18" Larue: 107 SMK or 120gr ELD-M or 123 ELD-M or.....?

[towerofpower93]

Just bit the bullet on a Larue UU and will have a case of American Gunner coming for barrel break-in and brass.

I'm a handloader and after the 200pcs of Hornady brass are emptied I'll be handloading exclusively after that.

With that said, and using sane loads in an 18" barrel, does the extra velocity of the 107g SMK beat the 120-123gr Hornady ELD-M to 1,100yds? Don't have my phone with me at the moment, so I can't play around in iSnipe for drop and wind, but I've generally been a fan of heavy for caliber projectiles just due to them holding better in the wind.

Research seems to indicate both the 107gr SMK and 123gr ELD-M are relatively easy to get a load dialed in, and the 107gr seems to like 8208XBR, which I keep around in abundance for my 77gr .223 loads, so of the three I've mentioned does it make sense to go heavier or does the 107gr SMK get it done to 1,100yds?

From what I've read, and based on my experience with the 155gr TMK in a couple of .308s, I wasn't planning on messing with the 107TMK. That ogive is just a little too long and lean and seems to be more jump sensitive. However, if I'm mistaken in that regard I'd love to be proven wrong, haha.

[LRRPF52]

Depends on:

* Twist rate, (in this case 1/8)
* altitude/barometric pressure
* wind conditions

Using a G7 drag modeled program, assuming a 2650fps mv, you're looking at 975yds of supersonic reach, with 3 mils of drift at 975 in 10mph full value wind.

At 4000ft elevation, you're supersonic to 1125yds with 3 mils of drift at that distance for 10mph/fv.

I personally don't like seeing that much wind drift at any distance, unless it's very steady and predictable.

[towerofpower93]

Consider it sea level or a bit lower with temps, humidity, and wind all over the place.

Northern Virginia, all the shitty weather you can handle and none of that thin air goodness

You didn't state which bullet you ran for the above, but I presume it was the 107gr SMK, based on the muzzle velocity and my research is showing 123s moving around 2400-2500fps for most 18" tubes on this forum.

[centerfire]

Based on my limited Grendel loading experience, the 107TMK is easier to load because of the retained case volume. 123gr and 130gr projectiles take up a lot of the case volume trying to fit them in an AR15 magazine. I'm not trying to hit 1K yards though, there are much better suited cartridges for that task.

[biodsl]

Based on my limited Grendel loading experience, the 107TMK is easier to load because of the retained case volume. 123gr and 130gr projectiles take up a lot of the case volume trying to fit them in an AR15 magazine. I'm not trying to hit 1K yards though, there are much better suited cartridges for that task.

Interesting. Do you have a OAL that seems to work best for you? I'm heading to the range in the morning with my first experiment with the TMK.

[towerofpower93]

Based on my limited Grendel loading experience, the 107TMK is easier to load because of the retained case volume. 123gr and 130gr projectiles take up a lot of the case volume trying to fit them in an AR15 magazine. I'm not trying to hit 1K yards though, there are much better suited cartridges for that task.

Definitely know there are better rounds to get to 1k and beyond. I use a 6.5x47 Lapua bolt gun for PRS and a local LR steel match that goes to 1,100yds....but taking an AR 15 to such things is fun too.

Have used my 18" DD SPR with handloaded 77gr SMKs at the later and ran my SVD with 174gr SMKs during the last PRS match Staff Shoot. Plenty of misses with both, but had a ton of fun doing it.

With that in mind, and knowing that anything from 0-400yds isn't too hard a task with the majority of the non-AK rifles in my safe, I'd be wanting to take this Larue 6.5G upper to 1,100yds at the local steel match.

Have a buddy shooting a 243LBC, which is basically a 6mm Grendel, at this match and I need to best him for bragging rights and so I don't buy ice cream at the end of the day. Hence the questions regarding bullet selection for the 6.5G. I run the 130gr Berger AR Hybrid in the x47L, but that would seem to eat too much case capacity in the G at Elander mag length and not get all the BC it is designed to have.

[centerfire]

Definitely know there are better rounds to get to 1k and beyond. I use a 6.5x47 Lapua bolt gun for PRS and a local LR steel match that goes to 1,100yds....but taking an AR 15 to such things is fun too.

Have used my 18" DD SPR with handloaded 77gr SMKs at the later and ran my SVD with 174gr SMKs during the last PRS match Staff Shoot. Plenty of misses with both, but had a ton of fun doing it.

With that in mind, and knowing that anything from 0-400yds isn't too hard a task with the majority of the non-AK rifles in my safe, I'd be wanting to take this Larue 6.5G upper to 1,100yds at the local steel match.

Have a buddy shooting a 243LBC, which is basically a 6mm Grendel, at this match and I need to best him for bragging rights and so I don't buy ice cream at the end of the day. Hence the questions regarding bullet selection for the 6.5G. I run the 130gr Berger AR Hybrid in the x47L, but that would seem to eat too much case capacity in the G at Elander mag length and not get all the BC it is designed to have.

There's half a MIL or less difference between the two projectiles at 1k yards (both are subsonic assuming 2650 and 2550) given your DA. I don't think the ballistics should be the deciding factor between the two.

[centerfire]

Interesting. Do you have a OAL that seems to work best for you? I'm heading to the range in the morning with my first experiment with the TMK.

Magazine length.

[towerofpower93]

There's half a MIL or less difference between the two projectiles at 1k yards (both are subsonic assuming 2650 and 2550) given your DA. I don't think the ballistics should be the deciding factor between the two.

Sorry, to which two projectiles are you referring? I assume the 107SMK and 123ELD-M, but I’ve littered this thread with five different bullets at this point, haha.

Thanks

[centerfire]

The two bullets in your first post. You might also take a look at the 108gr Scenar and 129gr ABLR. IMHO, the bullet that shoots the tightest group will perform the best given how relatively close they all are in external ballistics. Accurately making velocity is the real challenge.

[towerofpower93]

The two bullets in your first post. You might also take a look at the 108gr Scenar and 129gr ABLR. IMHO, the bullet that shoots the tightest group will perform the best given how relatively close they all are in external ballistics. Accurately making velocity is the real challenge.

Yeah, started playing with iSnipe last night and if an accurate load towards the top end of load data can be found for either the 107gr SMK or 108gr Lapua at 2600fps, 123gr ELD-M at 2500fps, or the 130gr AR Hybrid or 129gr ABLR at 2400fps the wind and drop differences are negligible.

Being that this is an AR with more trigger pulls than a bolt gun for a match, the ELD-M seems like a winner based on price and availability.

[roor]

The 108 and 123 scenars shot best out of my howa. Bruno shooters supply has them for about the same price as eld. I haven't tried them but I can't imagine they'd shoot any better as I'm getting under .5 moa

[towerofpower93]

The 108 and 123 scenars shot best out of my howa. Bruno shooters supply has them for about the same price as eld. I haven't tried them but I can't imagine they'd shoot any better as I'm getting under .5 moa

What OALs on those scenars? Wondering if the Lapuas have an ogive that’s more jump sensitive and maybe not doable while staying within mag length.

[roor]

[towerofpower93]

Overal length is always max mag length, for a howa bolt action is about 2.33. CBTO however is where the story changes. The difference between 108/123 scenar and 123 smk is about .03. I can always double check but these are the numbers I last remember.

I don’t have the tool to measure to the lands but of people are happy to donate I’m willing to give numbers for the howa bolt action!

Makes sense for the Sierras and Lapuas to be different in their CBTO measurements. A photo posted elsewhere showing them all side by side shows them all having some different ogive profiles.