Berger 85.5 Hybrid Maximum RPM to keep under for 20 shot rapid string fire.

[Titan]

Just looking for shooters that have tried this bullet for F Open or high round count short time window formats and can offer any boundaries on this use case. What is the maximum RPM, they can sustain is it 300k? Where have you experienced jacket failure with this bullet, what FPS, what twist rate? Was planning a build but before moving ahead I was looking to see if others had experienced jacket failure and under what conditions. Thanks.

 

[DR_2297]

I shot them for 2 years out of a Palma rifle - about 3000 bullets in total. 7T (.218) & 7.5T (.219) barrels both 5R finished @ 32” chambered at .200 total freebore. Pushed at 3050 +/-. Never lost a bullet to jacket failure. Wandering elevation was the major frustration.

 

[Titan]

I shot them for 2 years out of a Palma rifle - about 3000 bullets in total. 7T (.218) & 7.5T (.219) barrels both 5R finished @ 32” chambered at .200 total freebore. Pushed at 3050 +/-. Never lost a bullet to jacket failure. Wandering elevation was the major frustration.

Thanks for sharing your experience, was the poor elevation correlated to BC variance that could be observed with down range velocity? And did changing the diameter of the barrels or twist rate effect performance in any observable way?

 

[Ned Ludd]

There are a number of variables that go into the issue of jacket failure. RPM is one measure, but barrel length, bore/groove diameter, twist rate, and bullet bearing surface length are also important. Having experienced a jacket failure with Berger 90 VLDs in a match several years ago, I started looking into the probable cause(s) jacket failures and talking with fellow shooters that had also experienced this issue. To make a long story short, the one simple thing you can do to mitigate jacket failures is to use a barrel with 0.219"/0.224" bore/groove configuration, rather than 0.218"/0.224", which is far more common among reputable barrel makers. When you go to a 0.219" bore, many of the other variables such as twist rate and RPM that may contribute to the jacket failure potential simply disappear. In other words, if the barrel length and twist rate pushed a particular bullet/load into a vulnerable position with respect to jacket failure when using a 0.218" bore barrel, that can largely be mitigated by going to a 0.219" bore. For example, shooters that had previously been blowing up 90 VLDs in 0.218" bore barrels have found that they can use a twist rate as fast as 6.5 in a 0.219" bore barrel, or even slightly faster, without the risk of jacket failures that would have been an almost certainty in a 0.218" bore barrel of comparable length. Bartlein makes 0.219" bore barrels, perhaps there are other manufacturers that do, also.

One of the reasons bullets such as the 90 VLD, or Hornady's 88 ELDM have been associated with jacket failures in the past is also due to the jacket composition and the [very long] bearing surface length. The 85.5 BS length is slightly shorter than that of the 90 VLD or 88 ELDM, which should work in your favor. The 0.218" bore barrel I was using that caused jacket failures with both 90 VLDs and 88 ELDMs was 30" length, with a 6.8-twist. The loads I was using with those two bullets were generating RPM values in the 290-300K range. I ran a number of Sierra's 90 SMKs through the same barrel at approximately the same velocity and RPMs and never had a single bullet failure. So in my estimation, Sierra's jackets seem a bit tougher than those used in the Berger or Hornady bullets. The bottom line is that you can never know with certainty what is going to happen when pushing .224" heavies at velocities that will put them in the 300K RPM range or higher. But those that have switched to 0.219" bore barrels do not seem to be having the issues with jacket failures they previously experienced.

 

[762willdo]

I shoot them (85.5) out of my 22-250AI with a 7 twist barrel at 3200fps and they are fine….. (.218 bore)

 

[Titan]

There are a number of variables...

I was planning on an f open project with a .22 creedmore with a 30-32 inch barrel with a muzzle velocity target of around 3400fps but before ordering a barrel I was just trying to see if the effort was going to be inside the capabilities of the bullet jacket or the concept was outside what these class of bullets can withstand during fast string fire, I figured a 1-8 twist would keep the RPM to around 306k. So in your experience a .219 diameter barrel with 5r riffling is the ticket to make sure these reach the target? How about a 7 twist is 360K outside the realistic capabilities of this particular projectile?

