H4895 the safest bet for heavy M1A loads?

[Fatelvis]

I'm looking for a 175 SMK load for my M1A. I'm using a PFI RR900 scope that is calibrated for that bullet @ 2600fps. I realize I'm pushing the velocity envelope for the M1A platform with this goal, but I want the scope and rifle to work properly together, without beating the action to death. I also would like the chosen powder to be temp insensitive, due to the rifles use in a wide variation of temps. Would H4895 be the best place to look, given this has the perfect burn speed for the M1A's gas system? I like 8208 and Varget, but they both stray a bit from the H/IMR4895 speed. Any advice would be appreciated!

 

[Maj Dad]

2520

Accurate has long touted 2520 & the 168/175 gr bullets as _the_ load for M14s. My experience with it in my not-totally-match rifle has been super. I cannot say with 100% certainty it's the best powder, but it is one of them, and it sure loads easier through powder measures than the stick powders (though for match loads I meter then trickle to get an accurate charge). It doesn't do quite as well with 150s, but if you were forced to accept only one powder for the M1A, 2520 would do an excellent job. Accurate has also said it duplicates the pressure curve & burn rate of 4895, so from that standpoint you ought to give it a once-over...

P.S. Here's a link to an old thread http://www.thehighroad.org/showthread.php?t=508958

 

[Fatelvis]

I should mention that metering is not a concern for me, as I'm using an autoscale to throw charges. Thanks!

 

[Maj Dad]

You know, when I started reloading in the 60's I used a Lyman 55 (and still use it along with others) for all my metering. I don't recall using any ball powders, and for the stick powders I just developed my technique to cut the grains when I threw the handle. Now, stick or ball only figures in for loading on the Dillon, otherwise, it's what works best...

 

[Dave P]

I find H4895 is hotter than IMR4895, and I rarely use it.

An old favorite for the -14 is IMR4064 and a SMK175. About 41 grain.

 

[30Cal]

I use 4064 for the 175. You'll find that you need to make a substantial change in velocity to make a difference in come-ups. 100fps extra is worth, less than a minute at 600yds if I remember right. H4895 will work fine though.

Real data trumps data cards and scope knobs anyhow.

 

[USSR]

I would suggest something a bit slower burning than 4895, such as 4064, RL15, or Varget.

Don

 

[MEHavey]

When I look at what it takes to get a 175 to 2,600fps in an M1A barrel, 4895 still appears to win out on balance of chamber/port pressure:

IMR4895 43.0gr 2,600fps 53,284psi_chamber 8,362psi_muzzle(port)
IMR4064 43.2gr 2,600fps 57,545psi_chamber 7,921psi_muzzle(port)

Come to think of it, someone needs to tell me why any of these wouldn't be good candidates:
(Thats' RL-15 at the list bottom. No surprise that it would make the list)



DON'T start at these loads.
Depending on whose manual you have, some may exceed book loads

 

[Fatelvis]

Mehavey, thanks for that is awesome collection of info! Can I ask what program you're using, or where it came from? I never saw any way of determining port pressure before. I guess I'm stuck in the stone age! Lol Also, is that in a commercial case or a military case? Thanks!

 

[MEHavey]

That's QuickLoad, using the default (commercial) case -- pretty close to the Winchester case. QuickLoad will also let you calculate military case-volume effects.

I'm "assuming" port pressures are proportional to muzzle pressure, and therefore key off IMR4895's muzzle pressure as a reference point. Quickload will also give you exact (calculated) port pressures based on where the port actually is in the barrel, but Pmuzzle gets me close enough for gov't work.

Many folks will (correctly) note that it's not only port pressure that matters, but gas inertia relative to powder/gas mass as well. But all the powders weights above were "also" close enough to each other not to matter that much.

 

[Fatelvis]

I like RL15, but I know from experience it's temp sensitive in my AR. Could you plug in H4895 and Varget?

 

[Swampman]

My #1 choice for max M1a 175 gr. loads would be IMR 4064, with Varget in second place. I actually preferred Varget for several years, but large lot to lot variations in burn rate kind of soured me on it. RL15 is good, but velocity and pressure varies too much with temperature in my opinion.

I would strongly caution against the use of BLC2 in max velocity 175 grain loads unless you like having your cases automatically deprimed into your action as you shoot them.

All that you really need to do in order to get a definitive answer to your question is a Google search for:

"7.62mm Special Ball, Long Range, Mk316 mod 0".

NSW Crane put a lot more time, effort and money into this problem than a private citizen ever could.

The attached image shows what they came up with (Hint: THEY like IMR-4064 too...)




I think they made excellent choices, except for the case, I'd far prefer Lapua to Federal, but the military doesn't tend to worry too much about reloading their cases.

 

[MEHavey]

Higher (chamber) pressure for both.
That's why they didn't make the 1st list.

I'll be honest, BL-C2 (from that 1st list) looks awfully good.

 

[MEHavey]

Here's my actual Rangebook notes for the M1A load using IMR4895 and the 175SMK going for duping some LC81 Match ballistics:



So I know IMR4895 works to get you there.

 

[ArchAngelCD]

If it's temp insensitive you're looking for I would go with H4895 or Varget if you can achieve the velocity you're looking for.

I wouldn't worry too much about temperature unless you're shooting in very cold weather like zero degrees. If you won't be shooting in that cold of temps there's nothing wrong with IMR4895, IMR4064, AA2490 or AA2520. For your application I would go with IMR4064 unless you really want an "Extreme Powder" then it would be H4895.

 

[Swampman]

MEHavey: I never said it couldn't be done with either of the 4895s, It's just my belief that it can be done better with a somewhat slower powder.

