Bullet hardness and obturation

[montana_charlie]

I have a couple chambers that I call a PP chamber because that is all that I can load in it. They are so tight that just a groove diameter bullet will just fit the unsized case.

Did you mean 'bore' diameter ... ?

Orville shoots chambers that are ~.470" in the neck, so the ID of a fired mouth is ~.450".

That is what I understand to be a "PP chamber" in the most fundamental sense of the term.

CM

[Don McDowell]

I'm of the opinion after going down this road, that if a person isnt' happy with the chamber for paper patch shooting, then rebarreling the rifle is the way to go.
Also agree with Brent, I'm not convinced the current rage on "paper patch chamber" is going to prove out.
I do think like Kurt, the chambers with the 45 * lead are not the best, and the really low angles such as the 4* that CPA puts in the 45-90, and the 7* Shiloh is now putting on the 44-77 make it easier to come up with both patched and grooved bullet loads.

[Kenny Wasserburger]

I think the key to chambers is in Kurt's fitting the brass to the chamber. Ultimately, bore diameter paper patch bullets are best served by the tightest chamber you can get away with.

I'm also no fan of what is advertised as "The Paper Patch Chamber" as adversited around the internet. That of course, is bucking the current. What is currently claimed as"The Paper Patch Chamber" is a fine hunting chamber, but it's not one for the finest match accuracy in my opinion, but I think the numbers are on my side by a pretty good margin.

Brent,

I agree on on your statements, concerning the tightest chamber you can get away with.

what caught my attention the most.......about these paper patch chambers being fine for hunting but not so good for the finest match accuracy. Several folks that have had their rifles altered to these long throats-leads now have issues with verticle, they were suckered in my opinion, the leading proponent for these chambers busts rocks for testing, never posts any groups on paper. He is mainly concerned with buffalo era and hunting accuracy.

My tighter than normal Shiloh chamber of .480 at the mouth, has and continues too shoot very nice groups, and shoots well in match conditions. This is in my older Shiloh, my 25# Shiloh has a .482 chamber at the mouth, it shots well but it never has equalled the accuracy of the tighter chambered rifle. It is also a 1-16 twist vrs a 1-18 in the Older rifle. In 3 years it has not shot a score better than 91 at 800, while the older rifle has shot 96's on several occasions.
A very detailed diary has been kept on both rifles, in 13 I returned to the older LRE 18 twist rifle with the tighter chamber with the modern throat. I have been pleased with it's performance.

The bull barrel Shiloh, is a tighter bore my .446 bullet is a very tight fit with the thin Seth Cole Paper, the best accuracy has came with a .444 bullet and the seth cole paper.

So I have a heavy rifle with tight bore and larger std chamber 16 twist, vrs a Std LRE with tight chamber and standard bore. Neither rifle has a internet chamber-lead.

I also agree that ones brass needs to fit the chamber.

KW

[BrentD]

FWIW, my chambers are 0.475" at the case mouth with a 45 deg transition up to groove diameter and then a 3 deg per side taper to the top of the lands. 6 rifles have been chambered with that reamer for 5 different people. 4 of the rifles and 3 of the owners have won NRA BPTR or BPCR matches or both in the last 3 yrs. The brass is Starline shot as it comes out of the bag except for a light chamfer to the case mouth. No anneal, no trim. But the chamber was built for that brass specifically. After 4 yrs, I have trimmed and rechamfered the brass and annealed once. 3 of those rifles are 16 twist, and 3 are 18 twist both twists have won out to 1000 yds, but bullets must be appropriate for best results.

The #1 top dog of long range also uses 16 twist with his groove bullets. I'm convinced that they have a slight advantage.

[Lead pot]

Yes Charlie it should be bore not groove. My fingers and my mind sometimes have a communication problem

My .44's have a chamber neck of .464" with a 4 degree transition to a 1.5 degree lead. (4 degree/1-1/2 compound)
I have a reamer getting ground right now for a .45-90 project that will have a .475" neck diameter with a 3 degree transition to a 1.5 degree lead. (3 degree/1.5 compound)I will never go back to a smokeless jacketed bullet chamber again with any rifle I build again. That 45 degree started showing up during the transition of the cordite powder and gilded jacketed bullets. There is a reason the .22 rimfire chamber has never changed since it's birth.

[dave roelle]

Gentlemen:

Thanks again for the spirited discussion !!!!!!!!!!!!! the shift to chambers is certainly a part of how obturation within the case and its transition to travel down the barrel is dealt with-------lots of ideas here for sure.

Currently i don't plan any chamber changes---i will have a discussion with my smith---he has several original Sharps which we can investigate----they are 44/77 and 44/90

Finished the day with 3 alloys at10,11 and 12 Brinell-------hope to get casting underway
tomorrow.

Thanks again everyone

Dave

[dave roelle]

Gentlemen:

Shot a silhouette match yesterday with the 12Bn Money Bullet----74 grains of Swiss 1 1/2 Mr. Wasserburgers Napa rubber/fiber wad over powder------3/16 grease cookie----Milk Carton wad under the bullet------

I collected these



The paper is Strathmore Tracing paper--measures 0.0017 thick------the bullet was sized to achieve a "thumb push fit" to the 0.450 barrel I.D------------dry wrapped



After getting tuned up (i'm badly out of practice) shot this pattern on pigs----surrounded the first 5 killed the last 5



So when the shooter get his head out of his A&& things just might come together

Substituting a 3/16 cork wad for the grease cookie got this result :



So Kurt --yes there are lots of things going on that affect obturation-----certainly the relative compressibility of the wad stack is critical.

I'll experiment with harder alloys as time permitts and report back.

Brent:

I fabricated bore pigs base on your design----they worked well, not to hard to push ---when pushed with a dry patch the barrel was in good shape for the next shot--------no dirt diggers----no "lost bullets"---------no "socked" patches from too wet a chamber--------no leading.

I'm, going to fabricate a "pig holder" to keep them hydrated "squeegee end up" to get a quicker pick up and more uniform wetness

Thanks for the idea and design---i had been working on something similar with two patches but the brush/squeegee works much better !!!!

I'm going to continue with this load and wiping protocol for a bit and get enough trigger time to give it a chance to work.

Thanks everyone for the insights and help.

Dave