9 BHN casts

[JonB_in_Glencoe]

No one is splitting hairs.
Faster burning powders spike (pressure) sooner as velocity increases, whereas slower burning powders spike later.
This is why there is a general practice of using faster burning powders for lower velocity loads, and slower burning powders for higher velocity loads.
Gas cutting happens when there isn't enough pressure to obturate the boolit. So if you have a undersized boolit, it's more likely to have gas cutting on a low pressure load, than with a High pressure load.

[Thumbcocker]

Respondents are offering sound advice based on a lot of real world experience. Hardly splitting hairs.

Sent from my SM-G960U using Tapatalk

[Bigslug]

Methinks you're sweating hardness a little too much.

You're going to get gas blow-by if you're bullet is too hard to obturate and seal the bore at the pressures involved, or if the "funnel" of cylinder to bore is not an even and true taper, as you might find with bore constriction caused by frame crush. You're running at low speeds (compared to rifles) at a relatively slow rate of twist, and so will not be putting sufficient torque stresses on the bullet to open up a path for gas cutting.

Work up to the level desired. If it leads, look at where the leading is and isn't in the barrel, and assess the problem. If the accuracy begins to fall apart as speeds increase, assess the problem.

[hades]

My target BHN is 9-10 for all my handgun casting, 41 and 44 mag full power loads to 9mm, 40, 45 acp loads.

They all shoot great and no leading.

[castmiester]

No one is splitting hairs.
Faster burning powders spike (pressure) sooner as velocity increases, whereas slower burning powders spike later.
This is why there is a general practice of using faster burning powders for lower velocity loads, and slower burning powders for higher velocity loads.

At the top end of my powders I have, Blue dot will create higher pressures, maybe not lower velocity, yes, BUT say H110 will create lower pressures but still can get the same velocities. So Temps, are the concern no matter what powder you use sure even at lower velocities.
Gas cutting happens when there isn't enough pressure to obturate the boolit. So if you have a undersized boolit, it's more likely to have gas cutting on a low pressure load, than with a High pressure load.

With a good bullet fit, that prevents cutting ?

Any data I see or saw mentions on Lymans three casts that they say are a gas check base bullet. So I assumed that they are needed. Then over the years guys said as long as you stay under 1500 fps you don't need one, but hey never mentioned about alloy into the equation which I never felt fit protected the base from gas cutting, regardless of pressures and that was always brought into the conversation.

[gwpercle]

Fit of the boolit is Much more important than Hardness .

A BHN of 8-9 is perfect for a hunting boolit .

Slug your bore and size your boolits .001" - .002" over and ... load em up .

Most folks shoot boolits that are way too hard in handguns ...
BHN 9 ...You are Good !

Size beats hardness Seven Ways to Sunday in handgun boolits !
Gary

[castmiester]

Fit of the boolit is Much more important than Hardness .

A BHN of 8-9 is perfect for a hunting boolit .

Slug your bore and size your boolits .001" - .002" over and ... load em up .

Most folks shoot boolits that are way too hard in handguns ...
BHN 9 ...You are Good !

Size beats hardness Seven Ways to Sunday in handgun boolits !
Gary

Alot of varying information on the web and jacketed bullets were only designed for high velocity cartridges. So yeah I get it... softer casts can take it in handguns.

[Bigslug]

It all comes down to marketing.

Commercial cast is, or at least was, a lot harder than it needed to be mainly for shipping reasons. If customers opened the boxes to find a bunch of bullets that were dented and with rounded bases from rattling around in a box during shipping, they would not become repeat customers. They're also usually shipped with heat-applied hard wax lubes for the same reason. None of that is optimal, and hopefully they ship on the fat side for functional diameter. Thus began the vendor's pitch of "harder = better", and a lot of folks are swallowing that to this day. Remember, you're being told that by people who are trying to sell you something.

Good fit is going to be king, regardless of how hard you push them. Provided you have that, added hardness mostly becomes an issue for maintaining accuracy as the load intensity increases. I wouldn't sweat it until you reach a point where accuracy drops off, then harden up a little until it comes back.

[JonB_in_Glencoe]

With a good bullet fit, that prevents cutting ?

