Bullet Failure Midair disintegration

[woostri]

Ingredients for bullets coming apart. 26" Pacnor 3 groove 6mm Ackley Improved 1:8 twist. 51.4 grains of H1000 behind a 105gr Hornady Amax. No shade, 85 degrees 25 shots into a 45 shot string in an F-class practice match. No impacts into the berm and after too many of these unexplained disappearing bullets (hitting the 9 ring or better on all other shots) I DNF'd and went over to the short range. Shot a couple into a target at 25 yards and witnessed jacket separation and molten lead spray on the target. These loads were run over a chronograph in the shade in about 70 degree temps one week prior. Averaged 3180 fps. Anyone else disintegrated any bullets lately? My first experience. I did find a thread on another website where someone blew up some 105 amax's at just over 3250fps. Makes sense that hot temps could get my 3180 rounds near to 3300 I guess. Just enough to pop. May be time to back off the loads or switch bullets or both. Thoughts?

 

[Hink]

Re: Bullet Failure Midair disintegration

If you're pushing the bullet fast enough that disintegration is a possibility...I'd back off on the load.

If your 105s are shooting well, then I'd just back off on the load and start considering coming up with loads for different weather conditions...or use another powder that's not so sensitive to the heat.

 

[ChrisGarrett]

Re: Bullet Failure Midair disintegration

I'm going on memory, but I think the early DTACs were vaporizing off the line as a matter of course until things were straightened out on the production line.

Varmnint guys will usually blow up the light weight, thin jacketed bullets pushed to high rpms/velocities, so it's not unheard of in the least.

Maybe that lot of 105 AMAX has a flaw, or is just thin jacketed?

Chris

 

[Low Sioux]

Re: Bullet Failure Midair disintegration

Woostri,

3 grove barrels are notorious for smoking thin jacket bullets like the amax at high velocity. I dont have actual experience with the sierra 107 but I think it is supposed to be a thicker jacket and may hold together better. Maybe someone with first hand experience will chime in.

Sioux

 

[Clark]

Re: Bullet Failure Midair disintegration

Usually we hear about 22-250 fast twist with light thin skinned bullets getting them to spin too fast and fly apart.

 

[bohem]

Re: Bullet Failure Midair disintegration

I've been told by Hornady Tech Support that the Amax line doesn't like RPM's over about 250,000-275,000

If you're pushing more than that you are going to risk poor accuracy and bullet disintegration. The 105's will stabilize in slower twist barrels sometimes (8.5 and 9's), but another thing to think about is the Berger 108(?) Target version with the thicker jacket has been shoot over 3250-3300 from 8 twist and held together pretty well.

I have no experience with a 3 groove barrel, only standard 4's.

 

[GRIM]

Re: Bullet Failure Midair disintegration

Back off the load, the increase in temp might have upped your velocities a tad bit. What powder are you using?

I had a buddy with a 22 Cheetah - that thing would shed the jacket and literally leave what looked like a shotgun pattern on the target around 200 yds. He backed off the load and it didn't happen after that. Smoking little round.

 

[woostri]

Re: Bullet Failure Midair disintegration

Yep, assuming the hot conditions upped my 3180 to 3250fps that would make for 292,500rpm. Dang. I did email hornady for specifics on a-max rpm limits, maybe they'll come back with these specs again for confirmation. Back to the drawing board for load development. Or keep my bullets in a cooler until I'm on the line the next f-class event. I'm running these hot loads over a chrono tomorrow with a hot barrel in direct sunlight to see how much the velocity spikes. Will post results in case other aspiring 6mmAI people decide to shoot Amax on hot days. Btw, no pressure signs on any of these CCI 200 primers. Still a safe load, if you dont mind a little 6mm shotgun. Be great for snakes.

 

[WRM]

Re: Bullet Failure Midair disintegration

I've seen it happen, but never run them that hot myself. Seen then turn into a puff of smoke about 75 yards out....