While QuickLoad is an excellent resource, even their own advertising suggests that you check your QuickLoad generated data against known reputable loading data.

Here's your QuickLoad generated data.
H4895 42.1 gr. 2600 fps 55,096 psi
Varget 43.8 gr. 2600 fps 57,125 psi

And here's actual pressure tested, maximum load data from the Hodgdon website.

H4895 Max 42.7gr. 2647 49,000 CUP
Varget Max 45.0gr. 2690 48,600 CUP

You can check it here yourself.
http://data.hodgdon.com/cartridge_load.asp

I realize that PSI and CUP are not exactly linear in their relationship, but they're not opposites either.

Excluding Varget from a recommended list of powders for 175 grain loads in .308 due to its "Higher (chamber) pressure " seems a bit silly when the people that import and sell both powders claim higher velocity and lower pressures for Varget in that application.

 

[ArchAngelCD]

It's not the chamber pressures you need to worry about in the M1 and M1A, the the pressure curve. You don't want the pressure to be still building when the gases hit the port. That's why slower powders cause problems in those semi-auto rifles.

BTW Fatelvis, what are you using a 175gr bullet in an M1A? IMO a 165/168gr bullet would work better especially when you are looking for an exact velocity that is on the high end for a 175gr bullet but easier with a 168gr bullet.

 

[Swampman]

Varget and IMR 4064 are not slow enough to be problematic with the M1a gas system, 4064 in particular has been used competitively for many years.
The problem with the 168 grain MatchKings is that the BC is too low to allow them to remain supersonic at 1000 yards given the velocities possible in an M14 pattern weapon. The 175 grain SMK (as well as the 155 Palma) is able to accomplish this due to its higher BC.
I believe the main reason that Fatelvis wishes to use the 175s is that his optics are calibrated for the 175 SMK at 2600 fps.

Fatelvis: Have you considered installing a Schuster adjustable gas plug in your rifle? I didn't really need it because of any higher power level needed, I just wanted to extend the life of my brass. It has reduced case stretching quite a bit, I went from tossing the brass after four loadings to having some cases that have been loaded 9 times in an experiment to see how long they can actually last. In the interest of safety I've been doing both a paperclip test and an interior case inspection with an otoscope between firings.
Another benefit of the new plug is that the brass now lands about 3 feet to my right rather than 15 feet to my right and 10 feet in front of the line.

 

[MEHavey]

...realize that PSI and CUP are not exactly linear in their relationship, but they're not opposites either.
Excluding Varget from a recommended list...due to its "Higher (chamber) pressure " seems a bit silly

I do not debate that the Hodgdon site (and SAAMI itself for that matter) has higher pressure limits for tested loads.** And I do agree that CUP and psi are related (but not equal). I also agree that chamber pressure per se, is not the limiting factor in a Garand-type action. But that is not the point in any of this.

The OP is using an M1A, not a bolt action. A combination of chamber and port pressure/gas impulse (not simple pressure) is at work here. I will near always recommend a powder combination in those actions that has port pressure combined with powder weights "in the IMR4895 regime," AND total case fill, AND near (not totally complete) powder burn, AND the lowest chamber pressure.

There are at least six powders listed above that fit that that combination of requirements-- producing anywhere from 2,000-5,000 psi less pressure than VARGET -- for that 175gr bullet at that velocity. It's a fairly simple choice where to start at that point.
~~~~~~~~~~~~~~~~~~~~~~





**The poster notes that CUP and psi are not equal, and so they aren't. But they tend to become proportional when pressures approach the SAAMI maxes of 52kCUP/62kpsi. That translates to:

Hodgdon MAX
H4895 Max 42.7gr. 2647 49,000 CUP --> at least 58,400psi
Varget Max 45.0gr. 2690 48,600 CUP --> at least 58,000psi

Again, I'd simply not recommend operating that close to MAX if there are other options.

 

[Fatelvis]

Thanks for the replies guys. To answer your question, I am indeed using the 175SMK to match the PFI RR900 subtensions. I agree the 168 has been a wonderful bullet for me in Service rifle competition, but the ballistics fall a little short (at longer ranges) when compared to the 175.

Have you considered installing a Schuster adjustable gas plug in your rifle?

I've been kicking around the idea of venting somehow, and the Schuster plug and Sadlak grooved piston both came to mind. I think using one might allow the use of Varget and not worry about beating the action to death. Hmmmm.

 

[MEHavey]

Actually the adjustable plug will address the port pressure's impulse on the OP Rod (which isn't as big an issue for the M1A as it is for the M1), but still leave you with relatively high chamber pressure.

Probably not a problem, but your call.
(You sure I can't interest you in the newer mil-spec RL-15 ? )

 

[Fatelvis]

Lol, I can tell you really like RL15! Me too, but I've heard its pretty temp sensitive. I'm trying to cut out as many variables as possible to squeeze the most accuracy/repeatablility as I can out of this rig.

 

[MEHavey]

In the For-What-It's_Worth M1A column this afternoon:



Very blustery winds -- up to 35mpg gusts.
Figure 1/3 wind, 1/3 rifle, 1/3 my eyes.

Normal function.
Cases thrown to 2 o'clock.
Primers (a lagging indicator to be sure) "normal"

QuickLoad estimated 53.6ksi, 2,600fps

 

[Fatelvis]

(You sure I can't interest you in the newer mil-spec RL-15 ? )

Where can you get Mil-spec RL15? Is it any different than regular RL15?

 

[MEHavey]

The "new" RL15 is mil-spec since several years (~5?) ago when the military went to it as Lake City's M118 baseline.

Google RL-15 + "Lake City" + temperature + M118