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Hot 4064 Load vs. Maybe-Hot Varget Load?

Grump

Gunny Sergeant
Full Member
Minuteman
Oct 23, 2008
1,217
11
So. Utah
Advice and comment, please. Which would you go with and why? Am I likely to have longer barrel life with the Varget load?

These are with 155 A-Max bullets out of an M1A with a new barrel.

Load #1 tests quite accurately, .5 MOA for 4/5 and a called flyer, still under MOA with the flyer and it was NOT the steadiest bench that day.

It's 1/2-grain under the Sierra Max for their older Palma bullet, but about 30 fps faster than their max speed for their 26-inch barrel. The M1A is a 22-inch barrel, so I'd expect about 75-100 fps less
I get 2930 fps at about 90 degrees F.

Sierra shows 2900 fps max with Fed primers and a 26" Savage. My WLRs would be expected to boost velocity 20-40 fps anyway based on mine and others' experiences.

With Varget, I'm almost exactly 100 fps less at 2835, and the groups +.4 gr and -.4 gr from there are hitting the same at 100 and are only about 20-30 fps away as well. Haven't tested it for accuracy yet but it shows promise.

Sierra shows a max speed with Varget of 2800 with 155s, but with .4 grain less than what I'm using. Again, my shorter barrel would be guessed to be about 75-100 fps slower, so that "danger sign" on the load-to-velocity rationale is about equal with the 4064 load. Since so many people are running Varget loads and 155 SMKs to 2950, I wonder if the Sierra data for Varget is not quite realistic.

I'm inclined to go with the Varget load because I suspect slower will = maybe a bit less pressure and definitely longer bore life. BUT, the barrel life spreadsheet passed around here a few months ago shows Varget as burning noticeably hotter than 4064, shortening accuracy life.

I *could* test for a 2830 node with 4064, but the OCW startup down there wasn't giving great groups and they were not that close vertically.
 
Re: Hot 4064 Load vs. Maybe-Hot Varget Load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">Since so many people are running Varget loads and 155 SMKs to 2950, I wonder if the Sierra data for Varget is not quite realistic.</div></div>

2950-3000 fps is realistic for BOLT guns; just inside (or just at) sane limits to pressure. 2950 fps is way over the top for the M1A gas piston system.

I hope Greg comes by and answers more fully.
 
Re: Hot 4064 Load vs. Maybe-Hot Varget Load?

Thanks! What port pressure would you expect for a 2950 fps load with 155s? I could then decide whether to vent the gas plug.

I'm more concerned with bore life.
 
Re: Hot 4064 Load vs. Maybe-Hot Varget Load?

The 155 Palmas are designed to be optimal out of a longer barrel with a slower twist (typically, 30"-32" long, 1:12"-1:14" twist). You can get them going licketysplit out of the M1A/M14. but like the tale about the Hare, the old Tortoise wins in the end.

Use the 155 for SR/MR stuff, but trot out the 175 for beyond 600-ish yd. Good long range bullet, the 155 Palma, but the M1A/M14 isn't the rifle to be using it with all that way out there. My load for the 175 is 42.2gr of IMR4064 in Rem .308 brass. I would try the 168 and 150/155 with the same charge; the arsenal loads all used the same basic recipe with the various bullets. What's safe for the heaviest bullet should also be safe with the lighter weight pills.

Varget loads for the 175 are 45.0gr, for the 168, 45.5gr, and for the 150/155, 46.0gr. These are bolt gun loads, but the M1A/M14 can handle them in. People get concerned about moderately stout handloads in military gas guns, then think nothing of feeding them arsenal produced MilSurp ammo. That MilSurps stuff is actually pretty hot. I just can't say how accurate the Varget loads will be in the M1A. I think they'll probably do OK; but if they don't and you decide to develop them further, I wouldn't hardly go much higher at all.

Happy to see you're voicing concern for the gas system. All I can say about vented/regulated gas plugs is that if the rifle had been designed to handle the pressures they allow, they wouldn't be necessary. It seems sorta contradictory to be concerned about bore life and also be considering adding adaptations that permit hotter loads.

The important thing to understand about gas guns is that they prefer their fodder on the faster side, powder-wise, and lighter side, bullet-wise; and going heavy and slow is a nonono.

Too bad nobody makes a 26" M1A barrel. Hmmm. Can you envision a sniper and a spotter, armed with an M40A3, and an M14/M21 with the right barrel length to generate the same ballistic as the bolt gun? I see potentials here...

Don't overtighten the plug. The threads are not robust, and the system was designed to loosen up after about 60-80 rounds, then be retightened manually. The first symptom of a loose plug is erratic vertical stringing. Tighter than this risks stripping the plug/cylinder threads, and such items can be very hard find in order to replace. Those threads are the system's real Achilles heel, not the OpRod.

Final thoughts. Anybody can hotrod a bullet. Most hotrods end up either in the ditch or up on a lift with a rod sticking out the side of the block. Have a heart. The old dear is a great rifle if you accept its reasonable limits; but like most old sweethearts, it doesn't do so well as a race horse.

Greg
 
Re: Hot 4064 Load vs. Maybe-Hot Varget Load?

Well, finally got out for a re-test. Here's what I got:

155 A-Max
IMR 4064
WLR
FA63M Cases

43.1 avg. 2842.4 sd 12.4 ES 34.3

43.7 avg. 2883.5 sd 5.19 ES 15.9

I shot on a separate bull for each shot, then assembled groups on the grid target.

This test was a follow-up to some 5-round OCWs that showed some promise at 43.2 (2815.8) and 43.6 (2847.3). These, I cleaned out the necks with a Q-Tip after sizing.

This load (going with 43.4) might be tolerant enough of charge weight variations to use thrown charges instead of weighed for inside of 500 or 600 yards. Something like 7 fps per .1 grain difference, with the normal distribution overlapping the weigh-caused velocity changes.

I alternated firing the loads, and also numbered the cases in firing order. First shot from cold dirty bore was 1.5 MOA up from group center, and .75 MOA to the left. Curiously enough, the second shot (first with 43.7 gr) was about .75 MOA below and .25 MOA to the right of the first. The remaining 8 shots were in basically 1 group, about 1.3 MOA (one called flyer 1/2-inch right), and probably the limit for this barrel and rifle.

Varget loads shot lousy and velocities were erratic. VERY disappointing for weighed charges.
 
Re: Hot 4064 Load vs. Maybe-Hot Varget Load?

Well, QuickLOAD says that the speed I'm getting is overpressure for my barrel length.

Trying again with 42.5 4064, but it's a different lot. Made in CANADA?!?!?!? Okay. In the past, I've never had lot-to-lot variation with this powder, but that was back in the DuPont days.