Cannelure in case to determine seating depth

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cove posted this 28 September 2020

In an effort to produce consistent bullet pull for 38 HBWCs, I am contemplating the purchase of a cannelure tool to put a cannelure in the case so WCs can be seated to the proper depth using the thumb.  Bullet would then be retained with a mild crimp or seated so it would contact the 0.3575 throat at the front of the cylinder to provide resistance for efficient  powder burn ( WW 231).   My thinking is the slip fit in the unsized case would not deform the bullet and produce a more uniform bullet pull.  Any comments?

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45 2.1 posted this 28 September 2020

I don't believe the bullet pull would be consistent using the above method. What might work better, dependent on bullet diameter of 0.359" or slightly more, is the use of a 38 S&W or 38 Super carbide sizing die (they are one in the same usually). The bullet would have a friction fit in the case doing that and could be taper crimped slightly.

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RicinYakima posted this 28 September 2020

For maybe 10 ten years, I have been doing what 45 2.1 advocates; Lee carbide 38 super sizer, slight bell, seat .360" wadcutter and light Redding profile crimp. It works well in my revolvers, all pre-1950 S&W's, and .357 Martini single shot. FWIW.

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Ed Harris posted this 5 weeks ago

I've been using the RCBS .38 S&W Cowboy die set, otherwise same procedure as Ric for prewar Colts and pre-1957 S&Ws.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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John Alexander posted this 5 weeks ago

The original post was obviously inspired by concern that variations in "bullet pull" might affect performance of the ammo.

A good answer would have been, “stop worrying about variations in bullet pull. It will have no effect on performance.”

The MINIMUM bullet pull must be enough to prevent bullets being pulled from the case by inertia and recoil and maybe needed to help initiate early powder burn with some powders.  However, the very common worry that VARIATIONS in bullet pull might affect performance is wasted worry because the magnitude of the variations in bullet pull are totally insignificant compared to the variations in the other forces involved with bullet movement.

Think about it. The average force of bullet pull is similar to the force required to seat the bullet, or less. Probably under 100 pounds to avoiding damaging the bullet.  Even if the variation was as much as 30 percent the range of variation in force would be only be 30 pounds.

The other force involved right after the hammer falls is the force of the expanding gas. This force is equal to the pressure times the cross-sectional area of the bullet.  For the 357 this might be; 35K x .36 x .36 x 3.14/ 4 = 3500 pounds and about half that for a 38 special.  Chamber pressures vary around 10 percent and there is nothing we can do about it no matter how precise the powder is weighed. This translated to a force of about 350 pounds or about ten times as much as the variation in bullet pull.

 More importantly, this substantial variation in force on the bullet and the resulting variations in muzzle seems not to affect accuracy as any rifle shooters with a chronograph can tell you.  The most accurate load is seldom the one with the least variation in muzzle velocity. This is counter intuitive or as some would say counter to “common sense” but, unless we are flat earthers, we have to accept it or prove that it isn’t so.

To sum up, because the variation in the force of chamber pressure may be ten times the variation in the force of bullet pull and this much larger variation in the force of chamber pressure doesn’t seem to correlate with performance, it is unlikely that the much smaller variation in bullet pull could have any measurable effect on performance.

Doubters might say that the above is just theory although I would call it a rough mathematical check for believability.

However, if you are dubious of the above which after all it involved no shooting, there is very good published experimental evidence that comes to the same conclusion for precision cast bullets in rifles (Bottiger in TFS #223 & 224).  It is unlikely that experiments can show it is significant for pistols shooting groups many times as large.

My apologies to those who have heard it all before, but the constant stewing and fretting over variations in bullet pull makes me a little crazy.

John

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Ken Campbell Iowa posted this 5 weeks ago

...in addition ...

some pretty good benchresters assure me that the brass neck expands before the bullet has moved very far at all ... thus there is not really any significant " bullet pull " as the cartridge is fired.

even if these is a small "sticky " at first, at least in high pressure loads, as johna surmises above, the efrect is likely a lightening bug in a thunderstorm ...

however, i could believe there might be some effect of neck tension on extra low pressure loads, as in popgun loads for pistols.

