Is it common for velocity to drop off at higher charges?

[pps]

I was testing new loads for my first cast boolits (.357 lyman 358156 gas checked swc). The boolits were sized to .358, gas checked and lubed.

Testing started at 13.7grains of 2400 and were increased in .2 grain increments up to 14.5 grains. The velocity peaked at 14.3 grains at 1297 avg, ES of 3fps in 5 shots from a 5" model 627. At 14.5 grains velocity dropped to 1231 with an ES of 37fps.

There was NO leading, and the boolits actually expanded to .375" in the rubber mulch bullet trap even though they were not hollow pointed. The average bullet wt was 164.5 grains unlubed with gas check and were cast from scrap range lead with a little tin added for fillout...don't know BHN but suffice it to say it was soft.

Is this phenomenon of velocity dropping off at the higher charges common? If so, why would it drop off like that? Extraction was a little sticky but the primers were not flattened.

[357maximum]

STOP

OK I am a self admitted hotrodder...and you just scared me.


BACK UP AND NEVER USE OVER 14 GRS OF MODERN 2400 FOR THE MAGGIE WITH THE 358156 IN ANY ALLOY OTHER THAN PURE LINO...this is "my" rule from getting real close to where your at right now.


You are getting sticky extraction and your whole powder charge is not burning if your vel went down...what happens if it does all decide to burn?

I bet you are using new powder with antique data...right?

Someone may come along and correct me...that is their right.....at the very least STOP and think about what you are doing. Skeeter had a different powder back in the day..if you think you need more power go buy some LILGUN powder or a 357 max, 445 Super, or gulp something in 45 cal.

[45 2.1]

Aw come on Mike, 45s are fun..............:mrgreen:

[357maximum]

Aw come on Mike, 45s are fun..............:mrgreen:

I will not disagree with ya BOBBY ...I have several slow 45's...but I am the top of the foodchain in my wilderness and I do not find them a necessity to fill the freezer...but they are fun but then again so are soupcan mortars:Fire: I carry a 45acp when I am at work and no longer feeling at the top of the foodchain. I actually catch flack from the 9mm guys...I just tell them that when they get done making the badguy mad i will stop him with a 230gr gold dot HP.[smilie=1:...betcha thought i would never admit to such a thing huh?:roll:

[BABore]

STOP

OK I am a self admitted hotrodder...and you just scared me.


BACK UP AND NEVER USE OVER 14 GRS OF MODERN 2400 FOR THE MAGGIE WITH THE 358156 IN ANY ALLOY OTHER THAN PURE LINO...this is "my" rule from getting real close to where your at right now.


You are getting sticky extraction and your whole powder charge is not burning if your vel went down...what happens if it does all decide to burn?

I bet you are using new powder with antique data...right?

Someone may come along and correct me...that is their right.....at the very least STOP and think about what you are doing. Skeeter had a different powder back in the day..if you think you need more power go buy some LILGUN powder or a 357 max, 445 Super, or gulp something in 45 cal.

I'll have to agree with the "Max", even though he's been known to use his reloading room floor as a primer flipper.[smilie=1:

Anytime you see the velocity gains slow or go down, consider it a warning sign that something is amiss, pressure wise. With 2400 I usually see the heavily flattened primer and sticky extraction thing going on first. With WW 296 I may not see those signs until I'm way too hot. But, I do see it with the chronograph. Exactly the same as you have seen. I don't personally like Lil Gun, cause that **** just scares me. Every time I've worked up loads with it, it would get real spikey at top end. Usually with no tell-tale warning signs either. Been using 2400/296 too long I guess. Every powder has its own personality on how it works up. Something you just have to experience and learn.

[357maximum]

I'll have to agree with the "Max", even though he's been known to use his reloading room floor as a primer flipper.[smilie=1:.


OOOOOOH ...OUCH[smilie=1: You cannot be handing out trade secrets like that:roll:

[45 2.1]

OOOOOOH ...OUCH[smilie=1: You cannot be handing out trade secrets like that:roll:

He ain't the only one who knows the "details" behind that statement...............:mrgreen:

[357maximum]

He ain't the only one who knows the "details" behind that statement...............:mrgreen:

http://www.castboolits.gunloads.com/showthread.php?p=401623#post401623

The rest of the story...I B NOT TOO DAMN PROUD TO ADMIT WHEN I EFF UP...

[pps]

I definitely stopped when I saw the drop in velocity. I didn't know that was a sign of overpressure, but anytime I find myself saying *** I do stop. I'll load the rest of these up to 14.0, I'd go to 14.3 but since it sounds like the 14.5 is over-pressure I'll give myself a bit more safety margin.

Thanks for the advise. I had did not expect a drop in velocity with over-pressure loads. Anyone know why that occurs, I'm just curious.

