Chamber difference for PP

[phatman]

Hi Guys,
If you were building a rifle with the intent of shooting Paper Patch bullets through it, how would the chamber throught be different???
Or is there any real difference in the chamber for Jacketed Bullets VS Paper Patch??

Cheers, John

[docone31]

For me, I would just go with standard chambering. I do not think a different chamber would help with my rifles, they are more accurate than I can see with paper patch.
I would just go with standard chamber.

[pdawg_shooter]

Standard chamber, throat cut correct length for your bullet with a gentle taper into the rifling. Works every time.

[Nobade]

If you don't know about it, you can go to the SAAMI web site and see chamber drawings.

http://www.saami.org/specifications_and_information/index.cfm

From my experience you don't want a "accuracy" type chamber with parallel freebore only .0005" over nominal bullet diameter. You want something like the SAAMI 30-06 or 375 H&H with a gentle cone that starts a few thou over groove diameter.

[Nrut]

phatman,
You might want to have the chamber cut just slightly over Max. case length as listed in a loading manual..
When I make throat slugs I am finding that most chambers are cut way over length..
Chambers that are extra long invite paper extrusion during blast off which give you paper rings on your case mouth when you extract the case..
Long chambers don't help grease groove bullets either for the same reason..

[303Guy]

Thanks for the link, Nobade.

I have a theory that the ideal PPCB throat has a simple shallow taper throat. The boolit should seat fully against/into this taper and have a somewhat small radius nose. A heavier boolit would taper down further into this throat. The boolit to suit would have a parallel seating section and a matching taper to suit the throat. This is just a theory - how nice it would be to be able to actually test theories!

[barrabruce]

Not mine.

Mine has been cut with a extra long neck alla weatherby free bore with a sharp case neck end shoulder.
This leads into the throat with a sharpish lead angle.

So in effect I have 2x throats to go through.
I still get general jacketed accuracy out of it with PP thou after lots of head aches.

Barra

[nanuk]

Thanks for the link, Nobade.

I have a theory that the ideal PPCB throat has a simple shallow taper throat. The boolit should seat fully against/into this taper and have a somewhat small radius nose. A heavier boolit would taper down further into this throat. The boolit to suit would have a parallel seating section and a matching taper to suit the throat. This is just a theory - how nice it would be to be able to actually test theories!

303Guy:

are you describing the boolit Geargnasher designed for his 30cal PP challenge?

[Lead pot]

phatman.

I can give you an example what a chamber looked like back in the 1870's when the lead bullets naked and patched were used and what the chamber turned out to be at the event of the jacketed bullet.
The top cast is what a modern chamber looks like now.
The second cast from the top is what was used back in the 1870's.
Both chambers will work using the patched bullet if it is done correctly.
But the old chamber will work best for the patched and the naked (GG) because the sharp step of the top cast will not cut paper rings or lead rings and smear the bore with lead that gets carried forward with repeated shots fired.

http://i704.photobucket.com/albums/ww43/Kurtalt/IMG_0254.jpg

Here is a cast of a old .40-70 Sharps chamber.
http://i704.photobucket.com/albums/ww43/Kurtalt/IMG_0515.jpg

[303Guy]

are you describing the boolit Geargnasher designed for his 30cal PP challenge?You know, I do believe I am. I had forgotten about Gear's boolit.

[barrabruce]

Whats the first case and bullet lead pot?? 38/55 maybe. looks pretty.

[Lead pot]

No it's a .44-2-5/8 (.44-90 BN) Sharps

[phatman]

Thanks for the help Guys,
Man that 44/90 BN Sharps is a very modern looking cartridge for its time.
I'm going to build me a paper patch rifle one of these days. I've been patching for my CZ 550 in 9.3x62 with mixed results.
Now I can see what is wrong with it. Just need to work on the throat a bit.
I think I'll leave that to a gunsmith....lol A man needs to know his limitations.

Cheers, John
and have a great Thanksgiving

[Lead pot]

The bullet is wrong for that time period and it dont shoot for sour grapes past 400-500 yards.

[geargnasher]

Paper rings. I've been plagued with paper rings in a couple of applications, and figured out the common problem and the common fix for both of them. In both cases I was wrapping the boolit with thicker paper than normal to make a final diameter quite a bit bigger than the groove diameter in an effort to compensate for oversized chamber necks. I got my good chamber neck fit and good boolit alignment with the bore, but in both instances it took .003-4" over groove to fit the brass to the throat. When I changed tack and sized the necks slightly smaller, used a thinner patch, and sized to .002" over groove diameter the paper rings disappeared. Also, fuzzy papers like bond exacerbate the ring issues. Accuracy is slightly diminished with the thinner paper and smaller final diameter in those two guns, but not much, and I'm not sure if it's due to poorer boolit alignment or something else. The improvement in functionality is well worth it, as it isn't a lot of fun to pull the bolt and patch out the ring every shot.

