Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Known Loads too hot now..why
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Pdvdh" data-source="post: 384901" data-attributes="member: 4191"><p><u>Explanation of the prior photos</u>: Identical load as fired today except 0.5 grain heavier powder charge of H1000. The incipient case head separation was visible on the casing before I fired it in the back yard over the chronographs last weekend. To make matters worse, I had run the casing into my body sizing die with the wrong shellholder in the RCBS press, which headspaced the casing around 0.008" shorter than normal. Meaning I had excessive headspace on a casing that was already showing the separation ring of an impending case head separation. I debated whether or not to pull the bullet and toss the casing, but decided to take a chance and the photo is what I got for a result. Enough mess'in around.</p><p></p><p>I did fire one soapy water lathered up cartridge across the chronographs, as set up in back yard. Chronographs were used to catch higher or lower velocity - an indication of higher or lower cartridge pressure. Here's a photo of the chronograph arrangement with the soapy water in the spray bottle balanced on the skyscreen rail.</p><p></p><p><img src="http://i712.photobucket.com/albums/ww125/pdhorwath/ChronoSetupwithSoapyWater_4-24-10.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>This casing was slicker than snot on the outside. Almost dropped it on the ground. Velocity across the Oehler 33 was 2936 fps. Velocity across the PACT Pro was 2958 fps. This 2936 fps velocity is in comparison to the 4-shot string average velocity chronographed across the Oehler 33 last weekend of 2941 fps. Last weekend my PACT Pro was hit or miss and didn't give enough data to provide a 4-shot average comparison to today's velocity. But today's velocity data were good to go. The difference in velocities between the two chronographs run right about 20 fps when they're both hitting on all 8 cylinders - the Oehler ~20 fps slower than the PACT. So there was no evidence of any additional pressure based on the muzzle velocity obtained with this soapy-water lathered cartridge.</p><p></p><p><strong>In all honesty</strong>, there was a slight plunger hole indentation, and slightly increased resistance to bolt lift. <strong>So I'll eat some crow</strong>... I understand bigngreen's last post completely, about less friction between exterior of casing and chamber wall. And yes, anything that decreases the coefficient of friction between the case walls and chamber would be expected to result in a some increase in bolt thrust. If one had a tool/device both sensitive and accurate enough to measure subtle changes in bolt thrust (lbs force), that would be easy to demonstrate. I remain doubtful that the presence of water, restricted solely to the chamber/cartridge interface, will result in significantly increased case head setbacks into the bolt face with equally pressured cartridges. Otherwise cartridge manufacturers would place a warning on their factory ammo, "Shoot only DRY cartridges in rifles". Or, "Do not hunt and shoot in the rain." No?? If the placement of a film of water on the brass exterior jams a bolt closed, in all likelihood the loads are over book maximums - that would be my best guesstimate. And I'm guilty on that count. I'd say 75% or more of my hunting loads are over-charged with powder, relative to the maximum loads listed within reloading manuals.</p><p></p><p>Sorry about the mess'in with ya photos. Couldn't resist. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite8" alt=":D" title="Big Grin :D" loading="lazy" data-shortname=":D" /> BTW, that's the first time I've experienced partial case head separation. I knew I was pushing it. I decided to take a chance during maximum load workup with the Hornady 162 Amax bullets in the back yard last weekend. As I stated, the bright ring of incipient case head separation was visible about 1/3 of the way around that case before I touched (torched) it off. I did wear shooting glasses prior to letting fly with this casing. The big problem was that I had set the shoulder back too far on this .280 RCBS Imp, through use of the wrong shellholder. Also, in a stroke of bad luck, that powder charge was the greatest one I fired, and the first one to show plunger hole indentation on the case head of these Lapua brass cases. Other than less than stellar judgement and a little bad luck - in that this casing happened to be the one that pushed pressures over Max - the casing would have made it through one more firing. I don't think the partial case head separation would have happened, overload and all, other than the casing headspace was set back too far. The case was ready to let go and the extra 0.008" stretch was all that was necessary.