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Rifles, Reloading, Optics, Equipment
Reloading
Low pressure sign??? 300RUM
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<blockquote data-quote="capt.d" data-source="post: 444400" data-attributes="member: 27624"><p>I have had one event like this while loading for a 7mm ultra. A buddy purchased a used Rem 700 and after a thorough cleaning and inspection I discovered his rifle had what I thoucht was an abnormally long throat. Be it from a huge amount of free bore from factory or the previous owner melting quite a bit of the lands out of it, a 160 gr. accubond would not touch the lands until well out of the case mouth. I thought it was odd as my Sako does not have near this much freebore. We just seated them to mag length and loaded several diferent charge weights of Retumbo. The first round with book start load went across the chrono rather underwhelmingly i thought but no strange sounds or other conditions were observed. Upon opening the bolt I went numb as I saw the case that flopped out! Just below the shoulder were dents almost identical to yours but five of them all around the case, however, there was alot of black on this one. After much thought and discussion I determined that it had to be due to the low "start" load and extreme jump to the lands. What I believe happened is that upon firing while the bullet was "floating" in thin air before engaging the rifling, the low charge of powder did not develop enough pressure to expand the case to chamber dimensions to form an effective seal and some pressure caused the case to deform inwards/ implode somewhat. Upon reaching this conclusion we moved up to the next charge weight with me driving, as it was my conclusion, and never had a hiccup again all the way up to book max. Low charge weights in those big cases are no good, combine that with his long throat and I believe book start was too low for his particular situation as I have never seen it before or since. Could be a hair brained conclusion but makes sense to me.</p></blockquote><p></p>
[QUOTE="capt.d, post: 444400, member: 27624"] I have had one event like this while loading for a 7mm ultra. A buddy purchased a used Rem 700 and after a thorough cleaning and inspection I discovered his rifle had what I thoucht was an abnormally long throat. Be it from a huge amount of free bore from factory or the previous owner melting quite a bit of the lands out of it, a 160 gr. accubond would not touch the lands until well out of the case mouth. I thought it was odd as my Sako does not have near this much freebore. We just seated them to mag length and loaded several diferent charge weights of Retumbo. The first round with book start load went across the chrono rather underwhelmingly i thought but no strange sounds or other conditions were observed. Upon opening the bolt I went numb as I saw the case that flopped out! Just below the shoulder were dents almost identical to yours but five of them all around the case, however, there was alot of black on this one. After much thought and discussion I determined that it had to be due to the low "start" load and extreme jump to the lands. What I believe happened is that upon firing while the bullet was "floating" in thin air before engaging the rifling, the low charge of powder did not develop enough pressure to expand the case to chamber dimensions to form an effective seal and some pressure caused the case to deform inwards/ implode somewhat. Upon reaching this conclusion we moved up to the next charge weight with me driving, as it was my conclusion, and never had a hiccup again all the way up to book max. Low charge weights in those big cases are no good, combine that with his long throat and I believe book start was too low for his particular situation as I have never seen it before or since. Could be a hair brained conclusion but makes sense to me. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Low pressure sign??? 300RUM
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