Sig 77gr OTM velocities

nine9drams

nine9drams

Private
Minuteman
Jan 14, 2020
22
3
#1
Shot on a very rainy range today and took out the Garmin chrono for the first time. On my 12.5 Criterion Core barrel shooting .223 Sig 77gr OTM the 5 shot average was 2153. I was pretty shocked at how low these velocities were considering the box states 2750.

I ran out of time but have several other loadings I need to gather data on next trip. I know the Garmin is good to go since it was spot on for all my 6.5 creed loads I tested earlier in the day.

Anyone else seeing really low velocity for the Sig OTM or with the Criterion 12.5? I was expecting much higher but will continue testing other loads. Will also try without the suppressor next time as well tho I don’t think it was an issue. Wasn’t on my 6.5.
 
#2
After doing some digging around here and other forums it looks like the Sig loading is very very slow. 2750 is measured from 24” barrel and while it is fairly accurate 2100fps is not acceptable. I have several other 77gr loads and it just happens that I only chrono’d the Sig stuff today. Thankfully I don’t have much of it and I’ll move to another load next trip.
 
#3
I shot some of the Sig 77 OTM years ago and I can't remember the specific velocities but in was in the neighborhood of low 2600's out of my 18" barrel. To be fair it is loaded to .223 Remington pressure so the velocities are going to be lower but it was pretty consistently accurate stuff though, just like Federal 77gr Gold Medal Match, slow but stupid accurate.

If you want speed you need 5.56 NATO pressures behind a 77 OTM.
 
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#4
Seems like Black Hills has been dropping more 77gr smk & tmk in the last 5 months than they did in the previous 5 years. Would look to that for a hotter 77gr.
 
#8
Off the top of my head I get 2475 with the 77gr. Berger over Tac with a 12.5” barrel which isn’t super fast so the Sig ammo is pretty weak. Hell I get higher velocities with 110gr pills out of a 9” barrel with my 300 Blackout rifle.
 
#9
It's a 12.5" barrel.... Losing 100+ fps per inch isn't uncommon. You don't gain much past 18-20", but you lose a ton under 16".


Don't know why you'd bother with 77s in a short barrel anyways. It's going to be a short range gun, BC doesn't matter much.
 
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#11
I'll add too, that you could just have two slow variables stacked with that gun.

I'm not familiar with that sig loading. I use smk and ttsx in 77 and 70 in all my AR's. My 10.5 was around 2200 with my 77 loading. My 20" is 2650-2700 with the same loading in 40°, it should be around 2750-2800 on the hottest days I'll shoot.

I'd say the sigs loading is on the median side of things. Then there's the possibility of a slower barrel. I would try another 77 loading. IMI or MagTech would be my choice. Black hills if you can find it and willing to pay the premium.

If you handload I'd recommend the Barnes TTSX 70 grain bullet and Sierra 77 smks. You can work up a faster load instead of hoping the company made a load perfect for your gun.
 
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