Reloading and not achieving velocity as compared to Nexus Arms

[ReaperME]

Hey guys, long time reader: just joined because this is driving me bonkers in my reloads.

I've been running a 16" christensen Arms G2 rifle at the range, working out a setup with a maximum point blank range, etc. but for fun I like to work on my reloads to try and maximize muzzle velocities, and change the "curve" of the bullet's path to maximize my "I can just aim like a dummy and still hit" range.

For example: with a MV of 2525 (what I'm managing with my own reloads), I can point and click out to 275 yards and reliably hit a 4inch target without thinking about it (and I've verified it having a good ol' time plenty of times).

Recently, however, I was bringing a new box of reloads, testing various powder charges (Varget), and I was ranging around 2520-2530 on a hot day here in Vegas.
I had another "control" box of Nexus Ammo, something I picked up a while back, and the darned thing was shooting 2770-2780 fps on my rig without a problem (5 rounds in a row, it managed to maintain those speeds!).

This feels like one of those moments in reloading where you maybe accidentally "hit" that perfect powder charge, or primer, and suddenly everything starts to get really tight and zeroed in. Problem is: its with a manufacturer's load, and I have no idea how to replicate it with my reloads! I have the exact same bullet as they use (Sierra Matchking 175 grain HPBTs), and I'm happy to use the exact same brass (you bet your butt I will once I've shot them all out!), but I have no idea of the powder composition to match this.

I was running my OAL to around 2.810 because of my maximum magazine length (this is an AR-10 gas gun if I didn't mention it before). I measured their OALs and they were running a tad shorter at 2.798-2.805 in the 18 rounds I tested. And the primary reason I was TRYING to run as long of an OAL as I can, is because when I put 44 grains of Varget in, I was getting serious pressure concerns. Even popped a primer, so I decided to back off. My results were as follows:
44.4 grains varget - Popped primer, obvious flattening of primers (with the classic black look of doom)
43.0 grains varget - Obvious flattening of primers, but no popped out primers
42.0 grains varget - shot the tightest groups I had, but I THINK are still slightly showing signs of pressure, with ONE random cartridge dropping a primer. Not sure if that's randomly the case being loose BEFORE hand, or if I'm STILL over-pressured?
41.0 grains varget - Groups opened up slightly, but no signs of pressure... though now I'm starting to second-guess myself, and I'm maybe not great at spotting the pressure beyond the VERY obvious "dropping primers" level.

I'm fairly new to precision reloading. I've reloaded plenty, but the precision part is new to me. I know it may be silly to some to "precision" chase with an AR-10 gas gun, but my wife and I love having things capable out to as close to 400m as we can get without "holding over", so I really wanted to pursue this if possible.

If anybody has any tips on figuring out what on earth these guys did to achieve these muzzle velocities, or perhaps maybe I'm overlooking huge parts of reloading that I'm just whiffing on? For example: I'm measuring cases before I reload: and making sure they're all under 2.005", but sometimes cases are quite a bit under that, and I don't do anything different: I just load em the same as long as they're under the recommended trim length. Then when I seat, I do it based on the magazine maximum length (I manually measured it with a caliper before I realized magpul had posted it somewhere haha). So I'm achieving consistent OAL (but good lord: with a gas gun, how on earth WOULD you even test the jam, or test the lands? I've only seen it done on bolt actions). I'm using the same, CCI large rifle primers, No 200. Most of my brass is my old once-fired Hornady brass. Does anybody see any major issues I need to focus on more, or perhaps have an insight as to the powders these guys use (or whatever they use to achieve these speeds?)? I'm hoping to find any way I can to run lower pressures, but with higher MV. Any help would be greatly appreciated

And I apologize if this ran on too long: I just didn't want to leave anything out if possible.

Additionally: I've added pictures. My previous posting of this topic seems to have vanished (the top right shows "0" messages for me... unsure why?). I realize now, looking carefully, that EVERY case is showing pressure signs, even the nexus arms ones. Still, I'm hoping that I can at least ACHIEVE the "relative" higher MV's as Nexus with my own reloads, if that makes sense (while lowering overall pressure to remove those obvious signs - yes I realize those are over-pressure, in some cases by quite a bit... I'm doing my best to learn here, and improve as I go). Note: Nexus picture is named appropriately. The loads 1-4 are DECREASING in pressure (load 1 was the 44.4 grains, down to 41 grains).

