PP Pressure?

[brstevns]

If given the same bullet, one lubed and with gas check size to .001 over and the same bullet sized down and then patched back up to .001 over will pressure for the load be the same?

[geargnasher]

My impression so far based on velocity and impact point commparisons from the three guns for which I've PPd so far is that pressures are lower with lubed patched boolits than with lubed GG/GC boolits. Not sure why, but the paper sure does make them slicker, even if the sized paper OD is larger by .002-3" than the GC/GG boolit. I'm guessing that lubricated paper/steel interface must have a lower coefficient of friction than lubed lead alloy/steel.

Also, I use softer alloys for PP than for comparable velocity plain GC/GG cast, so that makes a difference in pressures too.

Just my dos centavos, I'm sure there are plenty of exceptions to my experiences.

Gear

[felix]

Yes, lubricated PAPER/steel interface DOES have a LOWER coefficient of friction than lubed lead alloy/steel. Remember, paper holds lube within its pores, making the lube viscosity extremely high by default. ... felix

[303Guy]

Also, the paper jacket is softer and easily compressable as the patched boolit gets launched into the bore.

[brstevns]

If this is true, then which bullet would give higher FPS using the same load?

[Lead pot]

Or your getting gas blow by which is common using smokeless powder

[Lead pot]

My impression so far based on velocity and impact point commparisons from the three guns for which I've PPd so far is that pressures are lower with lubed patched boolits than with lubed GG/GC boolits. Not sure why, but the paper sure does make them slicker, even if the sized paper OD is larger by .002-3" than the GC/GG boolit. I'm guessing that lubricated paper/steel interface must have a lower coefficient of friction than lubed lead alloy/steel.

Also, I use softer alloys for PP than for comparable velocity plain GC/GG cast, so that makes a difference in pressures too.

Just my dos centavos, I'm sure there are plenty of exceptions to my experiences.

Gear

Or you are getting gas cuts which is common using smokeless powder with a PP bullet.

[bcp477]

Generally speaking, with all other factors held equal (bullet weight, powder and charge wt,, etc, etc.)...... cast bullets will produce higher velocities than jacketed....and lower pressures. Oddly enough, lead against steel has a higher coefficient of friction than does copper against steel. But, cast bullets are always lubed - which no doubt makes a difference. As well, cast bullets are more malleable, so they take the rifling with less energy expended. As for the effects of the lubed paper patch, this probably reduces friction yet more.

In the few times that I have chrono'd patched and jacketed loads, using the same (or very close) bullet weights and the same charge.....the PP loads have always produced more velocity, often 100 - 200 fps more. That is, of course, my experience only.....and in no way is it to be taken as definitive.

[303Guy]

Or you are getting gas cuts which is common using smokeless powder with a PP bullet.Common? I would have thought non-existant. A complete seal. Here's a recovered patched boolit that held onto its patch.

http://i388.photobucket.com/albums/oo327/303Guy/DSCF5574_edited.jpg

And the base overhang ring from a faster boolit.

http://i388.photobucket.com/albums/oo327/303Guy/BSAMPATCH42GR.jpg

That's a full two wraps.

I've never found any evidence of flame cutting with a properly fitting paper patched boolit.

http://i388.photobucket.com/albums/oo327/303Guy/PatchBaseonFiredBoolit.jpghttp://i388.photobucket.com/albums/oo327/303Guy/MVC-607F.jpg

[MBTcustom]

I would have to agree with 303Guy on this one. My tests seem to suggest that any gas cutting whatsoever is detrimental to PP performance. My impressions are that paper is extremely strong on compression but it aint worth a ****e if it is unsupported, ie. it must create a perfect seal with the bore or it will vaporize instantly and you will learn new ways to cuss getting all the lead out of your barrel. Of course, I have only been doing PP for the last 7 months and certainly dont know all there is to know. These are just theories and impressions that I came up with while pushing a cleaning rod in and out, in and out, in and out.[smilie=b:
(I ended up fixing the leading problem by increasing the boolit size by a couple of thou.) :drinks:

[brstevns]

Lots to learn! Lots to learn!!!

