Amax blowing up?

[StraightPipes]

This might belong on the reloading board, but the traffic is here.

Just caught this today. Shooting 5 round groups at 100 yds, on a clean backer and a fresh target 1 round magically disappears. What the???????

I was asked this question, are you blowing up those Amaxs? Well, in the past Hornady has left me with the impressions that they are "thin skinned". I dont normally shoot them, but these Amax bullets seem to work for me.

The bullet; 7mm 162 Amax. breaking the speed limit @3100fps. 8 twist

I blamed myself in the start of this, even though this is not typical for me to miss my target by 12 inches. So, lets spread the shots out to 2" and do the count. Sure enough, on the next set of 5 rounds, 1 round missing!! The rest of the session produced 5 round groups.

Anybody finding this or am I too fast? Can anyone declare that they do in fact "blow up" the Amax?

 

[CJ6]

I've run the A-Maxs QUITE abit faster in an 8 twist and have had no issues with blowups.

 

[Preacher]

I lean on the 162 Amax a lot too in a 7mm SAUM AI and never had one blow up that I know of...

 

[therifler]

what kind of rifle are you shooting and barrel ?T.R.

 

[Wetz]

I shoot a 284 win at 1000 yards. I run 162 amax around 3100 fps. never lost a round in five years. 9 twist.

 

[StraightPipes]

I need to dig deeper into this one. ??? Thanks for getting back on this. I was hoping that blow-ups were my problem.

 

[StraightPipes]

I still havnt solved this problem.

A fellow shooter is having the same thing happen to him though. The only common factors between us are these;
1. we both shoot 4 groove barrels ( different brands)
2. we both plate our bullets

Mine dont make it to 100yds, his are jacketless at 300 yds.. The "bullet cores" do find their way to the target, with an accuracy problem of coarse. The "jackets" are pealing off.

I might add that the bullets come from different lots also. Now, to evaluate fairly. I have "0" problems with my Sierra loads at the same average speed.

More factors; mine is the 7WSM, his is the 300WSM. Mine is a custom barrel, his is a factory barrel. Mine is a 8 twist, his is a 10 twist.

The Amax is coming apart in both rifles, this is for sure. Anybody else seeing this?

 

[fivering]

I have seen many instances of A-Maxes blowing up with fast twists and hot loads, especially in the 6mm. I have had no problem at all with the .223 in 1:9 blowing up.

 

[CJ6]

Something else to look at . Are these OLDER A-Maxs. The original A-Maxs had a much bigger/longer TIP 1/4-3/8 or so,these were known to be fragil in fast twist /mid/higher velocity use. Hornady changed this style to the smaller tip now in use some years ago (5-6yrs maybe ). In the PLATING process are you getting TOO MUCH thickness? This would increase pressure on the bullet itself effectively increaseing the bullets diameter )like useing a .309-.310 dia. bullet instead of a 308 for example or .285 - .286 diam. for a 7mm.

 

[StraightPipes]

CJ6, these are new lots. I remember the older type. These aint it. The plating is quite thin, adhesion is not the best on the Amax for whatever reason.

I push these things to 3050 in the 8 twist 7mm. The 300WSM is only running at 2850-2900 with the 178 Amax. I stopped shooting Hornady some years ago because it was my belief that their jackets are "too" soft. Im inclined to think that this is "still" the problem. In going back to a load I had for the Sierra SMK, (plated) They run @3100 fps with out a problem.

Jackets? Cores? We will see what Hornady has to say. I did contact them with the earlier problems and of coarse it was the first they had heard of it. That was 3 years ago, probably get the same reply this time.

Just to be fair to those that dont have these problems, I will say that when the Amax holds together it is very accurate. I like the "point", saves on meplat trimming and pointing. But, if the new dog wont hunt he belongs at the back of the pack.

 

[queen_stick]

Not sure if you'd be willing to try it, but maybe send some 'naked' bullets down range and see if the problem still exists?

Not many people have responded yet, but so far you and your friend are the only ones with bullets blowing up, with the exception of trying to push the bullets to extreme velocities, like mentioned by fivering. You're also the only one's, that have responded, that are plating bullets. I agree that plating shouldn't cause the trouble, but it's only difference between your load and what others have loaded at the same velocity.

Walt

 

[Laurie]

A friend shooting 7mm A-Maxes 'lost' a couple of shots in a GB F-Class Assoc national round back in 2008 and switched away from this make to Bergers as a result. I've also 'lost' bullets in an 1-8" twist .223 Rem with modest loads from a Lilja barrel. It did it with three weights of A-Max, but not the others, nor with any other make - and I loaded Sierra, Berger, Lapua, and Nosler bullets for this rifle, well over 20 individual bullet models from 52gn to 90gn (the 90s didn't stabilise).

There has been a fair bit of work on bullet blowup by some people, notably Berger Bullets, who after they received reports of it happening in hot 6.5 and 7mm cartridges with the original thin-jacket VLDs, acted on them, rather than denying it happens or saying it's the customer's 'fault', which is the usual corporate repsonse to this sort of thing.

Surveys and tests done by those with an interest show it is very difficult to create blow-ups under controlled conditions as it is caused by the interraction of multiple factors including barrel internal configuration and land/groove design, amount and nature of wear of the barrel, amount and type of bore fouling, ambient and barrel temperature, as well as the ones you would expect - load, pressure and MV.

Two things that I noticed with 52gn A-Maxes blowing up from my .223R were (a) it only happened in very warm weather, and (b) the first few shots grouped tightly, then elevation consistency collapsed as a prelude to losing shots. Letting the barrel cool only partly helped once it was fouled. Bystanders saw the bullets explode in a puff of grey smoke at around 80-90yd range, while the 7mm failures in the F-Class round appeared to occur at longer ranges. This would suggest that even where bullets don't fail completely, it might be a cause for inexplicable fliers or accuracy deterioration in the last stages of a shoot.

