Ideas for exploding 90 gr .223 bullets?

[stuann]

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?

 

[Dusty Stevens]

That has to be the winner in the 22 cal twist race

 

[skiutah02]

Yep.

http://faculty.cord.edu/rutherf/12/90vldblowingup.pdf

 

[Ned Ludd]

From the title of your thread, I thought at first you were going to ask how to make an "explosive" 90 gr projectile. My suggestion was going to be to use 90 VLDs out of a 6.5-twist barrel with Varget or H4895 . Clearly, you've already solved the question of how to get them to blow up. My advice on how to prevent this problem is as follows:

Use a 7.0-twist barrel and don't try to push them faster than about 2850-ish. Out of a 30" barrel and a throat with at least 0.169" freebore, Varget loads with 90 VLDs will usually tune in around 2820 fps or so, H4895 about 2850 fps or so. With either of these powders, a 7.0 twist barrel will do everything you need. The only other realistic option is to tune them in at the next slower node, as has been mentioned by others.

 

[#40Fan]

Slow the bullet down might be the first step. Do you have any chrono numbers?

 

[stuann]

Slow the bullet down might be the first step. Do you have any chrono numbers?

The VLDs come labeled saying "Optimal twist rate = 1:6" .

Most recent set chrono'd at 2810 fps, though the temp at the time was prob 65-70

Anyone have experience with the new Sierrra 95's (or even the 90s) at 1000?

 

[Milo 2.0]

The VLDs come labeled saying "Optimal twist rate = 1:6" .

Most recent set chrono'd at 2810 fps, though the temp at the time was prob 65-70

Anyone have experience with the new Sierrra 95's (or even the 90s) at 1000?

I can get the full info, but have a friend shooting 95gr Sierra's in a 22 Creedmoor at 3100fps. I'd be willing to bet it's not a super fast twist barrel, we're at 4700 ft elevation. He claims it is accurate, I have not witnessed it in action.

 

[Jdne5b]

I'm shooting the new Sierra 95s in a 7 twist .223. But the throat is much longer than one for the 90s. (+.100 to .130 over a .169). They are working well for me currently at 2740ish.

If you dont want to throat your chamber, I'd give the Sierra 90s a try. Maybe the Hornady 88gr ELD.

 

[Twitchy]

I can get the full info, but have a friend shooting 95gr Sierra's in a 22 Creedmoor at 3100fps. I'd be willing to bet it's not a super fast twist barrel, we're at 4700 ft elevation. He claims it is accurate, I have not witnessed it in action.

I'd love to know his COAL, or better yet how long his throat is. I'm kicking around the idea of 22 Creedmoor specifically for the 95g SMK.

 

[Twitchy]

I guess I'll add that I've had zero issues (exploding) shooting 90g SMKs/90g VLDs upwards of 2930 in a 30" 1:7 223. I don't compete with them going that fast but did conduct velocity/pressure testing that high.

 

[Milo 2.0]

I'd love to know his COAL, or better yet how long his throat is. I'm kicking around the idea of 22 Creedmoor specifically for the 95g SMK.

I'll try get the specifics.

 

[dcali]

At the risk of stating the obvious, it's either the bullets (unlikely), the barrel (possible contributor - some barrels are worse than others), or you're shooting them too fast (it's more about twist and possibly pressure than raw velocity). But you're not the first to blow up 90s - just the nature of the beast when pushing them hard.

 

[watercam]

I shoot Sierra 90s w/ a 30" long/7" twist bbl, 23.7 gr. Varget, Lapua brass for 2830 fps. At 1000 they are still just about 1400+ fps. Sierra had blow-up issues with their 90s in the past and took pains to fix that issue.

 

[raptor1ronin]

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?

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.

 

[Bart B.]

As bullet's spin rate in rpm increases, sooner or later the rifling grooves in them that weakens the jacket at their edges gives way from centrifugal force.

If one must have extra high bullet rpm rates for their barrel, have the bore diameter opened up so the groove depth is only .001" and all bullets should remain intact.

RPM = muzzle velocity in fps X 720 ÷ twist in inches

 

[Fotheringill]

I am certainly not close to being in the league of any of the other posters here, but isn't that a pretty heavy load for what you are shooting?

 

[dcali]

I am certainly not close to being in the league of any of the other posters here, but isn't that a pretty heavy load for what you are shooting?

Depending on the overall length, it could be. 24.0 of Varget is book max-ish for 77-80 grain bullets. I'm going to go out on a limb and guess that this is a F TR rifle throated long enough to seat the bullet far enough out so that this is not as heavy a load as it might seem at first glance.

 

[raptor1ronin]

I am certainly not close to being in the league of any of the other posters here, but isn't that a pretty heavy load for what you are shooting?

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!!!

 

[barefooter56]

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.

You are correct. Heat and friction will cause any bullet to fail. I suggest that you use a barrel twist rate that is optimal for the ALTUTUDE(s) ( base your choice on the lowest altitude) that you will be shooting at. The 1-6 barrel twist rate we list is based on a worst case scenario of 59 degrees at sea level. Use the TWIST RATE CALCULATOR on the Berger try to use a barrel twist rate that gives you a stability factor ( SG) OF 1.5 (even 1.49 -1.48 will help and affect the BC very little. You can check those effects on our BALLISTICS CALCULATOR:http://bergerbullets.com/ballistics/). Rifling types like the 5R also can take stress off a bullet. Don't use undersize bore dimensions. Standard bore dimensions used for the caliber you are shooting are enough. Barrel length is another factor that can cause bullet failure. Walt Berger and I have talked about this at length. Barrel lengths greater that 28 inches can also add to the heat and friction that causes bullet failure. I know that barrel length can help velocities. However, just check and see what your velocity difference would be between a 28 and 30 inch barrel to see if the extra two inches is worth it to you in regards to the extra speed. Bore and throat condition can be issues also. Fire cracking of the throat , a nick in the rifling lands, ETC. Bore cleaning. Make sure you look for a carbon ring that may be forming just ahead of the throat. These need to be removed as does copper laying in the angle where the land and groove intersect. With a cold/clean barrel, running a patch with a light application of KROIL on it can help reduce friction until enough fouling can be built up in the barrel to help keep the friction off the bullet. Keep the action open and the bullet on the follower until the target is acquired and the condition checked before chambering the round can help cool the barrel some also. Especially on hot/humid days where the barrel can get exceptionally hot during string fire. These are a few things that can help with this issue. Hope it helps. As always you can contact us at the number below and in this string.

 

[NortexDM]

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.