22-284 and the new Sierra 95 MK's

[B23]

I just got the load tuned!!

But wait the lands are 5 thou further out!!! Need to retune.

Barrel burned up.

Start over.

Yeah, you're probably right, maybe I should just get a 6tw barrel and shoot them out of a .223 then I could actually watch the bullet go through the air since it'd traveling along at grandma speed.

 

[284winner]

It's a concern of mine which is why I contacted Sierra about possibly using a slightly slower twist, given the speeds I could possibly be launching these things at, but he ran the numbers on his end and said I still needed a 1-6.5tw.

As for barrel life, I think 1000 rounds is probably a little optimistic and it wouldn't surprise me if it's more like 6-800.

A gain twist barrel is something I've thought about and I plan to do more research on this idea. I've talked to the guys at Bartlein before, seem like really nice folks, and once everyone gets back from Shot Show I plan on discussing this with them. I've already talked to Krieger and Brux, it's a 4 groove or nothing with them.

Years ago when I was having my 6-284 built I brought up "barrel life" to the gunsmith that was doing the build, his response was much like some of yours, he told me those barrels are threaded on for a reason and if I'm concerned about barrel like maybe I should be having a 308 built. I don't think I've ever asked about barrel life since. lol

I haven't looked at the Berger stability calculator but my guess is, a 7.25- 7.50 twist will stabilize that bullet at the speeds you'll be pushing them. A 90 Berger vld can be stabilized at 3300+ with an 8 twist barrel.

 

[B23]

I haven't looked at the Berger stability calculator but my guess is, a 7.25- 7.50 twist will stabilize that bullet at the speeds you'll be pushing them. A 90 Berger vld can be stabilized at 3300+ with an 8 twist barrel.

Per the twist calculator on the Berger site, unless you increase the elevation a fair amount, even the Berger 90 is pretty marginal out of a 8twist.

When I gave the Tech I talked to at Sierra the velocity I thought a 22-284 could launch their new 95 grainer at, that being 3500 fps, If I recall correctly, his calculations said it'd take a 1-6.8tw. We didn't talk about elevation but I'm assuming he was plugging the numbers in based on sea level.

I just measured one of these Sierra 95gr MK's and ran the numbers through the Berger twist calculator and using 3500 fps at sea level a 7tw gives me 1.39 stability factor and the 6.5tw is a 1.61 stability factor. I'd guess the 7tw would probably work but it may not give you the full benefit of the BC at extended ranges like the 6.5tw will.

 

[daniel brothers]

If I remember correctly... have to check my notes.... but I think I made 90 bergers go puff, when I shot them up around 3500.. which was way too hot for my caliber out of my 8 tw.

 

[B23]

but I think I made 90 bergers go puff, when I shot them up around 3500..

And this is definitely a concern that I have but I will say, in the past, Berger's go puff long before SMK's. Typically, SMK's are pretty darn tough and will usually withstand a lot of abuse. I know in years past they were some of the only bullets that would withstand some of Kirby Allen's hotrod wildcat chamberings.

 

[MrMajestic]

BC and speed make up for my inability to judge the wind, barrel life is not in the equation. JMHO

 

[B23]

BC and speed make up for my inability to judge the wind, barrel life is not in the equation. JMHO

Barrel life may be a concern to some and that's fine, but for me, I could careless about barrel life as long as the thing shoots fast and is very accurate. If I were concerned about it, I'd probably have a safe full of 308's, but I don't own a single one of those.

 

[284winner]

And this is definitely a concern that I have but I will say, in the past, Berger's go puff long before SMK's. Typically, SMK's are pretty darn tough and will usually withstand a lot of abuse. I know in years past they were some of the only bullets that would withstand some of Kirby Allen's hotrod wildcat chamberings.

I think you'll have that same problem with the 95 Sierra, especially with a faster twist barrel. Definitely at 3500 fps. Unfortunately the happy medium is so tiny that at the risk of trying a certain twist barrel and bullet/speed combo, comes at a price. Price of a barrel and chambering it. You'll just never know till you try it. You may be better off starting at 3000 fps and moving up slowly. I know it's not why we build these big case capacity setups for small diameter bullets but you have to start somewhere. I think they'll be a happy medium in velocity that WILL stabilize the 95s and keep them from blowing up. Just won't be what you will want with that big 284 case.

