The 600lbs gorilla

[oxn316]

I know everybody is thinking this but havent found any threads yet. Is it better to shoot the 107/108s faster or the 123s that retain the speed better for long range. Based on some of the info bwaites provided us it looks like the 107s can travel 2920 to 2950. The 123s can get to 2750 based on my tests with a 24" tube. I have looked at the drop charts for both and the 107 is flatter to 1k but goes subsonic faster than the 123. I do have a 1200 yard target that I shoot at. Any help guys?

[ricsmall]

About the only thing you can do is test them yourself. I think out to 800-1000 in good conditions, the difference would be negligible,assuming your rifle shoots both projos accurately.With wind, change in altitude, or other external factors,all you can do is test. And youre right, I have often thought about this. Ive got couple hundred 123 amax factory loads, and plan to try some sierra 107's or lap. 108's. Havent decided yet. Keep us posted if you get to it.

[Azprc]

Here is my dope for last weekend where I shot my 1084 yard target. With the 108s I was 10.4 mils elevation and 2.1 mils for a 10mph wind (which I did not have but it was close). With the same enviromentals, the 123 scenar is 11.8 mils and 2.0 mils wind. So the 108's win out, unless you you want the .1 mil less wind, which is only 3.9 inches at 1084 yards but it is 1.4 mils flatter. My gun is a 20.8" grendel chamber. I can not push the 123 fast enough to gain ANY advantage within the grendel platform. I could only get the 123's to 2575 and run the 108's at 2780 ish. And the extra velocity is a huge advantage and closer distances where the added bc and weight do not help the 123's. Lets use 750 yards, the 123's take 6.5 and 1.3 mils. The 108's take 5.6 and 1.3. The only reason to run the 123's is energy. AT 1084 the 108's have 415.6ft-lbs and the 123's have 484.7 ft-lbs.

Here is a video of the 1084 target.

Just for the hell of it, here is the 1450 target.

[oxn316]

do you know if the 108s are stable at that distance? If i run the numbers through jbm ballistics and start at 2950 they cross the sound barrier around 1125 where as the 123's at 2740 cross at 1250. Im thinking the 108s win to about 1k then after the heavier bullet wins

[LRRPF52]

The truth is that neither of them are ideal at those distances, as they are really meant for the 600yd/m line. When the wind kicks up even a tiny bit, they're all over, like a .308 168gr or even 175gr at distance.

We're really stretching the repeatable ballistic potential of the Grendel when shooting at these distances, namely 700yds+, and it is exceptional that Azprc was shooting a freaking 12" plate at 1084yds with a 20" barreled anything, let alone a 31gr powder capacity cartridge. If you pay close attention to the 1084yd video, you're looking at a full value wind from right to left at the target of no more than 2-3mph, with unkown wind in-between.

If you were to have even a light 5mph full value wind anywhere along the bullet's flight path, I doubt you would see any possibility of holding a 108gr within 1 MOA of accuracy, let alone being able to make predictable 1st-round hits on a man-sized silhouette.

That said, the Grendel still is an amazing little cartridge for what it is, and does really well in low-wind conditions past 600yds, as evidenced. When I run my ballistics to see what kind of 1st-round hit probability I can get on a silhouette, I look at the 10mph windage column, paying attention to when the 1.0 Mil drift is exceeded. I look across to the range, and then I have an idea where I'm 1st-round effective to, and that's with accurate, up-to-moment wind calls, maintaining exceptional marksmanship given the pressure to shoot in the conditions.

If you guys are looking to get some more velocity from the 108, maybe you can find some Moly-coated pills, or coat them yourself, and continue to load them long, with more powder. I'm getting crazy velocity from the 123gr Silver Scenars loaded by Precision Firearms in my 16" Grendel, so I just may try the 108's too at distance to see what I come up with, although I usually shoot my .260 Rem at distance out in the desert, where the winds are usually pretty significant.

[LR1955]

The truth is that neither of them are ideal at those distances, as they are really meant for the 600yd/m line. When the wind kicks up even a tiny bit, they're all over, like a .308 168gr or even 175gr at distance.

We're really stretching the repeatable ballistic potential of the Grendel when shooting at these distances, namely 700yds+, and it is exceptional that Azprc was shooting a freaking 12" plate at 1084yds with a 20" barreled anything, let alone a 31gr powder capacity cartridge. If you pay close attention to the 1084yd video, you're looking at a full value wind from right to left at the target of no more than 2-3mph, with unkown wind in-between.

If you were to have even a light 5mph full value wind anywhere along the bullet's flight path, I doubt you would see any possibility of holding a 108gr within 1 MOA of accuracy, let alone being able to make predictable 1st-round hits on a man-sized silhouette.