[Nobade]

I would say the pressure with PP is lower. I have worked up loads in my 358 and 30-30 that would certainly pop the cork if used with GG boolits, but work fine with PP. I can get that 30-30 knocking on the door of .308 performance with PP, but no way to do that with normal boolits or those copper covered things.

[303Guy]

I can get that 30-30 knocking on the door of .308 performance with PP, ...Yeah? I always thought the 30-30 was an ideal cartridge for PP! I've being toying with the idea of reconfiguring a 303 Brit case to mimick the 30-30 so it will work in the Lee Enfield. But then I guess, there is no real need - just a desire![smilie=1: Truth is, I find the Brit case too large for my short barrelled Pig Gun and the neck too short to accommodate the long boolits I want to shoot out of it so I'm thinking of fitting a sleave thing up the front of the chamber to change the shoulder/neck configuration. That would allow me to dump the wheat bran filler at the same time.

[MBTcustom]

You mean like ream out the entire breech to say .500 inch and glue in a sleeve that has the new chamber dimensions? Maybe not glue, but freeze one and heat the other? Very interesting. If I am off base straiten me out. I am interested in how you visualize this.

[6.5 mike]

Goodsteel, on the mil-surp website they talk about using locktite to bound a 7.62x39 insert into a s/r mauser chambered for 7.62x51. It's a good read, outfit in AK makes them.

303Guy, you might be able to lenghten your 303 necks with a 30-40 krag die. I know you can make krag cases out of 303s but the neck is short, not sure how much other work this would take but the case head is the same.

[303Guy]

Actually, I was thinking of cheating a little and making a press/shrink fit insert and using loc-tite too. The loc-tite acts as a lubricant during press fitting and will fill any mismatch voids. I have to ream the neck though as having an interface in that area would be hard to blend smoothly. I might be able to bore/drill the neck area parallel to the start of the insert. I don't want to unscrew the barrel.

It might not be so difficult as there is goint to be a change of case wall thickness at the interface so I could allow for that and thereby get away with a simple insert (not that simple, mind you).

[barrabruce]

Why not face off a thread or two and just ream it with a 30-30 reamer. Relieve back face for headspace. No monkeying around.
Then you'd have a 303-30.
I think the 30-30 rim be close enough for no machining on the bolt face.

What yer' reckon???


Barra

Ohh any help on the 30-30 PP would be helfull for me me if you choose to tell. :)

[303Guy]

The idea is a good one. It is more work for me as I don't as yet have the tools to take off barrels nor do I have any reamers. I could just reduce the case volumes with an epoxy fill. I've just had an idea ..... I'll start a new thread.

[Lead pot]

Here are a couple PP bullets with gas cuts.
I can dig deeper in my records for more.


http://i704.photobucket.com/albums/ww43/Kurtalt/CopyofIMG_0546-1.jpghttp://i704.photobucket.com/albums/ww43/Kurtalt/IMG_0547-1.jpg

[303Guy]

I have had one or two gas cut patched boolits. Not as spectacular as yours. Mine could be explained by undersize core and casting flaws. Once those problems were sorted out there were no further signs of gas cutting.

Here's one.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-522F.jpg I think there was a casting flaw on this one.

Here the flame cutting is on the base edge.
http://i388.photobucket.com/albums/oo327/303Guy/untitled-2.jpg There were casting flaws on this one.

I have picked up inexplicable leading. However, it is rear for me. Perhaps a valid piont is being made for the proper fit of the boolit in the throat, i.e. tight!

[Nrut]

Here are a couple PP bullets with gas cuts.
I can dig deeper in my records for more.


http://i704.photobucket.com/albums/ww43/Kurtalt/CopyofIMG_0546-1.jpghttp://i704.photobucket.com/albums/ww43/Kurtalt/IMG_0547-1.jpg

Lead pot,
What size are your bullets (pre-wrapped) in relation to your bore size?

[geargnasher]

Or you are getting gas cuts which is common using smokeless powder with a PP bullet.

Common failures I suppose, but if things fit right smokeless won't even leave smut marks on the driving bands of the patch, so I would say ZERO blowby is the norm with properly constructed PP boolits and smokeless powder.