Lots of factors - rotational speed, bullet construction/jacket thinkness, and <span style="font-style: italic">rifling configuration</span> (depth/"sharpness" of rifling, and what it does to the jacket).

Cheers,

Bill

 

[patriotoutlaw]

Re: Bullet Failure Midair disintegration

Several yrs. ago, while I was working up a hunting load for my 6.5-.284 SST's were coming apart over 3,000fps. I backed off on the charge and they shot fine. However, I started using Barnes TSX's for my hunting round from that rifle and have not looked back.

 

[Fred_C_Dobbs]

Re: Bullet Failure Midair disintegration

Keep your bullets in a cooler. My use RL-10X in my varmint rifle, and it tends to be very temperature sensitive. Gains like 250 fps on hot days and my groups blossom. When it's over ~85° I carry my box of bullets in a soft sided cooler with a pack of blue ice. It brings my MVs back to normal and saves me having to work up a lighter load for use in hot weather.

Remember to carry a rag to wipe off the sweat before you chamber the round.

 

[woostri]

Re: Bullet Failure Midair disintegration

Yeah I thought about bringing a cooler to the next f-class match. That would work but I want a more stable option as well (after I shoot up the other 105gr Amax of course). Looking into the 115gr DTAC, running it perhaps at 3000fps. I know Tubbs won several competitions with this bullet using the 6xc which got it to 3000fps in a 7.5 twist barrel. I'm beginning to see that the 6mm AI would serve better as a light bullet long twist varmint rifle. Oh well, I'll make it work as an F-class gun. First build ever. Lots learned.

Anyone have a small batch of 115gr DTACs for sale? I see they only come in batches of 500. I would only need perhaps 50 or so for some load testing before I buy bulk.

 

[diriel]

Re: Bullet Failure Midair disintegration

I have a pac-nor 3 groove in 6.5x55 and like it a lot. However, I shoot heavy bullets that are slower.

One factor to consider is Bearing Surface Compression of the bullets. Often referred to as BSC%, most folks say that 22% or less is very important if you want to move a bullet Very Fast and not have bullets come apart.

One thing to consider is your average 6 groove barrel will usually be more gentle on a bullet than a barrel with less grooves. Another thing to consider is something like the Broughton 5C or Canted Lands barrels. Barrels of this general type are more gentle with the bullets.

http://bulletin.accurateshooter.com/2010...g-range-rifles/
-- Whidden shares his thoughts on barrels and bullets going very fast.

http://www.accurateshooter.com/forum/index.php?topic=3736491.0;wap2
-- this post by Livetohunt is also a good read

Good shooting

 

[Diablo]

Re: Bullet Failure Midair disintegration

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: woostri</div><div class="ubbcode-body">Yeah I thought about bringing a cooler to the next f-class match. That would work but I want a more stable option as well (after I shoot up the other 105gr Amax of course). Looking into the 115gr DTAC, running it perhaps at 3000fps. I know Tubbs won several competitions with this bullet using the 6xc which got it to 3000fps in a 7.5 twist barrel. I'm beginning to see that the 6mm AI would serve better as a light bullet long twist varmint rifle. Oh well, I'll make it work as an F-class gun. First build ever. Lots learned.

Anyone have a small batch of 115gr DTACs for sale? I see they only come in batches of 500. I would only need perhaps 50 or so for some load testing before I buy bulk.</div></div>

Someone had some uncoated 115 DTACs in the for sale section. If you don't want that many, shoot me a PM and I'll sell you a smaller lot, but all I have on hand right now are BN coated.

 

[fncannon]

Re: Bullet Failure Midair disintegration

Back in the day, I loaded some 71gr fmj .32 acp bullets sized to .308 in my 30 Herrett just for giggles. I upped the charge proportionally from what was good for the 110gr I was normally using. The result was a truly awesome muzzle blast and only about 1/3 of the bullets reaching the fifty yard target intact. The other shots gave groups of many fine random holes.

