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Posted: 11/17/2011 6:09:33 PM EDT
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Is there a noticble in POI when shooting different grain bullets?
Or do you have to rezero when changing from 55 to 62 to 77 grain etc?.. I'm trying to see if I can shoot the cheaper ammo for plinking, but prefer to have 62 grain loaded at home for self defense.. Any thoughts? |
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i noticed a big shift shooting different 7.62s over 500yrds.
i think you'll be ok with any load if home defense is your worry, just think "center mass"!!! the POI shift shouldn't be enough that you would all out miss a criminal in your home. that's what the 30 round mag is for anyway |
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Part of an answer sort of on your topic question, copy/pasted from another time:
I have done some experimenting using a Rock River Predator Pursuit and Leupold 1.5x5X Target scope off a bipod. All are 10 shot groups or averages of 10 shot groups. The windage did not change for any of the groups below. Same Windage zero for all weights/ammos. 200 Yard Info 0" impact: Federal GM .223 Match 69 grain Sierra OTM, stock #GM223M, (Groups in the 0.5-0.75 MOA range) 0" impact: Handload, 69 Sierra OTM, 25.3 and 25.5 Varget, CCI400 primers, mixed cases, intended to duplicate velocity of GM223M (Groups in the 1.0 MOA range) 0" impact: Black Hills 77 Match OTM .223 2650fps loading factory ammo. Groups at 1.0 MOA. Same exact point of impact as 69 grain loads factory and handloads. 1.5" low: Handload, 77 Sierra OTM, LC-08 Primed and crimped factory brass (not commercially available), 24.0 grains Varget, 2.25" COAL Groups at 1.0 MOA and very mild shooting. Fired cases just dribble out of the Rock River and go about 18"-24" to 1:30 on a clock. (roughly a 2550 fps loading and is too slow so impacts slighly low due to not enough muzzle jump at firing. Working on a faster loading.) 335 Yard Info 5.4" high impact: Hornady Superformance 5.56mm Match 75 grain OTM, stock #81264 (Groups from 1.8MOA through 2.5 MOA) 0" impact: Federal GM .223 Match 69 grain Sierra OTM, stock #GM223M, (Groups in the 0.5-0.75 MOA range) 0" or a hair down: Handload, 69 Sierra OTM, 25.5 Varget, CCI400 primers, mixed cases, intended to duplicate velocity of GM223M (Groups in the 1.0 MOA range) 0.7" low impact: Handload, 69 Sierra OTM, 25.3 Varget, CCI400 primers, mixed cases, intended to duplicate velocity of GM223M (Groups in the 0.75-1.4 MOA range) 2.4" low impact: Black Hills factory 77 grain OTM .223 Match loading (Groups in the 0.80-1.2 MOA range) 3.9" low impact: Handload, 77 Sierra OTM, 24.3 Varget, LC-08 USGI primed brass as above. (Groups from 0.72 to 0.96 MOA.)(extremely consistent verticle dispersion.)(Note impact of 0.5 MOA below BHA77OTM.) 5.7" low impact: Handload, 77 Sierra OTM, 24.0 Varget, LC-08 USGI primed brass as above. (Groups just over 1 MOA.) (Note impact of 1.0 MOA below BHA77OTM.) It would seem that the idea is useful. This rifle has been used at 200 yards for only one group of 55 grain .223 ammo, Federal FMJ, and that also landed at about the "0" but I need to check it more. The FMJ factory ammo is not so accurate as OTM loads. (Before any one yowls about the 24.0 Varget/77OTM loading, the Wylde chamber in the Rock River is neither a .223 nor a 5.56mm. The load is too mild if anything, pending further checking. On advice of the bullet maker's ballistic technicians, 24.3 grains Varget was tried with the results as above. That would seem the limit of Varget because while there were no case, primer, or ejection signs of pressure, the bolt velocity was increasing meaning the gas port pressure was moving up.) (The other item of note is the accuracy. The 1:8" twist's accuracy was fairly uniform. Note that these are 10 shot groups. The Hornady Superformance 5.56mm was terrible. It looked like shotgun pellet groups with no tendency to make a group center. My guess is that 55-69-77 grain ammo with "normal" full power recoil impulse puts the bullets at shorter ranges very close to the same point of impact using a heavy barrelled 20" rifle. There is a greater dispersion vertically from shorter and lighter barrels due to barrel jump and bore time. I would also note that the windage zeros were identical. All dispersion was verticle, if any.) |
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Quoted:
Is there a noticble in POI when shooting different grain bullets? Or do you have to rezero when changing from 55 to 62 to 77 grain etc?.. I'm trying to see if I can shoot the cheaper ammo for plinking, but prefer to have 62 grain loaded at home for self defense.. Any thoughts? Sub'd. So far I've only shot AE black box and remington 55gr .223, M-855 (my BUIS zero'd on this) and PMC X-tac 62grains (red dot zero'd on this). I'd like to know this answer as well. |
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Quoted:
Quoted:
Is there a noticble in POI when shooting different grain bullets? Or do you have to rezero when changing from 55 to 62 to 77 grain etc?.. I'm trying to see if I can shoot the cheaper ammo for plinking, but prefer to have 62 grain loaded at home for self defense.. Any thoughts? Sub'd. So far I've only shot AE black box and remington 55gr .223, M-855 (my BUIS zero'd on this) and PMC X-tac 62grains (red dot zero'd on this). I'd like to know this answer as well. You very well may notice different POI, but depending on range, this could be a very minimal or very significant difference. If you are relying on the rifle for HD (much less critical) or if it is your go-to gun when SHTF, zero with whatever ammo you would be relying on in those scenarios. At the distances encountered for HD it shouldn't really matter, as most encounters take place at very close range. You can always keep a record of the changes in POI with your different ammo selections and then adjust, i.e. two clicks left, 3 clicks up, when you change ammo. |
| The best advice that anyone can give you is this: Figure out what it is that YOU want to use, and put some trigger time in on it. Come up with your own dope for your own loads. That is going to be the only accurate way of doing things. What works in my rifles, works in my rifles. Not yours. I have rifles that shoot a lot of stuff same POI. Then again, I have a couple that are totally different. Just because somebody post my three loads shoot XYZ, has very liitle if any meaning to you. Good luck. Have fun with it, that is part of the adventure. 9080 |
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Just because somebody post my three loads shoot XYZ, has very liitle if any meaning to you. Good luck
*On one level, it is always good advice that a shooter should shoot his ammo in his own gun and develope his own data. *On another level, it is pretty much bullshit that guns are more than minimally different. Unless there is something wrong with it, one rifle of a type shoots about like another rifle of the type. 20" heavy barreled AR's are quite consistently similiar. 16" pencil barrels are likewise similiar. Dis-similiar guns don't necessarily shoot the same even with similiar/same ammo. There is a large variety of barrels, handguards, sights, etc, that beyond a general type, there is no exact answer. But, in general, experience with one of a type gives a really good clue as to what a second rifle of that type will do. It at least lets you weed out the stupid from the possibly useful. What is interesting sometimes is similarities. An el cheapo Model 1 Sales upper on a DPMS lower assembled as a fun blaster with a heavy SS 20 barrel turned out to perform very nearly like a fully developed RRA NM A4 with NM free float handguards, et cetera. Dam neared as accurate. The usual pile of medium weight barreled 16" CAR/Midlength AR's are so similiar, you might as well just throw them in a pile and pick one. 99% of shooters would never know the difference. The true oddity is a J&T Expedition 16" I have with ports/vents right in the end of the 16" barrel and no flash hider. It shoots differetly than most 16" CARs, etc. The recoil sensation is that it pulls the gun away from your shoulder but is horribly noisy. It has more than the usual bullet weight POI separation. |
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Quoted:
Is there a noticble in POI when shooting different grain bullets? ..Any thoughts? Depends on the range of the targets. At 50 yards I don't see a significant difference when shooting 55gr M193 and Hornady 75gr OTM. Checking again at 200 yards and you'll see differences in elevation and drift (not enough to miss a man sized target - but enough to miss a beer can). The old miltiary FM 23-9 used to have a chart showing the differences in impact between a M16A2 firing 55gr M193, then switching over to 62gr M855 - it also showed a shift in elevation and windage. ETA: If you're shooing precision you'll notice shifts between lots of the same ammo type. It's even more noticable when changing brands (even keeping the same weight/type of bullet). The further out you shoot the more it's noticable. |
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