****************

a simple test might be to load some extra light loads that barely ignite the powder .. and then increase the static seating grip until/IF the powder ignites cleanly .  hmmm . checking for stuck bullets during this exercise, of course.

and here i thought cast bullet shooting was pretty much cut, dried and hung for consumption ...

ken

 

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cove posted this 5 weeks ago

Thanks for the comments guys.  I sent an article to Glenn that should appear in an upcoming TFS. The article is titled "HBWC at 100 Yards-Velocity Matters.  In this article I show that a velocity change of  10 fps moves the point of impact approximately 11/2 inches vertically.  My ES for 5 shots is erratic and can be 50 fps.  If the velocity is 750 fps the shot is below the 4 inch target, and if the velocity is 800 fps the shot tends to be high. I have become quite good at calling the velocity based on where the shot hits vertically.  My goal is to be able to hit the 4 inch square and if I can keep the ES around 30 fps, that is possible.  I have tried numerous techniques and so far have reduced the ES but have not reached my goal. One thing I did learn is that the rumor that CCI small pistol primers have thick cups is true.  Loaded round are numbered and fired rounds show that if the dimple in the spent primer is very small, the velocity is low. One 5 shot sequence had 2 primers with minimal dimples, one was a misfire and both were around 750 fps where the average was around 775 fps.  This is a ongoing project and I will keep you informed. 

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max503 posted this 4 weeks ago

After inside neck expansion/balling my 357 cases measure .353. This is from steel RCBS dies. I've wondered if that was too tight. Thought about getting a larger NOE expander button for my Lee M Die.

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cove posted this 4 weeks ago

Max503: My PPC revolver has an M10 frame, but who knows what cylinder. The reason  I say that is that RP 2 cannelure (HBWC) brass after fired measures 0.362 ID and as cast 0.360 HBWC are a loose fit.  When I deprime/size this brass with a Lee carbide die, the ID is around 0,360+ which gives a snug fit for unsized bullets. I think the snug fit is mostly due to whiskers. I guess what this shows is that each revolver/firearm is unique and we who want to shoot cast bullets accurately, have to pay attention. I do not profess to to be any kind of an expert on the subject, but 0.353 sounds way to small to me.

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Eutectic posted this 4 weeks ago

I examining Remington 38 HBWC ammunition, I found milling off the slight crimp revealed in many rounds the bullet freely rotated in the case. It would not fall out because there was a cannelure in the bottom groove. There was another under the bullet probably to keep it from falling deeper in the case while the cannelure was applied in the lube groove.

Using a tight sizing die and small expander has been recommended for magnum loads to provide higher bullet pull for combustion of slow powders. This does NOT work for two reasons. First, as John says, the case expands. Looking at the strength of the case you find only 600 to 800 psi are needed for case expansion. The pressure rise is fast and quickly exceeds this even with light loads. Second, brass will only flex so much before it permanently distorts. Using an expansion plug of bullet diameter or at most 0.001 smaller gets you all the bullet pull possible. Seating a cast bullet into a much smaller diameter case is using the bullet as an expansion plug, a job for which it is ill suited. 

A heavy crimp has been promoted to provide resistance. But again this increase is small compared to the forces involved. The primary job of the crimp is to prevent bullet pull in revolvers from binding the cylinder. It does this quite nicely except with the new scandium-titanium magnums where even factory jacketed loads will pull. This may be an advantage, binding the cylinder might
prevent you from firing a second round and doing irreparable damage to your wrist. big_grin

Cove, if you are getting misfires and small indents you may not have enough hammer energy. I would check the tension screw, they can back out. Your PPC revolver probably has an intentionally lightened hammer spring to get a light double action pull. You might consider replacing it. Many PPC shooters used Federal primers because they have softer cups.

I have not seen any problems with CCI primers which were not gun related.

Steve

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max503 posted this 4 weeks ago

I examining Remington 38 HBWC ammunition, I found milling off the slight crimp revealed in many rounds the bullet freely rotated in the case. It would not fall out because there was a cannelure in the bottom groove. There was another under the bullet probably to keep it from falling deeper in the case while the cannelure was applied in the lube groove.

