For the new 197 grain SMK? Sierra recommends a 1:7.5 or faster twist. What common cartridge would push it fast enough get the most out of the .780 bc?

7mm rum, 28 nosler, or 7 stw

Only thing uncommon about a 7-300 is the reamer. I know a guy...

I didn't know Tony already had a reamer. That makes things interesting. What's the barrel life on one of those rigs, JG?

A 280 AI will give all the velocity you need and much better bbl life. Velocity is good, accuracy is final.

I am building a 7mm-300 Win Mag to shoot the 195 Berger's. I'm using a Bartlein 1:8" twist. The first rifle we built is getting 3000-3050 fps with the 195's in the 7mm/300 WM. The reason we went 7mm/300WM is how easy it is to get quality 300 WM brass, and to size your brass you simply run it up into the correct 7mm size neck bushing. Also, it holds less powder than the 28 Nosler and does not give up much velocity in doing so. Therefore the barrel heats up less.

A common round to push these big bullets is the 28 Nosler. It has really impressed me, to say the least. It's expensive to get the brass. It holds about 8-10 grains more powder, and pushes the same 195 Berger about 3100 fps. I have heard reports of 3150 fps with some aggressive double based powders, but that's fast!

I have played a lot with the 7 RUM, and it would be the LAST round I would ever select. It's way too finicky to get to shoot well. It's like having a top fuel drag motor in a ford pinto.

I got 2200 rounds out of my last 300 WM. With the smaller 7mm bore and similar powder charges, I would guess around 1200-1800 rounds, somewhere in there, if you didn't rattle of a lot of rounds quickly. But I could care less about barrel life on this rifle. The 26 Nosler was seeing 400-500 rounds barrel life. The 28 should fair better than that with around 700 to 1K rounds. The 7mm/300WM prob around 1200-1800.

Thanks for all.of that great info. Keep me posted on how yours shoots, Chad. It sounds like a sweet round so far.

Something to think about- The Berger 195 grain is a standard hollow point, meaning it is untipped or unpointed from Berger. Sierra says they are tipping the 197 grain SMK. I know from pointing a lot of bullets and testing them, that you gain about 3.5% increase in BC.

So, Sierra 197 SMK G1 BC = .780 at 2300+ fps
Berger 195 EOL G1 BC = .755

Now, if you point the Berger 195 EOL (which I plan to do), you can add the 3.5% increase in BC to the .755 figure. That's brings the new G1 BC of the Berger to .781 (.755 x 1.035= .781), which is slightly higher than the Sierra figure.

BUT, and I say a big BUT! I know from shooting Sierra SMK's, that their listed BC is generally higher than actual BC. To keep things consistent and more accurate, we should not be comparing the G1 BC's. We need to be comparing the G7 BC of these bullets. Why? The G1 drag profile is for a soft point flat base bullet, which these are not. The G1 profile is also velocity dependent, which is why Sierra lists the speeds and BC at that speed. The G7 is much less velocity dependent, and most importantly the G7 BC drag function is based on a boat tail design, which these bullets are. I say this multiple times a day to my customers- Do not use a G1 BC!! Use a G7 BC and you will be much more consistent at longer ranges. (Most shooters hit low at longer ranges because they calculate their drop with only 1 BC, and that G1 BC decreases as the bullet slows down, so you hit lower at longer ranges. To fix that, use a G7!! And a lot of bullet companies can inflate their G1 BC if they calculate it at a very high velocity, which would be much higher than typical rounds shoot. I NEVER compare different bullets by looking at the G1 BC. The G1 BC can easily be an inaccurate or manipulated number from the mfg.

So now, the bigger improvement is the G7 BC increase. The Berger listed G7 BC is .387. Add the 3.5% increase to the .387, and you have .400 G7 BC!! That is an absolute monster of a G7 BC. This 195 Berger has such a huge increase in BC that I am building a rifle just to shoot this bullet. If I can get to 3000 fps, which is easily attainable, this round will be supersonic out past 2000 yards!

Can we find out how long the new Sierra 197 SMK is? I searched but can not find any info on it. If I know the bullet length, I can calculate the actual twist rate needed. The 1:7.5" twist seems fast. Speaking to Litz about the 195 EOL, a 1:8.3" twist was minimum for that. I went 8" to help even more. I have 2 extra 8" twist Bartlien barrels, if you need one.

To answer you original question, what's the best? That's up to you. 28 Nosler would be a good one, if you can/want to afford the brass/ammo. I went 7mm/300 Win Mag.

I know a 7 Rem Mag will push the 195 to about 2850-2900 fps. Maybe a little faster if you stand on it.

Awesome, Kyle, thanks!

At 1.713" bullet length, I'm showing a stability factor of 1.47 at 2950 fps in a 1:8" twist barrel. This twist will work just fine for the 197 SMK.

No problem!

You're forgetting.

You couldn't get my 7 Rem Mag to shoot a 195 above 2850 fps, without pressure. And it can't out perform 180's at 3000 MV.

No it won't, not with a bullet the heavy. 7 Rem Mag won't push a bullet that heavy, as fast as it needs to go, no way a smaller case will.

I know a couple guys running 28 Nosler with 195 bergers at 3200. Freaking laser beams.

7mm-50bmg

Now we're talking baby!!!

My 32" AI will put up more velocity than most 7 Mags and severe the purpose very well.

Now I have to ask in all seriousness, how fast does it need to go?
Also, what is the barrel life of a 7mm Rem mag?

7/338LM It'll get the 195s going past 3350 with pierced primers!

I'm probably going to settle at 3150-3200 with slightly stick bolt lift.

I've tried RL33, Retumbo, H869, H50BMg and now RL50 which seems to be the winner. Seems to be just a tad better then the 28 Nosler.

7 Allen Mag is the fastest at over 3300FPs with no loading issues I believe.

I wouldn't this particular chamber again though as fired brass grew .02 headspace and neck needs to be turned.

a 7/300NM goes about same speed as 28 Nosler according to another guy.

To answer the original question, you have to ask yourself what you want out of it. You could build a 7mm/338 or something crazy like that, and it will be about as close to a laser as you can get... for about 400 rounds. Then you get into the allen mag, ultra mag, and even the 28 nosler. They will all run the 195/196 bullet from 3050-3200 depending on where they like to shoot. to get to that 3200 mark (if they like to shoot there, I know most 28 nosler's dont) you can reasonably expect 600-800 rounds out of the barrel. If you run them at 3100 ish it would be closer to 800-1000 rounds barrel life. It's all diminishing returns. If you take a 7mm-300 you can expect to get 3000-3050 and it does that with roughly ten less grains of powder than the 28 nosler, ultra mag ext.. If it's a gun you very rarely plan on shooting and letting it cool between shots, maybe a boomer wouldn't be such a bad idea. If you actually want to use it, a more reasonable speed and cartridge would make more sense. So there really isn't a best cartridge until you figure out which would be best for you.

Ah...the sweet voice of reason....Thanks "T T"

Hell no, live your life a 1/4 mile at a time!

All bullets have imperfections and the faster you push them the more those imperfections show down range, there is a node you can surpass when FPS will hurt more than help. Before y'all beat me down, I'm not saying its unattainable just saying. My experience with magnum cartridge's is I have to continuously chase the lands every 80-100 rounds from throat erosion to maintain the best accuracy. I think the best cartridge to go with would be something Lapua makes brass for and listen to ChadTRG42 use G7 and save yourself some head ache.