Post by yogurt on Jun 29, 2015 21:47:36 GMT -5
This is a thread I put together for another forum a while back for a couple guys that didn't understand the title of this thread.
I think the guy in the video did a great forensics job! Tell me what you think!!!
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There have been several questions I've seen regarding setting up new reloading systems.
I thought this an appropriate time to bring up headspacing as it relates to "rimless auto cartridges".
In a revolver cartridge, headspace is set by the rim of the cartridge resting on the back of the cylinder.
In a semi-auto example I'll use .45 ACP. Too much crimp does NOT hold the bullet in place and in fact can be dangerous. Rimless cartridges headspace on the case mouth. The chamber is cut to allow insertion of the cartridge only so far in. OVER crimping can allow the cartridge to slip further into battery resulting in pinching off and severely restricting the bullets travelling down barrel when fired. This can result in KABOOMS.
See rimless pic below
This is the one of the reasons for the "plunk test" for handloads. On rimless cartridges like 9mm, .40, .45, 10mm, the "bell" or "flare" the press introduced into the prepped brass should be only enough to allow insertion of the bullet without shaving copper from it. The taper crimp should be only enough to allow for the finished cartridge to chamber smoothly.
When ever I set the press up for a new caliber (ie changing from .40 to .45) I inset my toolhead already set up with the correct dies. Even though my .45 toolhead should be still set form the last time I used it, I still check it. I take 1 piece of brass, resize it without putting a primer in it. i next check the "flare in the next station. Don't want too much as this prematurely wears out the brass. I then make check the seating die to ensure correct seating depth. Lastly, I check the crimp. After applying the crimp, I take this "dummy " bullet and drop it into the barrel. It should go "plunk".
I should probably mention I'm using a 4 stage press, but the steps are essentially the same. Again, examine the .45 diagram above and notice the area in the chamber where the case mouth sits next to the "shoulder" in the chamber. That is were the round "headspaces" against in a rimless cartridge.
Have seen LOTS of people new to reloading (and using soft plated bullets for cost) taper crimp to where there is a dangerously low amount of rim left to headspace on. They, in their new to reloading beliefs, tend to overcrimp to ensure smooth feeding.
A taper crimp will help to retain the bullet a pico second longer on ignition, helping to build pressure for proper combustion... especially with slower powders.
Personally, I use nothing but real JHPs which are more forgiving of tight crimps. But then, I use almost exclusively, slow powders for maximum velocities. Have same issue in .40 with LongShot. Ran fine in my G22 but in my partners SR40, the SAME round would leave unburned powder in the barrel. Slightly tighter crimp solved that.
Additional, In the SR40, the cases were ejecting heavily sooted down one side of the brass. From the G22, they were clean. Assumption: Sr40 has slightly looser chamber, taking more initial pressure to seal.
From Ranier
Quote:
"We, at Rainier Ballistics, recommend using lead bullet load data when loading our bullets. There is no need for adjustment when using lead bullet load data. Our bullets are jacketed using an electroplating process and are softer than traditionally jacketed bullets; hence the recommendation to use lead bullet load data. If you only have access to traditionally jacketed load data, we recommend a starting powder charge directly between the listed minimum and maximum load. A roll or taper crimp may be used with our bullets; do not over crimp."
If the case mouth is closed too much during the removal of the belling step, the entire loaded round can chamber too deep in the chamber which would allow the mouth to get pinched in the throat. When the mouth gets pinched, it can't expand during discharge, thus delaying or preventing the gases and bullet from escape freely from the case, if the firing pin is long enough,the result is a KB. There are other undesired effects less catastrophic, yet still potentially dangerous, or damaging to the firearm.
Watch this whole video. And don't tell me this is "the unsupported Glock barrel issue". I as well have seen the HP bolt-in-barrel video and agree the HP is much more resistant to this kind of failure. This info however, extends to MOST modern semi autos. Again, watch the whole video and you will see the danger in over crimping. I have not yet re-found the article where an HP carbine suffered the SAME fate. But I will.
Load Data:
Case: Federal (once fired - bought rounds and fired myself)
Primer: CCI 500
Powder: 4.9 grains of Titegroup
Bullet: Rainier 165 grain HP
(Hodgdon shows5.1 as max load with 165 gn jhp)
Video description explains exactly what happened. Over bell removed all neck tension as the die wasn't a under-sizing die. Over crimp turned the mouth inward, impeding the barrel throat as well as causing setback ... pressure had only one way to go before it could overcome the resistance. Round landed on target lower left @ 7-8 o'clock position.
