Ideas for exploding 90 gr .223 bullets?

[barefooter56]

I really wouldn't think it's a rpm issue. I run 90gr Berger in a 7 twist 22 creed in the 3106-3300fps area (liad depending) which generates a bit more rpm with no issue's.

Even though at 3106 FPS your bullet RPM IS 319,474 YOU may not have a problem but for others it may be. Each situation , each rifle is different.

 

[steve123]

90 grain VLDs
Lapua brass
Wolf primers
24 gr Varget
approx 400 rounds through barrel, 6.7 twist Brux

happened last summer with 24.4 gr Varget; put it aside until cooler weather and tried 24 grains, which did OK

pulled it out recently (hot weather) and had witnessed disintegrations
shooting at altitude of 5500', if that means anything

anyone experienced something similar and have a fix?

Nope, no way, never gonna happen, a 22 cal 90 grainer gonna be giving way.... and for how many reasons do we have in this thread so far???

Just kidding....

I just picked up my 28", 6 groove, 7 twist, 223AI today, I've knocked on wood and fingers been crossed. 88vld's, Varget, CCI450, and virgin brass on the bench and slated for tomorrow morning.

 

[dcali]

I really wouldn't think it's a rpm issue. I run 90gr Berger in a 7 twist 22 creed in the 3106-3300fps area (liad depending) which generates a bit more rpm with no issue's.

It seems to happen fairly regularly with .223 shooters shooting at high pressures. I wonder if the extra pressure doesn't loosen up the jacket in some minor way if everything isn't quire right. Just speculating.

 

[Dusty Stevens]

It seems to happen fairly regularly with .223 shooters shooting at high pressures. I wonder if the extra pressure doesn't loosen up the jacket in some minor way if everything isn't quire right. Just speculating.

I bet it has more to do with rpm. That core can only hold into the jacket so much before it spins. When it spins it melts- thats the smoke puff you see. Then the jacket alone just acts like a shotgun wad

 

[boltman223]

Even though at 3106 FPS your bullet RPM IS 319,474 YOU may not have a problem but for others it may be. Each situation , each rifle is different.

Do you guys have a recommended max RPM?

 

[boltman223]

Sounds right, I have had my share of 90VLD come apart. I also had a 6.7 twist. It always happens later in the string when the barrel is warm. I have had many of talks with people who have similar problems. I really believe its a combination of RPM and heat which causes the bullet failure. I also have some suspicion that it happens on older lots, but that might just be me. I currently run a 7 twist and only had it happen once, but it was in a state championship. It was from an older lot (9881) so maybe that was the issue. I have sold all those bullets and will begin a new lot shortly.

Just curious, how many rounds did you have on these barrels before the bullets started coming apart?

 

[Ned Ludd]

Do you guys have a recommended max RPM?

From Berger: at 300K RPM or greater, the risk of jacket failure becomes an issue. In a .223 with 90s at 2850 fps, you hit 300K once you go faster than a 7-twist (somewhere between 6.9- and 6.8-twist). Coincidence? Sure, it could be. But it seems more than coincidence that Berger would mention 300K RPM as a potential failure point and the fact that the majority of the F-TR shooters experiencing 90 VLD jacket issues I've spoken to were using 6.8-twist (or faster) barrels. That's not incontrovertible proof; there could actually be many contributing factors and once you are working with than a certain number, the odds go way up. Nonetheless, the jacket failure rate with 90 VLDs seems to correlate with faster than 7-twist barrels.

In fact, the issue could be more than simply the RPM; the land angle and shape of the rifling itself could also play a role. For example, exceeding 300K RPM with a slower than 7-twist barrel (i.e. 7.2-twist) via greater muzzle velocity may not be quite as hard on the jacket as when the bullet exceeds 300K RPM at slower muzzle velocity with a faster twist rate. Who knows? But it's pretty clear that in .223 Rem F-TR setups, it's more likely to happen in a barrel with faster than 7.0-twist.

 

[raptor1ronin]

Just curious, how many rounds did you have on these barrels before the bullets started coming apart?

400 in a 6.7 5r

 

[boltman223]

400 in a 6.7 5r

How about the 7 twist?

 

[stuann]

Its a heavy load for sure, however for FTR its the only way to go if you want to be competitive. 97% of .223 FTR shooters will be running a 90grn bullet. I use 90grn bullets for any competition out to 600 yards. You should see the faces of the .308 guys when you beat them, priceless!!!

Does anyone know of any people who have experienced blow ups with the VLDs who have tried the Sierra 90/95 grainers?

I had my first blow ups with about 200 rounds on a 6.7.