 

[XLR308]

Sure you can match the Nexus ammo, just run dangerous presure levels and tear up brass then your rifle and then yourself.
Load to what the rifle likes not what you want the ammo to do.
Just out of curiosity have you pitted your bolt face yet?

 

[ReaperME]

No sir, no pitting. And I fear you may have misunderstood my purpose (understandably so) with this post. My goal here is to A) recognize the high pressure and back off until I DON'T see any pressure signs, and B) ONCE that's achieved, try to figure out how on earth a manufacturer load had such high MVs, but with seemingly LESS pressure signs than my own loads.

I apologize if that wasn't clear originally. I am not trying to pretend those loads are correct pressures, and "Match" the 2700+ MV. I am trying to drop pressure to safe levels, and THEN figure out what on earth Nexus did that I didn't, that led to such better results. I hope that makes sense.

 

[PinesAndProjectiles]

First thing I would do is use brass with the same head stamp.

Different brass has different capacities and you’re going to be all over the map when it comes to velocity.

 

[XLR308]

Most manufacturer's are running a non canister grade of powder that and many of the 308win factory loadings are running high pressure anyways.
Could you post a pic of the nexus brass?
Nevermind saw you posted a pic of the nexus, if i ha to guess they are using a slighty faster powder that has a lower port pressure than varget when it passes gas block.

 

[ReaperME]

Copy that, understood. I had used Hornady for my own reloads, as far as I know from the same set of boxes, but I will double check to make sure I group them all together the best I can. the Nexus was a "control load" from a manufacturer, I hope I'm not misunderstanding and I apologize if I am.

 

[ReaperME]

Most manufacturer's are running a non canister grade of powder that and many of the 308win factory loadings are running high pressure anyways.
Could you post a pic of the nexus brass?

Yes, the nexus brass was the 5th picture.

 

[6.5SH]

The Nexus .308 175's were rated at 2730 fps out of a 24" barrel (130 fps faster than FGMM). There is no way you are going even faster than that safely out of a 16".
If you still have any of it pull one apart and weigh the projectile.
The 2450 fps range is realistic for a 175 and a 16" gas gun.
ETA:
link to the product page on the wayback machine since the company is no more:

Nexus Ammo

Nexus Ammo provides discerning shooters high impact solutions through unparalleled, patent-pending automation processes.

web.archive.org

 

[ReaperME]

Ok, I'm trying to keep up, I apologize in advance I've taken more pictures of the Nexus brass in case I was misunderstanding. Now I've just thrown everything in there I can
I do have a couple of unspent cartridges in there, I'll pull one apart and weigh it now.

 

[hlee]

Manufacturers are not limited to the canister powders that consumers can buy.

 

[ReaperME]

The Nexus .308 175's were rated at 2730 fps out of a 24" barrel (130 fps faster than FGMM). There is no way you are going even faster than that safely out of a 16".
If you still have any of it pull one apart and weigh the projectile.
The 2450 fps range is realistic for a 175 and a 16" gas gun.
ETA:
link to the product page on the wayback machine since the company is no more:

Nexus Ammo

Nexus Ammo provides discerning shooters high impact solutions through unparalleled, patent-pending automation processes.

web.archive.org

Alright, I measured the bullet: 175.2 grains
And I measured the powder (I lost 1-2 little pieces) And got 44.2 grains (of whatever powder they'd used).

And I forgot to mention I was running a can. Not sure if that matters in this context.

 

[6.5SH]

Alright, I measured the bullet: 175.2 grains
And I measured the powder (I lost 1-2 little pieces) And got 44.2 grains (of whatever powder they'd used).

And I forgot to mention I was running a can. Not sure if that matters in this context.

The can won't make that much of a difference.
What are you using for a chronograph and how do you set it up? Have you chronographed other rifles with factory ammo and seen what would be a much higher than expected velocity?

Not bagging on you, the numbers just don't line up with reality and you can put yourself in a very unsafe spot quickly.

 

[ReaperME]

The can won't make that much of a difference.
What are you using for a chronograph and how do you set it up? Have you chronographed other rifles with factory ammo and seen what would be a much higher than expected velocity?

Not bagging on you, the numbers just don't line up with reality and you can put yourself in a very unsafe spot quickly.

I appreciate the response I don't mind taking my licks when I earn it with rookie mistakes, but I do appreciate the kind words!

