The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Rifles Medium Bore Rifles 7mm STW barrel length?Go | New | Find | Notify | Tools | Reply | |
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| One of Us |
Is a 27 inch barrel long enough to achieve maximum effiecency and velocity for the 7mm STW shooting 150 and 160 gr. bullets ? | ||
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I would think so. I have a 26" and have been happy with my performance. My 140s are at 3440 and are several grs below the point I got pressure signs. As usual just my $.02 Paul K | |||
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My own 7mmstw's deliver right around 3500fps with 140gr bullets.Both have 26" barrels. | |||
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If you cut the barrel off about three inches you won't notice the difference. /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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| One of Us |
I measured my barrel again, looks like after cutting the 1.25 inches off the muzzel end as the barrell manufacturer and squareing off the breech end I will actually actually end up with a barrel just barely shy of 28 inches. I think this should be long enough to get the most out of the STW case. Barrel is a light varmint contour Broughton. | |||
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This is an old topic, but exactly what I was looking for. I am planning on getting a 7mm STW barrel, with a 30" barrel what velocity could I get with the 140 grainers? What about Berger 168s and 180s? Love shooting precision and long range. Big bores too! Recent college grad, started a company called MK Machining where I'm developing a bullpup rifle chassis system.  | |||
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Ramrod340, What twist are you using and could you share a few loads with us? Thanks. DB | |||
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| one of us |
Erik, I just ran the loads I have used with 140gr bullets using H4831SC, H1000, Retumbo, and IMR7828 through Quickload. It looks like between 24 and 28 inches, the velocity changes average about 30 fps per inch of barrel. It seems that the velocity change is slightly higher between 24 and 26 inches than it is between 26 and 28 inches, but not significant. Also, with these powders, Quickload shows that with max or near max loads, the powder should be completely burnt in about a 27" barrel. | |||
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So could I expect 3600 out of a 30" with 140 ballistic tips? Love shooting precision and long range. Big bores too! Recent college grad, started a company called MK Machining where I'm developing a bullpup rifle chassis system. | |||
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| one of us |
Not necessarily. As the barrel gets longer, the pressure is dropping off fast, so the velocity gain per inch starts dropping off even more. I have three rifles in 7mmSTW. A custom Rem 700 and a Win M70 Classic, both with 26" barrels. The third is a 1000 yd benchrest with a 28" barrel. The best velocity I am comfortable with out of the two with 26" barrels is about 3350 fps. According to Quickload, that puts it just at or slightly above max pressure. My velocity shooting over and Oehler 35P vs. the Quickload predictions, are within 50 fps. In order to get them to 3500 fps, I would have pressures exceeding 75,000 psi. The CIP rating for the cartidge is 66,700. Quickload predicts that you would have to exceed 78,000 psi to get to 3600 with a 30" barrel. In my third rifle, the one the 28" barrel, I only shoot 180 Berger VLD with Retumbo. I get about 3100 fps with those, again right at max pressure. | |||
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| one of us |
I'm using a 26" varmint weight 1 in 9. I have two loads for this rifle. One for the 140 Accub and one for the 120BT. Both of these loads are several grains above the nosler max, at max for most posted STW loads and should be only approached very slowly. These loads are 1.5 grs below .0005" expansion in my rifle. However they were to hot for my buddies sister rifle. Built with same reamer, brass and barrel. Using necked down 8mm Rem mag brass( my rifle was built when the STW was still a wildcat) and CCI magnum primers both have a little over .25" freebore at 3.6". 120BT with 83grs of RL-22 3600FPS. This will turn a coyote inside out and a jack rabbit to a red haze. 140Accubond (built using BT and switched to Accubonds with no change in group or point of impact and maybe a 15fps higher velocity) with 83grs of IMR 7828 3440FPS. In my rifle both these group around .75MOA or a touch less. The group centers are close enough I can fire a 6 rd 1.5Moa group using 3 of each. This is a heavy rfile built for long range west Texas whitetails and coyotes. I did very little load testing with 160s. As to getting 3600 with a 30" in barrel and 140s I would call that very optimistic. Using loadtech and adding 4" of barrel to my load I get a little over 3500. As usual just my $.02 Paul K | |||
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Since I get 3500fps with the 140gr bullets with a 26" barrel,I would think that 3600 would be achievable with 4" more barrel. | |||
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Many thanks for the info. DB | |||
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| one of us |
With all these fast bullets used for hunting make a big area bloodshot Thats not eatable. | |||
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Well a shot in the chest behind the shoulder doesn't mess up any meat at least on a West Texas 130# deer. How much meat is there on a normal deer chest? Not only location of hit but type of bullet will impact the damage area. As usual just my $.02 Paul K | |||
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The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Rifles Medium Bore Rifles 7mm STW barrel length?
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