Gear

[Nrut]

Gear and others,
What are your thoughts on using the throat style shown in Lead pot's post #9 for "high vel. smokeless PP"?
I am thinking 35 Whelen..
Would there be any downside?



http://i704.photobucket.com/albums/ww43/Kurtalt/IMG_0515.jpg

[geargnasher]

Nrut, I personally prefer the "modern" type throat, with a step at the end of the brass so the throat goes immediately to just barely larger than groove diameter, with no long taper from the case mouth to the throat. The idea is to have a smooth and consistent extension of the inside of the case neck all the way to the throat. If the end of the chamber is tapered into the leade, there is a gap from the case mouth to the point that the patched boolit touches the leade, and gaps at this point leave the boolit unsupported in a zone that's under a lot of stress at launch. If the boolit is unsupported in the middle during launch while the nose is encountering the resistance of being engraved by the rifling, the middle part will "wad up" to an extent, then the base will rivet while trying to squeeze the plumped-up middle section throught the throat, then finally the whole thing gets squirted through the barrel like so much cake icing in a confectioner's tube, no two boolits being deformed exactly the same. This becomes a big deal at high velocity and smaller calibers (like .30) unless you're using boolits that are strong enough to resist permanent deformation of the peak pressure. That means straight linotype at less than 2100 fps with a 200 grain boolit in .35 Whelen unless the boolit fits the chamber well enough to not be distorted when fired. Superior fit is key to achieving accurate loads in any cast boolit gun, and once you exceed the strength of the alloy with chamber pressure the fit of boolit to barrel throat is the only thing that keeps the boolit from becoming a random blob of alloy.

Gear

[Nrut]

Thanks Gear..
What you say makes sense to me.

[303Guy]

I was thinking the same thing (although I could never have described it so well). I like the concept of an abrupt chamber ending with a slight radiusing from the chamber into the throat - as opposed to the normal 45° chamber end. Kind of like a case mouth head-spacing chamber.

[phatman]

The problem I've been having is with flyers.
I get one, 2 inches out of group at 50 yards, about every 6 to 8 shots.
When I get one I find a paper ring.:???:

I figured the old style throat would cure it, but if you guys have a better idea I'd love to hear it.:)

Oh, the gun is a CZ 550 in 9.3x62 with a 250 grain .360 bullet.

Cheers, John

[geargnasher]

Are you only neck-sizing the brass? Sounds like you might have a concentricity problem or the boolit getting crooked somehow upon firing. Also, check to be sure that your boolits aren't being "set back" when camming the action closed every once in a while. Unless you're patching out the chamber after every shot, how can you be sure that the flyer was caused by a paper ring from the previous shot which caused the next round to chamber hard and affect the boolit fit in the throat, or set it back some in the case? Reason I ask is I was having flyers every three or four shots in my .45/90 and they went away when I cleared the paper rings from the chamber after every shot. Same thing with my .30-'06 until I switched to a slightly thinner and much tougher paper that eliminated the rings entirely.

Gear

[phatman]

Geargnasher,
Sounds like I have a lot more testing to do.
It will have to wait untill after the holidays.

Cheers and Thanks,
John

[MBTcustom]

Im going to weigh in here, because I just got done making a custom PP rifle over the summer with the express intent of PPing the ammo. I learned a couple of things in the process I think, about PP chamber throat and fit dimensions.
#1 the case needs to be trimmed so that it kisses the end of the chamber/start of the throat. The size of that gap will determine the size of the paper ring left on the case rim.
#2 neck tension is important. The size of the neck portion of the case needs to be as tight a fit as possible. The ideal situation would be that you dont have to ever size the necks, just prime the fired cases, and load them over again. The trick is to get the size of the chamber, the size of the case neck after firing, and the size of the PP boolit to all line up in beautiful harmony. When this works it is so fun. No press, no dies, just powder, primer, and boolits!
Finally, dealing with the throat. I resurched and hunted far and wide to find info on this subject, and I can tell you that because nobody knows much about it, it is very hard to keep the thread on track so that people keep talking about this very important and overlooked factoid. The best I have come up with, is that the throat needs to match the profile of the boolits that you intend to shoot through it. ie. the BP paper patchers use a long gentile lead on their throats, because they use long tapered boolits.
Look at the profile of the boolits you intend to shoot through that rascal, what angle does the patch contact the rifling at? Your lead angle should be suitable to be a relatively close match to that angle. Make sense? In other words the perfect throat reamer would look like the boolits that you intend to shoot.
As far as freebore/ throat, whatever you call the unrifled portion between your case rim and the start of the lands, you want to keep that as short as you can. You want to be able to get the ammo in the chamber, that's true, but you need the rifling to purchase the boolit as quickly as possible.
I believe all this is true and trustworthy, but if anybody knows different, feel free to use these words for target practice.
Hope this helps.

