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Rimfire5 · August 23, 2020, 07:54 AM

I have only found one 55 grain bullet that really shoots accurately - the Berger #22410 Flat Base. Most of the other 55 grain bullets seem to be made with bulk bullet quality in mind.

I have a Savage 12 FV .223 and a CZ 527 Varmint .223.
Both have 1:9 twist barrels.
Both shoot 69 grain Sierra SMK and TMKs great.

I read on another site that someone had shot 77 grain SMKs in his Savage 1:9 and they shot great.
I was skeptical because all the stability calculators say they would be marginally stable.
But I tried the Sierra SMK 77 grain #9377 and they did shoot great.
Then I tried the Sierra TMK 77 grain #7177 and they shot just as well.

At 100 yards with bullets seated for a 0.020 jump (+/-0.005):
I have now shot 101 5-round groups with the 77 SMKs with IMR4166 and N140 powders and they have averaged 0.293.
I have shot 229 5-round groups with the 77 TMKs with the same two powders and averaged 0.280.

The 69 SMKs with the same two powders average 0.290 for 104 groups.
The 69 grain TMKs with the same powders average 0.287 for 199 groups.
The CZ averages 0.302 for the 77 grain bullets but for a much smaller sample.
The CZ is an older rifle with over 7,000 rounds through the barrel so I don't shoot it much anymore.

I cannot explain why these 77 grain bullets stabilize in two 1:9 twist barrels.
They both have high BCs (that ballistic stability calculators don't consider).
The SMKs are supposed to be more stable than the TMKs but the results don't show that.
I've had two shooting buddies with 1:9 twist rifles try the 77s and their results show that their rifles show no loss in accuracy over the 69 grain bullets.

August 23, 2020, 07:54 AM	#10
Rimfire5 Senior Member Join Date: January 2, 2009 Location: Northern Virginia Posts: 982	I have only found one 55 grain bullet that really shoots accurately - the Berger #22410 Flat Base. Most of the other 55 grain bullets seem to be made with bulk bullet quality in mind. I have a Savage 12 FV .223 and a CZ 527 Varmint .223. Both have 1:9 twist barrels. Both shoot 69 grain Sierra SMK and TMKs great. I read on another site that someone had shot 77 grain SMKs in his Savage 1:9 and they shot great. I was skeptical because all the stability calculators say they would be marginally stable. But I tried the Sierra SMK 77 grain #9377 and they did shoot great. Then I tried the Sierra TMK 77 grain #7177 and they shot just as well. At 100 yards with bullets seated for a 0.020 jump (+/-0.005): I have now shot 101 5-round groups with the 77 SMKs with IMR4166 and N140 powders and they have averaged 0.293. I have shot 229 5-round groups with the 77 TMKs with the same two powders and averaged 0.280. The 69 SMKs with the same two powders average 0.290 for 104 groups. The 69 grain TMKs with the same powders average 0.287 for 199 groups. The CZ averages 0.302 for the 77 grain bullets but for a much smaller sample. The CZ is an older rifle with over 7,000 rounds through the barrel so I don't shoot it much anymore. I cannot explain why these 77 grain bullets stabilize in two 1:9 twist barrels. They both have high BCs (that ballistic stability calculators don't consider). The SMKs are supposed to be more stable than the TMKs but the results don't show that. I've had two shooting buddies with 1:9 twist rifles try the 77s and their results show that their rifles show no loss in accuracy over the 69 grain bullets.