Anyone else seem to find the Sierra 77 gr TMK bc fall short from claimed?

[B Man]

I tried to switch again not long ago to the TMK just to feel more comfortable about expansion at extended ranges from my SMK’s (haven’t had an issue yet with opening tips). But after finding a good load i ran them awhile back and notice hits needed more elevation than called for using the listed bc. I remember one other person saying this and listed he found a g7 of .192 worked best for him. Plugged that in and immediate center hits to 800 yards. Here is the thing, my SMK’s use .190 with solid repeatable precision shots worst 1.2 moa groups at 850 yards. So in my mind the tmk shoots less accurate in all my rifles by about .25 moa+ rifle dependent and basically they copy the SMK’s dope. I’m pretty sure I’ve about decided I’ll be moving back to the 77 SMK.

Anyone else experience this.

 

[45custom]

Litz's tested G7 BC for 77 gr TMK is about 0.202 as I recall.

Quick question: Are you using a 1:8 barrel twist? 77 gr TMK will shoot out of 1:8s but starts out right at the edge of optimal stability (if not below altogether, depending on climate) out the muzzle and that story only gets worse as the velocity drops.

 

[B Man]

Litz's tested G7 BC for 77 gr TMK is about 0.202 as I recall.

Quick question: Are you using a 1:8 barrel twist? 77 gr TMK will shoot out of 1:8s but starts out right at the edge of optimal stability (if not below altogether, depending on climate) out the muzzle and that story only gets worse as the velocity drops.

1:7 20”

 

[BCP]

I tried to switch again not long ago to the TMK just to feel more comfortable about expansion at extended ranges from my SMK’s (haven’t had an issue yet with opening tips). But after finding a good load i ran them awhile back and notice hits needed more elevation than called for using the listed bc. I remember one other person saying this and listed he found a g7 of .192 worked best for him. Plugged that in and immediate center hits to 800 yards. Here is the thing, my SMK’s use .190 with solid repeatable precision shots worst 1.2 moa groups at 850 yards. So in my mind the tmk shoots less accurate in all my rifles by about .25 moa+ rifle dependent and basically they copy the SMK’s dope. I’m pretty sure I’ve about decided I’ll be moving back to the 77 SMK.

Anyone else experience this.

Isn't the tipped match king is just the match king with a polymer tip? And they say it's not a barrier/hunting round. So can't imagine it being much different than a SMK.

 

[45custom]

1:7 20”

That would certainly eliminate the most obvious cause of the BC discrepancy. The other possible explanation I can think of is bullet deformation induced by feeding. To test that out, you can try manually ejecting a round after cycling - look for any tip deformation that might compromise ballistic performance. The bullet will almost certainly also have marks on the jacket, but that can also come from ejection so it's hard to independently isolate.

Isn't the tipped match king is just the match king with a polymer tip? And they say it's not a barrier/hunting round. So can't imagine it being much different than a SMK.

That polymer tip can logically only disguise a massive hollow point in the nose underneath, and that's exactly what it does.

The TMK expands almost immediately upon impact, down to velocities of <1600 FPS. The SMK usually doesn't expand at all and only tumbles and fragments down to velocities of about ~2100 FPS. Jacket on the 77 gr TMK may also be a bit thinner than on the 77 gr SMK.

Sierra can say whatever they like about what the bullet is 'intended' for, it doesn't change what it actually does (or what it actually was intended for, for that matter - claiming a bullet wasn't made to expand is one way to dodge Hague-related prohibitions overseas). As it happens in practice, the 77 gr TMK appears to be a superb hunting bullet, though barrier performance is not the best.

 

[Tictacticaltimmy]

Let me ask you this: you went to the TMK over the SMK because of its greater fragmentation range. You are finding that it gives no exernal ballistic advantage over the SMK, but actually pretty much duplicates its trajectory. Why switch back to the SMK then? It sounds like you can use either bullet interchangeably with the same zero and dope. That might even be better than having a slightly flatter trajectory but having to learn new dope. This way you can use SMK's for practice and TMK's in the field. Further, I would think more reliable and longer range fragmentation is a great trade off for .25moa bigger groups.

 

[B Man]

Let me ask you this: you went to the TMK over the SMK because of its greater fragmentation range. You are finding that it gives no exernal ballistic advantage over the SMK, but actually pretty much duplicates its trajectory. Why switch back to the SMK then? It sounds like you can use either bullet interchangeably with the same zero and dope. That might even be better than having a slightly flatter trajectory but having to learn new dope. This way you can use SMK's for practice and TMK's in the field. Further, I would think more reliable and longer range fragmentation is a great trade off for .25moa bigger groups.

Only one rifle groups them within .25 Moa of my SMK’s which is my main 223 rifle so I can agree to your point there. My others are much over more like .75 Moa larger groups.

 

[ma smith]

Smk has a genius design that transition well into transonic...so net/net they are kind of a wash. Problem with both is low signature/splash and wind buffeting, at 800 only really usable n extremely calm and/or otherwise predictable conditions.

