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How much difference can a primer make?

Rossignol

The Original Sheriff
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I shot a couple five round groups today. I would have shot more but I was really quite surprised by the first group so I only just shot another comparison group.

The first group I shot American Eagle .223 black box. The second group was American Eagle .223 black box "AR". The only difference is that the "AR" black box has a milspec primer designed for use in ARs so says the box. The AR black box is what I used to zero the scope.

The first group with the non "AR" box of ammo grouped about 3" wide, well centered but high on the target not even touching the bull. The second group I shot for comparison using the "AR" box was still wide but printed nicely around the bull and that primer I mentioned being the only note worthy difference. The non milspec primer is about $2 less a box too.

IMG_0489.JPG
 

oli700

12g
Supporter
"Philanthropist"
they say it does.
I have seen differences from a cci400 to a cci450 with the same charge of powder.

one guess is that the AR ammo is the loaded famed mil spec cci#41 .
General consensus on the 41 is that it is a thick cup small rifle magnum primer,a thick cup cci450

the cci450 is a thicker cup than a 400, a 400 is just a standard small rifle primer

so if the black box is loaded with a standard sm rifle and the AR box is loaded with mag primer then there can be some group movement

some stuff is missing for me though

Yards?

Distance between groups ?

Head stamps exactly the same between the two boxes ?

100 yards and in you shouldn't see much difference , two groups close
 

Rossignol

The Original Sheriff
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My bad, I can fill in some info.

I was shooting at 100 yards. There is a difference of about 2-1/2" between the groups.

I'll have to get back to you on the head stamps.
 

Tuflehundon

.270 WIN
Having developed a load for my pistol and rifle, I can tell you that very small changes, can make a huge difference. Just a couple of tenths of a grain of powder can change the size of a group, and primers can make a big difference. The magnum primers can cause the powder to burn faster than the standard primers. That will effect barrel harmonics, which can easily give you a spread of 2 1/2" between groups. Try a bunch of different loads, and pic one your rifle and you like. Stick with that load.

Are you using the bolt gun in the pic? What's the barrel length and twist?
 

Water Monkey

The man, the myth, the monkey
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Having developed a load for my pistol and rifle, I can tell you that very small changes, can make a huge difference. Just a couple of tenths of a grain of powder can change the size of a group, and primers can make a big difference. The magnum primers can cause the powder to burn faster than the standard primers. That will effect barrel harmonics, which can easily give you a spread of 2 1/2" between groups. Try a bunch of different loads, and pic one your rifle and you like. Stick with that load.

Are you using the bolt gun in the pic? What's the barrel length and twist?

He's shooting the Savage Hog Hunter - 20" barrel 1:9 twist rate
 

Scoop

.30-06
My bad, I can fill in some info.
I was shooting at 100 yards. There is a difference of about 2-1/2" between the groups.
I'll have to get back to you on the head stamps.

Any chance you still have the target and could post a pic. I might be able to calculate the speed difference for you. And I've got some more trouble shooting advice, too. Pix first tho'. :)

[Do you have chrono data?]
 

Rossignol

The Original Sheriff
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Any chance you still have the target and could post a pic. I might be able to calculate the speed difference for you. And I've got some more trouble shooting advice, too. Pix first tho'. :)

[Do you have chrono data?]

The targets are still up but no pics tonight of those.

I do have pics of the two rounds.

On the left is the black box AR load with milspec primer, on the right is the black box "regular" load I guess we'll call it. The brass even looks somewhat different. The regular stuff is noticeably cleaner and brighter. The primers also are distinguishable side by side. The AR box is labeled AE223J and the regular box is AE223K.

IMG_0561.JPG

The next two photos are of packaging mostly which is nearly identical one to the other except for the "AR" on the one. Also, because of the way they're boxed differently, the regular box is
longer.

IMG_0564.JPG
IMG_0565.JPG
 
Last edited:

Scoop

.30-06

This may be of some help. I wish he had weighed the powder in each and I wish he had a chrono set from both. So it goes.
 

Rossignol

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This may be of some help. I wish he had weighed the powder in each and I wish he had a chrono set from both. So it goes.

Interesting. He did a pretty decent comparison and very up close. Among the slight differences, there's more to the primer than just being sealed but also the shape of the nose of the bullet could be contributing to the difference in POI shift.

I'm paying the same prices he mentions in the video but the AR is more accessible to me.
 

Rossignol

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Here's the difference in POI at 100 yards. The first was shot with the regular 223 Rem without milspec primer and the second group was shot with the AR 223 with milspec primer.

