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
Rifles, Bullets, Barrels & Ballistics
Case capacity gained with improved cartridges
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="Len Backus" data-source="post: 30441" data-attributes="member: 1"><p>Darryl</p><p></p><p>Respectfully.</p><p></p><p>It's not that hard to calculate a rough approximation of percentage increase in case capacity based on the differences in the reamers. The shoulder diameter is increased by .009 and the length from base to bottom of shoulder is increased by .020. Ignore the neck and shoulder. Multiply the new, longer base to shoulder dimension by the new diameter at the shoulder. Divide this by the same of the original, smaller reamer. That calculation shows 4.5% more capacity but then divide that in half because the increase in body diameter is only at one end of the case. The base end stays unchanged. So, about 2.25 % increase times 110 or so grains equals just under 3 grains increase.</p><p></p><p>Compare these numbers with with those of two 30-338 Lapua variants whose cases I have. Here the shoulder is blown out nearly 3 times as much, the base to shoulder dimension is more, also. And the result is still only in the range of 8 grains increase when actually weighed. </p><p></p><p>In addition, the one fired, unsized 300 Tomahawk case and the one new, unfired 300 RUM case actually showed only 4 grains of water difference. If I take one of my new 7 RUM cases and measure this same case both before and after firing it I get about 3 grains more water capacity with the now fired, unsized case. </p><p></p><p>Obviously the two .308 caliber cases, when new, started out with different case capacities before the Tomahawk one was fireformed. Even then, the capacity gain was so small as to not even exceed, or exceed by much, the normal variation in poor brass volume consistency of the 300 RUM case.</p><p></p><p>You are right, I think the sharper shoulder is a good thing.</p><p></p><p>[ 02-21-2004: Message edited by: Len Backus ]</p></blockquote><p></p>
[QUOTE="Len Backus, post: 30441, member: 1"] Darryl Respectfully. It's not that hard to calculate a rough approximation of percentage increase in case capacity based on the differences in the reamers. The shoulder diameter is increased by .009 and the length from base to bottom of shoulder is increased by .020. Ignore the neck and shoulder. Multiply the new, longer base to shoulder dimension by the new diameter at the shoulder. Divide this by the same of the original, smaller reamer. That calculation shows 4.5% more capacity but then divide that in half because the increase in body diameter is only at one end of the case. The base end stays unchanged. So, about 2.25 % increase times 110 or so grains equals just under 3 grains increase. Compare these numbers with with those of two 30-338 Lapua variants whose cases I have. Here the shoulder is blown out nearly 3 times as much, the base to shoulder dimension is more, also. And the result is still only in the range of 8 grains increase when actually weighed. In addition, the one fired, unsized 300 Tomahawk case and the one new, unfired 300 RUM case actually showed only 4 grains of water difference. If I take one of my new 7 RUM cases and measure this same case both before and after firing it I get about 3 grains more water capacity with the now fired, unsized case. Obviously the two .308 caliber cases, when new, started out with different case capacities before the Tomahawk one was fireformed. Even then, the capacity gain was so small as to not even exceed, or exceed by much, the normal variation in poor brass volume consistency of the 300 RUM case. You are right, I think the sharper shoulder is a good thing. [ 02-21-2004: Message edited by: Len Backus ] [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Case capacity gained with improved cartridges
Top