[303Guy]

That's my thinking exactly. That's why I like my over-sized bore rifle although it still has the three degree leade. My cordite lapped carbine barrel on the other hand has the oversize bore plus a long gentle throat and leade. Unfortunately, I can't close the case mouth gap 'cause my cases just won't 'grow' (that's what I get for keeping pressure moderate and lubing the cases).

[geargnasher]

Goodsteel, well written and expressed.

I know what you mean about the paper rings. l mentioned in a previous post about how case length can be shy of the end of the chamber by .010" or so and still not leave paper rings IF you wet-patch, use paper that isn't "fuzzy", size the boolits after wrapping and drying so the surface gets a "polish", and the step into the throat from the chamber mouth isn't razor-sharp, at least that was my experience with a couple of different guns, but of course that doesn't make it the Holy Writ!! Notebook paper, copier paper, and Meade sketch paper were the worst offenders IME, while 100% cotton rag paper, 25%, 16-lb rag, and some of the tracing papers didn't leave rings, even with short cases.

I'd like to know why sometimes BP patches use tapered boolits, I mean if there are other reasons besides the obvious of "guiding" the soft point of the typically under-bore boolit into a potentially fouling-choked throat. I think you're right-on with matching boolit to the throat, that's a critical thing with high-velocity grease-groove boolits, it prevents boolit distortion on launch. In fact, I've heard it said, and it makes sense, that the ideal boolit mould for a rifle would be cut with a cherry with the identical dimensions as the reamer used to cut the chamber throat and leade. Well, maybe a thousandth smaller so it would actually chamber! But you get the idea.

I had Tom make this boolit mould for me to fit the chamber slug of the rifle in which it was to be fired, and also compared that to several SAAMI drawings of similar .30 caliber rifles, I think it would work in many of them. It is patched-up to make a snug fit in the throat, and even has a short, bore-riding nose section that is patched. This makes wet-patching with stretchy paper a must, and car must be used when selecting paper grain direction. Very tedious to wrap without gaps or overlap, but so far they function as designed and shoot well at nearly 2700 fps with 13-ish BHN alloy.

The boolit as it would fit the chamber, note the patch would add exactly .010" to all band dimensions to make it a perfect fit in the chamber. I didn't draw the case neck to reflect the thickness of the patch, so that part of the drawing is wrong. When loaded correctly, a cartridge can be loaded into a sooty chamber and extracted, and the patch will be solidly "smutty" from about .012" ahead of the brass (brass .008" short of the end of the chamber) all the way to the end of the patch, with darker engraves of the rifling on the nose portion.
http://castboolits.gunloads.com/imagehosting/thum_89094e923d7fdf04c.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=2381)

The boolits:
http://castboolits.gunloads.com/imagehosting/thum_89094ea39a08d9d9c.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=2489)

Here are the paper rings left behind by the Meade sketch paper:
http://castboolits.gunloads.com/imagehosting/thum_89094ea4929b42a05.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=2491)

Gear

[MBTcustom]

IF you wet-patch, use paper that isn't "fuzzy", size the boolits after wrapping and drying so the surface gets a "polish", and the step into the throat from the chamber mouth isn't razor-sharp, at least that was my experience with a couple of different guns
I dont know how this idea has escaped me until now. I admit that I have a great fondness for dry patching. I might have to give it another go trying this new trick!

[phatman]

The other problem I'm having is recoil driving the bullets into the case in the mag.
I noticed it today. The bullets can handle 2 but not 3 recoil events and the mag holds 5.
I don't resize the cases at all. I just bell the mouth a little and taper crimp them. The 9.3x62 has a fairly short neck for its size and it just cant get enough grip to hold them under heavy recoil.
Will finding a powder that will do a 100% fill resolve this????

I'm thinking that I might have picked the wrong gun to learn on.
No worries, I have an old Krag laying in pieces. Might be time to get her together.

Cheers, John

[geargnasher]

If you drop-tube a 100% density charge, maybe. Compacting granular filler between boolit and powder will work for sure, just realize that it increases pressure in bottleneck cases so you have to reduce the powder charge appropriately.

Gear

[303Guy]

The other problem I'm having is recoil driving the bullets into the case in the mag.Might I ask what paper, boolits, powder and charge you are using? Any idea of muzzle velocity?

