Opinions needed on a 45 ACP question

Now I know this might be completely crazy 

Does anyone here think that a soft JHP might swell from the explosion of the powder and fill the lands and groves? Reason I ask is when Bullets from the same batch is recovered from water from a New barrel the lands and groves scratches are very noticeable! When compared to one on from the same batch on the same day but with a barrel with severely worn lands and grove the scratches are still on the bullet but are not as deep because of the worn lands and grooves. What’s everyone think?

severely worn lands have you slugged both to compare Diameter? my be you just need a bigger bullet.

The question has nothing to do with anything I have. My stuff is all good. I stumbled into something on youtube
Slugging would not duplicate the explosion! One rifle guy I know said that they don’t swell from the explosion but rifle bullets mostly are lighter than 185 and 200 grain

In a rifle, 65,000 PSI pushing a copper jacketed lead round compresses the bullet limited by the containment dimensions.

I’d assume a handgun would also

Bingo that’s what that guy was saying! Now with hard cast I don’t think the bullet swells but I do with a soft lead or even softer JHP!

I get all fidgety when people talk about the "explosion" pushing the bullet.
It is the combustion of the propellant that pushes the bullet thru the bore.
Explosion brings to mind grips in splinters & cracked slides...plus a fair amount of cursing (hopefully with all body parts intact).
It really is rocket science on most levels, so if you have an explosion you have made a grave error.

Lol! Ok combustion! But working all those years with Ford makes me think of gas compression and spark!

Cast bullets need to be of hardness to work at the pressure they are operating at.

Soft or swaged  (less than 12 BHN) below 1000 fps
 Maybe 18 BHN up to 1500 
Harder yet over that.

I was shooting 22 cal home cast out of a 22-250 at 2750 fps cast of pure linotype.  Should have been about 22-25 BHN.  They worked great with gas checks.  I have a target showing 14 rounds in 5.5" @ 300 yards.

These numbers are not exact.  The bullet needs to deform to fill the rifling.   Too much or not enough and it will foul the barrel with lead.

I have a Ruger Super Redhawk that shoots 18 BHN bullets up to 1400 fps.  Shooting the same bullet at 800 fps leads the bore because the bullet does not upset to fit the barrel.   It needs a bigger kick in the butt.  

Jackets are hard enough that the copper engraves in the rifling and seals.  If it does not seal, no damage is done. Bullet still spins and goes on its merry way.

David

James Hensler wrote:Lol! Ok combustion! But working all those years with Ford makes me think of gas compression and spark!

Car engine...combustion equals horse power
                  explosion/detonation equals pistons with holes on top

James Hensler wrote:Bingo that’s what that guy was saying! Now with hard cast I don’t think the bullet swells but I do with a soft lead or even softer JHP!

I don't get why you're referring to a JHP bullet as soft.

The "J" means jacketed, and gilding metal jackets are hard and generally require very high pressure to obturate.

S148 wrote:

James Hensler wrote:Bingo that’s what that guy was saying! Now with hard cast I don’t think the bullet swells but I do with a soft lead or even softer JHP!

I don't get why you're referring to a JHP bullet as soft.

The "J" means jacketed, and gilding metal jackets are hard and generally require very high pressure to obturate.

Winner winner chicken dinner
 Call Hornady or Sierra and ask them about jacketed bullet obturation......the answer will amuse you

james r chapman wrote:In a rifle, 65,000 PSI pushing a copper jacketed lead round compresses the bullet limited by the containment dimensions.

I’d assume a handgun would also

Note the word compress...not expand!

This question is one that is full of "ifs".
If SAAMI says that we have a groove O.D. of .450, and if jacketed bullets are supposed to be .451....why would the bullet need to expand to fill the groove????

James Hensler wrote:Lol! Ok combustion! But working all those years with Ford makes me think of gas compression and spark!

OK, I'll bite,

3 items neccessary for combustion are Air, Fuel Spark
4 cycle engine cycles ar Squeeze, Bang, Blow, Suck (them's the technical terms).

I think you got them mixed up.

I worked for GM, perhaps your definition is why my first Ford never liked to start on cold mornings? 

James Hensler wrote:Bingo that’s what that guy was saying! Now with hard cast I don’t think the bullet swells but I do with a soft lead or even softer JHP!

I re read this 

Take your fingernail and try to make a cut in a soft cast and hard cast bullet......then try on a JHP.  A hard cast bullet has a bhn  of what around 18+  Jacketed bullets have and this is a guess after a little reading of 36+ bhn.  

You may have your logic backwards
 Steve has the correct answer

What the OP is talking about is of some concern to Artillery she’ll designers and the technical term is “setback”.  

It is a function of the acceleration and the instantaneous acceleration is the pressure times the cross sectional area minus the friction.  In artillery, the peak pressure and peak setback is generally after the rotating band is engraved.  The setback forces are the result of the amount of mass in front of the area of concern.  In rifles the base to about one caliber is subject to setback expansion.  This can be designed out some by jacket design ( Nosler solid base Ballistic tip), but for cup and core bullets it’s basically the base.  In pistol applications you have some limits.  First is the low pressures involved.  In a 45 target load you’re lucky to exceed 15000 psi.  Second the short bullets don’t have enough mass to initiate setback at these low pressures.  So bullet expansion of a 185 JHP in a 45 target load is probably minimal.

The other issue here is that metals are unlikely to flow into small scratches in the barrel.  While engraving of bullets is one indicator of identifying a particular firearm in a court case it is seldom the fine scratches that are definitive.  It is the geometry specific to that firearm and even that is seldom conclusive.  The fine scratches you see are the result of dragging one surface against the other.  There may or may not be a mating scratch on the surface of the barrel.

Aprilian wrote:

James Hensler wrote:Lol! Ok combustion! But working all those years with Ford makes me think of gas compression and spark!

OK, I'll bite,

3 items neccessary for combustion are Air, Fuel Spark
4 cycle engine cycles ar Squeeze, Bang, Blow, Suck (them's the technical terms).

I think you got them mixed up.

I worked for GM, perhaps your definition is why my first Ford never liked to start on cold mornings? 

I just mentioned the 3 things not in any order
But back in the day of carbs you pumped the throttle 3 times before cranking!

James Hensler wrote:Bingo that’s what that guy was saying! Now with hard cast I don’t think the bullet swells but I do with a soft lead or even softer JHP!

I think the term "hard cast" is misleading and can mean any cast bullet from 12 BHN to 22 BHN. So, having said that any cast lead bullet will obturate, even linotype alloy. Some more than others, but a good fitting bullet will fill the lands of the barrel with normal loads, expanding into the confines of the barrel (I have fired 123 gr. balls with very light loads of Bullseye out of my 44 Magnum revolvers and recovered balls were oblong and had rifling grooves impressed on them...