I recently picked up a Geissele MRGG 20” 6.5cm. I have loaded for bolt guns for years but no gas gun experience. I’m going with Berger 130gr hybrids for bullets. I have Laupa srp and lrp brass, cci and federal primmers, and a ton of H4350 (not stuck on this powder just have a good amount). Anyone have starting points or tips for gas guns? Thanks in advance.
Hi Jwest,
I did some digging on other reloading forums to get a sense of what people are reporting with 6.5 CM in large-frame gas guns.
What I’m seeing most often is that gas guns tend to be more sensitive to bolt timing and extraction than bolt guns, and people prioritize smooth function and brass life over chasing top velocity. https://www.longrangehunting.com/threads/6-5-creedmoor-brass-ar10.328718/page-2
On H4350 specifically, the feedback looks mixed. Some shooters say they’ve had good accuracy with H4350 and 130-class Berger Hybrids in AR10-style rifles, while others caution that H4350 can keep port pressure higher and may contribute to early/rough extraction if the rifle is over-gassed or not tuned—those folks often suggest looking at slightly faster powders if you see extraction/brass issues. Anyone shooting Berger 130 AR Hybrids with IMR 4451 and H4350 powder in a gas gun? | Sniper's Hide Forum
For the Berger 130 Hybrids, a recurring note is that magazine length tends to be the limiting factor in gas guns (so seating depth options can be narrower than a bolt gun), and some people like the 130 Hybrid style for working well within mag constraints. Experiences with 6.5 Creedmoor in a gas gun | Sniper's Hide Forum
Since you have both Lapua SRP and LRP brass, I also saw multiple threads describing SRP brass as holding pockets tight longer, but with potential tradeoffs (including some mention of ignition considerations in extreme cold), and several people recommend treating SRP vs LRP as different “loads” rather than assuming data transfers 1:1. Lapua 6.5cm small rifle primer brass | Sniper's Hide Forum
If it were me, I’d start with published data for that bullet weight class/powder and work up slowly while watching gas-gun-specific indicators (ejector swipes/extractor marks/case head smearing and ejection pattern), and be ready to tune gas/buffer if the rifle is hard on brass. https://forum.accurateshooter.com/threads/6-5cm-ar-loading-questions.4003606
I have a AR10 6.5 18” bbl. I shoot supressed. My current load for pigs and varmits
H4350 43.5g 129 Hornady Sst. I am using Hornady once fired brass for this gun. F210m primer
2682fps 5 shot ES 17.8 SD 7
I found superformance powder faster, but way too gassy.
I will try bergers 130 next
Thank yall. Appreciate the info.