Lazy's 20" PSA test results with 90, 95, 123, 129 gr bullets with various powders

[lazyengineer]

Had a busy weekend. Fired 200 rounds on Saturday. My experience was good, with excellent reliability and pleasant performance. But to date, I don't find it as easy or forgiving in the accuracy department as 5.56 or 6.5 Creedmoor. It's very easy to get up into the 3 MOA or even much worse with this round. So, I loaded up about 200 rounds of a whole bunch of different test loads, to try out and see what it can do.


Test rifle:
20" PSA Stainless Steel free floated upper. While many besmirch PSA, in my experience with 5.56 and 6.5 Creedmoor (which will be the same BBL blank as 6.5 Grendel); they actually can shoot quite good accuracy. Dropped it onto a classic M4 style lower with H-Buffer and a 2-stage LaRue trigger.



Magazines: ELander 17's and 10 rounders. both magazines cycled 100%, though when full, they were sometimes a bit tight to insert into the mag-well.

Lower: basic Anderson lower with LaRue 2-stage trigger, H-buffer, and Magpul CTR stock, with an A2 pistol grip (my personal favorite, actually).

Optics: Meopta 4X scope.

Test firing: Bench with sandbags, along with a LabRadar for velocity data capture.

Targets: M16A1 25-meter sight in targets, all placed at 200 yards distance.

Conditions: Hot and lovely - 90's plus, some wind but not a lot.

Protocol: Fired from a sandbag at a rate of when on target well, and the LabRadar reset for the next shot. There was no cooling, except when went to change targets. Firing took place over 3 hours of range time, so barrel got hot, but not stupid-hot.


Loads tested, and results.
Powders:
MP530 (CFE223 bulk);
ARComp;
LT32;
8208;
Ramshot TAC


Bullets:
90 TNT,
Hornady 95,
Nosler 123 hpbt,
Hornady 129 SST,
Hornady 129 interbond lead-tip

Brass:
Mostly Hornady 1X
Some 7.62x39 resized to 6.5x39 for Grendel.



Wolf Steel: ~>2 MOA average; 2681 FPS (not bad - the gun does quite well with Wolf Steel, in my opinion)
Federal Gold Medal 130 gr: 2.1 MOA; 2341 fps (frankly, I've never been able to make this round shoot well in any of 3 Grendel's I've tried it in).
....


Actually, I have about 40 targets worth of results, this is going to take a bit to compile, so I'll finish this tomorrow, and we'll call this the "Test Methodology" Post, with Test Results post to come out tomorrow. The short of it is, there were a few winners, a lot of "meh", and some real losers.

Here's the brass:



Failures: Two failures, both ammunition related. One was a 129 gr round that apparently was so long it engaged the rifling and prevented the bolt from closing, and the other was a round where the mouth had gotten caved in by a mandrel die that I thought might still fit (wasn't going to count that round regardless, by the way); but it didn't fit after all. Neither was the guns fault. I'm actually rather impressed with the PSA 20" upper. It even reliably cycled a mag full of 7.62x39 resized to Grendel brass.

[BluntForceTrauma]

Looking forward to this data!

[lazyengineer]

Here is the data.


One's in green are the spec I intend to use going foward with those particular components.

Overall, best bullet in my Grendel is the 90 TNT, where I can get 1 MOA with multiple powders. The 95 gr VMAX with 8208 surprised me, with warm 8208 loads all over the place and just horrible performance. Nominal performance on average was in the 2 MOA range (ish), if you were to just grab something and go.

LT-32 seems a pretty good powder for accuracy, and did well with both the TNT 90 and VMAX. Only problem there is it's a bit on the fast side, so a poor choice for heavier bullets, and even with these, doesn't give one the fastest of velocity before you hit max.

Regarding the TNT 90's. Federal is claiming 3000 FPS. I can't get that, and my best velocity at max loads is about 150 fps slower. Best accuracy node appears a touch slower then that even, and my spec load of 31 gr 8208 only gives me 2814 FPS, but good performance. A fairly consistent trend with the 90's with all powders tested, is that once I get up to max load, accuracy suffers some.