IMG_0568.JPG IMG_0569.JPG
 

MikeD

I'm Your Huckleberry
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"Philanthropist"
Changing even 1/2 grain can make a difference depending on the gun. Some primers fire hotter than others and it will affect internal pressure, velocity, burn rate, etc.

I am far from an expert but I have reloaded enough to know that seemingly minuscule changes can have dramatic effect down range. How much varies and how noticeable it is will vary from gun to gun and shooter to shooter.

Anything beyond that is getting out of my technical knowledge.
 

Tuflehundon

.270 WIN
If you watch the video, the big thing I noticed was the AR223 projectiles were a hair shorter, and the fronts were more blunt. That will effect the ballistic coefficient quite a bit. That could easily give you the 2 inch shift in POI.

My 55 grain standard ammo and 69 grain match ammo have a POI difference of 3 inches at 100.

Something else to ask. Was this fairly rapid fire? Did the barrel have time to cool down between groups? If the barrel was warm for the 2nd group, that could also account for the shift. That's called thermal drift. My old AR barrel shifted 4 inches down, and 2 inches right at 100 as it warmed up. My new stainless match barrel does not do that.
 

Scoop

.30-06
Changing even 1/2 grain can make a difference depending on the gun. ...
I am far from an expert but I have reloaded enough to know that seemingly minuscule changes can have dramatic effect down range.

At 100 yds a muzzle velocity change from 3000 to 2000 fps would account for 2.4 inches of drop. I wonder if there is really that big of a delta V.
 

CaddmannQ

.50 BMG
The projectile is only inside the barrel for a tiny bit of a second and that's all the time there is for the propellant to deliver whatever pressure it can develop.

The primer only works for a fraction of that time.

On my AR, the projectile is only inside the barrel for 0.001 seconds. A lot has to happen in that one thousandth of a second, so getting it off to a good start is extremely important.
 

Rossignol

The Original Sheriff
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Something else to ask. Was this fairly rapid fire? Did the barrel have time to cool down between groups? If the barrel was warm for the 2nd group, that could also account for the shift. That's called thermal drift. My old AR barrel shifted 4 inches down, and 2 inches right at 100 as it warmed up. My new stainless match barrel does not do that.

Firing was slow and steady, deliberate. After the first group, I got up, had a smoke, walked around for a few minutes then reloaded and got back down. Then again, 5 rounds slow and steady, deliberate.

Now, you mention a warm barrel could account for the shift. But the first group I fired is the one that is high. That's the group that is shifted. The second group is the second photo which while wide, is still reasonably centered around the bull. That's the AR223 which I've been using and used to zero my scope.

At 100 yds a muzzle velocity change from 3000 to 2000 fps would account for 2.4 inches of drop. I wonder if there is really that big of a delta V.

These are essentially the same load, both claim a muzzle velocity of about 3200 fps. As mentioned, the guy in the video didn't weigh the powder, it's possible there ar some differences from load to load (but likely within tolerance). The biggest differences I see are the primer and the similar but slightly different shape of the bullet. My first group shot high which could be hotter primer and maybe the shape of the bullet?
 

Scoop

.30-06
images


OK, here is how I'd approach the problem given unlimited time and money. You can do that, right?

On a day with light wind <3 knots go to the range with sighting targets set at 200 yards, a box of each type of ammo, a rifle, a chronograph, an infra-red thermometer, a friend as a record keeper, and 3 gallons of patience.

Extract bullets from 2 cartridges of Type A and 2 cartridges of Type B and weigh the powder charges. Record same.

Fire two shots into the berm to foul and warm barrel.
Set rifle on bench rest with scope centered on aiming point. Alternate 5 shots each of type A and B. ABABABABAB with 5 minutes of cooling time between each shot.
During cooling time walk downrange and record [pix man!] each strike.
Fire at 5 minute intervals.
Bring targets back.

Chrono 5 of each type. ABABABABAB Don't forget to let the barrel cool. Record results.

Measure and record temp, wind, humidity, date and time.

Take a look at how the ammo types group and conclude it was pretty much a waste of time.

Send us the pix and numbers.
 

Rossignol

The Original Sheriff
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You done gone and drank the bong water. Leave the medicinal alone, lol!

So that's not gonna happen. For my purposes, it's not that big a deal. From an impirical perspective or perhaps curiosity, I was surprised by the differences between what had previously appeared to be the same load. I'm happy to stick with the AR223 I zeroed with. It's the easiest for me to get a hold of.
 
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