</p><p></p><p>I didn't include a photo of the case head from the soap lathered casing because the plunger hole indentation wasn't very impressive.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 384901, member: 4191"] [U]Explanation of the prior photos[/U]: Identical load as fired today except 0.5 grain heavier powder charge of H1000. The incipient case head separation was visible on the casing before I fired it in the back yard over the chronographs last weekend. To make matters worse, I had run the casing into my body sizing die with the wrong shellholder in the RCBS press, which headspaced the casing around 0.008" shorter than normal. Meaning I had excessive headspace on a casing that was already showing the separation ring of an impending case head separation. I debated whether or not to pull the bullet and toss the casing, but decided to take a chance and the photo is what I got for a result. Enough mess'in around. I did fire one soapy water lathered up cartridge across the chronographs, as set up in back yard. Chronographs were used to catch higher or lower velocity - an indication of higher or lower cartridge pressure. Here's a photo of the chronograph arrangement with the soapy water in the spray bottle balanced on the skyscreen rail. [IMG]http://i712.photobucket.com/albums/ww125/pdhorwath/ChronoSetupwithSoapyWater_4-24-10.jpg[/IMG] This casing was slicker than snot on the outside. Almost dropped it on the ground. Velocity across the Oehler 33 was 2936 fps. Velocity across the PACT Pro was 2958 fps. This 2936 fps velocity is in comparison to the 4-shot string average velocity chronographed across the Oehler 33 last weekend of 2941 fps. Last weekend my PACT Pro was hit or miss and didn't give enough data to provide a 4-shot average comparison to today's velocity. But today's velocity data were good to go. The difference in velocities between the two chronographs run right about 20 fps when they're both hitting on all 8 cylinders - the Oehler ~20 fps slower than the PACT. So there was no evidence of any additional pressure based on the muzzle velocity obtained with this soapy-water lathered cartridge. [B]In all honesty[/B], there was a slight plunger hole indentation, and slightly increased resistance to bolt lift. [B]So I'll eat some crow[/B]... I understand bigngreen's last post completely, about less friction between exterior of casing and chamber wall. And yes, anything that decreases the coefficient of friction between the case walls and chamber would be expected to result in a some increase in bolt thrust. If one had a tool/device both sensitive and accurate enough to measure subtle changes in bolt thrust (lbs force), that would be easy to demonstrate. I remain doubtful that the presence of water, restricted solely to the chamber/cartridge interface, will result in significantly increased case head setbacks into the bolt face with equally pressured cartridges. Otherwise cartridge manufacturers would place a warning on their factory ammo, "Shoot only DRY cartridges in rifles". Or, "Do not hunt and shoot in the rain." No?? If the placement of a film of water on the brass exterior jams a bolt closed, in all likelihood the loads are over book maximums - that would be my best guesstimate. And I'm guilty on that count. I'd say 75% or more of my hunting loads are over-charged with powder, relative to the maximum loads listed within reloading manuals. Sorry about the mess'in with ya photos. Couldn't resist. :D BTW, that's the first time I've experienced partial case head separation. I knew I was pushing it. I decided to take a chance during maximum load workup with the Hornady 162 Amax bullets in the back yard last weekend. As I stated, the bright ring of incipient case head separation was visible about 1/3 of the way around that case before I touched (torched) it off. I did wear shooting glasses prior to letting fly with this casing. The big problem was that I had set the shoulder back too far on this .280 RCBS Imp, through use of the wrong shellholder. Also, in a stroke of bad luck, that powder charge was the greatest one I fired, and the first one to show plunger hole indentation on the case head of these Lapua brass cases. Other than less than stellar judgement and a little bad luck - in that this casing happened to be the one that pushed pressures over Max - the casing would have made it through one more firing. I don't think the partial case head separation would have happened, overload and all, other than the casing headspace was set back too far. The case was ready to let go and the extra 0.008" stretch was all that was necessary. I didn't include a photo of the case head from the soap lathered casing because the plunger hole indentation wasn't very impressive. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Known Loads too hot now..why
Top