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178 AMAX and transonic stability? Matters, or no?

QuietShootr

Sergeant
Full Member
Minuteman
Feb 5, 2003
448
84
After nearly a year and a half of consistent irritation with
non-shooting bolt guns I finally got one that shoots, and decided to wring it out by taking it to a 1000 yard F-Class match last weekend. I was pretty happy with my scores since this was the first sanctioned match I'd shot in 7 years or so. I didn't intend this to be a match gun, but I'm afraid the bug has bitten me.

I am having a little trouble getting the 178gr AMAX to 2650 (to keep it supersonic at 1000) with accuracy and a respectable ES (to be competitive at 1000 the velocity ES needs to be under 10, and to be truly competitive it needs to be around 5-7). The load I wound up using turned out to be TERRIBLE on the chronograph in terms of ES, but I did
wind up with an X-count of 4, with three of those shot consecutively (you want to talk about a good feeling - put three rounds into a 5 inch circle at 1000 yards with a .308 in a constantly shifting wind and mirage. I was walking on air for the next couple of hours :-D). I didn't get to chrono the load until after the match, but it took me 12
mils of elevation to get to 1000 from 100 yards, which indicated 2550 - which proved to be right on the nose when I chronographed it.

According to Exbal (and my friend in the pit) it was going subsonic at about 975, but the bullet was still making nice round holes in the target and more or less hitting what I was shooting at. The problem is that the load I used was not safe (I kept the rounds in an MTM box inside a lunchbox cooler to keep them around 40 degrees instead of 92
after I saw the flattened and cratered primer when I shot three at 10 PM the night before) and though they seemed to shoot ok at 1000, the ES was truly horrible and the primer looks like it was licking its chops thinking about taking out my right eye. So I'm starting more or less over, and I had a couple of thoughts that I wanted to run by the
assembled multitude.

As you know, the general rule is that you need to have your bullet supersonic at the target, or you're out of range. However, some bullets do fly fairly true through the transonic zone, and it looks like the AMAX 178 might be one of them, at least at 92 degrees and 45% RH. Plus, I know some guys who are shooting essentially the same load out of 16" gas guns, which puts the MV at about 2450, and they're getting hits to 1200. So what I'm thinking is that maybe I should stop trying to push that bullet faster than 2550 and just work on the accuracy and ES, and just quit worrying about the supersonic burnout range unless or until I start seeing screwy behavior at the 1k line. Opinions are welcome here. My gun seems to really like 43.0 of Varget - groups are dramatically tighter than any other charge weight I've tried so far.

I know I'm mixing my metaphors here by talking about a "precision rifle" in the military sense and working on match shooting as well, but it would be nice to have a load that's usable in both arenas (I know it won't be optimized for F-class competition, but I'm just doing that for
fun, not trying to climb the ladder in that world).

For reference - the load was:
New Lapua brass, FL resized in Redding die
43.0 gr Varget
178gr AMAX
Federal Gold Medal Match Magnum primer (GM210M)*
COAL 2.800"

*I did this because of the 50fps ES I was getting with the standard primer. Preliminary tests indicated substituting the magnum primer brought the ES down to under 10 - but that's not what happened later that afternoon. When I chronographed the load after the match, the ES was 91!

I got some RL-15 and am interested in trying it to see if I can safely get a little more velocity, but it seems my rifle really wants to throw the 178s at about 2550 for best accuracy.

Thanks gents.
 
Re: 178 AMAX and transonic stability? Matters, or no?

What did the primer look like? Is this a REM700 that craters primers due to the oversized bolt hole? Only reason I ask is it seems your load is on the light side for pressure issues. I've had good results with 44.8g Varget using Hornady match brass with no pressure signs. Of course case volume may be different.

Just a thought as you may find another accuracy node with a higher charge.
 
Re: 178 AMAX and transonic stability? Matters, or no?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: xmark</div><div class="ubbcode-body">What did the primer look like? Is this a REM700 that craters primers due to the oversized bolt hole? Only reason I ask is it seems your load is on the light side for pressure issues. I've had good results with 44.8g Varget using Hornady match brass with no pressure signs. Of course case volume may be different.

Just a thought as you may find another accuracy node with a higher charge. </div></div>

It's an FN A3G. I'll get a pic of the primers.
 
Re: 178 AMAX and transonic stability? Matters, or no?

i too want to see your primers. is it the listed load above you are concerned with for pressure? if so, there is no way in hell you have a high pressure load with 43gr of varget in lapua brass. i also have a really hard time believing your velocity is only 2550. i ran 43gr of varget in win brass which has a little bit thinner wall which is less pressure running 2610 out of my 24" 1/12 schneider with the 178 amax. i wasn't even close to a pressure node. i ran 45gr varg in the same set up with absolutely no pressure as well and it yielded 2700ish.

i'm still at the same stand point with the ES stuff man. the round on target tells the story. the bullet has the final say if the load is good not the es or sd.
 
Re: 178 AMAX and transonic stability? Matters, or no?