 

[fredo]

I'm interested in trying these too. But, I asked myself, "whats the perceived benefit of going that heavy?" High b.c. #s are sexy, but those heavy-azz-for-caliber boolits need to be pushed to a certain "x,xxx" FPS where it makes sense (ballistically speaking) to warrant switching...

When you run the numbers of your projected speed with the 95s, against an established 80@3750 (courtesy of Mr. Maj), at what distance does the "gift of b.c." begin paying' dividends?
Surely, the heavier pill will negatively impact short range POINT BLANK holds that hunters hold so dear. At what distance would a 95 shoot flatter, and with less wind drift?
And, do those downrange dividends pay enough to suffer the penalty at short range?

If/when that theoretical #crunching is established, then one might ask if it'd it be worth it to spin up a super fast twist tube that will most likely nuke any lighter boolits, just to actually prove the theory?

Naturally, those questions are focused around what and how you'll be shooting.

Just rambling here, for conversations sake...

 

[B23]

I'm interested in trying these too. But, I asked myself, "whats the perceived benefit of going that heavy?" High b.c. #s are sexy, but those heavy-azz-for-caliber boolits need to be pushed to a certain "x,xxx" FPS where it makes sense (ballistically speaking) to warrant switching...

When you run the numbers of your projected speed with the 95s, against an established 80@3750 (courtesy of Mr. Maj), at what distance does the "gift of b.c." begin paying' dividends?
Surely, the heavier pill will negatively impact short range POINT BLANK holds that hunters hold so dear. At what distance would a 95 shoot flatter, and with less wind drift?
And, do those downrange dividends pay enough to suffer the penalty at short range?

If/when that theoretical #crunching is established, then one might ask if it'd it be worth it to spin up a super fast twist tube that will most likely nuke any lighter boolits, just to actually prove the theory?

Naturally, those questions are focused around what and how you'll be shooting.

Just rambling here, for conversations sake...

fredo, not ramblings at all as those are all very valid points. There are many unknowns with a project/idea like this and I find that I'm second guessing myself on many of these ideas. I'm, typically, not one to venture into things without, first, doing an extensive amount of research and even then the research has to point in a reasonable direction and to be honest, the deeper I get into this idea the more I'm second guessing it.

 

[fredo]

Well, it sure makes for interesting chit chat, anyway!

Trying a 'new' bullet in a platform you've already got is one thing, you're only out the cost of the bullets plus some powder and fun time to shoot em...

Whereas, building a purpose built bullet launcher requires a lot more skin to play the game. I'm not a fan of painting myself into a corner with an extreme twist rate, unless the benefits of doing so are clearly evident, and tangibly superior to a twist rate that's more forgiving to a wider range of bullet possibles...

With regard to the new 95SMK vs. an old 80AMAX @ 3750, looks like you'd need somewhere in the vicinity of ~3600fps to match the 0-500 yd ballistics of the 80. From there, on out, the 95@3600 begins to walk away...shooting flatter and exponentially (albeit mildly) better in the wind.

Risk vs. reward, with application being a strong deciding factor. If you're lobbing bullets at fixed range paper, dialing a bit more drop means nothing and you'll enjoy the added wind-buck-ability. But for killin chit, which mostly is a short-mid range endeavor, fast & flat is where it's at!

 

[284winner]

Well, it sure makes for interesting chit chat, anyway!

Trying a 'new' bullet in a platform you've already got is one thing, you're only out the cost of the bullets plus some powder and fun time to shoot em...

Whereas, building a purpose built bullet launcher requires a lot more skin to play the game. I'm not a fan of painting myself into a corner with an extreme twist rate, unless the benefits of doing so are clearly evident, and tangibly superior to a twist rate that's more forgiving to a wider range of bullet possibles...

With regard to the new 95SMK vs. an old 80AMAX @ 3750, looks like you'd need somewhere in the vicinity of ~3600fps to match the 0-500 yd ballistics of the 80. From there, on out, the 95@3600 begins to walk away...shooting flatter and exponentially (albeit mildly) better in the wind.

Risk vs. reward, with application being a strong deciding factor. If you're lobbing bullets at fixed range paper, dialing a bit more drop means nothing and you'll enjoy the added wind-buck-ability. But for killin chit, which mostly is a short-mid range endeavor, fast & flat is where it's at!