Its a caldwell ballistic precision blue-tooth enabled chrono. The classic (1st edition, I think they made a 2nd and maybe third since). I've used it with many, many rifles over the years, and I've never once seen a velocity OVER manufacturer's standards, which is part of what threw me off a bit. The wind was kicking quite a bit today, maybe 15-20 mph, but it was blowing INTO my shot, so I'm assuming that wouldn't affect the chronograph negatively like that.

Ballistic Precision Chronograph | Shooting Chronograph | Caldwell

Ballistic Precision Chronograph

www.caldwellshooting.com

The above link is the chrono I've been using. I set it up about 15 feet in front of my shot on its tripod. I read the numbers straight off the machine (I don't bother with the bluetooth... I've built a habit of just scribbling down everything in my little notepad).

And I definitely don't want to end up getting myself in an unsafe spot. I'm here, hopefully, to be able to get myself on the right track to making my loads better, as opposed to getting myself hurt.

 

[ReaperME]

And to add to that a bit: that's sort of what threw me off when I saw the numbers: my numbers were what I'd sort of read/expected for a 175 grain bullet out of 16", but the nexus went above the manufacturer's stated 2730mv, multiple times, consistently.

 

[ReaperME]

So what would the next step be in this process? Considering my "Load 4" picture in the original post was still showing signs of too much pressure, and that was at 41 grains (where the reloading manual indicates 40 is the base), should I back off before 40, and start even lower, and work my way back up until I see cratering begin again? Should I take the rifle to a smith, and have them check the throat, see if its "tight" or whatever it would be called? I'm trying to figure out a path to enlightenment here, so I can start chasing those SAFER high velocities (even if its only up to around 2450-2500, I still want to make sure I know how to carefully "figure that out" and then chase the optimal).

Should I change powders, and see if maybe AR comp is a little better for my rifle than the varget (I know rifles have their own "tastes" so I'm guessing it would be worth a shot)?

Any further insights would be amazing, thank you guys in advance!

 

[6.5SH]

With an optical lots of things can induce errors; unit not level, angle of the sun, too much or too little light, dust blowing, the precision of the sensors etc.

To give an anecdotal story a friend was having issues with blowing primers in his 77gr SMK/8208 XBR loads, he stated velocity while on the higher end was within normal. He setup his optical, I set up my LabRadar and had him fire a few series over both at the same time. His optical was consistently reading 75 fps low, his load was actually over-pressure and the chronograph was giving him a false sense of safety while the brass was telling a different story.

Little variances are normal, 200+ fps doesn't happen for free. The Nexus brass does have a pretty good gouge from the ejector but the primers on it look fine. I suspect that if you tried it with a MagnetoSpeed or LabRadar you'd see a velocity in the 2530-2570 range, which is still pretty spicy for a 175 out of a 16".

 

[ReaperME]

With an optical lots of things can induce errors; unit not level, angle of the sun, too much or too little light, dust blowing, the precision of the sensors etc.

To give an anecdotal story a friend was having issues with blowing primers in his 77gr SMK/8208 XBR loads, he stated velocity while on the higher end was within normal. He setup his optical, I set up my LabRadar and had him fire a few series over both at the same time. His optical was consistently reading 75 fps low, his load was actually over-pressure and the chronograph was giving him a false sense of safety while the brass was telling a different story.

Little variances are normal, 200+ fps doesn't happen for free. The Nexus brass does have a pretty good gouge from the ejector but the primers on it look fine. I suspect that if you tried it with a MagnetoSpeed or LabRadar you'd see a velocity in the 2530-2570 range, which is still pretty spicy for a 175 out of a 16".

Ok copy that, I appreciate it.

From what I've found in my recent searches about my specific rifle, the gas gun is fairly well known for "punching" with the ejector, and people have said I need to shave it down a bit, but I could screw it up if I try that (so I'll accept a little punch so long as its not a long term issue) so I'm avoiding changing that now.

So spicy is a good thing to me, but the dangerous levels of pressure that were in the other loads, I definitely don't want. Would you recommend pulling the powder back to 40, and trying again, or going even lower based on my brass damage on those first 4 loads?

