A-Max problem?

buffalorancher

Well-Known Member
Joined
Mar 14, 2006
Messages
178
Location
Nebraska
I'm going to try a long range prarie dog tomorrow at a friends ranch so today I found a good load for my 6-284 using a 105 gr A-Max and 49 gr RL-22. It shot a five shot one hole group at 100 yds going 3265 fps with no pressure signs. This was using new sized Lapua brass so I shot another 5 shot group with twice fired brass. There were 2 shots touching and then the zinger, I had one keyhole about 1/2 inch left and a half inch low. This shot chrono'd at 3272 and the next two shots completed a group that was about .3 inch. I am far from an expert and these groups are very good for me. There have been about 30 of these bullets down the barrel with no problems and it seems to me that an unstable bullet wouldn't have been so close to the other shots. Was this a bullet failure that was just a fluke or what? Should I be concerned as I was hoping to use this bullet on whitetail this fall? My rifle is a CRF M 70 with a 30 inch ABS/Rock 1-8 twist. Any input would be helpful.
Thanks
Lance
 
If it was just the one bullet that flew off target i probably wouldnt worry about it. The Amax is one of my favorite bullets but like any mass produced item there will be the occasional flaw. I also like the amax for a varmint bullet over alot of the berger or sierra bullets because the polymer tip ensures better expansion at low velocties than the other bullets tend to produce.

go shootin and have fun

take it easy
steve
 
There was nothing the bullet could have hit except maybe a bug. I'm not sure what kind of possible solution I'm looking for as I think this was something of an oddball.
Lance
 
You will find my friend that in most cases, a 6-284 with a 1-8 twist will be limited to around 3250 to 3300 fps with the 105 gr A-Max.

I would be currious to see how wide the lands are on that Rock barrel. I got one of Mikes 7mm barrels for my 7mm AM to shoot the 200 gr ULD RBBTs as the Lilja 3 groove barrels were tearing them apart after a few hundred rounds or less in some cases.

Well, right from the start the Rock was tearing bullets apart at any velocity. The reason, to much bullet baring surface compression.

Called up Rock Barrels, their main barrel maker worked with me, thinned the lands and now their bullets work perfectly.

I would suspect this is a similiar problem as you are seeing.

You are just not tearing them apart but if the jacket core bond is weakened, accuracy will suffer ranging from poor groups to total bullet failure in flight.

Since this was just one bullet, I would not worry to much about it but pay attention. If those bullets seem to not make it to target like they should, make a mental note.

Good news, you can always use the 107 gr SMK as it will take alot more velocity before loosing accuracy.

My personal 6-284 will get 3550 fps with the 105 gr A-Max. Only problem is that anything over 3250 fps will cause accuracy to go to hell instantly, same with the Berger 105 gr VLDs. THe SMK can be driven to 3550 with fine accuracy all the way up with its thicker jacket.

Anyway, just something to be aware of. If your getting more then around 25% baring surface compression on your bullets from the lands, you may be having this problem and I suspect your well over that if the 6mm Rock barrels are similiar to the original 7mm Rock 5R barrels.

Again, just pay attention when your shooting. May be a one time deal, may not. Time will tell.

Kirby Allen(50)
 
Hi no one here in Australia uses 105gr A Max's in 6mm284's because they do seem to blow up regularly. The 107gr Siera seems to be the most stable projectile in the larger bored 6mms

Cheers Bill
Australia
 
The 107 gr SMK's shoot very well in my rifle with about any reasonable load, they just don't perform on deer way out there. I was hoping the A-Max would work better as some people have indicated it would. The accuracy and velocity is fine with me, I just don't need a bullet going goofy at the wrong time. I loaded some 87 gr V-Max and got I think 3700 fps but it was good then bad on the consistency. It's time to stop working on paper and try some fur. We'll see what happens tomorrow and I have some 105 gr Berger and some 110 gr Wildcat that may work better but there has been quite a bit of powder burnt on some mediocre results.
Thanks
Lance
 
I would agree, the 6mm SMK leaves a bit to be desired as far as on game performance. The A-Max would be much better. That was my thinking as well with my 6-284 but I could not see limiting my rifle to 3250 fps when it was built and easily capable if 3500 fps with this class bullet.