It's quite a trade off tho. Don't really see the value in it for the long run. Or should I say short run. I think your results with your newest project will shine plenty with the 75-80 grain bullets at 3650-3750. IF you could get 3600 with the 95, what twist would it take ? Also what's it worth not knowing if the bullets would hold up at those speeds and RPMs ? The cost of a barrel, bullets, time and frustration ? Na, I think the 75-80 grain option certainly speaks clear enough for me. Especially if YOUR newest toy will send em into the next zip code straight and with authority. I'm sold at that point.

 

[fredo]

John, even if I could see an honest 3600 from this new 95 out of the REDLINE, I'd be comparing it against a 75gr that might clear 3900 from the same cartridge. Whoops, there goes the performance pendulum swinging back toward the lighter bullet!

And, beyond the ballistic inadequacy, how would that super heavy bullet hold up and perform terminally, when subjected to the extreme RPM stress that may be required to 'stabilize' it?

So, there again, and to tie into another thread, comparing these things illustrates the point of how a bullet from a 'niche' weight range can and will outperform the heaviest(highest b.c.) bullet...

That's not to say I won't try them in the REDLINE, I will. But mostly, for chits&giggles, because I'm building this to push an envelope that is of particular interest to me. If anything, showing how a 'niche' weight bullet will beat a super heavy bullet, even with the aid of a massive capacity hotrod to push it, will further prove a point I've subscribed to for a while now. That being, super heavy for caliber bullets have little/nothing to offer over a more balanced harmony of b.c. and muzzle velocity...

That's not to say I'm not interested in seeing How other reloaders make out, we're all here to learn from each other!!! And who knows, someone may just stumble into a truly better mousetrap...

Good shooting!

 

[284winner]

I haven't looked at the Berger stability calculator but my guess is, a 7.25- 7.50 twist will stabilize that bullet at the speeds you'll be pushing them. A 90 Berger vld can be stabilized at 3300+ with an 8 twist barrel.

Rethinking this. Looks like a 7-7.25 is needed. It will give 326,000 rpm. That's a bit high but it appears stable at 3200-3300.

 

[284winner]

PS... send me some of those 95's and I'll let you know how fast and accurate they are in my 22-243AI 8tw.

Did you ever run them 95s from that 8 twist barrel ? Real curious as to your results.

 

[JBT47]

I tried and tried the 90 Bergers from a .22-250 8 twist Brux and they were very unstable. Over 6” groups at 100.

 

[Ned Ludd]

It's a simple exercise to run whatever velocity you think you'll be able to get through Berger's Twist Rate Calculator and get a pretty good idea of the minimum twist rate required for a given gyroscopic stability (Sg). For example, running a .223 Rem with 90 VLDs at 2820-2850 fps through a 7-twist barrel will give you an Sg of about 1.44-1.45. That means you're giving up about 2% of the intrinsic BC of the 90 VLD. However, they will not exhibit gyroscopic instability issues and you'll be running them under 300K RPM. Going over 300K RPM is where jacket failure will start to show up. Some of the hot-rodded .22 cartridges like the .22 BR will push the 90s in the 3000-3050 fps range. To keep a similar ~1.45 Sg at that velocity, you need a minimum 7.2-twist barrel. Again, you'll be giving up a very slight amount of the intrinsic BC, but gyroscopic instability won't be an issue.

A more important issue with the 95 SMK has to do with its increased weight, which means slower velocities when loaded to equal pressure. For the 95 SMK to be an improvement over the 90 VLD in terms of wind resistance, it must have a sufficiently higher BC than the 90 VLD to more than make up for the velocity deficit. Otherwise, you'll never be able to get increased performance because you simply can't push them as fast as you can the lighter 90 VLD without raising the pressure significantly. The 95 SMK requires a faster twist than does a 90 VLD, because it's a slightly longer bullet. However, it's only about a couple tenths of twist rate, so not a huge difference. Whether the 95 SMK can be loaded in such a way as to offer a significant advantage over a 90 VLD will largely depend on the actual difference in the BCs of the two bullets, and what specific velocities they actually tune in at in a given cartridge.

If you know the real-world velocities and BCs for optimally-tuned loads with the two bullets in a given setup, any ballistic calculator will give you a pretty good idea of whether one will have noticeably better ballistic performance than the other.