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7mm???
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<blockquote data-quote="MontanaRifleman" data-source="post: 850013" data-attributes="member: 11717"><p>There are a lot of factors in barrel life but overall you can reasonably predict what to expect based on how you shoot it and take care of it.</p><p></p><p>The RUMs have about 107 gr of H2O capacity. The STW about 93 and the 300 WM about 87, So there is a little bigger step between the 300 WM and the RUM vs the STW and the RUM. If you calculate an overbore index based on the bore diameter and volume of the case you will get 1468 for the STW, 1689 for the 7 RUM, 1436 for the 300 RUM and 1167 for the WM. Volume to bore ratios don't tell the whoule story in that case design plays a part as well. These case are not too different with the RUMs having slightly sharper shoulders. So you can see the 7 RUM has a very high overbore index and the STW a little higher than the 300 RUM. I think the "burnout" factor is more exponential than linear the higher you go with overbore factor.</p><p></p><p>So if you accept that you can get say 1000 rounds of good accurate life from a 300 RUM, you might deduce that you can get 900-950 out of an STW running at the same pressures and a good bit less from a 7 RUM. How much less... who knows? but I've read some reports of guys toasting them in about 500 rounds.</p><p></p><p>Another consideration is when do you consider a barrel burned out? 1/2 MOA? 3/4 MOA? 1 MOA?</p><p></p><p>As mentioned, the 7 AM is more overbore than the 7 RUM. I'm guessing it be about 115 gr or so H2O in capacity. That said, it does have a sharper shoulder. I just read yesterday I think, that Kirby's AM had over 1000 rounds through it and it's still shooting good, good meaning sub 3/4 MOA. He says he never shoots it hot (more than 1 or 2 rounds at a time) and takes very good care of it. Some guys consider a barrel toasted once it exceeds 1/2 MOA accuracy. But 3/4 MOA is plenty good for hunting out to a good long distance.</p><p></p><p>So I think you can expext 200-300 rounds less out of a 7 RUM than an STW under the same conditions.</p></blockquote><p></p>
[QUOTE="MontanaRifleman, post: 850013, member: 11717"] There are a lot of factors in barrel life but overall you can reasonably predict what to expect based on how you shoot it and take care of it. The RUMs have about 107 gr of H2O capacity. The STW about 93 and the 300 WM about 87, So there is a little bigger step between the 300 WM and the RUM vs the STW and the RUM. If you calculate an overbore index based on the bore diameter and volume of the case you will get 1468 for the STW, 1689 for the 7 RUM, 1436 for the 300 RUM and 1167 for the WM. Volume to bore ratios don't tell the whoule story in that case design plays a part as well. These case are not too different with the RUMs having slightly sharper shoulders. So you can see the 7 RUM has a very high overbore index and the STW a little higher than the 300 RUM. I think the "burnout" factor is more exponential than linear the higher you go with overbore factor. So if you accept that you can get say 1000 rounds of good accurate life from a 300 RUM, you might deduce that you can get 900-950 out of an STW running at the same pressures and a good bit less from a 7 RUM. How much less... who knows? but I've read some reports of guys toasting them in about 500 rounds. Another consideration is when do you consider a barrel burned out? 1/2 MOA? 3/4 MOA? 1 MOA? As mentioned, the 7 AM is more overbore than the 7 RUM. I'm guessing it be about 115 gr or so H2O in capacity. That said, it does have a sharper shoulder. I just read yesterday I think, that Kirby's AM had over 1000 rounds through it and it's still shooting good, good meaning sub 3/4 MOA. He says he never shoots it hot (more than 1 or 2 rounds at a time) and takes very good care of it. Some guys consider a barrel toasted once it exceeds 1/2 MOA accuracy. But 3/4 MOA is plenty good for hunting out to a good long distance. So I think you can expext 200-300 rounds less out of a 7 RUM than an STW under the same conditions. [/QUOTE]
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