 

[Titan]

I shoot them (85.5) out of my 22-250AI with a 7 twist barrel at 3200fps and they are fine….. (.218 bore)

Thanks for sharing your experience, is the 22-250ai used in high volume of fire scenarios, I was planning a f open rifle on a 22 creedmore long barrel 30-32 and at least 25 shots in rapid succession. Any thoughts on this bullet outside of durability does it shoot well at 3200?

 

[762willdo]

1 sighter 20 for record x 3

 

[Jdne5b]

I shot 90vlds, 88eldm, and 95smk at ~330k rpm and didn’t blow any up in the configuration Nedd posted. .219/5R. I had quite a bit less velocity but I made it up in twist rate.

360k may be more than those bullets could handle.

I didn’t shoot that barrel out, I need to start using it again to see if I lose any as the throat gets worse.

 

[Ned Ludd]

I was planning on an f open project with a .22 creedmore with a 30-32 inch barrel with a muzzle velocity target of around 3400fps but before ordering a barrel I was just trying to see if the effort was going to be inside the capabilities of the bullet jacket or the concept was outside what these class of bullets can withstand during fast string fire, I figured a 1-8 twist would keep the RPM to around 306k. So in your experience a .219 diameter barrel with 5r riffling is the ticket to make sure these reach the target? How about a 7 twist is 360K outside the realistic capabilities of this particular projectile?

As Jdne5b noted, you're talking about velocity/RPM far beyond anything I would normally ever see from a .223 Rem. So I cannot state with any certainty what will happen at 360K RPM when using a 0.219" bore barrel. It may be that some of the other major variables (barrel length, twist rate, etc.) that can potentiate jacket failure issues would still be mitigated with a 0.219" bore as they are with slower .223 Rem loads. However, you're in uncharted territory with respect to my experience, so it could also be that some of these factors again become limiting with respect to jacket integrity at RPM values that high, even with the 0.219" bore.

In your situation, I would use something like Berger's Twist rate calculator with the best estimates you have for velocity, etc., to determine the absolute slowest possible twist rate you could go with and still achieve a gyroscopic stability coefficient (Sg) of about 1.4 (or higher) so that you wouldn't be giving up too much BC by under-spinning the bullets. That would then set the maximum twist rate for a new barrel. At that point, the only thing you can do is test and see what happens. In the event 3400 fps velocity was causing jacket failure, you would still have a few other options such as tuning the load 85.5s in at a slower velocity, using either the SMK 90 or 95 gr bullets, which seem to have tougher jackets, or switching to a lighter bullet with a lower BC and a shorter bearing surface. The downside to these alternatives is that a chamber freebore dimension optimized for the 85.5s will not be ideal with much shorter or longer bullets. With the 6.8-twist 0.218"/0.224" barrels I had that were blowing up 90 VLDs and 88 ELDMs, I resorted to running two or three patches of Kroil through the barrel after each 20-shot relay, followed by three dry patches. This removed much of the carbon fouling, which seemed to be a contributing factor, but not the copper. My first sighter in the next match would be slightly low (slow), but not enough to put me out of the 10-ring. I can tell you that doing this at a match was a PITA, but I wanted to shoot the rifle and not have it become a safe queen. Once I adopted this procedure, I never lost another bullet during a match from those barrels, but I 'd rather not have to do that procedure again just to keep from losing jackets. There was also a general lack of trust in those barrels from that point on, which is really not where you want to be.

Unfortunately, this is the risk we take when starting a project such as this with a lot of unknowns. The good news as DR_2297 and 762willdo posted above is that even if you have to slow the load down a bit, you'll still end up with a rifle that can push the 85.5s well in excess of 3000 fps, even if not quite the 3400 fps you had hoped for. At one time, I had the notion of building an Open rifle to shoot 90 VLDs from a 22 BR case, but I never went any further with it due to the exact same limitations you seem to be coming up against. If you decide to go ahead with the project, best of luck with it.

 

[Titan]

As Jdne5b noted, you're talking about velocity/RPM far beyond anything I would normally ever see...

I appreciate you sharing your experience I will look into sourcing a 219 diameter barrel for the project thank you for the input.

 

[Scooby-93]

Thanks for sharing your experience, is the 22-250ai used in high volume of fire scenarios, I was planning a f open rifle on a 22 creedmore long barrel 30-32 and at least 25 shots in rapid succession. Any thoughts on this bullet outside of durability does it shoot well at 3200?

A 22creedmoor after 25 shots in quick succession will be very HOT