Any data I see or saw mentions on Lymans three casts that they say are a gas check base bullet. So I assumed that they are needed. Then over the years guys said as long as you stay under 1500 fps you don't need one, but hey never mentioned about alloy into the equation which I never felt fit protected the base from gas cutting, regardless of pressures and that was always brought into the conversation.

boolit fit prevents cutting.

See post #2 in regards to what a GC does...at least that's been my experience. As you read through this thread, you'll see varying theories...I've been in conversations with some of those posters and many of them are the most knowledgeable people I know.

https://castboolits.gunloads.com/sho...-on-Gas-Checks

[castmiester]

It all comes down to marketing.

Commercial cast is, or at least was, a lot harder than it needed to be mainly for shipping reasons. If customers opened the boxes to find a bunch of bullets that were dented and with rounded bases from rattling around in a box during shipping, they would not become repeat customers. They're also usually shipped with heat-applied hard wax lubes for the same reason. None of that is optimal, and hopefully they ship on the fat side for functional diameter. Thus began the vendor's pitch of "harder = better", and a lot of folks are swallowing that to this day. Remember, you're being told that by people who are trying to sell you something.

Good fit is going to be king, regardless of how hard you push them. Provided you have that, added hardness mostly becomes an issue for maintaining accuracy as the load intensity increases. I wouldn't sweat it until you reach a point where accuracy drops off, then harden up a little until it comes back.

So someone says this...

Generally speaking, a .431" will be larger than most if not all production made .44 spl/mag revolver barrels. Groove diameter is normally .429" ~ .430" so there really isn't a need to slug the bore. Same with .45 caliber revolvers, unless you are dealing with an old Colt or wartime S&W, it will have a groove diameter nominally .451" so using a .452" boolit is acceptable as being larger than groove diameter.

And then says this....so now maybe you can understand why I ask the questions I do and think what I do.

The easiest thing to do is slug the bore, and without even measuring the slug, see if it will go into the cylinder throats from the front. If all is correct with the throat diameters, the rifled slug you pushed through the bore should slide right into the cylinder throats. If it won't then that tells you right there the throats are smaller than the bore and probably could stand to be reamed and honed to have the gun shooting it's best. Fitment is KING, and for proper fitment, the throats should be sized slightly larger than the groove diameter of the bore, you should be able to slide the slug through them with finger pressure at the most.

or this.... from a guy here who is supposed to be well respected

Gas checks work better when there is a heavy for caliber, softer alloy boolit on top of them

I can't post another comment from the same member, I deleted a PM, but he did say this..

I don't concern my self with barrel dimensions

Ruger groove dimensions have always been .429-.430

[castmiester]

boolit fit prevents cutting.

See post #2 in regards to what a GC does...at least that's been my experience. As you read through this thread, you'll see varying theories...I've been in conversations with some of those posters and many of them are the most knowledgeable people I know.

https://castboolits.gunloads.com/sho...-on-Gas-Checks

the guy hasn't posted since 2015.....

this kinda goes along the lines of what you're saying..

The gas check increases the shear strength of the alloy so can allow higher pressure than the alloy alone.

And he doesn't sound he's speaking from experience here...

In fact I think a gas check at pressure below or just barely adaquit of what is needed for obturation may prevent a good seal. Depending on how high the pressure is the base is what will obturate to make a seal.

And here he's along the lines with you..

The higher the pressure the more length of the bullet will obturate.

and here...

If pressure is not high enough to obturate past the check you may loose the seal.

I would say a copper GC prevent damage to the bore. However it should be soft enough to allow obturation of the cast.

[JonB_in_Glencoe]

I'll stick with what I said in post #13.

My comments in post #21 and #29 are how I've experienced this topic. I included the link, so you could see there is varied theories by members. It appears the lowly GC does more than one thing, quite possibly a half dozen things, or more, depending on the various applications/conditions.

[brasshog]

I'm running 44 mag cast boolits at 1200fps (measured) with zero leading issues. They are about 10-11BHN and sized .430. The mix is 93-3-3 alloy.

[castmiester]

I'll stick with what I said in post #13.