TMK is pointy, but TMK gets squirrely in transonic, so the BC difference is over-hyped if talking about "long range" etc. For true long range use...IMHO you need 80-90gr bullets.

 

[dskoruppa]

I just shot some 77 tmk today out of a 24" 1:10 twist. Had to lower the bc to .193

 

[B Man]

I just shot some 77 tmk today out of a 24" 1:10 twist. Had to lower the bc to .193

Which basically mirrors what I found. Thank you

 

[JR1200W3]

What Chrono are you using?

Are you dialing data? What scope?

What ranges have you zeroed or confirmed?

Trying to true BCs by just shooting targets is dodgy.

 

[BurtG]

Isn't the tipped match king is just the match king with a polymer tip? And they say it's not a barrier/hunting round. So can't imagine it being much different than a SMK.

It is worlds different. Most deadly 556 I’ve used. And I’ve shot a few things

 

[DeaconBlue]

I personally have never gotten the 77gr TMK to shoot as accurately as the SMK using only TAC. However I’m about to rebarrel an upper with a SOLGW 18” SPR barrel and am going to go through load development again with the SMK and TMK and this barrel to see how much accuracy can be rung out with this setup.

 

[BurtG]

I personally have never gotten the 77gr TMK to shoot as accurately as the SMK using only TAC. However I’m about to rebarrel an upper with a SOLGW 18” SPR barrel and am going to go through load development again with the SMK and TMK and this barrel to see how much accuracy can be rung out with this setup.

Douglas have shot tmk lights out for me. Bh mk262 tmk and stand1 tmk

 

[matt33]

I'm far from an authority on long range shooting, but I stopped using BC quite a while ago. Applied Ballistics and Hornady 4DOF have impressive libraries filled with custom drag curves for most of the popular bullets. I have found these to work better than ballistic coefficient.

 

[RTH1800]

That would certainly eliminate the most obvious cause of the BC discrepancy. The other possible explanation I can think of is bullet deformation induced by feeding. To test that out, you can try manually ejecting a round after cycling - look for any tip deformation that might compromise ballistic performance. The bullet will almost certainly also have marks on the jacket, but that can also come from ejection so it's hard to independently isolate.


That polymer tip can logically only disguise a massive hollow point in the nose underneath, and that's exactly what it does.

The TMK expands almost immediately upon impact, down to velocities of <1600 FPS. The SMK usually doesn't expand at all and only tumbles and fragments down to velocities of about ~2100 FPS. Jacket on the 77 gr TMK may also be a bit thinner than on the 77 gr SMK.

Sierra can say whatever they like about what the bullet is 'intended' for, it doesn't change what it actually does (or what it actually was intended for, for that matter - claiming a bullet wasn't made to expand is one way to dodge Hague-related prohibitions overseas). As it happens in practice, the 77 gr TMK appears to be a superb hunting bullet, though barrier performance is not the best.

Your statements regarding the SMK not expanding, and they they tumble and fragment is 100 % contrary to what I see on hundreds of kills over the last 25 years . I see uniform expansion and zero tumbling. Perhaps your critters are built differently?

 

[BurtG]

Your statements regarding the SMK not expanding, and they they tumble and fragment is 100 % contrary to what I see on hundreds of kills over the last 25 years . I see uniform expansion and zero tumbling. Perhaps your critters are built differently?

SMK is 100% trash compared to TMK as far as killing things. Zero comparison. Hell 50-60 Vmax or eld is better than smk.

 

[RTH1800]

Neither I nor the many hundreds of critters I shoot with them agree. I find them uniformly excellent. No idea what the difference could be.

 

[DeaconBlue]

Douglas have shot tmk lights out for me. Bh mk262 tmk and stand1 tmk

I shoot mostly CHF/CL and am eager to run these through a quality stainless barrel.

 

[padom]

Neither I nor the many hundreds of critters I shoot with them agree. I find them uniformly excellent. No idea what the difference could be.

I don't shoot critters.. but I did some backyard expansion testing in wet phone books with denim layed across the front of the first book..

77 SMK @ 2785 out of 20" 1-7 AR didnt expand at all, stayed fully intact and bent in the shape of a banana..

77 TMK same everything expanded nasty like a 124GR Federsl HST pistol round

I also tested this with 125 SMK and 125 TMK 300blk supers and found same results. SMK again stayed intact and bent slightly


I also tested the 224 60gr TMK and same results..

This is by no means claiming of a perfect expansion test but that's my results from testing SMK vs TMK

 

[BurtG]

^ have you tested the eld m or the new vt bullets

 

[padom]

Yea the Amax stuff literally just explodes. Haven't tested ELD

 

[Supersubes]

^ have you tested the eld m or the new vt bullets

Ive shot a few small critters with the 6.5mm 100gr VT at 2600-ish impact velocities. Devastating. Very accurate too. I use them in short barreled guns.

 

[CaptArab]

The 100vt makes me reconsider even owning my 6mm and 473 22 cal stuff.

I could done everything I need with the 223, 6.5, and 9mm.