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pinzgauer

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Do you know what the sweat spot will be for bullet grains for the Grendel II? When our group buy barrels come in i'm going to do some load testing from the 123gr SST and 129gr SST up to the 140gr SST just to see whats in the realm of possible as far as accuracy and velocities go. If Nosler every releases the 129gr LR that will be on the agenda as well. 


There has been a ton of work done in this space, and some fairly clear conclusions. 

Assuming you are shooting AR's there are really two main constraints that come into play:

  • Overall cartridge length, which is determined by the AR mag clearances
  • usable case capacity with a given bullet, which is impacted by the seating depth, ogive shape, and bullet length. 

Note that I did not list throat, the differences in throats have very little impact on bullet weight sweet spot, though it can impact accuracy.

In general, you'll find:

  • The 123g Hornady AMAX & SST were optimized for Grendel, and are very hard to beat for accuracy & versatility in a wide range of guns & loadings
  • Nosler 123 Custom Competition shoots well in Grendel, but I'm not convinced it's any more accurate. 
  • the 129, 140, and even 120 AMAX's & SST's are too long for the grendel AR applications. You have to seat them very deep, and you end up with reduced powder capacity & compressed loads. (The 120 AMAX has a very fat ogive and has to be seated way deeper than similar bullets)
  • the 120 & 123g Sierra SMK's work well. Surprisingly the cheaper 120SMK for many people works better. They are a bit more finicky than the 123g amax's, and not any more accurate. So many people like myself have switched. 
  • The 115g range may be the sweet spot for long range hunting. I've not done much in this area, but there are some good (but expensive) bullets. You need the extra velocity the 115 has to have reasonable expansion in hunting bullets past 300 yards. 
  • The 100-105 range shoots great for target work. They are also handy for fireforming brass, etc. I used to use them for plinking because they were cheaper, etc.

But I have settled on the 123 AMAX as it's as accurate as the alternatives, Inexpensive and widely available, shoots to same point of impact as the SST in my rifles, etc. The 123 SST works great in grendel, and I use the same loads and seating depth. Deadly on hogs and whitetails. 

If I was in a situation where I wanted to hunt past 300 yards I'd be looking at some of the 115g TTSX type bullets. 

I know everyone wants to talk about throats, but you'll find the constraints of the AR platform and general ballistics constrain bullet choice far more. I will say I like and will always use the compound throat as it shoots many bullets well and reliably. And it's in the longest/broadest usage (See TX65's comments in the throat thread. The 6.5 CSS used the compound throat.)

If all you ever plan to shoot is the 123 AMAX, the LBC throat may be OK, but users I know of have seen no advantage in the real world. 

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Borrego Bob

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A 129gr SST loaded to 2.27in with 31gr of CFE223 gets a MV of 2662fps (6.5 Grendel Reloading Handbook Vol 2). So i would have to respectfully disagree with your assessment. When you can load longer in the mag you leave room of newer powders like CFE to do there magic. ASC mags allow just shy of 2.3 at about 2.295in.
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pinzgauer

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Quote:
Originally Posted by msrhunt
A 129gr SST loaded to 2.27in with 31gr of CFE223 gets a MV of 2662fps (6.5 Grendel Reloading Handbook Vol 2). So i would have to respectfully disagree with your assessment. When you can load longer in the mag you leave room of newer powders like CFE to do there magic. ASC mags allow just shy of 2.3 at about 2.295in.


Great! How did it perform for you when you tried it out???

You asked about sweet spots. I'm in my sixth year of shooting Grendel with a target/hunting/defense emphasis. Others been doing it much longer, but I had to learn some on my own, and early on, there was less data available. (no handbooks like you referenced. The people that wrote that handbook were fellow shooters!)

The advantage of Grendel is that it shoots many bullets well. Extremely well. 

There are some natural sweet spots, and you'll find it when you explore loads more. 

My recommendation would be to factor in down range ballistics, as there are significant differences in the BC's, etc. There is a reason certain bullets are in wide usage, and others not so much. (Prime example would be the 140g 6,5mm pills. Excellent in larger cartridges, abysmal in Grendel)

I've not spent as much time in the lower weight ranges, (85-100) as for it it's getting a bit light for what I want to do. 

Once you start loading long you need to be on the lookout for throat, jump, etc. Some bullets like a bit of jump, some not. But you'll figure that out.
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Borrego Bob

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I actually am loading a little shorter in my Liberty SAMMI barrel at 2.265in with 30.8gr of CFE223. With my 18in barrel i'm getting 2590fps with 123gr SST's. Here's my 200 yard group. I have a 22in Grendel II on order as part of our group buy. It has the lapua throat and plan to experiment loading long with CFE223 just to see whats possible. 

