities of about 1,500 fps. So I'm guessing they're obturating nicely and filling the throats for the last .0005" or so. I think Elmer was right on the money about getting the front driving band started in the throat.

EdS - 1 1/2" groups at 25 yards off a rest isn't as hard as one might think. That's the average group size so some are a little less and some a little more, but that's generally a good standard I believe. My goal is always 1" or less but my eyes aren't what they used to be so I've relaxed that requirement a bit. Most of my revolvers are Ruger SA's and I always have to do quite a bit of tuning to get them to shoot well, like install a Belt Mountain base pin, 30 oz trigger return spring, action tuning, sometimes open the throats, etc. But Rugers are capable of excellent accuracy with a little work and the right hand loads. I have a Freedom Arms 454 on order and I've heard they're capable of excellent accuracy out of the box so I'll see. They should be for the price, but they are some of the finest revolvers I've ever fondled. As much as I like the FA's revolvers, I very much enjoy taking a mediocre factory revolver and getting her to shoot well. There's a lot of satisfaction in that.

[DougGuy]

I very much enjoy taking a mediocre factory revolver and getting her to shoot well. There's a lot of satisfaction in that.

^^^^ THIS.....

Take any Ruger SA without thread choke, the fast and easy "accurizing" consists of 1. Resize cylinder throats and get them all even. 2. Recut and polish forcing cone to 11°. 3. Remove one leg of trigger spring and let it hang, -or- swap in a Wolff 30oz spring. That's IT! You will see more improvement in just these three things, for less than the price of a decent pair of grips.

The rest of it, is developing a load and discovering which alloy your gun/load combo likes the best. It definitely will show preferences and as you work with it you will see what it likes most.

After that, it's all in the shooter's hands and how well he/she can shoot a single action revolver.

I think the jury is still out on the Belt Mountain base pin. Some guns may improve with it but if you take the slack out of a Ruger, it will start to batter the bolt latch. Rugers need the slack in the cylinder so it is free to align with the bore. As the boolit enters the forcing cone it will cause the cylinder to move to the closest alignment and when you restrict this movement, it begins to wear the gun in other places.

[Outpost75]

DougGuy - it is sure nice to read a post from someone who understands revolver mechanics.

You made my day!

[Char-Gar]

As always, I reserve the right to be wrong--and this goes double when I'm operating from very dated memory.

There are very good reasons that most modern factory revolver ammunition uses an ogival form for its bullets--such forms do away with the entire throat fit question, and plunk right into chambers with a slight gravity assist.

I don't recall having read Mr. Keith's sizing recommendations for the 44 or 45 calibers, but both of those values listed above are indeed the Usual SAAMI Spec (c). Just speculating here, but bullets so sized would certainly not cause issues with chamber fit. Also, given Keith's usual binary revolver bullet alloy of 16:1 lead/tin, I imagine there was some "bump-up" possible with smokeless powders.

Keith wrote an article that was published in Guns Digest and again in one of their "Treasuries" entitled Sixgun Miscellany" where he stressed the important of knowing your revolvers barrel groove and cylinder throat diameters vis-a-vi the ability of the cast bullet to "slug up" to form a gas seal in the throat and barrel forcing cone. Bottom line was he thought .001 under cylinder throat was just fine for 38/357 bullets and .002 under was the proper number for 44/45 bullets.

I don't have any issues with these numbers unless a fellow is using those granite hard water dropped thingies which I don't use. Those are going to expand absent pressures I won't shoot in my revolvers.

As to the .451 cast bullets in 1917 revolvers, I think that was a short piece in a 1950s Guns Magazine. I reread it about a year ago and about dropped by teeth when he said that .451 was tested most accurate. Mine you, he was talking accuracy and not easy drop in fit, which a .451 would certainly do.

I enjoyed reading Keith's stuff and learned allot from him, but he was not infallible and did from time to time contradict himself in print. The guy was trying to earn a buck to stay afloat in Idaho, so I don't think any less of him for shooting from the hip in his writings from time to time. It wasn't until after his death, that he became Saint Elmer and folks started to build alters for his worship. :-) While he was alive, he was just another knowledgeable gun guy from Idaho with a big hat and a penchant for using the possessive "mine" to excess. Every new firearm that came on the market he tested and allowed as how it was using this or that feature of his old design. He was not shy about claiming credit.

I shared a few drinks with him and others around a table at an NRA convention in Dallas many years ago. He "held court" and was as interesting and colorful in person as you would imagine he was. I was a young man in my early 20's and was in awe of him. It wan't until later that I became somewhat cynical about human nature including my own.

[376Steyr]

About .45 Auto Rim: I get amazing accuracy using rock-hard commercial-cast 200 SWCs that might measure .452 on a good day from a S&W 25 with .455 throats. Soft SWCs that should be "slugging up" are mediocre performers at best. This is using AR cases and 5.8 grs of W231. This just happens to be a combination I stumbled upon before I "knew" better. ACP cases in clips don't shoot nearly as well. Go figure.

[cbrick]

I take a different approach than DougGuy, I match the throats to the groove diameter and then match the bullets to the throats. Cut the throats to fit the bullets? Really? Also, depending on what your shooting, too soft of an alloy at high velocity causes premature forcing cone wear.

As for the front driving band inside the throat when chambered it will always aid accuracy when it's possible to do so. Most of my Rugers make this difficult having relatively short throats, crimping in the groove prevents the front driving band from reaching the throat. In long range revolver competition I use FA's which have a longer throat and I always size the bullets to a mild snug fit in the throats and the front driving band is inside the throats on a chambered round. On my 357 FA that's .357" groove diameter, .357" throats and my .357" sizing die sizes my alloy a few tenths under .357" for a mild snug fit.

