Sierra 90 and 95 gr SMK bullets and velocity

[wboggs]

Does anyone have experience with these bullets at 3300+ fps in a 1-7 twist? I wonder if they will stand the rotational velocity.
Bill

 

[linebaugh]

I have taken the 90gr smk to 3200 fps and there is no problems. Same for 90 bergers. I would suggest you do not need a 7 twist if you plan to run that velocity. 7.5-8 would likely be fast enough for the 90's. I think the bullets blowing jackets is in the past and has been for some time.

A side note. I did some limited (like 100 bullets and 2 powders limited) work with the 95's and I can't keep them from throwing fliers. 3 or 4 shots into .250-.300 and then 1 or 2 fliers that open groups to .650-.750 or bigger. I will revisit them next year with more velocity. I ran them up to 3,000 fps.

 

[wboggs]

What twist using the SMK 95?
Thanks for the info.

 

[linebaugh]

What twist using the SMK 95?
Thanks for the info.

7 twist. That may be the problem but I would not bank on it. I have stabilized the 90's at 3050 fps out to 800 yards with an 8 twist.
My guess is I need to either push the 95's harder or less to get to the sweet spot for them. Of course it is always a possible conclusion that my bbl just does not like them or that I just failed to find the correct load... or all the above. I just can't afford the bbl life of finding out the answer at this time.

 

[wboggs]

I am going to do a new build with a 22 creedmoor and have not ordered the barrel yet. My plan is to use the 95s and obviously I want to order the right twist. Hopefully, the answer will become clearer as these bullets are more widely used.
Agree, don't want to burn out the barrel working up loads.
Thanks
Bill

 

[B23]

I was considering doing a 22-284 when these new 95's first came out and I talked to the bullet techs at Sierra about it. They told me even at the speeds a 22-284 could launch these at, a 7 twist would be marginal so at speeds down around 3000-3200 you'd probably need a 6.5 twist barrel.

 

[linebaugh]

I am going to do a new build with a 22 creedmoor and have not ordered the barrel yet. My plan is to use the 95s and obviously I want to order the right twist. Hopefully, the answer will become clearer as these bullets are more widely used.
Agree, don't want to burn out the barrel working up loads.
Thanks
Bill

What barrel length?

 

[wboggs]

Probably 30. I'm not carrying the rifle. It will be used from the bench and prone for fun shooting, no matches.

 

[wboggs]

I was considering doing a 22-284 when these new 95's first came out and I talked to the bullet techs at Sierra about it. They told me even at the speeds a 22-284 could launch these at, a 7 twist would be marginal so at speeds down around 3000-3200 you'd probably need a 6.5 twist barrel.

I was considering doing a 22-284 when these new 95's first came out and I talked to the bullet techs at Sierra about it. They told me even at the speeds a 22-284 could launch these at, a 7 twist would be marginal so at speeds down around 3000-3200 you'd probably need a 6.5 twist barrel.

I will have the see some real life data from shooters before I go to a 6.5 twist. I know that is what Sierra says but as far as I know, they did not test with twist rates and velocity.
Call me a little skeptical until.shooters report this.

 

[Colt77845]

Ump this up to the top for some more range reports... I to want to push the velocity limits of the 95gr smk... if any one knows what that is? 22-284 sounds FUN!!!

 

[Ned Ludd]

At ~2850 fps from a .223 Rem cartridge, a 7.0-twist barrel (30") is optimal for the 90s. It may not net you a full 100% of the intrinsic BC, but it also lessens the potential for jacket failures. Notice I stated "lessen", not eliminate. In the last couple years, the number of F-Class shooters using Berger's 90 VLDs out of .223 Rem for F-TR has risen noticeably. So too, has the number of shooters experiencing jacket failures. I'm not sure how anyone gets 90s to work reliably in a 7-twist barrel at 3000+ fps when they exhibit failures at velocities of 2850 or less out of a comparable twist barrel. In the past, I have seen others shooting 90s at 3000+ fps from various cartridges such as 22BR and 22-250 reporting that they were using 7.25 twist barrels. Again, they may net the full intrinsic BC, but their bullets are probably more likely to make it to the target intact.

With the 95s, a 6.9-or 6.8-twist is necessary "on paper" to obtain the full intrinsic BC at 2750 fps (1000 ft elevation, 70 degrees F). With a 7-twist, you'd be giving up a very tiny amount of BC (~1%). I recently worked up a load with the 95s in .223 Rem with a 6.8-twist barrel chambered with a very generous freebore (> .200"). They tuned in at about 2750 fps with H4895 and the precision has been quite good. Presumably at ~2750 fps, the propensity for jacket failure will be minimized. No issues with that as yet.