Gear

[brstevns]

Common failures I suppose, but if things fit right smokeless won't even leave smut marks on the driving bands of the patch, so I would say ZERO blowby is the norm with properly constructed PP boolits and smokeless powder.

Gear

Does it seem failures come more from improper paper patch? or bad fit of the patched bullet?

[geargnasher]

Blowby/leading failures could be caused by a number of things, oversized boolits and paper too thin come to mind. When I first tried PP many years ago I used .308" Loverin boolits and two wraps of gummed cigarette paper with a twisted tail in my .3095" groove Marlin (12-groove Micro-groove rifling), and they leaded to buggary. I didn't use any lube on the patch, and it wouldn't stretch enough to take all that land surface area without tearing, and since the bore was .302" the boolit wiped out too much of the patch anyway. Today I'd try .303" boolits patched up to .312" and sized .311" with two wraps of 16lb paper lubed with any kind of soft groove lube like beeswax/Vaseline. Need to balance effective patch cutting for proper patch jettison at the muzzle with enough patch material to stretch into the multiple grooves without tearing big gaps in the patch that allow excessive metal-to-metal contact or allow blowby in the groove engraves.

Gear

[303Guy]

An important consideration with regards to patch lube is that the lube should be not sticky so that it 'glues' the patch to the boolit. I've had that with cig paper. The patch was still stuck onto the recovered boolit after penetrating wet rags.

Usually recovered patches are squeaky clean and show no flame damage whatsoever. They do discolor from the rifling impression.

[MBTcustom]

You know, rereading the entire post (especially words by lead pot) it occurs to me that we jumped on him pretty hard without noticing that those boolits look suspiciously like black powder boolits. We know that the bp guys have two ways to skin this cat, one of witch involves an undersized boolit that is depended on (in theory) to obturate, "ie. bump up" to catch the rifling. This is a common practice over there and it works really well for the BP fellas even though I have not read one single case where this method was successful with smokeless powder.
I guess my theory is, that those boolits could have been shot in this way with BP, and it might have worked extremely well, (never underestimate a guy with a sharps rifle. I'm pretty sure one of those guys could explain how to shoot paper patched rock-salt into a 4" group at 600yrds, and have proof targets to back 'em up) I mean its obvious that there was serious gas cutting on those boolits, but that could be business as usual for a BP rifle.
Just a thought. :drinks:

[303Guy]

Good point goodsteel. Heck, I hope we didn't jump on Lead pot! It's just that while it does or can happen it's not really a common event - I think? Those sure are interesting photo's by Lead pot! I'd like to know the history behind them. (Well, knowing what makes things work right is interesting but so is knowing what makes things fail!)

[barrabruce]

Hmmm I fired some Jacket stuff last week-end.
They shot pretty well out of my 30-30. (don't do it much at all)
My groove diameter is 0.309 and they measured 0.308.
I should have gas cutting and no performance if the 40 or so BHN copper jacket don't bump up to the bore.

My pressures are lower with PP-ing cos I get unburnt powder in the bore and boot less althou velocities are pretty well book stuff for my barrell length for j-word.
Maybe they just slip through the tube like a greased suppository unless I bump up the charge more!!!!
I have gone up a powder burn rate to get it to burn proper.

Maybe my PP are on the limit to to small.

My bore is 0.302"
I size to 0.302"nose but base is up to 0.303" (light scratches on bullet nose when seating and good firm fit at the crown) and the ones I have dug out of a tractor tyre at 300 yrds appear to grown a thou or so from what I can deduce amoungst the mutilation from the re-enforcing wire etc.

Barra

[geargnasher]

Copper jacketed bullets DO gas cut sometimes, and they almost always leak due to being (necessarily) undersized, recover one and look at the groove (high) engravings, you'll see the burn marks. Difference is, they don't cut as badly as lead, and the effect is much less deleterious to accuracy than with lead.

I was reading the Matthews book again last night and came across his opinion on pressure, his experience has left him with the distinct belief that J-words make the most pressure for a given weight and charge, followed by GG boolits, then lubricated PP boolits, even smooth-sided PP ones.

Gear

[Lead pot]

Let me tell you a little about Lead Pot.