Okay - first the primers:
05022471.jpg


and a printout of the chronograph from after the match:
69aa0169.jpg


The primers are, as I said, Federal GMM LR Magnum. Those don't look pretty flat to you guys?
 
Re: 178 AMAX and transonic stability? Matters, or no?

Why are you using magnum primers? Use the 210M and not the 215M. You might be able to get better spreads and more powder to get more velocity.

Those primers look fine to me. I can still see the rounded edge and there's no ejector marks either.
 
Re: 178 AMAX and transonic stability? Matters, or no?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">Why are you using magnum primers? Use the 210M and not the 215M. You might be able to get better spreads and more powder to get more velocity.

Those primers look fine to me. I can still see the rounded edge and there's no ejector marks either. </div></div>

I was trying to lower the ES, and I read a couple of places that that was worth trying. When I increase the charge of Varget, the accuracy drops off.
 
Re: 178 AMAX and transonic stability? Matters, or no?

i see no pressure signs there at all. the crater from your firing pin is about like every other non custom action pin mark i've ever seen. i think they all do that. the shoulders on the primers look fine and no ejector marks equals carry on. you got bigger groups because you bumped your charge into a scatter node. keep going up. i go up in .2 increments until i find the node then play around with .1 around it till you are in the center of the node.
 
Re: 178 AMAX and transonic stability? Matters, or no?

How far did you go with your charge weight? You may have to go a ways past 43 to hit another accuracy node. I can understand not wanting to though if you are concerned about pressure. Are there any other pressure
symptoms such as heavy bolt loft? Ejector swipes don't seem to be a problem yet.

As Rob stated might be worth trying another primer.
 
Re: 178 AMAX and transonic stability? Matters, or no?

I'll let the other guys continue to advise on ES and SD. I try to look at the % variance for loads, but overall you're on the right track IMO.

For the stability/transonic questions my experience is this:

11.25tw 308 20" tube - 178's @ 2545fps hit point first and were easily repeatable at 1275yd.

8.5tw 308 21.125" tube - 178's @ 2555fps hit point first and were easily repeatable at 1275yd.

10tw 30-06 26" tube - 178's @ 2945fps hit point first and repeatable (and supersonic) at 1275yd. At 1500 they hit in a tight waterline but my ability to judge the wind at that distance with such a setup was eating me up and the group in the dirt was about 1MOA tall x 6 MOA across.
 
Re: 178 AMAX and transonic stability? Matters, or no?

Check your loads on a different chrono. Or, try a different set up to see if something was amiss with the screen readings, new battery etc.. And, as stated try non-magnum primers.
 
Re: 178 AMAX and transonic stability? Matters, or no?

I don't know if this has been mentioned yet, but have you checked the accuracy of your powder loads? Perhaps your scale is off and deviating by a few tenths of a grain.
 
Re: 178 AMAX and transonic stability? Matters, or no?

You could probably seat the bullet out a little farther. My FN SPR with DBM accepts a 2.835 COAL. The throats on these rifles are usually pretty long, but check it to be sure. Seating out another .020-.030 will tend to drop pressure a little and let you go a little higher on the powder.
 
Re: 178 AMAX and transonic stability? Matters, or no?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kolkio</div><div class="ubbcode-body">Check your loads on a different chrono. Or, try a different set up to see if something was amiss with the screen readings, new battery etc.. And, as stated try non-magnum primers. </div></div>

I am now beginning to suspect a chronograph malfunction. Will report back with more details.

And yes, I will push them harder and see if I can get to the next node. Maybe with RL15?
 
Re: 178 AMAX and transonic stability? Matters, or no?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chavezz556</div><div class="ubbcode-body">I bet it's your powder charge . Have you double checked them on a triple beam style scale ? I like to use 43-44 grns of varget for all my 168-178 loads .... </div></div>

No, I'm using a PACT dispenser/scale unit. I toss back anything that isn't dead nuts, and I calibrate it with a check weight before every use. I don't think it's the charge.
 
Re: 178 AMAX and transonic stability? Matters, or no?

I wouldn't believe those chrono numbers. I hand throw most everything and never see 90fps swings with my varget loads.

~12 mils to 1k yards sounds about right. That is what it took my 308 to get there when it was shooting around 2500-2550fps.

Go faster imo. Maybe like 44 or 45 varget and a little messing with seating depth. Ditch the magnum primers as well they aren't necessary. Mild primers like CCI reg or match are what you want with varget.
 
Re: 178 AMAX and transonic stability? Matters, or no?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body">I wouldn't believe those chrono numbers. I hand throw most everything and never see 90fps swings with my varget loads.

~12 mils to 1k yards sounds about right. That is what it took my 308 to get there when it was shooting around 2500-2550fps.

Go faster imo. Maybe like 44 or 45 varget and a little messing with seating depth. Ditch the magnum primers as well they aren't necessary. Mild primers like CCI reg or match are what you want with varget. </div></div>
+1 Agree 100%! Just work up slowly and watch for pressure.