[phatman]

Hi 303Guy,
16 lb. 100% rag paper, Cast 250 grain .360 bullets 20 to 1 alloy, Powder Reloader 17, 66.5 gr.
Velocity is averaging 2710 fps with no bad pressure signs.

Oh, these are wet wrapped with a tiny bit of Elmers glue in the water. Dried in a warm oven and sized with a little Alox to .368.

Cheers, John

[phatman]

One more thing,
I had to use a magnum primer, for some reason the standard primers I use in jacketed loads were not consistant at all.

Cheers, John

[Nrut]

Hi 303Guy,
16 lb. 100% rag paper, Cast 250 grain .360 bullets 20 to 1 alloy, Powder Reloader 17, 66.5 gr.
Velocity is averaging 2710 fps with no bad pressure signs.

Oh, these are wet wrapped with a tiny bit of Elmers glue in the water. Dried in a warm oven and sized with a little Alox to .368.

Cheers, John
John,
16 lb. 100% rag paper sounds perfect to me..
Where did you get it and what is the brand name, manf./product #..
Thanks

[phatman]

Hi Nrut,
The paper is called Mars Drafting paper, I got it at Staples. Its not cheap but it will go a very long way.

Cheers, John

[303Guy]

OK, that's a pretty stiff load (for my recoil-shy self). 250gr boolit trundling along at 2710fps. Holy Cow, that's moving! I see why your boolits are shifting in the neck. I find that cheapo printer paper that really compresses on seating hold my boolits pretty well. But not for your recoil levels. Mind you, if the pressure curve is right the shock on the boolits in the magazine is not necessarily that great.

Something that could be happening to your boolit on launch is a ring of expansion at the case mouth chamber end junction. I got that even with low velocity loads.

Something to consider when oven drying patched boolits is expansion of the alloy. It means the patch is drying on an expanded core which could well loosen on cooling. At luke-warm temperature it should not be a problem.

[phatman]

Hi 303Guy,
I have a 300 gr. .366 mold that I can push a gas check bullet to 2200 with out leading and with no issues. I might just switch back to that.
I really don't think I have enough neck on this case to hold the recoil of almost a 4000 fpe load.
On the other hand. The paper is not moving on the bullet, its sliding into the case. So what if I lightly sand the inside of the case neck with some fine sandpaper. Would that help???

Cheers, John

[303Guy]

phatman, I don't know. I lube my patched boolits just so they will seat. I roll them on the lube pad with STP on it which put a very small amount of lybe on the surface which quickly soaks away leaving the boolit well gripped. Roughening the neck would likely make pre-seating lubing necessary but your paper might not soak the lube away. It might likely quickly polish away and you don't want to keep sanding the necks. Do you absolutely want that high of a velocity? Dropping the powder charge would slow the pressure rise rate but since you are already using magnum primers for consistent ignition, that might not work. A different powder with a slower pressure rise might solve the problem. Non-compressible powders will hold the boolit in place but they need to be settled fully for consistency. I used to load my hornet with compressible powder that I compressed to the seating depth with a tool I made. That's not easily possible with larger cases. Do remember that I patch for a 303 Brit with different characteristics to your gun so while some things that work for me might similarly work for you, they are at best only thought initiation points and at worst just conversation. Of course it's interesting to me what you are doing (I think I'm doing well getting a 192gr boolit up to 2250fps in my long barrelled Brit!:mrgreen:)

[phatman]

I really was not trying to go for 2700 fps when this started. It just got there so easy.
That load is very accurate when single loaded and hits like Thor.
I have a hell of a lot to learn and making mistakes is one way to learn. As long as you dont get hurt that is.

Yes the 303 is a totally different situation, it has a nice long neck. I wish I had a 2 caliber neck to play with, I wouldn't be loosing a grip on my bullets....lol

Cheers, John

[303Guy]

It sounds like you actually have it all worked out. Ummm ..... photo's would be great! [smilie=1:

[phatman]

HaHaHa,
If I was any good at taking a pic I would have.
It would have saved a lot of typing...lol

Cheers, John

[303Guy]

Aah, but you see, that's the beauty of digital cameras. You just keep on clicking until one comes out reasonable. It's what I do anyway.:roll:

[geargnasher]

Hey, that sounds like my load development! :kidding:

Gear

[GaryN]

Wow John, 2700 fps with a 250 grain slug, that is some load. I just started reading over here a few days ago and I had no idea you guys were getting this kind of performance. Oh no, I feel another dimension of my hobby coming on. I wonder how much this one will cost. I guess I better read some more. Maybe buy the Paper Jacket.