[1479430_10152089887984520_1273449126_n] 



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Tedward

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Do you think the 22" will have more benefit over the 20"? What does Steve say? I got some of the 20" ordered up but thought that was about the extent of getting any extra velocity. I have a 24" AR-Stoner and just never reached out far enough to see a benefit.
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Borrego Bob

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I have not talked to Steve about it but i'll do some testing when i get it can't wait!! I'm thinking its going to do well with the 129gr SST. 
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Borrego Bob

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Bwild97 is getting 2662fps from a 24in Grendel loading to 2.27in with 31gr of CFE 223. Lets say we get the same performance adjusted to barrel length with a MV of 2622fps. You run that through a calculator and you get a hunting round that has an effective range to a couple yards shy of 500 yards. If you mark the effective range at the point it drops below 1800fps. I would not shoot any anything beyond 400 yards and at 400 yards is still going at 1940fps. Of course those are sea level numbers. I hunt pig at 4000ft and so get a bit more performance. At 4000ft its still going 1900fps at 500 yards. That and the bullet stinking problem that is seen sometimes with the compound throat of course is gone. Of course this is me talking without testing one so we shall see when the barrels come it.
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Borrego Bob

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Reply with quote  #8 
GLshooter is getting 2750fps with his 24in BHW 264 LBC Grendel using 123gr SST loaded to 2.295in with 32.5gr of CFE 223 loaded behind it. With the similarities of the 264 LBC and Grendel II like velocities maybe possible. 
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Borrego Bob

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Quote:
Originally Posted by pinzgauer


  • The 115g range may be the sweet spot for long range hunting. I've not done much in this area, but there are some good (but expensive) bullets. You need the extra velocity the 115 has to have reasonable expansion in hunting bullets past 300 yards. 


No 115gr 6.5 pills exist as far as i know.

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pinzgauer

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Reply with quote  #10 
It's the 107 & 108gr that I was thinking of. (Lapua)

There were also experiments done by early grendelers with lightened 120g bullets to 115g that indicated that range might be optimal in terms of case capacity, MV, down range performance, etc. 

The 120's work very well, but are a little slow at very extreme ranges in carbines. The 100's start giving up BC.


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Borrego Bob

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Right I get you the 123gr though has the longest range because if the bc even in 16in barrels.
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pinzgauer

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Originally Posted by msrhunt
Right I get you the 123gr though has the longest range because if the bc even in 16in barrels.


Yes, as it's very close to the Grendel sweet spot. But it's more than BC as case capacity vs long bullets also factors in. There are heavier bullets with nominally better BC, but can't get the velocity due to case capacity/seating length constraints, etc. Which then leads to dropping below expansion thresholds and/or dropping subsonic at extreme ranges. 

There is a reason the 123g AMAX was developed when there was a perfectly good 120g AMAX... Same for the 123 SST, and from memory I recall it has lighter jackets as well to deal with AR-15 platform constraints. H did the exact same think with a projectile optimized for 6.8 SPC. 

There are also anomalies... many people find the 120g SMK works better (accuracy/velocity) in grendel than the 123g SMK, which is arguably a better bullet. Before we go down the throat rathole, similar anomalies also exist with the LBC throat. 

There is a big jump in the monocore hunting bullets when dealing with AR mag & seating depth constraints. (110-120g). Never as much of an issue in bolt guns, they have more flexibility. 

May have been on the old grendel forum, but someone did some next experimentation with 110-115g bullets modified from 120g's. Want to say it was something like taking the tip off a ttsx, drilling the HP deeper to reduce weight, then reinstalling the tip. But might have just been with a meplat tool or something with a TSX. 

But that was before the 123g AMAX & SST, which really addressed many Grendel wishlist items. 


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Borrego Bob

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Reply with quote  #13 
I'm going to be trying the 140gr nosler partition on the Grendel II chambered barrel when it comes. It's actually shorter than a 129gr SST. If I can go mag length the 140s maybe make on the Grendel reloading bench. With my 22in barrel even if a mv of 2435fps it would be a 400 yard hunting round before it drops below the recommended 1800fps.
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Borrego Bob

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Quote:
Originally Posted by pinzgauer
Quote:
Originally Posted by msrhunt
Right I get you the 123gr though has the longest range because if the bc even in 16in barrels.


Yes, as it's very close to the Grendel sweet spot. But it's more than BC as case capacity vs long bullets also factors in. There are heavier bullets with nominally better BC, but can't get the velocity due to case capacity/seating length constraints, etc. Which then leads to dropping below expansion thresholds and/or dropping subsonic at extreme ranges. 


When you measure the velocities at 400 yards the 123gr, Amax and SST bullets have higher velocities that any other bullets from the Grendel. The smaller 100gr bullets are much faster at the muzzle but loose velocity to quickly. The 108gr pills aren't hunting pills so they are out the window. 

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