120 class powders

[Dt219]

120gr ELD-M is meant for 6.5CM or chambers with parallel freebore, not the compound throat of the 6.5 Grendel SAAMI chamber.

123gr ELD-M is your friend for 6.5 Grendel. Notice how short your COL is with the 120gr ELD-M.

Your speeds are about where I would expect them to be for a 20” with that charge weight, based on numerous published loads as reference.

My chamber doesn’t seem unusually short does it ?

[Klem]

Dt,

That threaded case you screw onto the Hornady OAL gauge will be a different shape to the spent cases from your gun. Your gun's spent cases are a closer mimic of the chamber because they have expanded to take its shape. The threaded Hornady case will have been crushed to death in a factory somewhere to fit all Grendel chambers on the planet.

The threaded case is still fine, but you have to account for the difference between its shape and your chamber's shape. To do this, measure the length from base to shoulder with the Hornady B350 headspace gauge, or even an empty 9mm case. Then do the same with a spent case or two from your gun. Note the difference. If the threaded case is shorter than your spent cases (likely) then add the difference to any measurement you take with the Hornady OAL gauge. If the threaded case is longer than your spent cases (less likely) then subtract the difference.

Another easier way is to use a spent/unsized case from your gun as the gauge. You have to drill out the back and thread it for the Hornady plastic stem. This way you don't have to account for any difference as it is the shape of your chamber.

Hard to know if your chamber is short until you can confirm you have accounted for the difference between the Hornady threaded case and your own spent cases.

You don't need to use Blutack. Gently bring a cleaning rod (I use a length of flexible plastic cord so it's not abrasive) in from the muzzle end and stop it just short of the chamber. Push your OAL gauge in and to get the bullet back our you can give the rod a little press against the bullet to unstick it from the throat.

[Dt219]

Dt,

That threaded case you screw onto the Hornady OAL gauge will be a different shape to the spent cases from your gun. Your gun's spent cases are a closer mimic of the chamber because they have expanded to take its shape. The threaded Hornady case will have been crushed to death in a factory somewhere to fit all Grendel chambers on the planet.

The threaded case is still fine, but you have to account for the difference between its shape and your chamber's shape. To do this, measure the length from base to shoulder with the Hornady B350 headspace gauge, or even an empty 9mm case. Then do the same with a spent case or two from your gun. Note the difference. If the threaded case is shorter than your spent cases (likely) then add the difference to any measurement you take with the Hornady OAL gauge. If the threaded case is longer than your spent cases (less likely) then subtract the difference.

Another easier way is to use a spent/unsized case from your gun as the gauge. You have to drill out the back and thread it for the Hornady plastic stem. This way you don't have to account for any difference as it is the shape of your chamber.

Hard to know if your chamber is short until you can confirm you have accounted for the difference between the Hornady threaded case and your own spent cases.

You don't need to use Blutack. Gently bring a cleaning rod (I use a length of flexible plastic cord so it's not abrasive) in from the muzzle end and stop it just short of the chamber. Push your OAL gauge in and to get the bullet back our you can give the rod a little press against the bullet to unstick it from the throat.

I do not use the hornady gauge. I truly think it’s Mickey Mouse. Thats why I use fired cases from my rifle

[Klem]

I do not use the hornady gauge. I truly think it’s Mickey Mouse. Thats why I use fired cases from my rifle

Works for me.

[StoneHendge]

Dt, a short chamber if fine. My JP is real tight and a 123 gr Scenar is 2.26" on the lands. But it's the most accurate barrel I've ever had after a former carbon fiber Proof Research 6.5CM. Just go easy on the powder. I max out 0.7-0.8 gr below what most other guys use. Even more with XBR.

[Dt219]

My chamber dimensions when rifle was nearly new. I made dummy rounds with all the bullets I had on hand so I would have them written down. Max lengths. Do they look in the ball park ?

85gr Sierra varminteer
CBTO 1.685. COAL 2.280

90gr Speer TNT
CBTO 1.730. COAL 2.240

90gr Nosler Varmageddon
CBTO 1.700. COAL 2.390

100gr Nosler ballistic tip
CBTO 1.708. COAL 2.350

120 Barnes MB
CBTO 1.700. COAL 2.255

120 ELD-M
CBTO 1.645. COAL 2.190

120 Sierra Pro Hunter
CBTO 1.675. COAL 2.155

123 ELD-M
CBTO 1.685. COAL 2.280

123 SST
CBTO 1.690. COAL 2.280

123 Sierra MK
CBTO 1.700. COAL 2.310

[mdram]

since temp stability has been mentioned, here is a study, with 223, and various powders mentioned
https://www.wlcastleman.com/equip/shoot/t223/index.htm

[VASCAR2]

Thanks for posting that study mdram! I had never seen that before and never knew AR Comp was a Swedish powder. I always found AR Comp a little more expensive and this might be the reason.