One more question, Are you seating the A-Max into the lands? This will be your best bet to get them to handle as much velocity as possible. YOu do not want that bullet to get linear velocity before engaging the rifling. You want it turning from the moment it starts down the barrel.

May have to drop your load off a bit if your off the lands now but 49.0 gr should not be a very hot load in a 6-284 unless the throat is VERY short.

I would be amazed if the Bergers acted any different then the A-Max. They have not in my experience but they are worth a try. In my rifles, they are limited to the same 3250-3300 fps as the A-Max.

With the 110 gr Wildcats, take 10% off your load to start with that bullet. For some reason, they seem to pressure up quicker then one would think. Once you find a comfortable starting point your fine but they do generate more pressure then a SMK will from what I have seen and heard. I believe they have a thicker jacket, at least the ones I have do.

One other option you may consider is the Berger 115 gr VLD. YOu could get up to the 3200 fps range and still get better expansion then a SMK. Higher BC as well.

From all the 6-284 I have built, I will never put another 1-8 twist on one that is ment to shoot the 105 to 107 gr bullets. The only barrel I will use is a 1-9 6 groove Lilja. With that barrel you can get 3500 fps with the A-Max easily. Amazing what an inch slower twist will do and a much thinner land for less baring surface compression.

Keep us posted.

Kirby Allen(50)
 
I have also had issues with the 115gr Berger when run fast and believe they are on the edge of holding together when shot through a 6mm284. The 115gr DTAC seems to hold up much better at high velocity but it will be similar to the 107gr Sierra in performance. Their is light at the end of the tunnel though David Tubb has had Sierra re design the 115gr to a 117gr it has a plastic tip and should be coted with Boron and have a BC around .6+ so if it shoots it could be the best long range mass produced 6mm projectile available to us.

Cheers Bill
Australia
 
Pickup some 105 Bergers you will be happy you did. They will work on anything from P-dog's to Deer way out there. They really seem to have a whitetails number I was amazed on all the ones I shot this last season.
 
Well, it was a nice day for shooting prarie dogs yesterday. Maxed out at 60 deg. with light and variable winds, not bad for northern Colorado. The A-Maxs wound up performing about like Kirby said they would. The first five shots were dead on out to 417 yards then the bullets started wobbling about 1 out of 3 times and hitting the dirt all over the place. This went on for about 15 shots then they started blowing up until they did it every shot. All this happened over about 3 hours with the temp steady except for a couple rounds that showed ejector marks from getting warm in the sun. These barely made it out of the barrel if at all. The build up in the barrel seem to be the culprit that pushed them over the edge as I started cooling everything down in the AC to see if it made a difference and it didn't. I am dissapointed as the bullets seem to perform well when they stayed together but if I need slower velocity I would have built a **** 243 and not worried about it. It seems the 6-284 works better with slow twist barrels and light bullets going like hell. I think I am going to slow the A-Max down or try the Berger but I would have to agree with Kirby on the barrel twist after my experience. The few SMK's I had shot great after the blow ups so I have that option and the prarie dogs didn't know the difference. On a completely difficult note, I wonder how hard you can push the ABS barrel as you can't tell how warm it really gets. I remember the post with the thermal camera but it makes me nervous blasting away so I try to avoid it but when you miss a PD by inches way out there you have to keep on him if he let's you.
Thanks
Lance
 
I have had many potential customers bring in their 6-284 for rebarreling because the barrels were shot out, Supposedly. These were not rifles I built but they did exactly what your rifle is doing now.

The cure was the SMK in most cases.