I think the guy in the video did a great forensics job! Tell me what you think!!!
********************************************************************************************************************************************
There have been several questions I've seen regarding setting up new reloading systems.
I thought this an appropriate time to bring up headspacing as it relates to "rimless auto cartridges".
In a revolver cartridge, headspace is set by the rim of the cartridge resting on the back of the cylinder.
In a semi-auto example I'll use .45 ACP. Too much crimp does NOT hold the bullet in place and in fact can be dangerous. Rimless cartridges headspace on the case mouth. The chamber is cut to allow insertion of the cartridge only so far in. OVER crimping can allow the cartridge to slip further into battery resulting in pinching off and severely restricting the bullets travelling down barrel when fired. This can result in KABOOMS.
See rimless pic below
This is the one of the reasons for the "plunk test" for handloads. On rimless cartridges like 9mm, .40, .45, 10mm, the "bell" or "flare" the press introduced into the prepped brass should be only enough to allow insertion of the bullet without shaving copper from it. The taper crimp should be only enough to allow for the finished cartridge to chamber smoothly.
When ever I set the press up for a new caliber (ie changing from .40 to .45) I inset my toolhead already set up with the correct dies. Even though my .45 toolhead should be still set form the last time I used it, I still check it. I take 1 piece of brass, resize it without putting a primer in it. i next check the "flare in the next station. Don't want too much as this prematurely wears out the brass. I then make check the seating die to ensure correct seating depth. Lastly, I check the crimp. After applying the crimp, I take this "dummy " bullet and drop it into the barrel. It should go "plunk".
I should probably mention I'm using a 4 stage press, but the steps are essentially the same. Again, examine the .45 diagram above and notice the area in the chamber where the case mouth sits next to the "shoulder" in the chamber. That is were the round "headspaces" against in a rimless cartridge.
Have seen LOTS of people new to reloading (and using soft plated bullets for cost) taper crimp to where there is a dangerously low amount of rim left to headspace on. They, in their new to reloading beliefs, tend to overcrimp to ensure smooth feeding.
A taper crimp will help to retain the bullet a pico second longer on ignition, helping to build pressure for proper combustion... especially with slower powders.
Personally, I use nothing but real JHPs which are more forgiving of tight crimps. But then, I use almost exclusively, slow powders for maximum velocities. Have same issue in .40 with LongShot. Ran fine in my G22 but in my partners SR40, the SAME round would leave unburned powder in the barrel. Slightly tighter crimp solved that.
Additional, In the SR40, the cases were ejecting heavily sooted down one side of the brass. From the G22, they were clean. Assumption: Sr40 has slightly looser chamber, taking more initial pressure to seal.
From Ranier
Quote:
"We, at Rainier Ballistics, recommend using lead bullet load data when loading our bullets. There is no need for adjustment when using lead bullet load data. Our bullets are jacketed using an electroplating process and are softer than traditionally jacketed bullets; hence the recommendation to use lead bullet load data. If you only have access to traditionally jacketed load data, we recommend a starting powder charge directly between the listed minimum and maximum load. A roll or taper crimp may be used with our bullets; do not over crimp."
If the case mouth is closed too much during the removal of the belling step, the entire loaded round can chamber too deep in the chamber which would allow the mouth to get pinched in the throat. When the mouth gets pinched, it can't expand during discharge, thus delaying or preventing the gases and bullet from escape freely from the case, if the firing pin is long enough,the result is a KB. There are other undesired effects less catastrophic, yet still potentially dangerous, or damaging to the firearm.
Watch this whole video. And don't tell me this is "the unsupported Glock barrel issue". I as well have seen the HP bolt-in-barrel video and agree the HP is much more resistant to this kind of failure. This info however, extends to MOST modern semi autos. Again, watch the whole video and you will see the danger in over crimping. I have not yet re-found the article where an HP carbine suffered the SAME fate. But I will.
Load Data:
Case: Federal (once fired - bought rounds and fired myself)
Primer: CCI 500
Powder: 4.9 grains of Titegroup
Bullet: Rainier 165 grain HP
(Hodgdon shows5.1 as max load with 165 gn jhp)
Video description explains exactly what happened. Over bell removed all neck tension as the die wasn't a under-sizing die. Over crimp turned the mouth inward, impeding the barrel throat as well as causing setback ... pressure had only one way to go before it could overcome the resistance. Round landed on target lower left @ 7-8 o'clock position.