My comments in post #21 and #29 are how I've experienced this topic. I included the link, so you could see there is varied theories by members. It appears the lowly GC does more than one thing, quite possibly a half dozen things, or more, depending on the various applications/conditions.

And I'll stick with what I said in post #20. And based on your comment...

If you have a problem, then ask a question.

I ask questions before hand to know what to do, when the problem arises....it's called doing your homework, first.

[SoonerEd]

I have 1,700 lbs of range lead at 8bhn. It seems to do good till about 1,100 w/o gas check. PC seems to get me to 1,200.

[Forrest r]

And I do believe you guys are splitting hairs in regards to velocity, increased velocity increases pressure.

From your 1st post:
"I have heard in the past as long as you don't load to high velocities it won't gas cut."

Interesting:
That 11.5gr load of unique I posted is about max for the 44mag. Lyman lists their 429667/240gr fn at 11.7gr max. My cast bullet actually runs closer to 260gr with that 8/9bhn alloy.

Even though it was shot in a contender (+/-1400fps) I don't want to increase the pressure to 44mag p+ levels. Now I didn't have a problem switching to 2400 and getting +/- 1500fps with the same bullet.

I never bothered to chronograph those loads, nothing more than blammo ammo/plinking loads.

The only reason I chronographed those 308w loads was because I was getting into powder coating bullets (2014) and was doing head to head testing.

This was what I posted, a pc'd bullet using no gc.
[IMG][/IMG]

This is the other 1/2 of the test. Same bullet/same cast alloy (8/9bhn). But this bullet was traditionally lubed (ben's red + a coat of 45/45/10) and had a gc installed. Same 9.0gr load, same rifle, same 50yd 10-shot test on the same day.
[IMG][/IMG]

You're the one asking about "gas cutting" and velocity.

This is an excellent example of what "gas cutting" is and it's relationship to velocity.

[castmiester]

Good stuff thanks

[Bigslug]

You're not getting any bad advice from what I'm seeing.

One of the key functions - perhaps the key function - of a gas check is to act as a driving key at higher speeds than would otherwise be ideal for hardness of the alloy. This is not so much related to the pressure behind the bullet as it is the rotational torque from the rifling. That torque can get sufficient that the impressions made by the lands want to start opening up. The gas check - being harder - limits this.

Note that this is going beyond mere obturation. At these increased rotational speeds, we've gone beyond the bullet needing to be /soft/plastic enough to seal from being squeezed between pressure from behind and bore constriction from the front. Now we're in a territory where that rotational force on the sides is asking us for a harder bullet.

At rifle speeds (roughly considered 1,600fps+, definitely 2,000 fps+), especially through faster twist rate barrels, we cease to have lead-based alloys that can handle that torque, so the gas checks become pretty much 100% necessary.

With pistols or lower speed rifles, the main asset a gas check brings is that it allows you to shoot alloys that are otherwise softer than ideal for the speeds in question - - such as if you wanted a bullet to expand on impact. In effect, the gas check is making the gun think it's shooting a bullet that's harder than it actually is. If you aren't looking for expansion; have the ability to tweak the hardness of your alloy; have your bullet fit issues understood and addressed in conjunction with a lube or PC that provides an adequate gasket boundary layer, you aren't going to need gas checks at handgun speeds.

You're going to get a lot of good general advice here about where those speed, pressure, and torque limits roughly lie, and that will typically serve you pretty well. If you're chasing the outer fringes of those limits, each gun starts having its own rules, and you'll ultimately have to test the electric fence with your own urine.

[castmiester]

Bigslug...true that, good advice thanks.

[Apple Man]

Very good information from what I am reading. This reinforces concepts of what I have always believed and only have one good friend who casts that understands what I am talking about. (Until I found this forum)

IMHO, bullet casting successfully is all about matching chamber pressure with the BNH of the boolit. Too soft, leading in front of the forcing cone, too hard yield leading towards the muzzle from gas cutting getting around the lube groove.

Every once in a while when the snow is melting and turns into "corn snow", boolits can be recovered laying on top of the snow with zero deformation and proper obturation is evident as is the rifling marks. Gas cutting is evident in "shiny" bands perpendicular to the lube groove(s).