1 1/2 inches at 25 from a rest is very doable and not good enough for long range competition. That would be 3 inches at 50, 6 inches at 100 and 12 inches minimum at 200. 1 1/2 at 50 yards from a rest would be a mediocre long range load and would be 6 inches at 200, some of the 200 yard targets are smaller than that.

Rick

[DougGuy]

I take a different approach than DougGuy, I match the throats to the groove diameter and then match the bullets to the throats. Cut the throats to fit the bullets? Really?
Rick

I have zero complaint about your method, both ways work. Fitment is king and there's more than one way to achieve it.

[MtGun44]

Char-gar -
I once tried to see if the Keith load for the 1917 would work. My M1937 Brazilian
will shoot my Lyman 452423s at .453 diam about 6" left and about 5" in group diam with
a number of different "mild" loads. Keith recommended 7.5 gr of Unique . . . . :shock: !!!

Not being that brave (or foolish), I tried 5.0, 5.5, 6.0, 6.5 and finally 7.0 but no more.

The 5.0 was 6" left, about 5" diam and each successive load marched a bit right and
the group was smaller, until at 7.0 it was about 2.5" and about 2" left at 25yds. I
tend to think that, assuming the gun survives, the Keith load would shoot to POA
and be pretty decently accurate at 25 yds, even with .451 diam. But I think the
diam is a bit irrelevant because I am guessing that when cast in 16:1 alloy,
it will bump up to .456 in the throats.

In any case - I do NOT shoot loads that hot normally, and struggle with accy unless
I use specially cast .455 diam boolits from an oversize MP mold copy of the Lyman
that we call the 455423. Still, I don't ever shoot over about 6.5 of Unique and that
is pretty hot. One string of five at 7.0 is all she will ever see in my hands.

Bill

[44man]

^^^^ THIS.....

Take any Ruger SA without thread choke, the fast and easy "accurizing" consists of 1. Resize cylinder throats and get them all even. 2. Recut and polish forcing cone to 11°. 3. Remove one leg of trigger spring and let it hang, -or- swap in a Wolff 30oz spring. That's IT! You will see more improvement in just these three things, for less than the price of a decent pair of grips.

The rest of it, is developing a load and discovering which alloy your gun/load combo likes the best. It definitely will show preferences and as you work with it you will see what it likes most.

After that, it's all in the shooter's hands and how well he/she can shoot a single action revolver.

I think the jury is still out on the Belt Mountain base pin. Some guns may improve with it but if you take the slack out of a Ruger, it will start to batter the bolt latch. Rugers need the slack in the cylinder so it is free to align with the bore. As the boolit enters the forcing cone it will cause the cylinder to move to the closest alignment and when you restrict this movement, it begins to wear the gun in other places.
True understanding, cylinders have a tiny movement for a reason and many belt Mountain pins fit too tight have ruined accuracy and promoted wear. They are good if not fit too tight.
Worst I ever seen was a Freedom .454 that wore the throats oblong, half the cone and into the rifling because the cylinder could not clock. Done with less then 300 factory loads. Very expensive for a "feel good" gun. That super tight lockup is not your friend.
The Freedom owner had no money so I worked on it, cut the cone and reamed the cylinders and also put a few thousandths play in the cylinder stop.121644
left is before and right is after at 50 yards.
Reamer did not touch the worn side of the throats but it still worked.
If you want a Ruger to shoot better, toss the hammer spring and replace with a Wolfe over power variable of 26#. The hammer spring has nothing to do with trigger pull so leave it alone or replace it. I do that to all BFR's too. Never, ever lighten the strike to the primer. S&W owners, never loosen the strain screw.
Yes I have been in deep do-do over Freedoms but have never been wrong or proven wrong, some are super but not all of them are. I insist they are too tight.

[44man]

I take a different approach than DougGuy, I match the throats to the groove diameter and then match the bullets to the throats. Cut the throats to fit the bullets? Really? Also, depending on what your shooting, too soft of an alloy at high velocity causes premature forcing cone wear.

As for the front driving band inside the throat when chambered it will always aid accuracy when it's possible to do so. Most of my Rugers make this difficult having relatively short throats, crimping in the groove prevents the front driving band from reaching the throat. In long range revolver competition I use FA's which have a longer throat and I always size the bullets to a mild snug fit in the throats and the front driving band is inside the throats on a chambered round. On my 357 FA that's .357" groove diameter, .357" throats and my .357" sizing die sizes my alloy a few tenths under .357" for a mild snug fit.

1 1/2 inches at 25 from a rest is very doable and not good enough for long range competition. That would be 3 inches at 50, 6 inches at 100 and 12 inches minimum at 200. 1 1/2 at 50 yards from a rest would be a mediocre long range load and would be 6 inches at 200, some of the 200 yard targets are smaller than that.

Rick
I stand with rick too, as an IHMSA shooter that knows long range.
I do NOT believe in "bump up" of any kind either. That is so far from accuracy it is a waste of boolits. Noise is what you have. Bump up means slump and boolit destruction. Groove size is the key and throats just over with a fit boolit TO GROOVE or .001" over is best.
Still today some want to shoot over throat size and think it is a cure.
Will this stuff ever go away? Will "bump up" ever go away?
Thread choke and a softer boolit that will "bump up" after the choke is a huge laugh.