 

[ranger1183]

Re: Bullet Failure Midair disintegration

I pushed some 6.5mm SMK's well over 3000 fps and pepperred my target with molten lead. Glad I wasn't shooting in a match when it happened!

 

[woostri]

Re: Bullet Failure Midair disintegration

Finally got around to testing this bullet failure issue. After having read some test articles provided by Berger when they had similar issues with some of their VLD lines. Aparently it's not so much a velocity/rate of twist problem as it is a friction creating heat in excess of melting point of lead issue....compounded by long bearing surface thin jacketed bullets. To prove this I allowed my barrel to cool for 30 minutes (plenty) so that it was cool to the touch. Fired one A-max into a target at 25 yards. Clean hole, no fail. Then i fired 15 rounds rapid fire (as rapid as a bolt gun will go) from another batch. Barrel was sizzeling hot. Then fired another amax in the hot barrel at 25 yards. Molten lead and jacket shreds all over the target. Both A-max chrono'd at around 3180fps. Only difference was a hot barrel. Now testing some 115 DTAKs with the BN coating and can't create a failure even pushing them around 3150. Barrel just doesnt heat up as fast and they have thicker jackets.

 

[eddybo]

Re: Bullet Failure Midair disintegration

I have yet to lose a dtac, but have lost many 115 bergers. They leave funny looking holes in your target backer, kinda looks like a boomerang went through the target.

 

[Country]

Re: Bullet Failure Midair disintegration

If the barrel is cut rifling it may be deeper and have sharper land edges than a button rifled barrel . Add this to tight twist , high velocity and maybe a thinner jacket than required and bullets can blowup .
Try the Berger thick jacket bullets. They have been developed for this problem . If cores are melting before jacket seperation then Moly coating might help. Start witha super clean barrel then don't clean the barrel too often let some moly build up also backing of on the load a bit .
However it is hard to say what part of the bullet is failing first , The jacket , the core or the ogive .
The barrel could also be rough inside and lapping may reduce friction could help if it is.
Heat can be an issue . If firing repeated times and the barrel is hot , the day is hot , the round left in the chamber watching the wind etc. Then add this to the other issues and it can be too much for the bullet to stand .

 

[Victor N TN]

Re: Bullet Failure Midair disintegration

If you're shooting a standard factory jacketed bullet OVER 3,000 fps you're on the ragged edge.

3000 fps
X 60 seconds in a minute
X 1 turn per foot from a 1:12 barrel
= 180,000 rpm That would make most things fly apart.

 

[woostri]

Re: Bullet Failure Midair disintegration

I thought the rpm's were the problem at first, but check my last post. Bullets measured at 3180 fps. All failed bullets and ones that made it down range were the same velocity. Only difference was whether I had a cool barrel or whether I got it nice and hot with other ammo before firing the A-max. Appears to be just a jacket thickness/bearing surface/friction issue. I've heard about the original Berger VLD's failing in similar situations but they have remedied that with the thicker jacket versions. I'm shooting 115 DTAK BN coated bullets now. Not only do they not fail but I have a hard time getting the barrel to heat up! Not that I want it hot, just an interesting observation. BN significantly reduces the friction. As long as nothing is melting, it should be hard to make a chunk of lead and copper fly apart, especially one with a very small angular moment of inertia like a 6mm. All that mass is still really close to the axis of rotation.....wow I just nerded out bad...sorry.

 

[vinconco]

Re: Bullet Failure Midair disintegration

My buddy and I had Colt H-bars (new) and after we put about 5000 rounds down the tubes start they smoking bullets (52 gr sierra @ about 3150) We had both bought them at the same time same shop and competed in the same competitions so when we changed out barrels we sectioned our old ones and found the chrome lining had flaked off closest to the chamber and was eating the jackets causing the bullets to smoke blue streaks. First it was the thin skinned varmint bullets but eventually the barrels would even smoke FMJ's. This was back in the early 90's and I haven't heard of this happening since.

