I'm confused

[stoney1666]

First time to shoot these so why do 2 bullets, same weight (68 gr), but different brands (Speer, Sierra), same load, same AR, one shoots one inch left and the other one inch right. shooting pattern, not sight in, 16" barrel, mid length gas at 50 yards?

 

[AJC1]

Different powder, different bearing surface, different bc for wind drift..... exactly why stock piles of random ammo is nonsensical.

 

[BW460]

The answer to your question involves many different aspects of physics: ballistics, harmonics, acoustic waves, etc. The bullets do not have the exact same shape. They may have a different center of gravity and Ballistic coefficients. Extremely minute differences will affect the point of impact.

 

[Walkalong]

I loaded up som 50 Gr plastic tipped varmint bullets and some 52 Gr match JHPs with the same load sometime back, they hit about 3/4” apart at 100 yards. I really thought it was going to be closer.

 

[Rolynstone]

May be operator error. Try more groups and watch technique before blaming ammo. Factory ammo is pretty good. May be chamber too. Eliminate shooter errors first.

 

[BW460]

One thing you can try to get them closer using the same load is to seat the bullets so that the base of both bullets are seated to the same depth. This will give you a different over all length for the finished cartridges. Since the distance between the base of the bullet and the top of the powder are the same, the pressure generated will be nearly the same for both brands of bullets.

 

[BW460]

I dont believe he is shooting factory ammo.

 

[dweis]

I dont believe he is shooting factory ammo.

In his original post he cited shooting Speer and Sierra. So he is on factory ammo. I think there are so many possible contributing factors that he ought to do a real bench test to rule operator influence on POA vs POI.

 

[BW460]

He may be using factory. I have both Sierra and Speer bullets sitting on the shelf ready to be loaded. I figured that since he said "same load" and that this is a reloading forum, bets are that is what he is doing. Regardless, I agree that you can't get away from proper bench rest techniques if you are trying to evaluate the performance of any cartridge.

 

[higgite]

In his original post he cited shooting Speer and Sierra. So he is on factory ammo. I think there are so many possible contributing factors that he ought to do a real bench test to rule operator influence on POA vs POI.

He also said "same load". If it's factory ammo, how would he know that?

Edit: BW460 types faster than I do.

 

[mkmoy]

If the question is hand load, it really is amazing how different bullets/powders change the point of impact. Below is charting of 3 shot group's average point of impacts, when I was trying combinations for a new 22-250 1:9 twist rifle. Dashed lines are 1" apart. Bullet 0 and 3 are separated by 4" horizontal and 2.5" vertical, at 100Yds. Fouler and 0 were 55gr FMJ/31.0gr 3031. I settled on the 69Gr Sierra, adjusted zero and developed load from there.

 

[.308 Norma]

In his original post he cited shooting Speer and Sierra. So he is on factory ammo.

Huh? I can't even remember the last time I saw a box of Speer factory ammo, and I'm pretty sure I've never seen a box of Sierra factory ammo.
The OP is talking about Speer and Sierra bullets - not factory ammo.

 

[Yankee1986]

Huh? I can't even remember the last time I saw a box of Speer factory ammo, and I'm pretty I've never seen a box of Sierra factory ammo.
The OP is talking about Speer and Sierra bullets - not factory ammo.

I do think you're right about OP talking about handloads but the link below has several different kinds of Sierra ammunition.

https://globalordnance.com/ammunition/?_bc_fsnf=1&brand=3001

 

[.308 Norma]

I do think you're right about OP talking about handloads but the link below has several different kinds of Sierra ammunition.

https://globalordnance.com/ammunition/?_bc_fsnf=1&brand=3001

Thanks, I learned something. I've still never seen any Sierra factory ammo for real though.
On the other hand, I've literally shot thousands upon thousands of Sierra bullets, and I use Sierra 165gr BTHPs in my beloved .308 Norma mag.
BTW, Speer used to build factory ammo too. It seems like it was called Speer "Lawman" ammo, and I think it was mostly (if not all) handgun ammo.

 

[GeoDudeFlorida]

I do think you're right about OP talking about handloads but the link below has several different kinds of Sierra ammunition.

https://globalordnance.com/ammunition/?_bc_fsnf=1&brand=3001

@.308 Norma is probably a lot like me: never go looking for or at factory stuff. The last time I was in a gun store shopping for ammo I was looking for some DW .357Max. The kid behind the counter gave me that deer in the headlights look. Then he told me very firmly, like I was the idiot, that Dan Wesson made guns, not ammo. Ever. Fortunately for me the owner was in the back having lunch and he set the kid straight, sold me the last six boxes on the shelf, and we had a good laugh about it. Yea, that was quite a while ago.

 

[gwpercle]

It's just the nature of Guns and Ammo ... No two are ever the same .
You have to find a brand / load your gun "likes" and then lay in a good supply .