That said, the Grendel still is an amazing little cartridge for what it is, and does really well in low-wind conditions past 600yds, as evidenced. When I run my ballistics to see what kind of 1st-round hit probability I can get on a silhouette, I look at the 10mph windage column, paying attention to when the 1.0 Mil drift is exceeded. I look across to the range, and then I have an idea where I'm 1st-round effective to, and that's with accurate, up-to-moment wind calls, maintaining exceptional marksmanship given the pressure to shoot in the conditions.

If you guys are looking to get some more velocity from the 108, maybe you can find some Moly-coated pills, or coat them yourself, and continue to load them long, with more powder. I'm getting crazy velocity from the 123gr Silver Scenars loaded by Precision Firearms in my 16" Grendel, so I just may try the 108's too at distance to see what I come up with, although I usually shoot my .260 Rem at distance out in the desert, where the winds are usually pretty significant.

LRRP52:

Has anyone done any true pressure testing with those 108's and 107's at 2950 fps out of a Grendel and an AR-15? I would like to see what the results are. That sounds like way too high a velocity for those long bullets out of a Grendel AR-15. I don't mean guys saying the brass looks OK but real pressure testing.

LR55

[LRRPF52]

Azprc is running them at 2780fps, from what I gather in his post, which doesn't seem too bad. If I get 2700fps from my 16" with 100gr NBT's, it seems reasonable that he isn't pushing things too much at 2780fps from a 20" gun with the 108's. That is impressive to be able to hit the 12" plate at 1084yds 4/5.

[Azprc]

do you know if the 108s are stable at that distance? If i run the numbers through jbm ballistics and start at 2950 they cross the sound barrier around 1125 where as the 123's at 2740 cross at 1250. Im thinking the 108s win to about 1k then after the heavier bullet wins

The 108 and 123's out of the grendel are not ideal for anything beyond 750 or so. That being said, will I limit myself to that distance on steel, NO. Just because they are not ideal does not mean that they will not do the job. I also agree with LRRPF52 that I will shoot the 6.5x47L at these distances normally.

[nincomp]

When Arne Brennan, one of the co-developers of the Grendel shot in competition, he found he 108 Scenar better in his particular rifle. His competition rifle, however was a custom made bolt action with a tighter chamber, the 6.5ppcx.
He wisely, in my opinion, refused to share his loads on this site because he knew that they would be overpressure for an AR-15. There probably is some idiot who would have blown his AR to bits using that load.

As noted above, the 6.5 Grendel is really not competitive at 1000 yards, although it can, indeed shoot that far.
Ironically, Mr. Brennan, last I read, switched to the 6.5x67L for competition. Seems Azprc has one too for "serious" long range shooting.

[bwaites]

6.5x47, maybe?

[BluntForceTrauma]

This is a fascinating discussion. One very worth having in order to get a lot of solid data.

John

[Azprc]

When Arne Brennan, one of the co-developers of the Grendel shot in competition, he found he 108 Scenar better in his particular rifle. His competition rifle, however was a custom made bolt action with a tighter chamber, the 6.5ppcx.
He wisely, in my opinion, refused to share his loads on this site because he knew that they would be overpressure for an AR-15. There probably is some idiot who would have blown his AR to bits using that load.

As noted above, the 6.5 Grendel is really not competitive at 1000 yards, although it can, indeed shoot that far.
Ironically, Mr. Brennan, last I read, switched to the 6.5x67L for competition. Seems Azprc has one too for "serious" long range shooting.

I indeed have 4 of them but for long range work we use the 338 Edge or 408. The 47L is a fantastic round for 1760 or so in, not that it would be my first choice for any animal at distance due to energy. For competition 1250 yards and in the 47L is perfect. I am tempted to use the grendel at the SRM at Raton next weekend since all targets are 875 and in.

Wind, when read correctly, is not that evil or the 600 # gorilla. It just takes practice and rounds down range. For new shooters wind at max ord is the most effective way to eyeball wind without forgetting wind matters over the entire bullet flight path.

For the Grendel, I can not see the use of any other bullet than the 108 or 107 (although the bc for the 107 is horrible and excludes it). Find a load that the 108 and your gun like and run with it.

[BluntForceTrauma]

AZ, something just seems, well, "off" about Sierra's listed BCs for their 6.5 107 SMK. Do you think real-world shooting confirms their listed BCs? I admit I'm hoping they're, in reality, higher.

John

[Azprc]

I run the 108/123/107/130Berger and JLK through the acoustic setup a few months ago. The 107 is at .390 at 2700+ which is significantly lower than the .430 as advertised by Sierra. JFI, the JLK's were at .625 for a 130 bullet compared to the .565 for the berger 130.

[BluntForceTrauma]

Thanks. Surprising, since it's based on the same jacket profile as the 123 SMK, no? With simply a different amount of lead fill? Or is Sierra's BC of .510 for the 123 also suspect?

John