Anyone have first hand experience if one is more accurate then the other?

Most precision guns I see are DI so I'm assuming it's more accurate but I'd rather not just assume.

Di!
Let the shit storm begin!

You're probably not going to be able to see a practical difference accuracy wise. Technically the DI should be more accurate due to less movement but again, you probably won't be able to tell a difference in the real world. My PWS is no less accurate than my DI gun. both are 1 moa in normal shooting and sub moa when I slow down and focus. What it's going to come down to is whether you shoot primarily suppressed and/or how much you want to clean.

Years ago, I conducted a direct comparison of a DI operated AR-15 and a piston operated AR-15, using the same Colt 16” 6920 barrel.

A.R.M.S. SIR with Ares GSR-35.












100 Yard Accuracy Comparison

Prior to installing the Ares GSR-35 unit on the 16” M4 barreled upper with the ARMS SIR free-float rail, I tested the accuracy of that upper in its direct impingement configuration from a bench-rest at 100 yards. Using hand-loaded 52 grain Sierra MatchKings, three 10-shot groups were obtained which had extreme spreads of: 1.59”, 1.55” and 1.73” for a 10-shot group average extreme spread of 1.62". While not the most accurate barrel I own, it’s still perfectly suitable for “government work.”

The three 10-shot groups were over-layed on each other using the RSI Shooting Lab software program to obtain a 30-round composite group. The mean radius of the composite group was 0.54”.

After the upper was converted to the GSR-35 piston system, accuracy testing continued in the same manner as above. Three 10-shot groups were obtained using the same load of 52 grain Sierra MatchKings. Those groups had extreme spreads of: 1.77”, 2.54” and 1.85” for an average 10-shot group extreme spread of 2.05". The mean radius of the 30-round composite group created from those three groups was 0.69”. This demonstrates a decrease in accuracy of approximately 0.45 MOA for the ARES system.







On the outside chance that the increase in group size was caused by the Ares configuration simply “not liking” the 52 grain MatckKing load, I fired an additional three 10-shot groups using a hand-load of 55 grain V-MAX bullets charged with a different powder. Those groups had extreme spreads of 2.65”, 2.14” and 1.78” for an average 10-shot group extreme spread of 2.19" with a 30-round composite mean radius of 0.72”.

I had pretty much the exact same results until I backed my powder charge down one full grain. It seemed to reduce pressure and maintain the same velocity with my AA system. But accuracy was not any better than the the DI system. The only thing I liked better is my cases are cleaner with the GP system and it seems case life is a bit longer due to extended dwell time. I’m using a Les Baer barrel with Adams Arms gp in 6.5 Grendel.

What in the late 2000s is going on here?

DI.

Having said that …. the external piston HK MR762A1 is a remarkably accurate rifle.

Either piston or DI is fine for accuracy.  There are extremely accurate examples for both.

I remember this.   The difference might also be due to the fact that, that particular AR wasn't designed for use with a piston.  Maybe a more accurate test would involve an AR that was designed as a piston gun vs an aftermarket modification.

This. My MR762 shoots better than me.

DI will be inherently be more accurate than piston … less harmonics … less moving parts …

Both my Robinson XCR and DI precision ARs (all the preceding in 5.56) get the same groups using handloads: .75" at 100 yards. There's a lot more to accuracy than the operating system.

It's not going to be an accurate test unless you can use the exact same barrel for the piston and DI portions of the test.

.....

Common lore being what it is, I just got a brand spanking new LMT 14.5" piston barrel and with Black hills MK262, it shot 1.92MOA in their 100yd shooting tube.

Not exactly impressed for the price