Will 77 grain bullets stabilize in a 1:9 twist barrel?

[TommyD11730]

Having read this thread I thought I too would try 77 TMKS in my 12fv.
For reference my pet load is 69SMKs at 24.6 grains of Varget. Consieved accidentally as they turned out a COAL 2.237 VS the 2.298 I had intended. They shoot very well. Less then .5moa at 100 and under 1 moa at 200.

So today I gave the 77 TMKS a try. With ten thousands jump the COAL is 2.385. Powder was 21.8 and 22.0 varget.

Accuracy at 100 yards was good. Matching my 69s. With only a few rounds left I tried the 77s with 21.8g varget a try. Oh boy, they sank like rocks and the group really opened up.

So I'll load some up at 22.5 next time out.

How did everyone else do when moving out past 100 yards?

[hamiltonkiler]

Having read this thread I thought I too would try 77 TMKS in my 12fv.
For reference my pet load is 69SMKs at 24.6 grains of Varget. Consieved accidentally as they turned out a COAL 2.237 VS the 2.298 I had intended. They shoot very well. Less then .5moa at 100 and under 1 moa at 200.

So today I gave the 77 TMKS a try. With ten thousands jump the COAL is 2.385. Powder was 21.8 and 22.0 varget.

Accuracy at 100 yards was good. Matching my 69s. With only a few rounds left I tried the 77s with 21.8g varget a try. Oh boy, they sank like rocks and the group really opened up.

So I'll load some up at 22.5 next time out.

How did everyone else do when moving out past 100 yards?

I don’t reload. I shoot a standard mk262 mod 1 load. They are still .5moa at 500yds with no wind. 2.5-3” groups all day. Ringing 10” plates at 700yds.


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[charlie b]

FWIW, the above loads were 23.5gn Varget with 77smk in my 22" Axis heavy barrel running 2800fps.

[TommyD11730]

FWIW, the above loads were 23.5gn Varget with 77smk in my 22" Axis heavy barrel running 2800fps.

At a COAL of 2.28?

Looks like I have plenty of headroom in terms of my powder charge.

Thank you sir.

[CFJunkie]

with my 12 FV .223, my best loads are seated at 2.296 to 2.305 C.O.A..L. with the 77 SMKs.
For the 77 TMKs my best loads are seated at 2.339 to 2.342 C.O.A.L.

But my chamber has over 3,000 rounds down the tube.

[charlie b]

At a COAL of 2.28?

Looks like I have plenty of headroom in terms of my powder charge.

Thank you sir.

Yes, at 2.28" oal. That used to be about .020 off the lands, but, that was measured about 1500 rounds ago. :)

[TommyD11730]

FWIW, the above loads were 23.5gn Varget with 77smk in my 22" Axis heavy barrel running 2800fps.

Welp loaded up 20 or so rounds to try out. @ a COAL of 2.285 and 23.5g of Varget quick load says this is nearly @ PMax. A little hotter then I normally like but the velocity is very close to a 69G SMK I nearly shoot.
So, tomorrow Ill send 20 @ that recipe. Think Ill fire them last in case it pops a primer. =)

Also have a new scope to try. Purchased a Athlon Argos. Not as nice as my Midas but should be better then my 15YO Bushnell that was on it.

Have a wonderful Thanksgiving guys!

[CFJunkie]

TommyD,

Seating your bullets out beyond SAAMI recommended O.A.L. is primarily a means of achieving a desired jump to the rifling on your specific barrel.
If you have measured your chamber and know where the rifling is in your specific barrel for the 77 SMK bullet, you should already know the specific O.A.L. to that will achieve the desired jump you are aiming for that bullet.
I assume that you did that and aren't just using someone else's data.
I also assume that you also know that the desired O.A.L. will be different for each bullet type and brand, since the position of ogive changes with bullet weight and design parameters.

As both charlie b and I have noted, that desired O.A.L. will change as the rifling erodes with use.
My rifle actually changed 0.036 with 3,000 rounds of wear, so my seating depths to maintain the jump I desired have grown from what they were when the barrel was new.

Just so you know, every 0.002 you increase your O.A.L. reduces your velocity by 1 about fps with a .223 or 5.56x45 cartridge.
It also lowers the pressure as well by a smidgen. That little bit of change won't make enough difference to reduce the impact of loads near Pmax, but sometime a bigger change may help. QuickLOAD will help you figure that out.
But I would suspect that you already know that if you are using QuickLOAD and are observent to the impacts of changes in seating depth and trim length.

[TommyD11730]

Yes Sir, I used the Lock and load to find the ogive. That being said when I accidentally created a load with more jump 2.23 vs 2.29 I thought I would also try the TMKS "short" as well. Mostly to see if increased jump did help along with the increased velocity of the shorter round.
Thanks for your reply, and as always your information.

[TommyD11730]

What's the old saying about a bad day at the range vs a good day at home. :)
The weather here was truly a gift, very warm and dead calm.
I fought my rifle pretty much all day. More so the scope. Now I know the Athlon Argos is hardly a high end scope. However I had a lot of trouble keeping a clear target picture at 200 yards. Even turning the mag down to 24 or so power it just looked blurry to me.
Anyway enough about that. The 77 TMKS I loaded were ok... Just ok at 200. The COAL of 2.285 is well short of the 2.385 I fired the week before. So while the new rounds had much less drop (23.5 vs 22) the groupings were less tight.
So, I'll go back to my original COAL and keep the charge at 23.5 for next week.
My 69SMKS did ok, considering the scope issues.
Hope everyone enjoyed their Thanksgiving!