Ol Lead Pot is a 71 year old retired retired plumber that has been dumped on from above, walked through laid in a time or two and pulled stuff out of pipes with his bare hands that is worse then any of the replies I read on this one eyed monster.:roll::) my skin is tough.
In the winter when the snow is deep enough that a long legged Alaskan moose drags his belly through and the temps are cold enough that the tears freeze your eyes shut I study bullets on how wads protect the bullets and what works with patched bullet diameters, alloy temper using all types of powder, smokeless and blk.
I just melted down a full three gallon bucket again from recovered bullets :Fire:

So dump away :) a good healthy exchange of thought is always good. Just keep the facts straight about what you tell people that are looking for your straight knowledge.

LP.

[geargnasher]

Nobody's jumping on anybody here, at least not the way I saw it, if someone saw it otherwise from me, I'm sorry about that, no offense intended.

Goodsteel pointed out that those gas-cut boolits looked like BP boolits, and I concur. I also concur that there are two approaches to sizing BP boolits, and it looks to me like the boolits might have been too small, or not patched thickly enough to create a good seal. The very shallow, almost non-existent rifling engraves makes me think the boolit was under bore size and failed to "bump" sufficiently to seal the patch to the bore completely. Like I've said before I'm far from any kind of expert since I've only been doing PP for a short time, but I maintain that if a patched boolit leaks and gas cuts, the solution lies in correcting fit.

Gear

[Nrut]

Lead pot,
What size are your bullets (pre-wrapped) in relation to your bore size?

That's why I asked..
I have read Lead pots excellent posts on the BP/PP forum regarding throating for BP/PP and I was wondering if the bullets pictured are "bore size" or smaller..
If those bullets pictured are bore size + before patching then that gives me pause to stop and think what is causing the blow by and what can be done to stop it....:-)

[Lead pot]

Lead pot,
What size are your bullets (pre-wrapped) in relation to your bore size?

I cast and patch all of my bullets for the purpose of what I'm going to use it for.
All my PP moulds and swage dies are of several different diameters.
I patch under bore for hunting and I patch my match loads over bore diameter because of the better accuracy.
That particular bullet in the photo is not just for just one type of powder, it works great for blk or smokeless. For smokeless I have only one .45 caliber rifle I use for it and that is a old early run Pedersoli Quigley when Cabala's stocked them and the patched bullet are groove diameter when I use smokeless.
Regardless of what you think about abtuation of smokeless powder it does do it even when you use a jacketed bullet that is in print in a Reloaders Magazine article, not my findings. I never ran any tests using jacketed bullets.

Instead of people on this forum speculating what happens to a bullet using smokeless or black powder run the tests yourself you can learn a lot from doing it.

LP.

By the way I dont feel I been dumped on :)

[Nrut]

Quote >>> [For smokeless I have only one .45 caliber rifle I use for it and that is a old early run Pedersoli Quigley when Cabala's stocked them and the patched bullet are groove diameter when I use smokeless.]

Is the pre-wrapped bullet smaller than bore diameter?
Thx.

The reason I ask is I have two modern 38-55's that have .381 + grooves and will only chamber .379 bullets..
I was thinking later on down the line when I have time for these rifles that I might try a soft undersized PP bullet with a faster smokeless powder to help kick them up to fit the groove dia..
That would be the first move..
If I get gas cutting like you showed above then I am going to try using PSB..

[DIRT Farmer]

I had second thoughts about jumping in here as my experience is limited. From what I know swaged slugs even round from a Whitworth bore (muzzle loaders ) are recovered very much intact and sized to bore. Even the paper seam shows on the recovered slug. Burned patches would lead a bore in a hurry. Not all use wads, most that I have talked to do. The patched slug will slide down the barrel very easy and can be dislodged forward with any rough handling I have been warned. The recovered patch fragments are much larger than anything I have found with smokeless.
I started working with faster powders and wheat bran fller in the 303 just to see if the theary will cross over. Initial work is promising.
I do know that a Lee .285 135 grain 10 grains of Green Dot in a 7X57 will shoot fairly well even at 0.001 undersized if it is stuck in the rifling, but seat it back and it will lead.
I don't know the answers but things don't always follow the rules.

