Reloading For An AR-10 In 6.5mm Creedmoor LMT MWS

Fire4EffectCA · Dec 24, 2024

I have the following components I would like to use to load for my LMT MWS with a 20” 6.5mm Creedmoor barrel. The LMT MWS is stock except for a BRT EZTUNE gas tube.

Hornady 6.5mm 140 gr EDL Match bullets with Hodgdon H4350.
Hornady 6.5mm 147 gr EDL Match bullets with Hodgdon H4350.

https://www.snipershide.com/shooting/threads/lmt-mws-brt-eztune-gas-tube.7032995/

All of the published reloading data for the Hornady 6.5mm 140 gr EDL Match bullets with Hodgdon H4350 powder were tested in bolt action rifles.

Hornady Reloading Data: Max load 41.5 gr.
Hodgdon Reloading Data: Max load 40.0 gr

All of the published reloading data for the Hornady 6.5mm 147 gr EDL Match bullets with Hodgdon H4350 powder were tested in bolt action rifles.

Hornady Reloading Data: Max load 40.3 gr.
Hodgdon Reloading Data: Max load 41.8 gr

I am assuming these numbers are safe in bolt guns, but may not be in the AR10 platform.

Can anyone recommend a good starting point and not to hot max for these components in an AR-10?

Thanks.

mgoodrich · Dec 25, 2024

There is a 308 AR reloading sticky that you would probably want to take a look at and see what has been posted there. Comparing this data with the bolt section would give you an idea on how much to back off.

I used this and sierra's reloading manual for the AR15 as a reference, for when I started to reload my 243 AR. The load I used with the particular bullet and powder turned out to be ~ 3.5 gr down from the max load from the bolt gun.

Your results may vary.

Fire4EffectCA · Dec 26, 2024

mgoodrich said:
There is a 308 AR reloading sticky that you would probably want to take a look at and see what has been posted there. Comparing this data with the bolt section would give you an idea on how much to back off.

I used this and sierra's reloading manual for the AR15 as a reference, for when I started to reload my 243 AR. The load I used with the particular bullet and powder turned out to be ~ 3.5 gr down from the max load from the bolt gun.

Your results may vary.

I did go through the sticky before I posted here and I could not find what I was looking for. I did post over on the Accurate Shooter’s Forum and received some responses that leg me to believe others were running at max or hotter for their AR-10’s.

I have the following Hornady factory ammo:

Hornady 6.5 Creedmoor 140 gr EDL Match
Hornady 6.5 Creedmoor 147 gr EDL Match
Hornady (American Gunner) 6.5 Creedmoor 140 gr BTHP

I have a chronograph and will fire 10 rounds each of the above through my LMT MWS to observe and record data. If all looks good I will try my 140 gr EDL Match handloads and work my way up the ladder until I see pressure signs. I will do the same for the 147 gr EDL Match handloads.

This is what I loaded yesterday with my available components:

********************************************************************

For the 140 gr EDL Match I loaded the following with Hodgdon H4350:
40.3 gr
40.6 gr
40.9 gr
41.2 gr
41.5 gr (Max load according to Hornady)

Hodgdon states 40.00 gr is a max load. Can this be correct?

Brass: New Lapua small primer
Primer: CCI Small primer magnum #450.
COAL: 2.81”

********************************************************************

For the 147 gr EDL Match I loaded the following:
40.0 gr
40.3 gr
40.6 gr
40.9 gr
41.2 gr

Hornady states 40.3 gr is the max load.
Hodgdon states 41.8 gr is a max load.

Brass: Once fired Hornady.
Primer: Winchester WLR
COAL: 2.81”

********************************************************************

Trailgomer · Dec 26, 2024

Check 6.5 creedmoor AR only sticky thread! Great info!

Fire4EffectCA · Dec 26, 2024

Trailgomer said:
Check 6.5 creedmoor AR only sticky thread! Great info!

