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> POI change hard vs soft rest
POI change hard vs soft rest
@ 10:28 pm (GMT) |
Matt ReidHi there,Wondering if anyone had experimented with different forend rest types and the change on POI. I was shooting in the weekend with my .308 and established zero at 100, using a soft rest (gun bag). Moving back to 500m, shots were going higher than expected, but I had also changed to a hard sandbag rest up front. I setup a target again at 100m, this time using the sandbag rest, and shots were heading around 0.5moa high. Wondering if anyone else had experienced this? |
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@ 09:21 am (GMT) |
Nathan FosterRe: POI change hard vs soft restHi Matt, yes that's perfectly normal.The key is to do your range (rifle / load testing work) over sand bags, then switch to either a bipod or back pack after the load testing is finished. You then obtain your final zero over the pack or bipod and at this point, look for errors in shooting methods. Set the zero you want, usually 3" high at 100 yards, then away you go. Back packs versus sand bags give vertical shifts in POI as you described. Bipods can give both vertical and horizontal shifts. The horizontal shift can be as much as 1MOA, greater in heavy magnum calibers. Sling tension changes can shift the POI of the light weight Tikka T3 by 1 to 1.5 MOA, usually horizontally but also with some elevation. You will see smaller shifts in POI with your rifle regarding sling tension but its always something to keep in mind. Keeps you on you toes eh. |
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@ 02:36 pm (GMT) |
Matt ReidRe: POI change hard vs soft restThanks for that Nathan. I had suspected it may be the case. The combination of additional elevation and a 4m/s crosswind were messing things up pretty good sending me way off target, but was a good learning experience.You mention zeroing 3inch high at 100m, would this be the same when setup for dialing? I currently zero bang on at 100m and dial up from there. |
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@ 04:40 pm (GMT) |
Nathan FosterRe: POI change hard vs soft restBy zeroing dead on at 100 yards, it handicaps the cartridge, causes lost time at intermediate ranges where animals are more likely to pick up on your scent in eddying winds, and brings about the need to add more info on your drop chart where space on the sheet can be precious.Set 3" high with the 168gr A-Max, you'll be dead on around 246 yards. Roughly 5" low at 300 yards, then 9" low at 325, 12" low at 350 yards, 18" low at 375 yards and 24" low at 400 yards. If you round the 5" figure to 6, you have a simple method of calculating drop in multiples of 3. That said, I usually try to dial at ranges past 300 yards. Nevertheless, this method allows for fast calculations inside 300 yards and simple calculations at ranges of around 300 yards and out to 400 yards if need be. Set the beginning of your printed drop charts at 300 yards. If using the shooter app, set the app to 'zero range' 100, 'zero height' 3". If using metric, good luck. Just kidding, metric settings should be 3" high at 100m or 75mm high at 100m. The traditional 3" high zero was initially promoted by Jack O'Connor way back in the late 1920's and early 1930's after he had become familiar with the .270 Win and realized that even a flat shooting cartridge could easily be handicapped. It was adopted by hunters world wide and it worked. Snipers have also used a high trajectory and it is common on a lot of military rifles such as the SMLE with 300/600 yard flip up aperture sights. For some reason this old knowledge has been forgotten. It was used by the cullers on the tops of the south island NZ many years ago but again, even this knowledge seems to have faded, perhaps it was because of the meat/skin hunting trade years when the .222 and neck/head shooting became common. In its simplest form with Oconnor's pet .270 Win and a 130 grain bullet, if the hunter set the rifle to print 3" high at 100 yards/paces, bullet drop was roughly 3" low at 300 yards. In the .308, it greatly extends the usefulness of the cartridge without having to dial. It does take a bit to get used to, having to aim a tad below center on game at ranges between 100 and 200 yards but its worth it. |
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@ 07:12 pm (GMT) |
Matt ReidRe: POI change hard vs soft restOk, that makes sense. Less dialing has got to be a good thing!Matt |
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