[Klem]

My chamber dimensions when rifle was nearly new. I made dummy rounds with all the bullets I had on hand so I would have them written down. Max lengths. Do they look in the ball park ?

85gr Sierra varminteer
CBTO 1.685. COAL 2.280

90gr Speer TNT
CBTO 1.730. COAL 2.240

90gr Nosler Varmageddon
CBTO 1.700. COAL 2.390

100gr Nosler ballistic tip
CBTO 1.708. COAL 2.350

120 Barnes MB
CBTO 1.700. COAL 2.255

120 ELD-M
CBTO 1.645. COAL 2.190

120 Sierra Pro Hunter
CBTO 1.675. COAL 2.155

123 ELD-M
CBTO 1.685. COAL 2.280

123 SST
CBTO 1.690. COAL 2.280

123 Sierra MK
CBTO 1.700. COAL 2.310

Yes, looks in the ballpark. Nothing to be worried about.

[Dt219]

Thank you Klem. Now should I roll on with the 120 eldm at 26.6 running 2430 and crunching ar comp or try a different bullet and powder I wonder

[LRRPF52]

My chamber doesn’t seem unusually short does it ?

ETA: Just saw your dummy cartridge COLs. Those are all within spec, right where they should be, and now you see the confirmation about 120gr ELD-M.

Make a dummy with a 123gr A-MAX, ELD-M, Scenar, or SMK and see what you can load.

120gr A-MAX and ELD-M have never been able to be loaded to mag length. Hornady actually had a factory 120gr A-MAX load that was quickly discontinued because of that, and why they developed the 123gr A-MAX.

ELD-M is an A-MAX with the new harder polymer tips. A-MAX used softer tips.

Precision Firearms cuts with a SAAMI reamer, which has the compound throat proven to exhibit better accuracy across a wide range of projectiles.

Most manufacturers use a non-SAAMI reamer with a parallel freebore for ease of mass-production and reamer life.

I’ve a bit of back-to-back testing using the same barrel profiles and manufacturers with the SAAMI vs parallel freebore, and the SAAMI chamber would shoot bug-holes while I could barely hold 1-1.5 MOA with certain loads in the parallel freebore chambers.

This was especially apparent when I pulled the barrel from the same rifle and replaced it with the same barrel from Lilja, only a Manson reamer-cut SAAMI chamber on the replacement pipe. These were heavy bull profile 22” fluted pipes from a heavy bullet rifle as well. With the SAAMI chamber, I was rapid-firing .3” to .6” 5-round groups at 100yds, with photos and witnessed.

With the SAAMI chamber, you should be able to load the 123gr A-MAX, ELD-M, SMK, or Scenar to 2.260” without jamming the lands. It will kiss a little bit for alignment, but not jam.

[mdram]

Thanks for posting that study mdram! I had never seen that before and never knew AR Comp was a Swedish powder. I always found AR Comp a little more expensive and this might be the reason.

possibly, but remember 8208 comes from Australia, just like some other hodgdon powders

[Dt219]

ETA: Just saw your dummy cartridge COLs. Those are all within spec, right where they should be, and now you see the confirmation about 120gr ELD-M.

Make a dummy with a 123gr A-MAX, ELD-M, Scenar, or SMK and see what you can load.

120gr A-MAX and ELD-M have never been able to be loaded to mag length. Hornady actually had a factory 120gr A-MAX load that was quickly discontinued because of that, and why they developed the 123gr A-MAX.

ELD-M is an A-MAX with the new harder polymer tips. A-MAX used softer tips.

Precision Firearms cuts with a SAAMI reamer, which has the compound throat proven to exhibit better accuracy across a wide range of projectiles.

Most manufacturers use a non-SAAMI reamer with a parallel freebore for ease of mass-production and reamer life.

I’ve a bit of back-to-back testing using the same barrel profiles and manufacturers with the SAAMI vs parallel freebore, and the SAAMI chamber would shoot bug-holes while I could barely hold 1-1.5 MOA with certain loads in the parallel freebore chambers.