As I mentioned above, I checked out that sticky thread before creating my post here.

mgoodrich · Dec 26, 2024

Running quickload on your 140 ELD-M, it shows that 42.5 gr of H4350 is the max (62,000psi chamber) with a 51.5 gr water brass capacity, and the overall cartridge length of 2.8 in.

With Lapua brass though probably need to take off about 1gr though since its case capacity tends to run smaller.

With the 147 ELD-M it is 41.2 max, same pressure etc.

There is also a spec on the gas port for max pressure of ~ 12,500 psi for the AR15. I don't know if an AR10 is the same.

I helped a friend of mine get his ruger 308 AR, set up for a hog hunt he went on. He had 4 boxes of ammo from different manufactures shooting a 168 gr. bullet.

3 boxes shot fine out of his AR, the 4th was tearing the rim off his brass like crazy. The chrono was showing around a 100 fps faster in that round, and it was ejecting at ~ 1-2 oclock position. The others were betwenn 3-4 oclock.

Watch where you are ejecting and your brass condition to tell you where your max should be as you work up.

Fire4EffectCA · Dec 27, 2024

mgoodrich said:
Running quickload on your 140 ELD-M, it shows that 42.5 gr of H4350 is the max (62,000psi chamber) with a 51.5 gr water brass capacity, and the overall cartridge length of 2.8 in.

With Lapua brass though probably need to take off about 1gr though since its case capacity tends to run smaller.

With the 147 ELD-M it is 41.2 max, same pressure etc.

There is also a spec on the gas port for max pressure of ~ 12,500 psi for the AR15. I don't know if an AR10 is the same.

I helped a friend of mine get his ruger 308 AR, set up for a hog hunt he went on. He had 4 boxes of ammo from different manufactures shooting a 168 gr. bullet.

3 boxes shot fine out of his AR, the 4th was tearing the rim off his brass like crazy. The chrono was showing around a 100 fps faster in that round, and it was ejecting at ~ 1-2 oclock position. The others were betwenn 3-4 oclock.

Watch where you are ejecting and your brass condition to tell you where your max should be as you work up.

I have been reloading 308 and 223 for 50 years and it was only in 2020 that I started looking into 6.5 Creedmoor when I picked up a 6.5 Creedmoor barrel for my LMT MWS. I only shot with that barrel twice in 2020 and I commented on Snipers Hide about my experience. I also purchased a Tikka T3TAC A1 in 2021 that I still have not shot

https://www.snipershide.com/shooting/threads/lmt-mws-brt-eztune-gas-tube.7032995/

Back in 2020 I had planned to start reloading for 6.5 Creedmoor and I purchased what was at the time the go to bullet and powder. COVD and major health issues sidelined me from moving forward with reloading for 6.5 Creedmoor until recently. As time and my health permits, I plan to shoot both the LMT MWS and Tikka T3TAC A1 in 6.5 Creedmoor.

From everything I am reading here and on Accurate Shooter, what I have reloaded so far would be fine for my Tikka T3TAC A1. For the LMT MWS my starting loads will be fine, but the higher grain loads may be too warm. I am also getting the impression that 140 gr bullets with H 4350 presents significant challenges for a gas gun platform and 130 gr bullets and a different powder would be more fulfilling.

I am open to trying 130 gr bullets with a different powder. Can anyone recommend a 6.5mm 130 gr bullet and powder combination for AR-10 platform?

RegionRat · Dec 28, 2024

This advice is a little late to your party and I apologize for not answering your direct question... but since the alternate AR10/SR25 designs have a less diverse background than an AR15, the compatible ammo recipes that match lengths and port sizes are less well known.

If you stick to one recipe, you can certainly dedicate the port size and relax to some degree.

For the folks who want to experiment or don't have the luxury of testing in cold weather ahead of time, an adjustable gas block can help with tuning the cycle.

There are even tool-less ones that make it easy to change port settings to specific loads or shooting conditions and to change to suppression without much fuss.

