I did a comparison 120 SMK vs 123 SMK vs 123 AMAX

[RStewart]

Since I'm beginning to reload with 8208, I decided to do some checking if I should decide to single load my Grendel for more precise competition shooting. I found a few interesting (at least to me) items while doing research. I used my AA Hunter upper as the test bed.

120 SMK-
Bullet length ~1.181"
OAL to Lands- 2.236"
Ogive to Lands- 1.736"

123 SMK-
Bullet Length ~1.291"
OAL to Lands- 2.323"
Ogive to Lands- 1.720"

123 AMAX-
Bullet length ~1.236"
OAL to Lands- 2.282"
Ogive to Lands- 1.710"

What I took away from this-
1- The shortest bullet had the shortest OAL to the lands, but also is bluntest with a tip to ogive of .5 (120 SMK)
2- The 123 SMK is 0.055" longer than the 123 AMAX
3- The OAL to lands on the 123 SMK and the 123 AMAX is a difference of 0.041" (In favor of the 123 SMK)
4- But, the overall difference between the Ogive to lands of the 123 SMK and 123 AMAX is only 0.010" (The 123 SMK hits the lands slightly longer)
So, it will be interesting to see how they stack up when I load some rounds 0.010" off the lands and see what happens.

I am just an average guy reloading ammo and this may not mean much in the big picture, but I found it interesting. If my data conclusions are incorrect, please correct for me.

[Nimrod]

I appreciate the effort and the info.

[mlmiller1]

Nice job, good measurements. Will any of those lengths that run into the lands fit in an AR magazine? I think, (not that far into it yet), but I think your mag will be your length constraint, not the lands. I'm starting my loads at the longest I think will run in my mags & working from there. I know they are clear of the lands so there will be a "jump". Off the top of my head, I'm thinking that is 2.226". There is a slight variation in lengths loading with the redding dies due to variations in actual ogive of the bullet but I'm trying to keep total length under that number. Nothing worse than having a bullet drag in the mag when you need it to feed.

MLM

[steel89]

I did the same measurements in my AA 16" tactical. In the chamber the SMK measured .104 longer than the AMAX, to where the oglive meets the Lands (1.797SMK vs 1.693AMAX). The Total cartridge length of the SMK in chamber was 2.295 vs the AMAX at 2.265. The interesting thing is when you load them both to Mag length 2.260, the AMAX is .020 longer to the oglive than the SMK. Less jump to the lands.

[LR1955]

Since I'm beginning to reload with 8208, I decided to do some checking if I should decide to single load my Grendel for more precise competition shooting. I found a few interesting (at least to me) items while doing research. I used my AA Hunter upper as the test bed.

120 SMK-
Bullet length ~1.181"
OAL to Lands- 2.236"
Ogive to Lands- 1.736"

123 SMK-
Bullet Length ~1.291"
OAL to Lands- 2.323"
Ogive to Lands- 1.720"

123 AMAX-
Bullet length ~1.236"
OAL to Lands- 2.282"
Ogive to Lands- 1.710"

What I took away from this-
1- The shortest bullet had the shortest OAL to the lands, but also is bluntest with a tip to ogive of .5 (120 SMK)
2- The 123 SMK is 0.055" longer than the 123 AMAX
3- The OAL to lands on the 123 SMK and the 123 AMAX is a difference of 0.041" (In favor of the 123 SMK)
4- But, the overall difference between the Ogive to lands of the 123 SMK and 123 AMAX is only 0.010" (The 123 SMK hits the lands slightly longer)
So, it will be interesting to see how they stack up when I load some rounds 0.010" off the lands and see what happens.

I am just an average guy reloading ammo and this may not mean much in the big picture, but I found it interesting. If my data conclusions are incorrect, please correct for me.

RS:

OK....but how does this relate to the type of consistent precision you are requiring?

Tangent ogive bullets tend to shoot more consistently from any rifle and gas blasters particularly as they are much less sensitive to jump. That's why I have a saying that if your Grendel blaster won't shoot a 120 Sierra, chances are it won't shoot anything.

The 123 Sierra is a decent bullet from a bolt gun. Hard seat and hot load. Never messed with the 123 AMAX so I don't know but the guys on this forum claim it is outstanding and apparently isn't as sensitive to jump as the 123 Sierra.

If you are going to shoot High Power at the real ranges, you will have problems at 300 and 600 if you have winds. It won't matter what bullet you use, either. So, choose the most consistent one you can find and be prepared to crank windage every time you see the slightest bit of shift.

LR55

[RStewart]

There is no real motive behind this experiment other than fact-finding. Since everyone at one time or another has mentioned all of these and I have all 3, thought it would be a good chance to size them up.