 

[6.5SH]

So what would the next step be in this process? Considering my "Load 4" picture in the original post was still showing signs of too much pressure, and that was at 41 grains (where the reloading manual indicates 40 is the base), should I back off before 40, and start even lower, and work my way back up until I see cratering begin again? Should I take the rifle to a smith, and have them check the throat, see if its "tight" or whatever it would be called? I'm trying to figure out a path to enlightenment here, so I can start chasing those SAFER high velocities (even if its only up to around 2450-2500, I still want to make sure I know how to carefully "figure that out" and then chase the optimal).

Should I change powders, and see if maybe AR comp is a little better for my rifle than the varget (I know rifles have their own "tastes" so I'm guessing it would be worth a shot)?

Any further insights would be amazing, thank you guys in advance!

Perhaps listing the velocity you got with each charge weight then comparing it with what Hodgdon's online tool says for .308 Winchester Service Rifle will get you a better idea. Their data is for a 24" barrel, so reducing it 20-25 fps per inch will give you what you need to look for.

As @hlee mentioned manufacturers have access to powder reloaders do not.

 

[ReaperME]

Ok, I've pulled it up on the online tool, and it mentions that I should start at 42.0 grains, which would give a 2,583 fps velocity. With the ~22.5 fps loss per inch (at 8 inches), I should expect 2403 fps with my barrel, which sounds about right.

The problem now that I have, is that 42.0 grains of varget powder is what its calling for, but image number 3 in my original post is EXACTLY that, and image #4 in my original post is 41.0 grains of varget, with still signs of over-pressure (I believe - again I'm starting to second guess myself?).

Should I be going even lower? I'll list my velocities with my charge weights below:
44 grains (picture 1): 2614, 2642, 2688
43 grains (picture 2): 2585, 2618, 2603
42 grains (picture 3): 2548, 2532, 2573
41 grains (picture 4): 2486, 2494, 2490

EDIT: I'm stupid. I just read through my chart, and I'd mis-quoted the Nexus MV. 100% my fault, I apologize for the terrible information. I'll add the MVs I got (for real this time) that I got with it below. Ugh, I'm an idiot. At least that solves that problem for me.
Nexus with 44.2~ish grains (5th picture): 2700, 2693, 2709

And if you need any further data, please let me know: I'll give you what I have. Yes, I'm an idiot, but I'll try hard to make up for it

 

[6.5SH]

Ok, I've pulled it up on the online tool, and it mentions that I should start at 42.0 grains, which would give a 2,583 fps velocity. With the ~22.5 fps loss per inch (at 8 inches), I should expect 2403 fps with my barrel, which sounds about right.

The problem now that I have, is that 42.0 grains of varget powder is what its calling for, but image number 3 in my original post is EXACTLY that, and image #4 in my original post is 41.0 grains of varget, with still signs of over-pressure (I believe - again I'm starting to second guess myself?).

Should I be going even lower? I'll list my velocities with my charge weights below:
44 grains (picture 1): 2614, 2642, 2688
43 grains (picture 2): 2585, 2618, 2603
42 grains (picture 3): 2548, 2532, 2573
41 grains (picture 4): 2486, 2494, 2490

EDIT: I'm stupid. I just read through my chart, and I'd mis-quoted the Nexus MV. 100% my fault, I apologize for the terrible information. I'll add the MVs I got (for real this time) that I got with it below. Ugh, I'm an idiot. At least that solves that problem for me.
Nexus with 44.2~ish grains (5th picture): 2700, 2693, 2709

And if you need any further data, please let me know: I'll give you what I have. Yes, I'm an idiot, but I'll try hard to make up for it

I don't see a missing primer in your 42 grain picture 3 load. I do however see at least one different brand of brass.
The primers look normalish for a large frame AR, edges are still rounded, the little bit of cratering on some of the primers is normal with a non "HP" small firing ping bolt. Given you are using different brass and primers you will have some variance from Hodgdon's data, but not 200 fps worth.

The most accurate load is seldom the fastest one. I do doubt the accuracy of your chronograph during these sessions though. Outside the safety issues where you will quickly see the velocity is exaggerated is shooting at distance, the drop won't match any ballistic calculators predictions.
As an example @400 yards @2400 fps you'd need 2.6 mils (this is where the 42 grain load should be around). At the 2600 fps average you are showing it would be 2.1 Mils.

 

[ReaperME]

I don't see a missing primer in your 42 grain picture 3 load. I do however see at least one different brand of brass.
The primers look normalish for a large frame AR, edges are still rounded, the little bit of cratering on some of the primers is normal with a non "HP" small firing ping bolt. Given you are using different brass and primers you will have some variance from Hodgdon's data, but not 200 fps worth.

