Why the 69 gr SMK when we have the 53gr VMax?

[helotaxi]

It's too slow for that weight bullet. Doesn't reach max pressure though it does sustain the reduced pressure well. Just a bit faster powder like X-Terminator/AA230 in a ball powder or Benchmark or IMR 8208XBR would yield better velocity and the latter two are known for producing excellent accuracy. I've heard of people getting excellent results with CFE 223 and it produces the highest velocity in Hodgdon's data as well.

 

[Waywatcher]

[Tac is] too slow for that weight bullet. Doesn't reach max pressure though it does sustain the reduced pressure well. Just a bit faster powder like X-Terminator/AA230 in a ball powder or Benchmark or IMR 8208XBR would yield better velocity and the latter two are known for producing excellent accuracy

I'm not sure this is the whole story, helotaxi. I have used both Benchmark and Tac over a chronograph, on the same day from the same gun with the same bullet, same primer, same case and even the same charge weight (of 25.0 grains.) Benchmark, at least the lot that I have, grouped badly at 25.0 grains and had close to the same average velocity as Tac; which grouped much, much better. (From my DPMS Bull 20 with 55 grain NBTs.)

25.0 grains of Tac gave me an avg. of ~3000fps with a 2% extreme spread.

25.0 grains of Benchmark gave me an avg. of ~3070fps with a 3% extreme spread. I was getting consistent flyers as well which blew the groups to about 2".

25.0 is close to max for Benchmark, and close to the middle-of-the-road for Tac, when consulting multiple sources of data. I had very good luck with 25.5 grains of Tac which gave me about 3050fps, a 2% ES, and nice consistent groups. Also burns just a touch cleaner.

 

[helotaxi]

Hodgdon's has published loads for a 55gn bullet with 25.6gn of Benchmark...and we're talking about a 53gn bullet with Hodgdon's published max of 26.0 and several published sources listing accuracy loads @ 25.7gn.

TAC is a good powder but I've not personally had great accuracy results with it. It is on the slow side for a light bullet in a .223. I have had good results with Benchmark and it was one of the powders I tried with the 53gn VMax. I got better results with 8208, however.

 

[Waywatcher]

Right, Hodgdon's max is 25.6. Hornady's is 24.5, Nosler's is 25.0, and Sierra's is 25.2. Averaged out, it's about 25.1.

But my real point was that it isn't really all that faster burning for practical purposes. Either way, within the pressure envelope, both get the bullet going about the same speed. I have had better results with Tac lately, especially in getting the velocity I want out of a 55 grain bullet.

 

[35 Whelen]

I have been trying to figure out a "long" range bullet solution that will let me at least hang in the dust of my buddy and his Savage 308 rig-done-right. I have a 20" bbl with a 1in9" twist in 223 and I had my heart set on a 75gr pil but it seems that they will likely be right outside of the optimal range of twist for my rifle. I started to look at the 69gr SMKs and was very surprised to see the drop table out to 1k yds. My 53 gr V-Max going 3300 fps beat the SMKs flyin @2900fps in spades. Why would anyone shoot the 69 gr SMK? Am I missing something?

Also, as a side note, I would love to hear any suggestions for bullets that my 1in9 rifle might like out past 500 yds.

First of all, don't let the Greenhill Formula (barrel twist calculation) or internet common knowledge determine what will or will not stabilize in your rifle.
Whether or not a bullet will stabilize has less to do with its weight and much more to do with its length.I have an old Rem. 788 .223 with a 1-14" twist that according to common knowledge shouldn't stabilize any bullet with a length much over that of most 55 gr. bullets. Last week I tried some 60 gr. Hornady SP's and not only did they stabilize, at 3023 fps MV, I got 5-shot groups of a hair over 1" @ 100 yds.

I'm sort of in the same boat as you in that I recently built an AR twhose barrel has a 1-9" twist. I am shooting High Power with it and want to shoot out to 600 yds. The guys with whom I shoot tell me sometimes a 1-9" will stabilize a 75 gr bullet, so I intend to try some Hornady 75 gr. HP's as I think they're about the shortest 75 gr. bullet available. You might want to at least try some of these as well.
Have you considered the Hornady 68 gr. BTHP? It's B.C. is .355 which a bit better than the 53 gr. A-Max.

Good luck in your quest!
35W

 

[helotaxi]

My 1:9's have no problems with the 75gn HPBT, don't even bother trying the 75gn AMax. They are a good bit longer.

The Greenhill formula was based on relatively short (relative to caliber) projectiles. It does a poor job of covering the typical long range bullet. The Miller Stability index does a much better job.

 

[35 Whelen]

My 1:9's have no problems with the 75gn HPBT, don't even bother trying the 75gn AMax. They are a good bit longer.

The Greenhill formula was based on relatively short (relative to caliber) projectiles. It does a poor job of covering the typical long range bullet. The Miller Stability index does a much better job.

Thanks for the tip. I'll definitely look into the Miller index. One other problem though is determining the length of various bullets without having to buy them. Maybe that should be a Sticky!

35W

 

[helotaxi]

Berger lists them on their website, as does Nosler. Sierra, Speer, Hornady and Barnes leave you one your own, but most all of them provide recommendations for min rate of twist.

 

[mwsenoj]

Just an update, I have been able to get the 75 gr Bergers to stabilize out to at least 300 yds. I have been fighting with life and wife and weather to get out and finish load dev. I will try to remember to post here, but I have another post here http://www.thehighroad.org/showthread.php?t=658916&p=8161676#post8161676 that has been covering my grouping.