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Rifles, Reloading, Optics, Equipment
7mm STW
Starting loads are a good thing
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<blockquote data-quote="dok7mm" data-source="post: 1217498" data-attributes="member: 90080"><p>I'm glad I used starting load data, instead of saving a little bit of components. The rifle is, of course, a STW on TAC 300 action, 26" Bartlein 5R, nine twist. Barrel is nitrided and I'm using HBN coated 180 Berger hvld pills. I was gonna use IMR 7828, but fill was only about 80%, so I opted for Retumbo, Nosler brass and Fed 215M primers. Rifle has .316 neck and brass is turned to .014" for .004" clearance. Loaded nk is .312".</p><p></p><p>I started @ 75.0 grs. and loaded to 78.5 grs. in .5 increments. I shot 5 foulers @ 75 grs to stabilize velocity. COAL was 3.786" and CBTO was 3.090, with .010" jump. Groups started to tighten up @ 76.0 grs. with sd- 5.4 and ED of 11 fps. But average was running well over Berger manual prediction @ 2964 fps. Chrono was LabRadar.</p><p></p><p>Hit another node ? at 77.0 grs and average velocity of 3032 fps. SD was 3.1 and ED of 6.0 fps. This was slightly above my target of 3000+/- for the 180. At 77.5 gr, group opened up and started getting a pretty good ejector smear. I was a full grain below Berger's usually conservative max load, but running about 200 fps faster than max load speed.</p><p></p><p>Temperature was in the low to mid 90's, but ammo was in ice chest and was close to 60 degrees according to thermometer.</p><p></p><p>I'm just wondering why velocity was so much higher, compared to manual, than it should have been. Was it the nitride, the HBN, the low round count (37), the 5R rifling, the new brass (headspace increased by .010" after firing), an out spec powder lot, or a magic barrel ??? </p><p></p><p>Anyone run into this or is it just one of those "rifles are different" things?</p></blockquote><p></p>
[QUOTE="dok7mm, post: 1217498, member: 90080"] I'm glad I used starting load data, instead of saving a little bit of components. The rifle is, of course, a STW on TAC 300 action, 26" Bartlein 5R, nine twist. Barrel is nitrided and I'm using HBN coated 180 Berger hvld pills. I was gonna use IMR 7828, but fill was only about 80%, so I opted for Retumbo, Nosler brass and Fed 215M primers. Rifle has .316 neck and brass is turned to .014" for .004" clearance. Loaded nk is .312". I started @ 75.0 grs. and loaded to 78.5 grs. in .5 increments. I shot 5 foulers @ 75 grs to stabilize velocity. COAL was 3.786" and CBTO was 3.090, with .010" jump. Groups started to tighten up @ 76.0 grs. with sd- 5.4 and ED of 11 fps. But average was running well over Berger manual prediction @ 2964 fps. Chrono was LabRadar. Hit another node ? at 77.0 grs and average velocity of 3032 fps. SD was 3.1 and ED of 6.0 fps. This was slightly above my target of 3000+/- for the 180. At 77.5 gr, group opened up and started getting a pretty good ejector smear. I was a full grain below Berger's usually conservative max load, but running about 200 fps faster than max load speed. Temperature was in the low to mid 90's, but ammo was in ice chest and was close to 60 degrees according to thermometer. I'm just wondering why velocity was so much higher, compared to manual, than it should have been. Was it the nitride, the HBN, the low round count (37), the 5R rifling, the new brass (headspace increased by .010" after firing), an out spec powder lot, or a magic barrel ??? Anyone run into this or is it just one of those "rifles are different" things? [/QUOTE]
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7mm STW
Starting loads are a good thing
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