I have one bolt action 30-06 rifle that shoots most ammo and loads accurately ... not to the same POA - POI ... it must be sighted in for each bullet weight but it will group 110 gr. to 220 gr loads all very nicely ... Most rifles like one bullet weight and one brand and that's it .
Gary

 

[tmd16556]

I’d be worried my scope was loose with the poi in a line like that. That’s usually the culprit for me. Some are picky on boat tails vs flat bases. I have a 30-06 that shoots cloverleafs with Herters (Winchester, the monster crimp is a dead giveaway) 150 gr factory loads but I couldn’t get but 2 MoA with hand loaded 150 Hornady boat tail interlocks.

Rifles are quirky like that.

 

[stoney1666]

more info, powder 335, 27.2 gr, bullets seated to the same length, 1 in 8 twist.

 

[LiveLife]

2 bullets, same weight (68 gr), but different brands (Speer, Sierra), same load, same AR, one shoots one inch left and the other one inch right. shooting pattern, not sight in, 16" barrel, mid length gas at 50 yards?

... more info, powder 335, 27.2 gr, bullets seated to the same length, 1 in 8 twist.

My guess is change in POI could be due to reloading variables affecting barrel harmonics/timing to change how/where bullet exits the muzzle as it swings up/down and left/right.

Rifle barrels, especially free-floated AR barrels vibrate with different nodes from different ammunition/reloading variables, more affected as barrel heats up for thinner walled barrels. As you continue to shoot groups, holes on target will represent where in the muzzle vibration/swing at the time bullet exited. If the bullets exited the barrel when muzzle was near the bore line, this group represents what we often call "accuracy node". As bullets scatter at extremes of muzzle swing, we often call these "flyers" or not accuracy nodes.

So let's say reloading variables are the same other than the projectiles and what we see as POI/holes on target grouping left or right could mean different projectiles induced different barrel harmonics/timing so bullets exited at different muzzle position in swing cycle.

That's my guess.

shooting pattern

Perhaps we are putting cart before the horse? I am thinking proper load development hasn't been done to identify accuracy node(s)?

Now, if you have indeed identified accuracy node for the particular bullet/projectile (load consistently produces the smallest groups of the two bullets), then all you have to do is just use the bullet that produces smaller groups and adjust your sights/scope to move POI.

Am I thinking the same?

 

[ms6852]

Don't know your level of experience in hand/reloading ammo or in shooting so do not take offense. Have you weighed each bullet in the box, you will see that not all of them will weigh the same. Also the pressure in one brass case may be higher than the other case because one case may have different wall thickness. Weigh your cases if you want more consistency. Also neck pressure holding the bullet will affect poi. Agree with what everyone else has posted prior to me as well.

Also as I said don't know your level of experience in shooting so getting back to basics is always key. Keeping the same sight picture, trigger control, breathing , maintaining the same cheek weld but very important also is follow through. Many novice shooters do not follow throw and right when they squeeze the trigger they lift their head up. It is important to keep your head down and your rifle on the pocket of your shoulder as bullet has not exited the barrel the moment you squeeze trigger.

If you are experienced than, never mind and the information is for the new shooters entering this great activity.

 

[Varminterror]

Kinda like wondering why a Ford F-150 and a Chevy Silverado get different gas mileage, even though you put in the same grade of gas, and drove down the same road.

There are a ton of variables between two different bullets. Jacket alloy, ogive design, jacket thickness, bearing surface length and diameter, core balance, base design, heel design, etc etc etc... But...

It's just a few clicks in the scope, so there's no substantial consequence here. Don't overthink it - nothing is wrong, you just need a different zero when you shoot different ammo.

 

[cfullgraf]

There are a ton of variables between two different bullets. Jacket alloy, ogive design, jacket thickness, bearing surface length and diameter, core balance, base design, heel design, etc etc etc... But...

Yes, just because bullets weigh the same does not mean they are constructed the same and all the important centerpoints are in the same place.

During the recent shortages, I’ve had to change bullets for my rifles from time to time. The new brand of bullet never shot to the same point of aim as the old brand even though the weight was the same.

Also, I always had to tweak the load to get the best accuracy.

 

[.308 Norma]

Kinda like wondering why a Ford F-150 and a Chevy Silverado get different gas mileage, even though you put in the same grade of gas, and drove down the same road.

Don't overthink it - nothing is wrong, you just need a different zero when you shoot different ammo.

Good analogy. My Dodge Ram pickup was pulling to the left a bit last week. I took it in and had the wheels aligned. It cost me a hundred bucks though - a lot more expensive than adjusting/changing the zero on one of my rifles. Besides, I don't have the equipment to align wheels and I had to go to town to get it done, while adjusting the zero on one of my rifles when I change to a different ammo is easy, fun, and I can do it while sitting in a chair on our rear deck.