Mag length would not be a good comparison, so I wanted to see where to load as related to the lands. I already have shot High Power several times at "real ranges" (not sure about that one). Shooting High Power requires the 200 and 300 yards loads to be mag length, but 600 slow fire is single load. So this would be a 600 yard load.

Once I check these out at 100, I will recheck the most consistent at 600 yards. I am already a F-TR shooter using a .223 bolt, so I know a little about reading wind and it's affect on bullets. Not being rude, just pointing out I do have some knowledge of the subject to rely on.

[burnsome]

thanks for that info OP. I had a 123AMAX factory load stick in my chamber the other day in my rifle. loaded up a couple more and sure enuff', am getting some bullets that are just touching the rifling ahead of the chamber. Wolf ammo does not do this so i guess in my particular chamber, the Hornady loads are touching the lands pretty tight. the gun shoots them great with no other signs of chamber pressure or messed up brass. only issues is unloading an unfired round after chambering. i need to do some measurements on my chamber and see how much interference i'm getting.

[RStewart]

I did the same measurements in my AA 16" tactical. In the chamber the SMK measured .104 longer than the AMAX, to where the oglive meets the Lands (1.797SMK vs 1.693AMAX). The Total cartridge length of the SMK in chamber was 2.295 vs the AMAX at 2.265. The interesting thing is when you load them both to Mag length 2.260, the AMAX is .020 longer to the oglive than the SMK. Less jump to the lands.

That's why I checked all in the same rifle. Throats on rifles can vary and so each person can come up with something different in their respective rifles.
Example: in my bolt .223 I was loading to 2.460" to be .010" off the lands with a PacNor barrel. I recently rebarreled with a Bartlein. I now have to load to 2.410" to be the same .010" off the lands.
I'm going to load up some mag length and when I do I think I will find a very similar finding as you did.

[RStewart]

Nice job, good measurements. Will any of those lengths that run into the lands fit in an AR magazine? I think, (not that far into it yet), but I think your mag will be your length constraint, not the lands. I'm starting my loads at the longest I think will run in my mags & working from there. I know they are clear of the lands so there will be a "jump". Off the top of my head, I'm thinking that is 2.226". There is a slight variation in lengths loading with the redding dies due to variations in actual ogive of the bullet but I'm trying to keep total length under that number. Nothing worse than having a bullet drag in the mag when you need it to feed.

MLM

The 120 SMK would fit in a mag at 2.236", but I have found the 120 SMK's shoot best for me at 2.220" and the 123 SMK and 123 AMAX are too long to fit in the mag. The max I have loaded 123 SMK's to is 2.255." YMMV

Rick

[LR1955]

There is no real motive behind this experiment other than fact-finding. Since everyone at one time or another has mentioned all of these and I have all 3, thought it would be a good chance to size them up.

Mag length would not be a good comparison, so I wanted to see where to load as related to the lands. I already have shot High Power several times at "real ranges" (not sure about that one). Shooting High Power requires the 200 and 300 yards loads to be mag length, but 600 slow fire is single load. So this would be a 600 yard load.

Once I check these out at 100, I will recheck the most consistent at 600 yards. I am already a F-TR shooter using a .223 bolt, so I know a little about reading wind and it's affect on bullets. Not being rude, just pointing out I do have some knowledge of the subject to rely on.

RS:

Are you going to use the Grendel for High Power? Been there, done that, immediately dropped 15 - 20 points and never got them back. The wind blew the bullets around too much and holding elevation became a problem at 600. Went to a 6 mm AR and picked back up those points on the first match, plus a few more, and never looked back. Although I won't shoot a Grendel in High Power simply because there are tens of more effective cartridges out there, I still shoot it in practice periodically just to exercise my wind doping ability and to have some fun.

As and edit to this, the problems I encountered could well have been due to the use of the various ball powders that were our only real choice a few years ago. Unless you wanted to lose another hundred or two hundred feet per second by using Varget. So, I used TAC, 2520, and a few other common ball powders for the Grendel and lost points in a dramatic way. I used Varget and H-4895 for the 6 AR as the ball powders I tried (TAC / 2520) did not perform and had no problems what so ever across a wide spectrum of temperatures.

So, it could well have been the difference between ball powders and how they act in varying temperatures and extruded powders. Could well be that the 8208 XBR may be the key to success with the cartridge in varying environmental conditions.

Not sure how else to put it in terms of real verses reduced range shooting. I know that you probably have more reduced courses than where I live simply because of range availability. Not to be rude about it, just don't know of any other term to use. I would think the Grendel would be relatively competitive for reduced courses at 100 and 200 and even 300 providing the winds are consistent.

LR1955