Problem with down loading the 6-284 is that yes you can get velocities down to where the A-Max will survive the launch but this posses another problem, carbon fouling. As the chamber pressure decreased, carbon fouling will increase and this is a minor reason why the bullets come apart the more you shoot them.

I have also recommended to a couple of my customers that they give the 95 gr Ballistic Tip a try. Now before all you long range 6mm guys jump on me because this is not a long range bullet, remember this bullet will handle any velocity you can out to it in a 1-8 twist barrel with any rifling design. Because of the velocity advantage, This bullet may suprise you.

To test my theory before recommending it to my customers, I tested this bullet in my rifle. In my 30" Lilja 3groove 1-8 twist I was able to push 3700 fps with top end loads. THis was a load that would allow 4-5 firings per case which I consider my criteria for top end pressures. If you compare the 95 gr Ballistic Tip to the 105 gr A-Max out to 1000 yards it suprised even me. Here are some numbers:

These numbers are using a BC of .38 for the 95 gr BT and .5 for the 105 gr A-Max. Both zeroed at 100 yards.

Muzzle energy
95 gr...........2887 ft/lbs
105 gr..........2462

500 yard energy
95 gr...........1203
105 gr..........1235

750 yard energy
95 gr...........733
105 gr..........847

1000 yard energy
95 gr...........436
105 gr..........571

Now certainly much past 500 yards, the A-Max has an edge in kenetic energy but not much. Even at a full 1000 yards it has less then 140 ft/lbs more energy. For hunting deer, I like at least 1000 ft/lbs and an expanding bullet. Using that limit, the 95 gr will have that level of energy out to around 590 yards. The 105 gr will carry that energy out to 640 yards so there is really only a 50 yard different. Energy is not the only criteria however.

For smaller game, both have plenty of energy for shooting out to well past 1000 yards so energy is not a concern with varmint hunting and both are tipped bullets so they will expand as well as any bullet will at long range.

Lets look at bullet drop numbers again, both with 100 yard zeros. I will list the bullet drop in moas so you can see what you would need to dial into your scope.

500 yards
95...........5.75 moa
105..........7.15 moa

750 yards
95...........12.17 moa
105..........14.18 moa

1000 yards
95...........21.5 moa
105..........23.5 moa

So as far as bullet drop is concerned, the 95 gr BT with the velocity advantage has less drop even out to 1000 yards, a full 2 moa less drop or roughly 20" less.

Certainly the higher BC bullet will have an edge as far as wind drift but not by a great deal. At 500 yards, the 95 gr pill is blown only 2" more by the wind then the 105 gr. At 1000 yards, it has about 16 more inches of windage in a 10 mph wind or roughly 1.5 moa.

My point is that yes the 105 is a better long range pill but there are other options and the 95 gr bullet will offer very good performance and out to the 600 yard range, it is hand down a better game bullet for deer size game.

Also to be fair and to those just coming into the conversation, yes, if the 105 gr A-Max were loaded in a rifle that would allow it to be driven to 3400 fps which is totally practical in the 6-284, this would not be much of a comparision, but in some rifles this is simply not the case so we look for alternatives that give good performance with good terminal results as well.

The 95 gr Ballistic Tip and Ballistic Silvertip are not bad choices in rifles like these. They are worth a try at least as they will allow the 6-284 to run at full pressure and at least they will shoot cleaner then a low pressure load with the A-Max.

Just another idea.

Kirby Allen(50)
 
Kirby,
Thanks for all the input on this. When I was trying to get a good load for the 87 gr. V-Max I noticed how the velocity really made up for the lost BC on drops out to 1000 yds. There are a couple of boxes of 95 gr. BT sitting on my bench that I picked up at a gun show so I'll see how they shoot.
Thanks
Lance
 
Let us know, may get you close to what you want until you get that barrel burnt out and then get a 1-9 6 groove and really rip those A-Maxes out fast.

Kirby Allen(50)
 
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