 

[woostri]

Re: Bullet Failure Midair disintegration

Resurrecting this post from a long time ago. I've been using 115gr DTAKs, boron nitride coated since 2010.

I still have:

Not enough sense to read and follow the rules of the site so i think I will take a little vacation.

 

[BuzzBoss915]

Re: Bullet Failure Midair disintegration

I have a 22-250 Ackley with a Hart 6 groove 1X14". I had good accuracy with the 55 Berger, initially at over 4400fps max load, but settled on 4250 with a 1.5 grain reduction for hunting.

As it happened, I never fired a bullet over 100 yards until I took it to Az and had a coyote stand there while I attempted to kill him at over 200, maybe 250? Subsequent investigation showed that while they held together and made tiny bug holes at 100 yards, they did not arrive at 200 yard targets, and I don't shoot hot barrels.

This caused me to switch to a 65 Berger and I have been happy ever since. 3925fps gives me excellent terminal performance and acceptable accuracy for what I am doing. My conclusion: excessive RPM. BB

 

[woostri]

Re: Bullet Failure Midair disintegration

Wow 4000+ fps. I've never owned any calibers in that realm. Hows the copper buildup at those speeds? I noticed significant copper fouling with my 6mmAI as compared to my .308.

 

[Kinsman]

Re: Bullet Failure Midair disintegration

I tried 50 gr Sierra soft points in plastic sabot ( 65 gr total) over 77 gr of IMR 3031. Packed this in a 300 WM. 10 twist. Tried it at 25 yds, and the bullets never got to the target.
They was calculated to go 4700 fps.
Never did it again with a tuffer boolit.

 

[81Z4ME]

Re: Bullet Failure Midair disintegration

I've seen it with the thin jacketed varmint bullets in .223 when fired through a mini14 (1 turn in 9"). The reloading manual said not to shoot them through a mini14 due to the twist but I wanted to see what it looked like. You could see a vapor trail coming off the bullet (if you were watching someone else shoot it) and not all of them made it to the target.

The jacket has to be strong enough to withstand the speed/spin rate.

 

[woostri]

Too long a vacation away from snipers hide. Ruffled my feathers when I got kicked off for trying to sell bullets before I got to 100 posts. Oh well, that'll teach me to read the rules huh?

So I still have the a-max bullets that were failing. Never sold them. The new idea is to coat them myself with HBN and see if that will reduce the friction enough to avoid failures and hopefully keep the same velocities. Seems like I was getting around 3200fps when I settled on a good tight grouping load. I ordered 0.4oz of HBN powder at 0.5 micron from Bullet Coating Reloading Moly Hex Boron Tungsten Powder. Vitamin bottle plus 4.5oz of steel T-shot plus 1/4 teaspoon of HBN powder and a box of 105gr A-max bullets in a vibratory media tumbler for 2 hours. Came out nice and slick. Noticed they are a lot cleaner looking than the 115gr DTACs that I've been shooting from SSS.

 

[BigdaddyWSM]

Last night, my sons new (used) savage 10 GRS in 6mm creedmoor 1-7.5 twist blew 105 Amax about 20-25 yards from barrel with loads about 1 grain down from max. I gave him a few of mine which are same bullet with 3160 MV from my 1-8 twist Shilen and he blew them up also but mine don't.

any solutions, his barrel did have a lot of copper fouling & I didn't get all of it before we went shooting.

 

[BJames]

Wow. Blast from the past thread. I’ve run the 105 Amax’s to 3175 in 75 degree heat and never had a problem, 8tw, everything impacted where it was supposed to. More importantly, where did you find Amax’s in this day and age?!

 

[BigdaddyWSM]

Wow. Blast from the past thread. I’ve run the 105 Amax’s to 3175 in 75 degree heat and never had a problem, 8tw, everything impacted where it was supposed to. More importantly, where did you find Amax’s in this day and age?!

Gun shop had a few boxes on shelf still last week.