 

[nmkid]

I have been shooting the 90's at 3390 with no problems. 1:8 twist.

 

[284winner]

Does anyone have experience with these bullets at 3300+ fps in a 1-7 twist? I wonder if they will stand the rotational velocity.
Bill

90s are fine at 3200-3250 in an 8 twist (with no jacket failure). Not sure about the 95s. Guessing 3400-3500 and they would be fine. I'll know soon.

 

[Ned Ludd]

The 90s are not "fine" in an 8-twist, even at 3390 fps with fairly generous atmospheric conditions. They might make it to the target ok, but you're giving up a substantial amount of the intrinsic BC by under-spinning them, just so you can push them faster. A lighter bullet with a slightly lower BC that has a shorter bearing surface and can take the RPM at much higher velocity with the appropriate twist rate (i.e. Sg >/= 1.5) and net you 100% of the intrinsic BC is a better approach.

 

[Bigguy1951]

N Ludd, your example is for a Berger, which is longer than a Sierra. The Sierra is 1.169 inches and has a .563 G1 bc. Using that information at 1000 ft will cost only 3% of the bc. A loss that you will not likely be able to detect. I don't think that I could detect a 9% difference. I shoot the 90's in an 8 twist at 2981fps, but at 4500 ft of elevation and the twist calculator has me at comfortable stability.

 

[284winner]

Sierra 90s do FINE in an 8 twist barrel pushed around 3300 fps. Never tried the Berger's. Not sure about the 95 SMK. My meaning of fine is...they make it to the targets stabilized with round bullet holes and accurately so. My thought is that the 95s will as well but need to be pushed at least 3400-3500. I'm pretty sure my 22-250 Ackley can't do those numbers. A 22-243/22-284 will make them tho.

 

[Ned Ludd]

N Ludd, your example is for a Berger, which is longer than a Sierra. The Sierra is 1.169 inches and has a .563 G1 bc. Using that information at 1000 ft will cost only 3% of the bc. A loss that you will not likely be able to detect. I don't think that I could detect a 9% difference. I shoot the 90's in an 8 twist at 2981fps, but at 4500 ft of elevation and the twist calculator has me at comfortable stability.

FWIW - 9% difference in BC is HUGE!

 

[284winner]

So a BC of .500 for a 90 grainer would drop to .450 with a 10% difference. Yes decently huge difference, however there's no 10% difference due to twist rate. There is however that 9% difference going from 4500' down to 1500'. That is something that can be changed geographically pretty easy. If you live and shoot at 1500' it just is what it is. Can't do much about it.

The 90s are not "fine" in an 8-twist, even at 3390 fps with fairly generous atmospheric conditions. They might make it to the target ok, but you're giving up a substantial amount of the intrinsic BC by under-spinning them, just so you can push them faster. A lighter bullet with a slightly lower BC that has a shorter bearing surface and can take the RPM at much higher velocity with the appropriate twist rate (i.e. Sg >/= 1.5) and net you 100% of the intrinsic BC is a better approach.

View attachment 1079945

I think if it came down to perfect stability with way too much rpm possibly causing bullet separation vs less stability losing some bc, I'd choose the lower bc and keep accuracy and bullets making it to the target. With a 223 it's pretty easy to make things work well across the board but dealing with big case 224 cartridges pushing speeds of 3500-3600 fps with heavy bullets, it's not that simple.

 

[Ned Ludd]

I don't usually pay all that much attention to the actual BC numerical value, per se. What catches my attention is the difference in a 10 mph full value wind deflection at 600 to 1000 yd for two 90 VLD bullets moving at the same initial velocity, but with a 10% difference in BC. At 600 yd, the predicted difference in windage is ~2.4", or about the width of the F-TR target X-ring. At 1000 yd, the predicted difference is ~8.6", close to the width of the 10-ring. Differences in wind deflection of that magnitude can also make a noticeable difference in scores at the end of a match.

If a slower twist rate and resultant decrease in effective BC is amenable to the precision requirements for the type of shooting being done, then it's really no issue to go with the slower twist rate. But for some types of shooting, it can make a difference. Jacket failure issues are also another important consideration when choosing barrel twist rate. Higher velocity means higher propensity for jacket failures with the long 90 gr .224" bullets. From personal experience, bullets that don't make it all the way to the target will kill you in a match, and I'd imagine they're not too pleasant even when someone's "score" isn't on the line. The good news is that modern barrel makers have no issues cutting twist rates to the tenth of an inch if suitable twist rate blanks are not readily available commercially; I have a couple unique twist barrels cut specifically for 90 VLDs. The only down side is that a long lead time is usually required for custom barrels.