Laurie,
York, England

 

[StraightPipes]

Queen stick, thanks for the reply. Yes, naked or not they still frag at 100 yds or so. As to the 300wsm, they come apart about 300 yds. To note the extreme velocity, our speeds arent there yet. Its been noted that this problem exists in other calibers also, re; 6mm-6.5mm and some others. Im looking at the 4 groove factor currently. This is common to my problem. Considering the width of the 4 groove land, could the "friction" due to the width of the land be "smearing" the jackets off of the core. Well, even with the Ws2 plating? I wonder. Keep in mind that the Sierra wont frag.

Laurie, It sounds like you might have been around this problem in the past.??? Your experience is noted. As to ambient temps, this is going on around 50*fh.
I dont believe that anyone here will flat out "bang" Hornady for what is happening, but I do think that the Amax design has proven itself. Well, at max speeds and max ranges something should be corrected in the design or under "controlled" conditions a compatibility issue should be offered to the shooting industry. Who will take the time to discover it?
Im getting closer to suggesting that it is a friction or temp issue due to "soft jackets". But then it was just mentioned that a "thin" jacket could cause my problem.

 

[StraightPipes]

Hey Laurie, I just reread your post. I think this is making some sense. Would "you" think or agree with me on my "jacket smearing" theory? What you explain in your post is "temp" related, yes? Also, as the copper builds up in the bore(enter my theory) you find your accuracy going away very early in the game.
If this is simply the problem, then I have a simple answer to the problem. I will continue to think about "land width" as being part of this. In the case of the Amax that is.

 

[Laurie]

I haven't seen anyone mention the number of grooves before, but Boots Obermeyer, Dr Geoff Kolbe (owner of the UK's Border Barrels) and now it seems Bartlein Barrels among others argue the 5R rifling form provides greater bullet support and less stress on it due to a land always being opposite a groove with the radiused grooves also easier on the jacket.

From what I've gathered on discussions on this, and I'm no engineer or technical sort so may have misunderstood some of them, there are probably not only multiple causes or factors that contribute to blow-up, but also more than one process in play, so the jacket and core might slip in one scenario, and the jacket fails under another, say.

What I can say is that my 0.224" Lilja barrel and some, but not all, Hornady bullets didn't get on. It would 'lose' 1 or 2% of Hornady 68gn HPBTM bullets for instance, but I've never heard of anybody else having this happen with this bullet. I never had a 75gn A-Max fail though despite firing hundreds in both load development and competition, and I also fired a fair few 80gn A-Maxes without trouble, although the accuracy was never that good with this bullet. What is noticeable about the 0.224" A-Maxes is the jackets must be on the thin and/or soft side as the seating stem mouth on my Redding Comp seater die would impress a noticeable ring in the shoulder if the bullet was at all a tight fit in the case-mouth, something I never saw with Sierra 69s, 77s or 80s, for example.

Incidentally, my barrel (since taken off, remelted and turned into kitchen sinks or knives or something, probably in China) was a four-groover, so that part fits your thesis. I only have a stock Remington 700SPS Tactical in .223R at the moment but have two 1-7" twist build projects in the pipeline if and when I can get barrels - a custom F/TR rifle with a 30" True-Flite (New Zealand) 6-groove barrel, and a rebarrel job on a .204 Ruger cal Savage 12 LRPV with a factory Savage 30" 1-7" twist tube that will come off a new .223 Savage 12 F/TR rifle when the rifle builder gets one. The idea in the first rifle is to see if .223 can stack up in F/TR at all ranges against .308W and will be chambered to suit the Berger 90gn VLD seated right out; the second is a 'poor man's' F-Class rifle for use up to 600yds, to see how that performs.

Laurie

 

[skeetlee]

I have had them blow up in 6mm barrels!!! There are better bullets on the market so i dont buy them anymore! Thats how i fixed the problem i was having. the bergers made little dots!!!

 

[yat3b35]

First a question , What die are you using to seat your bullets ?
This may be your problem , I blew several 105 amax bullets up in a 243 AI , then after talking with Lonnie Hummel of Hornady switched to one of their seating dies with a seating stem designed especially for the amax bullet. Seems the standard seating stem was weakining the copper near the tip causing it to come apart. The amax seating stem is designed as to not harm the tip. Problem solved , never blew up another one .
Hornady part # for amax seating stem from their web page is 397107 . You may want to give it a try , course you'll need one of Hornady' seating die too.
Just food for thought. John

Forgot to add that with a regular seating stem that you could see a small ring around the bullet just below the juction of the tip and where the jacket began. When I got the new seating stem I also took a piece of emory cloth and polished the inside of the seating stem just to be sure there was no burrs or inperfections.

 

[StraightPipes]

jhadams, all good points. I use the Forester Benchrest Seater. The stem was replaced with a Forester J-7 stem if my memory serves me. This stem was designed for seating "tipped or long ogive " bullets.

Yes, this stem will leave the "ring" that you mention just below the tip on the Amax. BUT, it will not leave the ring on any other bullet that I shoot, "0".. I still have to maintain that the Amax jacket is too soft. I dont think that I will start changing out dies and parts to shoot the Amax at this time. Its been noted that there are better bullets out there.

I tried, not until the end, but enough.

What say you, Hornady?

 

[blue avenger]

I had some 6mm 105gr a maxs I used to site in a 6br saturday. dead center at 50yds and not on the 8x11 paper at 100yds
tried again today and they looked like they were tumbling at 50 yards. nothing at 100 again.

 

[StraightPipes]

Well guys, thanks for the input. And Laurie, will you shoot another 4 groove??