The most accurate load is seldom the fastest one. I do doubt the accuracy of your chronograph during these sessions though. Outside the safety issues where you will quickly see the velocity is exaggerated is shooting at distance, the drop won't match any ballistic calculators predictions.
As an example @400 yards @2400 fps you'd need 2.6 mils (this is where the 42 grain load should be around). At the 2600 fps average you are showing it would be 2.1 Mils.

Eesh, understood, and yea: that seems like a big issue if my chrono is lying to me. Any way to get that tested or re-calibrated, or does it mean I need to step it up and buy a more expensive/newer chronograph?

Alright, thank you for the opinion on the 42 grain pictures. I'll have to get myself better at spotting the difference between pressure indicators on gas guns/AR-10s, as I'm clearly not familiar enough on those. I appreciate the help greatly! I will stick to 42 grains, with the Hodgdon reloading tools recommendations, and I'll take the chrono out on a day that is less hot/sunny, and with less wind, and see if I can't get a little bit more accurate readings to fine tune the load. I really appreciate your help!

 

[ReaperME]

One last quick question for you: the recommended MV with the 42 grains... they recommend a federal 210M primer... I'm using CCI no 200. Could THAT difference somehow be adding quite a bit of FPS? Or am I simply hoping too hard that my chronograph is accurate going forward haha?

 

[6.5SH]

One last quick question for you: the recommended MV with the 42 grains... they recommend a federal 210M primer... I'm using CCI no 200. Could THAT difference somehow be adding quite a bit of FPS? Or am I simply hoping too hard that my chronograph is accurate going forward haha?

Primer choice can make a difference in velocity and accuracy but not that extreme. The extreme condition with the wrong primer choice will be with a magnum cartridge and a primer too weak to properly ignite that much powder.

 

[ReaperME]

Copy that, I greatly appreciate the assistance!

I will first install an adjustable gas block, fine tune that so I stop ejecting @2 o clock (as we'd discussed), and then I will report back. Appreciate all of the help! I will ensure that I use the exact same brass stamped cases on my future reloads as well.

 

[XLR308]

Eesh, understood, and yea: that seems like a big issue if my chrono is lying to me. Any way to get that tested or re-calibrated, or does it mean I need to step it up and buy a more expensive/newer chronograph?

Alright, thank you for the opinion on the 42 grain pictures. I'll have to get myself better at spotting the difference between pressure indicators on gas guns/AR-10s, as I'm clearly not familiar enough on those. I appreciate the help greatly! I will stick to 42 grains, with the Hodgdon reloading tools recommendations, and I'll take the chrono out on a day that is less hot/sunny, and with less wind, and see if I can't get a little bit more accurate readings to fine tune the load. I really appreciate your help!

My optical chrono has now been retired for archery and air rifle use only.
I have had it switch from fps to mps multiple times and go into error from the concusion from muzzle blast with shooters near me. It was irritating as hell.

 

[ReaperME]

My optical chrono has now been retired for archery and air rifle use only.
I have had it switch from fps to mps multiple times and go into error from the concusion from muzzle blast with shooters near me. It was irritating as hell.

Yea, when the guys I know are the best at what they do say "screw that tool", I don't use that tool, haha. I'm going to order myself a new one, and start using that for more accurate reloading.

I hugely appreciate all of the advice on this stuff, and hopefully I'll be able to turn this all into a positive learning experience, and come out better for it on the other side!

 

[XLR308]

Yea, when the guys I know are the best at what they do say "screw that tool", I don't use that tool, haha. I'm going to order myself a new one, and start using that for more accurate reloading.

I hugely appreciate all of the advice on this stuff, and hopefully I'll be able to turn this all into a positive learning experience, and come out better for it on the other side!

Dont take that the wong way i bought my optical chrono before the magneto speed or lab radar came out.
The hot shit back then was the Oehlor35 and i should hve bought one.

 

[ReaperME]

Fair enough, and no worries I won't take offense when people who know subject matters better than I do are willing to help me out. I make mistakes, I ask for assistance, you guys come in and help out - I'm always assuming good intentions Appreciate you guys a ton, and like I mentioned: I will report back when I get the gas block tuned properly, start using the same brass for each reload, and I'll hopefully have better results!