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Rifles, Reloading, Optics, Equipment
Reloading
Too much pressure in the 300 RUM?
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<blockquote data-quote="Brent" data-source="post: 67363" data-attributes="member: 99"><p>I have a cheap RCBS dial caliper that I use at the bench and can pretty easily split a thou into at least 1/4 thou's. In other words, resolving .00025" increments isn't too difficult if I use consistant pressure and keep the blades clean. For taking relative measurments, this is completely repeatable with any caliper I've used and works just fine. </p><p></p><p>If you measured a once fired case for a baseline, then found that a twice fired case measured .0008 - .001" over that diameter, I'd say you are on the very upper end of a max load, possibly experiencing "some" bolt lift and/or extraction resistance. Cratering of primer, enough that you can begin to really catch a fingernail on, with the Federal primers usually begin to manifest at around 67,000 psi or more, sometimes not until 69-70 Kpsi. Over 70 Kpsi cratered rim is usually getting pretty high, .010 - .020 tall or so... definitelly very pronounced in the majority of fired cases.</p><p></p><p>In my experience, if expansion gets around .0005 - .0007 over, you are probably still safe but getting into higher than SAAMI rated pressure specs. </p><p></p><p>I would also venture to say that most people handloading for top MV and running at the red line would probably see somewhere around .0008 - .0012 increases in casehead diameter if they actually measured them... in a correct manor. I would also say that most of them run loads up into the 70+ Kpsi range without knowing they are, or some just really not caring. The rifle actions and brass will tolerate it and thus they are pushed to higher levels than the majority of handloaders load to.... because no ill effects are realized this is done. </p><p></p><p>If you want to go faster, the simple answer is to use a case that holds more powder. Other things can be done so you don't have to run tip top pressure to produce the very best accuracy the barrel is capable of, and it's my opinion that something is wrong if the rifle will not shoot top groups with anything other than a top load. It's either the bullet, powder etc, the rifle or the barrel but something isn't quite right. Best to do everything you can to accurize the rifle, use a quality barrel, the best mounts and scope you can buy to set yourself up for the very best possibility your rig will not be finicky and lead you on a wild goose chase in order to resolve a problem.</p></blockquote><p></p>
[QUOTE="Brent, post: 67363, member: 99"] I have a cheap RCBS dial caliper that I use at the bench and can pretty easily split a thou into at least 1/4 thou's. In other words, resolving .00025" increments isn't too difficult if I use consistant pressure and keep the blades clean. For taking relative measurments, this is completely repeatable with any caliper I've used and works just fine. If you measured a once fired case for a baseline, then found that a twice fired case measured .0008 - .001" over that diameter, I'd say you are on the very upper end of a max load, possibly experiencing "some" bolt lift and/or extraction resistance. Cratering of primer, enough that you can begin to really catch a fingernail on, with the Federal primers usually begin to manifest at around 67,000 psi or more, sometimes not until 69-70 Kpsi. Over 70 Kpsi cratered rim is usually getting pretty high, .010 - .020 tall or so... definitelly very pronounced in the majority of fired cases. In my experience, if expansion gets around .0005 - .0007 over, you are probably still safe but getting into higher than SAAMI rated pressure specs. I would also venture to say that most people handloading for top MV and running at the red line would probably see somewhere around .0008 - .0012 increases in casehead diameter if they actually measured them... in a correct manor. I would also say that most of them run loads up into the 70+ Kpsi range without knowing they are, or some just really not caring. The rifle actions and brass will tolerate it and thus they are pushed to higher levels than the majority of handloaders load to.... because no ill effects are realized this is done. If you want to go faster, the simple answer is to use a case that holds more powder. Other things can be done so you don't have to run tip top pressure to produce the very best accuracy the barrel is capable of, and it's my opinion that something is wrong if the rifle will not shoot top groups with anything other than a top load. It's either the bullet, powder etc, the rifle or the barrel but something isn't quite right. Best to do everything you can to accurize the rifle, use a quality barrel, the best mounts and scope you can buy to set yourself up for the very best possibility your rig will not be finicky and lead you on a wild goose chase in order to resolve a problem. [/QUOTE]
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Too much pressure in the 300 RUM?
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