This was especially apparent when I pulled the barrel from the same rifle and replaced it with the same barrel from Lilja, only a Manson reamer-cut SAAMI chamber on the replacement pipe. These were heavy bull profile 22” fluted pipes from a heavy bullet rifle as well. With the SAAMI chamber, I was rapid-firing .3” to .6” 5-round groups at 100yds, with photos and witnessed.

With the SAAMI chamber, you should be able to load the 123gr A-MAX, ELD-M, SMK, or Scenar to 2.260” without jamming the lands. It will kiss a little bit for alignment, but not jam.

Where is a good distance to start from the lands with those projectiles ? I know you have been up and down this path with every bullet mentioned.

[LRRPF52]

Where is a good distance to start from the lands with those projectiles ? I know you have been up and down this path with every bullet mentioned.

I try to load as long as my chambers and magazine will allow.

For the magazine, that doesn’t mean the top feed presentation slot, but the stack as you load more and they tilt a bit, requiring more length for clearance.

Learned that the hard way in the middle of a match with an AR-10 that I had loaded really long. I caught it before a stage, realizing I could only load 12-15rds if I recall, so I didn’t hurt myself when it came time for us to shoot that stage.

The issue I have to consider now with the various Grendel mags I have is that some allow 2.295”, while some won’t let me go past 2.260” (Elander).

Last thing I want is to go to load up and can’t. CProducts have allowed the longest COLs so far.

[Klem]

Dt,

You cannot load longer than the mag in an AR and this is often the primary limiter. Stainless mags should give you a little longer than the calibre's standard of 57.4mm, so up to 58mm is reasonable but no longer.

If your distance to touch lands is shorter than the mag length then 0.5mm jump is a good starter. But be careful, especially with lighter bullet that there is enough shank being gripped by the case neck. It is more important to have no movement of the bullet as it gets violently pushed into battery. Enough grip depends on a how ductile your brass is, how much shank is in contact, how heavy the bullet is, and whether you crimp or not. I would square this away before thinking about how much jump. Frankly, jump-to-lands in an AR is almost a luxury given the mag length and all the usual influences of group size tend to be exaggerated in such a light-weight gun.

[Remington Jim]

I do not use the hornady gauge. I truly think it’s Mickey Mouse. Thats why I use fired cases from my rifle

Ok use the gauge but cases fired from your own rifle and drilled tapped for the gauge ! The Horn pre drilled cases are with in 1000 s of your own rifle cases ! I have compared them both and found no REAL difference it’s not worth my time ! But JMHO your findings may be different ! Cheers

[Dt219]

Ok I loaded up a ladder of H4895 with 123 eld-m. Starting at 25.7gr ended up at 27.5 using .2 increments. COAL 2.250 will post results hopefully tomorrow

[Dt219]

Ok got to shoot my ladder today. Strapped on magnetospeed and got data. 20” PF criterion
H4895- 123 eldm. CCI 450. Coal 2.250. 75 degrees

25.7 - 2274
25.9 - 2254
26.1 - 2301
26.3 - 2327
26.5 - 2316
26.7 - 2378
26.9 - 2391
27.1 - 2383
27.3 - 2457
27.5 - 2469

Play between 26.7 and 27.1 ? Thanks

[StoneHendge]

Ok got to shoot my ladder today. Strapped on magnetospeed and got data. 20” PF criterion
H4895- 123 eldm. CCI 450. Coal 2.250. 75 degrees

25.7 - 2274
25.9 - 2254
26.1 - 2301
26.3 - 2327
26.5 - 2316
26.7 - 2378
26.9 - 2391
27.1 - 2383
27.3 - 2457
27.5 - 2469

Play between 26.7 and 27.1 ? Thanks

That is all over the place. Satterlee has sent me on enough wild goose chases that I would try another combo. I'd wager the curve looks flat in that range simply by chance - some zigged while others zagged. How did they group?

[Dt219]

I did see some big jumps, and is that ladder bad ? ? ? I didn’t shoot them for groups yet. The magnetospeed kills my groups. I do wish just once I could get a load with low sd and it group good at least 3/4 moa and be consistent. I believe his method will work fine getting low sd consistently but I have yet to get small groups using it. Most of the time my low sd groups ain’t pretty lol. Well it’s not really funny.