[geargnasher]

Col. Harrison mentioned that PP won't make it if not seated very firmly into the rifling or throat upon chambering. I've always heeded his advice and had success.

Gear

[MBTcustom]

I don't know the answers but things don't always follow the rules.
Aint that the dad-burned truth.
I am still trying to get my head around what leadpot is saying. Not trying to be argumentative at all, but I have recovered quite a few boolits from the backstop and they dont look anything like those in the picture.
First of all, all of my boolits where mushroomed out to a certain degree which may have obscured some of my findings. (How the heck did you manage to stop them so gently anyways? Snow maybe?) Consequently the recommendation to:
run the tests yourself you can learn a lot from doing it. kind of have me scratching my head wondering how I could do more than I have already done? I tell you that I have seen gas cutting, but when I recovered those boolits, I gave them very little thought because accuracy was atrocious and my barrel was leaded. It was one of those "well, back to the drawing board" kind of things. The assertion seems to be that gas cutting is fairly common place and is not directly associated with loss of accuracy. I admit that this was definitely an assumption on my part that seemed to be born out by the facts while I was developing my loads and seemed to be one of the very few fundamental truths that have been offered on these forums for smokeless PP shooters. However, I am willing to consider the possibility that this was nothing more than cosmic coincidence. But if it was cosmic coincidence, and this hard and fast rule had been debunked, I wonder what all of our tests have proved. There is something there. If gas cutting was just a convenient scapegoat, then what was the real issue? Ie. what if those gas cutting marks dont necessarily mean that the patch failed!?! Ow my poor brain owwww![smilie=b:
Seriously, we may have something here. Is there any more info that you can add to this leadpot? Maybe you could expound a little more on your readings/findings?
I am definitely curious. I may take the 'ol PP gun out and run a few tests. (I dont know about you other fellers, but here in Arkansas we have finally gotten a break in the heat and shooting is fixin to be enjoyable again.)

[303Guy]

Col. Harrison mentioned that PP won't make it if not seated very firmly into the rifling or throat upon chambering. I've always heeded his advice and had success.It's all making more and more sense!

I've developed the idea that the patched boolit should sit very firmly into the throat and leade. It seems to work for me, so much so that I favor worn throats for patching.


Seriously, we may have something here. I do believe so.

If things defy the rules it means the rules are wrong or incomplete! Usually incomplete, I would think.

This is an interesting thread. A good thread, in fact! :drinks:

[barrabruce]

Hey Lead pot a penny for your thoughts.

See If I got this right.

J word gas cuts because they are a bit smaller than groove.

The holy black shooters who PP are shooting a clean bore of wiped fouled bore of consistent fouling to obtain consistent accuracy.

For more shots the just over bore patch gives more shots before the fouling plugs things up some and destroys accuracy.

Gas Geckers try and seal the grooves and have enough lube to get the lead through in one piece.

Plain base low velocity stuff you just need some lube and a good tight fit and plug away.

So to this here Smokeless PPing.

I should hope for the same as black powder and ride the bore debri and aim for consistent fouling for consistent performance.
Lube the patch and hope the lube protects the patch with gas cutting/leakages and all things that try and rip gring or tear it to peices before it leaves the crown.

What protects the lands near or at the bore from the cut patch on its way through???

I belive the patch is supposed to bend and conform but it still needs to be cut to come off.

I read that harry pope reckons that pp was not as accurate as plain based bullets for accuracy and wouldn't hold up to many firings due to fouling build up.

Then a again he was breach seating of even better muzzle seating with cases full of black and one of his things was a powder thrower that dropped a duplex load. Un be-known to his rivals.

Barra

[HammerMTB]

If given the same bullet, one lubed and with gas check size to .001 over and the same bullet sized down and then patched back up to .001 over will pressure for the load be the same?


To the original question:
I will reference an experiment I did in '09 with my 1895GG and PP boolits. I did not use a GC boolit, but that shouldn't be the variant that makes or breaks this experiment.
I did not measure the pressure. I measured the velocity. I'm going to GUESS the pressure was the same, but the vel slightly higher due to lower friction of the PP boolit. The thread (http://castboolits.gunloads.com/showthread.php?t=69340)
anyone else care to attempt to make deductions based on the experiment?