My calculated RPM at 2800 fps is > 300,00
Dropping it to 2700 fps would make it <300,000 and going down to 2600 fps would make the rpms about equal to my .243 in a long barrel where the B105s hold together (280.000 rpm).

 

[dcali]

I bet it has more to do with rpm. That core can only hold into the jacket so much before it spins. When it spins it melts- thats the smoke puff you see. Then the jacket alone just acts like a shotgun wad

I agree - it's predominantly rpm. I'm just wondering if there's somethign about .223 usage that exacerbates it. It could be just that lots of people use .223s with 90s, so you see them blowing up more with .223s.

 

[dcali]

From Berger: at 300K RPM or greater, the risk of jacket failure becomes an issue. In a .223 with 90s at 2850 fps, you hit 300K once you go faster than a 7-twist (somewhere between 6.9- and 6.8-twist). Coincidence? Sure, it could be. But it seems more than coincidence that Berger would mention 300K RPM as a potential failure point and the fact that the majority of the F-TR shooters experiencing 90 VLD jacket issues I've spoken to were using 6.8-twist (or faster) barrels. That's not incontrovertible proof; there could actually be many contributing factors and once you are working with than a certain number, the odds go way up. Nonetheless, the jacket failure rate with 90 VLDs seems to correlate with faster than 7-twist barrels.

In fact, the issue could be more than simply the RPM; the land angle and shape of the rifling itself could also play a role. For example, exceeding 300K RPM with a slower than 7-twist barrel (i.e. 7.2-twist) via greater muzzle velocity may not be quite as hard on the jacket as when the bullet exceeds 300K RPM at slower muzzle velocity with a faster twist rate. Who knows? But it's pretty clear that in .223 Rem F-TR setups, it's more likely to happen in a barrel with faster than 7.0-twist.

Just thinking outloud, the force to blow them up certainly comes from the rpm (and perhaps drag plays a slight role, but I doubt it - the drag force is tiny compared to the others involved). The thing being torn apart also plays a role. Jacket thickness matters, as does the rifling profile - square edges will create weak spots. This may be a legitimate benefit of 5R rifling which won't create as severe of a stress concentration. Other things I could imagine mattering would be any deformation of the base by the pressure - even if elastic, that would contribute to the overall stress state of the jacket, though I would think that would dissipate as soon as the bullet left the rifling. But it could be a contributor. Bullet length probably matters, even beyond the fact that it requires more twist. If you have longer bullets, there are more opportunities for a core/jacket interface that isn't quite right that could be the starting point of the whole thing unzipping. Similarly, a long bearing surface, which means longer rifling marks, presents a larger area where stress concentrations could create weak spots.

IF the above is correct, and that's a huge IF, then I would expect to see a bullet designed with a slightly shorter bearing surface, longer nose and shorter boattail shot from a 5R barrel would be more tolerant of spin without giving up much BC, if any. It's an interesting hypothesis, at least. It might be worthy of investigation. It will also be interesting to see if the new Sierras have the same issues.

 

[raptor1ronin]

How about the 7 twist?

Only one but the barrel and day was hot. I also think it was a bad lot. However my friend shoots a 7 twist without one problem. I think 7 works just fine.

 

[boltman223]

Only one but the barrel and day was hot. I also think it was a bad lot. However my friend shoots a 7 twist without one problem. I think 7 works just fine.

You only had one round on it?

 

[raptor1ronin]

Does anyone know of any people who have experienced blow ups with the VLDs who have tried the Sierra 90/95 grainers?

I had my first blow ups with about 200 rounds on a 6.7.

My calculated RPM at 2800 fps is > 300,00
Dropping it to 2700 fps would make it <300,000 and going down to 2600 fps would make the rpms about equal to my .243 in a long barrel where the B105s hold together (280.000 rpm).

I also had SMK 90 blow up too. But Sierra was all over it and traced the lot back. Found out it was an old lot that had the old jacket. They sent me 2 boxes of 90’s new lot and not one problem.

 

[raptor1ronin]

Ha sorry it w

You only had one round on it?

as shot 15 in my string so the barrel was at temp. I have tried the 95SMK. They shoot great at 2750 but just don’t know if it’s worth it yet. I will say not one has gone puffff

 

[boltman223]

Ha sorry it w

as shot 15 in my string so the barrel was at temp. I have tried the 95SMK. They shoot great at 2750 but just don’t know if it’s worth it yet. I will say not one has gone puffff

Sorry, I'm trying to ask how many rounds total were on the barrel when you had a 90 vld blow up in the 7 twist?

 

[raptor1ronin]

Sorry, I'm trying to ask how many rounds total were on the barrel when you had a 90 vld blow up in the 7 twist?

280 rounds.