Using a tight sizing die and small expander has been recommended for magnum loads to provide higher bullet pull for combustion of slow powders. This does NOT work for two reasons. First, as John says, the case expands. Looking at the strength of the case you find only 600 to 800 psi are needed for case expansion. The pressure rise is fast and quickly exceeds this even with light loads. Second, brass will only flex so much before it permanently distorts. Using an expansion plug of bullet diameter or at most 0.001 smaller gets you all the bullet pull possible. Seating a cast bullet into a much smaller diameter case is using the bullet as an expansion plug, a job for which it is ill suited. 

A heavy crimp has been promoted to provide resistance. But again this increase is small compared to the forces involved. The primary job of the crimp is to prevent bullet pull in revolvers from binding the cylinder. It does this quite nicely except with the new scandium-titanium magnums where even factory jacketed loads will pull. This may be an advantage, binding the cylinder might
prevent you from firing a second round and doing irreparable damage to your wrist. big_grin

Cove, if you are getting misfires and small indents you may not have enough hammer energy. I would check the tension screw, they can back out. Your PPC revolver probably has an intentionally lightened hammer spring to get a light double action pull. You might consider replacing it. Many PPC shooters used Federal primers because they have softer cups.

I have not seen any problems with CCI primers which were not gun related.

Steve

 

This is why I'm wondering if it would be worthwhile getting a larger expander plug, in order to keep the bullet from getting tightly squished down.

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Ken Campbell Iowa posted this 4 weeks ago

well, here i go again mentioning those pesky 22 lr match catridges where for a mere $1500 you can buy 5000 shots that will all go into a half-inch group at 50 yards ... and 90 per cent into a 0.3 inch group ...and 50 per cent will go right on top of your crosshairs ... ( all if the wind doesn't blow 

if you pick up one of these little puzzles you will note that you can easily twirl the bullet in the case .... it it held in the brass only by the lightest crimp posible.  in one of my guns with a really tight throat i had to shoot the cartridge or it would de-bullet upon extraction ...

***************

maybe for a cartridge that does everything wrong 

( short bullet dead soft alloy no gas check heeled design rimfire etc. )

the no-pull seating is a clue to it's accuracy ...

ken

 

 

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GP Idaho posted this 4 weeks ago

Cove: Take a look at the Noe site. The expanders that fit in the Lee universal case expander (flare) die let you choose the exact amount of expansion you would like. Very handy tool,  Gp

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cove posted this 4 weeks ago

Steve: I take your point concerning hammer energy but that is not the problem.  I also suspected a light hammer as the trigger pull is very light. I placed a spacer (spent primer) on the end of the screw to add tension and that solved the problem.  I also stoned the hammer and frame to remove any contact points. Was able to get some Federal primers and the dimple is deep, uniform and to date have had no misfires.  What makes me suspect the variation in thickness in CCI small pistol primers is that when I cycle the cylinder and fire the misfired cartridge a second time, the dimple is still very  small. I have examined spent primers and am not able to detect a significant difference.  Another reason I have switched primers is when I showed the primers with small dimples to the guy where I buy primers, he said that CCI primers had thicker cups. There is a guy on you-tube that did a very good/accurate test of the sensitivity of small rifle primers and CCI primers detonated with a little less pressure than the Federals.  He needs to do the same test with small pistol primers. The more I learn, the more confused I become. 

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max503 posted this 4 weeks ago

Cove, et,al

When I size a case in my RCBS steel dies the ID of the case measures .349". (I could do a little more research here.  Maybe measure more cases.  Different brands, old and new.)

After expanding and flaring the ID measures .353".

The expander button in the die measures .355". 

My rifle bore measures .357".

I size my bullets to .358"

Looks like the brass springs back .002" after expanding/flaring.

I'm guessing a .359 or .360 expander would be the right size.  Thinking if I buy one that's too big I could polish it down.

Sound like a plan?

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TRKakaCatWhisperer posted this 4 weeks ago

You might could consider honing out the sizing die so that it reduces the brass to the desired ID; thus working the brass minimally.

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