[felix]

Powder being pushed too far from the center of ignition will not burn properly. It is not a sign of an overload of pressure per se, but more of an indicator of too sharp of a rise to appropriate pressure for good burn, and/or the projectile moving too fast for the powder to continue the progressive burn, both of which make the powder closest to the projectile be an adjunct to the projectile and not contribute to velocity. Using a powder of a different geometry/composition with same "overall" speed might not show that drop in velocity. ... felix

[Bret4207]

Powder being pushed too far from the center of ignition will not burn properly. It is not a sign of an overload of pressure per se, but more of an indicator of too sharp of a rise to appropriate pressure for good burn, and/or the projectile moving too fast for the powder to continue the progressive burn, both of which make the powder closest to the projectile be an adjunct to the projectile and not contribute to velocity. Using a powder of a different geometry/composition with same "overall" speed might not show that drop in velocity. ... felix

Let me translate Felixs rocket scientist talk. (Sometimes he forget there are dummies like me out here)

You're wasting your powder and something bad might happen someday.

Glad I could help. And just so you know, I think like Uncle Felix and Cousin Al talk, but by the time it gets to my mouth it comes out im "po'white trash" talk.:mrgreen:

[felix]

Yeah, Bret, I fell off my rocker and became delusionally employed again. It happens every once in a while, no?

Nah, "po'white trash" is defined below, and in no way will you qualify for any portion of that 70B that you gainfully worked for.

http://www.atlah.org/broadcast/ndnr09-03-08.html

... felix

[pps]

.357maximum. I see what you are saying about not going to that high of a charge with anything softer than lino. Here are pics of one (first pic) of the boolits after gc and sizing (before pan lubing) and another boolit recovered from the rubber mulch trap (pic 2)

http://i94.photobucket.com/albums/l96/pps_2006/GCdBoolit.jpg

http://i94.photobucket.com/albums/l96/pps_2006/20080926003.jpg

I love how well the boolit mushroomed even without the HP (looks like I'll be sending this mold off to Buckshot to get it HP'd). The obturation was so complete that there isn't a sign that a lube groove even existed.

If I ever do venture to the edge of 14.5gr again it will definitely be with an alloy of lino hardness.

Thanks again for the feedback and wisdom/caution.

[bobk]

Dumb question, why is there lead on the sides of the gas check?

Bob K

[Ricochet]

Gas check's scraping off a bit of bore leading.

[bobk]

OK, that brings me to my next question. Is there a tight spot where the barrel screws through the receiver, and is too soft a boolit "stopping" there while swaging down, causing more gas to vent to the side, lowering available pressure to continue accelerating the boolit down the bore? A lead lap could detect this tight spot (which is supposedly not uncommon), and correct it. Excessive torque tightening a barrel into position can cause this reduced diameter. A hard boolit might show higher velocity, then, but horrible leading. The leading on the GC means there is SOME leading going on, but the check makes it less obvious in the barrel.

Do this enough, and the erosion at the forcing cone will progress rapidly.

Bob

[pps]

OK, that brings me to my next question. Is there a tight spot where the barrel screws through the receiver, and is too soft a boolit "stopping" there while swaging down, causing more gas to vent to the side, lowering available pressure to continue accelerating the boolit down the bore? A lead lap could detect this tight spot (which is supposedly not uncommon), and correct it. Excessive torque tightening a barrel into position can cause this reduced diameter. A hard boolit might show higher velocity, then, but horrible leading. The leading on the GC means there is SOME leading going on, but the check makes it less obvious in the barrel.

Do this enough, and the erosion at the forcing cone will progress rapidly.

Bob

There is, in fact, a tight spot there in the barrel. When I slugged the bore the lead egg weight had to be tapped a bit harder at that spot in the barrel. How can this cause forcing cone erosion? I can see where flame cutting of the top strap might happen, but I've not seen any appreciable flame cutting on this revolver.

As far as leading, there was hardly any lead on the Lewis Lead Remover, but then again, I fired only 25 shots. In fact the bore is nice and shiny after a normal cleaning. I've never considered fire lapping the barrel because this has been an extremely accurate gun and I didn't want to mess with it.

[runfiverun]

antimony is an abrasive, as is that g/c notice how it scrapes lead? you will also have a bulid-up of hot gasses at that spot.
wow 14 grs huh? i thought 12 was plenty.
the powder thing is that they like to burn at pressures like rl-19 at 45-50k
4831 at 47-52k etc.
when you see this drop off it is because there is no efficiency there.
it is like under loading a slow powder you will have many unburned grains in the bbl.
over doing it is the same thing in reverse.

[bobk]

pps,
To cut the top strap, first the gasses have to escape sideways through the barrel-cylinder gap. This will erode the sharp edge at the back of the barrel. I had a .357 like that. Shot well, but spit lead, bad! I used to rest the revolver against my left hand, while grasping a tree, fencepost, whatever. That gun burned through a cloth glove in five shots, and embedded lead in the web of my hand between the thumb and index finger. Had those lead slivers in me for many years.

Had I though about it, I could have turned the barrel shoulder and the rear of the barrel back one thread, and refit. John Jovino had 8" Python barrels for $10, so I fit one of those.

Bob K

[pps]

I've not had problems with the gun spitting lead except for the one instance when I failed to bell the cases enough while reloading. The boolits were essentially resized to .357 with no lube left on them. Other than that incident, nada.