Has anyone shot this ammo through their M1A?

[Red State]

I tried this ammo this weekend and got my best ever results. A 1.1" group from my 18" Scout Squad M1A. Other than mounting a scope over the reciever and having some trigger work done, it is a bare bones unmodified gun.

Anyway, this ammo shot really well.
http://www.midwayusa.com/viewProduct/default.aspx?productNumber=916481

AFTER shooting half the box I found a warning label on the bottom: "not for use in semiautomatics".

***! Its not a heavy bullet, so I hadn't considered that there might be any kind of issue. I called Hornady and a tech told me that it uses a slow burning powder that is optimized for the long barrels found in Palma matches and that the gas pressure may be too high when the gas hits the M1A gas port.

I am bummed now. This was by far the best ammo I have found for my M1A and I have tried several different 168gr match loads. Too bad that using it long term is probably a no-no.

 

[Red State]

Here is a picture of the group.

 

[TonyAngel]

I'm guessing that the "Palma" designation refers to the powder load used, rather than the bullet, because I'm not aware that Hornady released a new A-Max.

In any case, no need to get bummed. You just need to get into reloading, if the warning worries you. You can shoot the bullet that gave you good results and tailor the load to your rifle.

 

[Hangingrock]

One if they wish may rotate the spindle valve cutting off the gas flow thus a straight pull action manipulating the operating rod.

 

[henschman]

Or you can always get an adjustable gas plug and turn the gas down to a setting where it is just enough to cycle the rifle with that load.

 

[Slamfire]

I think you are restricted to a 155 grain bullet for Palma.

Palma shooters have weight restrictions on their rifles and bullet restrictions. They put the longest barrel they can to up the velocity as much as they can. Slower burning powders make sense in this application.

Slow burning powders do not make sense for a gas gun, especially for Garands and M1a's.

High pressure at unlock accelerates the bolt and connected parts. Garand operating rods are long and thin and get bent, probably at impact with the receiver. M1a operating rods are much stiffer but the saddle will end. In both rifles the bolt rebounds off the receiver heel.

Given enough impacts the back of the receiver will crack. Springfield Armory thickned the sidewalls of their action but receiver cracks will happen given enough rounds. A bud of mine gat a small crack around his 5th or 6th barrel.

Slow burning loads will just cause the bolt to rebound faster.

This is an example of a cracked Garand receiver. May have taken a long while but it happens.

 

[fragout]

You mentioned that you have tried other match loads, but nothing specific, so....

I have had great results with FED 168gr OTM M852 with my M1A-A1 Bush rifle.

The stuff is reasonably priced, and is loaded specifically for the M1A's gas system.

Worth looking into if you haven't already.

11B

 

[bigedp51]

The 7.62 in the M14 was set up for powders in the burning rate of IMR-4895, if you use IMR-4350 you bend the op-rod from high gas port pressure.

Please note the Lyman data is from 1968 before the transducer method was adopted and is in CUP. The ARMY TM is also using the CUP method BUT lists the pressure in PSI because both the CUP and transducer method are in Pounds per square inch.

Also note the Lyman loading is 42.5 grains of 4895 and the military loading is 42 grains of 4895 and the pressures are very close for the powder loaded with the same bullet.






Please note that 50,000 cup is equal to 60,000 psi (transducer method)

 

[Slamfire]

Please note the Lyman data is from 1968 before the transducer method was adopted and is in CUP. The ARMY TM is also using the CUP method BUT lists the pressure in PSI because both the CUP and transducer method are in Pounds per square inch.

Army TM's are not reloading manuals. It just happens to be happen stance that 42.0 grains of the particular lot of 4895 gave 2550 fps.

IMR 4895 sold to the public will have a different burn rate because these lots are mixed to a nominal pressure curve.

The military buys unmixed powder, develops loads with pressure barrels, uses what quantity of powder is needed to give appropriate port pressure and velocity.

I would not use 42.0 grains of IMR 4895 with a 174 or a 168. The most common 168 grain load was 41.5 grains IMR 4895, LC brass. For a new rifle I would cut that to 40.5 grains.

 

[Red State]

Well I talked to both Hornady and Springfield yesterday.

Hornady reiterated that the ammo was "not recommended" due to the slow burn rate of the powder.

I called Springfield and talked to a tech about this issue. He looked at the Hornady website while on the phone with me and he didn't see any problem. He said that I could put a stronger recoil spring on the bolt if I was worried about.

So with either the Schuster adjustable gas plug or a strong Wolff spring, I should be good to go.
http://www.midwayusa.com/viewproduct/?productnumber=699378

http://www.midwayusa.com/viewProduct/default.aspx?productNumber=490842

The nice thing about the adjustable gas plug is that I could really slow down the bolt operation for smoother cycling and less wear on the receiver. The Schuster guys also say that you can get increased accuracy, but I don't know about that.

 

[Slamfire]

Techs in customer service can give out some real bad advice. I think this is an example.

I would try the Schuster vented gas cylinder lock and not go to a heavier spring.

You will find if you examine the dynamic equations that spring constants are almost ignored for dwell considerations compared to port pressure.

What you will find with a heavier spring is that your chances of a slamfire increase.

The faster that bolt goes forward the faster that firing pin is moving. At bolt turn down that firing pin rebounds off that primer.

Most ammmunition on the market has sensitive commercial primers and people do have slamfires with the things. With regular springs.

 

[Red State]

Thats actually a good point.

I love that a guy named slamfire has cautioned me about slamfires. So appropriate.

 

[velocette]

In agreement with above stated loads with IMR 4895, There are darn few .308 rifles that do not shoot extremely well using 41 ~ 41.5 gr of IMR 4895 and the 168 gr Sierra (or Nosler) HPBT match bullet.
41 using GI or Federal brass, 41.5 using Winchester brass.

Roger

 

[henschman]

Just get the Schuster gas plug. They're only $50. It'll be nice if you ever decide to get a suppressor too!