I haven't talked with them in a long time, but is it possible that LMT would have some advice on coordinating ammo to their 6.5 CM rigs?

I saw your first thread back in 2020 and was a little surprised at the original port size. It made me wonder if that was intended to match up to a specific load? Sorry if this was covered, but did you consult LMT?

wade2big · Dec 28, 2024

Properly gassed AR10s can shoot max bolt gun loads just fine although not the Hide’s 80,000psi standard bolt gun loads. The LMT 20” barrels use a gas system that is too short resulting in a much too long dwell time which causes early unlocking of the bolt. Even with the EZ Tune gas tube and running the heaviest buffer you can, you’ll likely see “pressure signs” early because of this.

Fire4EffectCA · Dec 28, 2024

RegionRat said:
This advice is a little late to your party and I apologize for not answering your direct question... but since the alternate AR10/SR25 designs have a less diverse background than an AR15, the compatible ammo recipes that match lengths and port sizes are less well known.

If you stick to one recipe, you can certainly dedicate the port size and relax to some degree.

For the folks who want to experiment or don't have the luxury of testing in cold weather ahead of time, an adjustable gas block can help with tuning the cycle.

There are even tool-less ones that make it easy to change port settings to specific loads or shooting conditions and to change to suppression without much fuss.

I haven't talked with them in a long time, but is it possible that LMT would have some advice on coordinating ammo to their 6.5 CM rigs?

I saw your first thread back in 2020 and was a little surprised at the original port size. It made me wonder if that was intended to match up to a specific load? Sorry if this was covered, but did you consult LMT?

I spoke with LMT back in 2020. Their position was that their 6.5 Creedmoor barrel was operating as intended.

Fire4EffectCA · Dec 28, 2024

wade2big said:
Properly gassed AR10s can shoot max bolt gun loads just fine although not the Hide’s 80,000psi standard bolt gun loads. The LMT 20” barrels use a gas system that is too short resulting in a much too long dwell time which causes early unlocking of the bolt. Even with the EZ Tune gas tube and running the heaviest buffer you can, you’ll likely see “pressure signs” early because of this.

I went back and searched my computer for any notes or photos from my two visits to the range in 2020 with the 6.5 Creedmoor LMT MWS. I found photos of the cases that were badly beaten up on the first visit. I don’t have photos from the second visit, but things improved with the BRT gas tube installation. I had also planned to remove one coil from each ejector spring, but had not done it. It was also suggested to me to break the sharp points on the barrel extension inner lugs, but I decided I was not qualified to do that.

Below are two photos of targets from after I installed the BRT gas tube. This was a significant improvement from the previous shoot.

Fire4EffectCA · Jan 2, 2025

I made it up to our rifle range on New Year’s Eve and recorded good results for the 6.5 Creedmoor reloads with 140 gr and 147 gr Hornady EDLM bullets. The ejected brass looked fine except for the slight denting on some of the necks which is normal for an AR. I did not see any pressure signs with any of the 140 gr EDLM loads and some slight pressure signs with the max 147 gr EDLM loads.

I measured all my fired cases with a Whidden headspace gauge and all measured +4.5 (0.0045”), except for the 147 gr EDLM with 41.2 gr of H4350. That was a max load and it measured +5 (0.005”).

My Winchester WLR primers are 35 years old and they have performed fine with my 308 loads and I did not experience any issues with the 6.5 Creedmoor loads. I have a few targets where I have a nice 4 shot group, but the fifth shot opens it up. Not sure if this was my shooting or some other factor is in play. I will repeat these loads the next time I go to the range and fire more five shot groups to obtain a larger sample.

I have not shot any of my loads with the new Lapua Small Rifle Primer Pocket brass. They are already loaded, but someone here mentioned I should reduce the loads by 1 grain.

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Reloading For An AR-10 In 6.5mm Creedmoor LMT MWS

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