Oh, and with 7.62X39 brass show about on par with regular brass, giving me 2.5 MOA groups, with that 123 Nosler CC bullet, that I just can't get to shoot. The particular load is likely on the hot side, as velocity seems a little high for a 20". But that said, the thicker 7.62X39 brass doesn't really appear to have much impact on velocity, and is in line with what you would expect based on 65G-50 and -51. I'm fine with 7.62X39 brass in the Grendel, and intend to keep picking those up and loading them; though of course with their own load.

[LRRPF52]

Are you double-seating for concentricity during bullet-seating step?

Stroke the ram halfway with the projectile into the neck, then rotate the cartridge, and final stroke.

It's a proven and repeatable technique for reducing runout.

I would also break the upper down and do an accuracy checklist build with it.

[lazyengineer]

Are you double-seating for concentricity during bullet-seating step?

Stroke the ram halfway with the projectile into the neck, then rotate the cartridge, and final stroke.

It's a proven and repeatable technique for reducing runout.

I would also break the upper down and do an accuracy checklist build with it.

Thanks for the quick reply. When I run single stage, I indeed do the double seat; but these were run on the progressive. In my experience run-out generally isn't a factor in anything that's in the 1 MOA or greater range already, and in this case, the performance of some duplicate loads to prior single stage loads, was the same as before.

I don't know what the accuracy checklist is, is there a link to a thread with that?

[grayfox]

Lz, your pic doesn't seem to expand so I can't read any of the data.
The little green hi-liter lines look cute though!

[grayfox]

Just looked back thru my notes on the Fed 90's, and my 20" runs them at 2890 at about 1"/100, and my 16 at 2800, again about 1". The 20" is 200 below the Federal posted speed. When I load them myself (H335) I find accuracy at about 2800 in the 20".

[lazyengineer]

Lz, your pic doesn't seem to expand so I can't read any of the data.
The little green hi-liter lines look cute though!

Yea sorry about that. Easiest trick is to hold down your CTRL button and Scroll you mouse, which will zoom your screen. Still a bit fuzzy, not sure what happened, but that will work until I get another screen shot and post it again.

on an aside - bummer: tinyPic has served me well for 20 years, but is closing this year, so looks like I'll need to figure out another image hosting option soon.

[grayfox]

If you can find it, Paint shop Pro v.6 (another oldie)... resizing of pix works like a champ in it. plus you can crop out that right-side of the screen shot.

[Rosecrans1]

On my 20" PSA upper bought in February of this year, the 123gr Nosler Custom Competition HPBT's were all over the place. So were the 123gr Hornaday SST and 129 SP Interlocks. HOWEVER.................after 250+ shots fired of factory Blacks, reloaded ELD-M, Gold Dots and Lapua Scenars, I revisited the Nosler and Hornaday reloads and they were on target and could easily be dialed into sub-MOA in my upper.
I don't know how many rounds you have in your PSA upper but the point of my post is to revisit some of these loads you posted if you are under 250-300 rounds fired. You may be surprised.
And in turn, I'm going to look at some of the 90gr loads I did with Machkings that were horrible early on in my barrel break in. My PSA is very accurate but I was convinced I had a dud the first 6 weeks I owned it.

[lazyengineer]

On my 20" PSA upper bought in February of this year, the 123gr Nosler Custom Competition HPBT's were all over the place. So were the 123gr Hornaday SST and 129 SP Interlocks. HOWEVER.................after 250+ shots fired of factory Blacks, reloaded ELD-M, Gold Dots and Lapua Scenars, I revisited the Nosler and Hornaday reloads and they were on target and could easily be dialed into sub-MOA in my upper.
I don't know how many rounds you have in your PSA upper but the point of my post is to revisit some of these loads you posted if you are under 250-300 rounds fired. You may be surprised.
And in turn, I'm going to look at some of the 90gr loads I did with Machkings that were horrible early on in my barrel break in. My PSA is very accurate but I was convinced I had a dud the first 6 weeks I owned it.

r
You know, I wondered about that. My rifle started with about 51 rounds on it, and finished at about 260, by my count. And I couldn't help but wonder if it was getting more accurate as the day went by. Some of the later strings with Nosler 123's still seemed spotty, but... yea, I'm going to revisit that.