AA#2 vs AA#5 in .45acp m1911-A1 Govt. Model

[Thirties]

From the AA loading manual it shows a certain charge of AA#2 will give just about the same velocity as a certain charge of AA#5 using Rainier 200 gr plated semi wadcutter bullets in a 5" gvt. model 1911-A1.

My question is what is the difference (besides the extra cost of the AA#5 charge) between the two powders? I know the #2 is faster than #5. I am asking what is the perceived difference to the shooter in areas such as accuracy, recoil, or other observable differences in the above scenario.

I didn't list the actual loads since I'm concentrating on velocity equivalence.

Thanks . . .

 

[Unclenick]

A faster powder burns more completely before the bullet has moved as far forward as it will when the same percentage of a slow powder charge has burned. This means its gas is evolved in a smaller volume, so that if it made an equal quantity of gas to that made by a slower powder, the fast powder's peak pressure will be higher. As a result, you can pack more of a slow powder in a case, and if you pack enough in to reach the same peak pressure as you got with a fast powder load, the slower powder will get you a higher velocity. That is because its larger charge has made more total gas which has maintained driving pressure longer. It's pressure peak just won't be reached as early in the bullet travel, so it peaks in a larger volume than the fast powder does. That extra gas needs that extra volume to avoid exceeding pressure limits.

When both a fast and a slow powder produce the same velocity, the slow powder will be doing so with a lower peak pressure. The actual burning rate achieved in your gun (not the order on the burning rate charts, necessarily) will depend on pressure. Chemical reactions generally speed up with pressure. Thus, the slower the powder, the more it needs pressure burn completely. So, when you use a lower pressure with a slow powder to obtain the same velocity as you get at a higher pressure with a fast powder, you get less complete burning, tossing more unburned powder out of the muzzle with the bullet. You also get more fouling, because of the less well-combusted chemistry, and often also get more erratic muzzle velocities because small, cartridge-to-cartridge physical differences have a disproportionate effect on getting the powder burn established when the pressures are marginal for good burning.

Generally, the only reason to use a slow powder is to take advantage of the higher velocity it can produce at full pressure, so it is only showing its value at the warmer end of the cartridge's pressure rating.

 

[Mal H]

My guess would be that the #2 loads would feel slightly snappier than the #5 loads, all other things equal as you stated (same bullet weight, same MV). This would be due to the #2 load causing the bullet to get up to speed a bit faster, thereby compressing the recoil force over a shorter period of time than the #5 load. The measured recoil force of both loads should be just about equal, but the time period of the recoil would be different which creates the feel of more perceived recoil with the faster powder.

 

[Thirties]

Thanks for your thoughtful replies. As soon as I get my replacement chronograph sensors (yes, I shot them), I'll test the theory and post my observations.

 

[Unclenick]

I did some experimenting with Hodgdon Clays and VV N310, which are very fast, in the 1911, and found that for a given produced MV, perceived recoil was actually lower. The quick kick of the low weight charges got the slide moving inertially, but because the bullet was out of the muzzle sooner than with Bullseye or Universal Clays, the muzzle exit occurred in an earlier portion of the unlocking cycle. The result was the muzzle didn't climb as much so the recoil was straighter back into the hand where it isn't as noticeable.

A lesser factor (in handguns) is that in a straight wall case about 70% of the powder is pushed forward with the bullet, burning from the bullet base forward, so a larger weight load of slower powder adds to the mass being accelerated. It then keeps the pressure up longer so the muzzle pressure is higher at bullet exit, and rocket effect from the gas accelerating out of the muzzle is thus increased. Both factors add to the total recoil. The effect is much more dramatic in rifles, but makes some contribution even in .45 ACP loads.

 

[brickeyee]

Bullseye is typically rated as even faster than AA #2, and has been used in many .45 ACP loads.

 

[Jim Watson]

AA #2 was rated for the lowest muzzle flash of 14 powders tested in an early IDPA Tactical Journal article.

I found it to give HIGHER than the manual velocity. I was at the starting load with plenty of zip for major power factor.

You can take the fast powder + heavy bullet = low recoil theory too far. There were some IPSC shooters beating their guns up with high pressure loads that felt very mild.

The American Theory of Shotgun Recoil calls for a slow burning powder to accellerate the shot charge gradually, but the European Theory of Shotgun Recoil favors a light charge of fast powder to get it over with quick and minimize the ejecta and muzzle pressure.

 

[NWPilgrim]

While there may be a slight difference between felt recoil using AA2 or AA5, I think there are other factors that would drive a decision. Anything between Bullseye and AA5 is good for .45ACP, generally.

If two powders give similar velocities I look at:

- Which powder do I have the most of?

- Will the faster powder be such a light charge that it will be hard to see in the case while loading? Or conversely, will the slower powder fill up the case enough to ake double charges easy to spot?

- Which powder gives me the best accuracy?

If velocity, availability, safety and accuracy factors are about equal then I would go for the faster powder.

 

[Mal H]

... all of which goes far beyond the specific question asked, "I am asking what is the perceived difference to the shooter in areas such as accuracy, recoil, or other observable differences in the above scenario."

 

[NWPilgrim]

The short answer is: I don't think you will see a hill of beans difference between the two. The only real factor would be accuracy and that is specific to your firearm and none of us can tell you what that difference, if any, will be.

If you like to tinker: then do the reloader's approach and work up various loads of each and test them to find the most accurate, and best feel.

If you want to get to a quick answer I would go with AA5, just because the only powders I see frequently mentioned in manuals as being particularly good (accurate) in .44ACP are: Bullseye, WW231/HP38, AA5 and to a lesser degree Unique, Universal and Power Pistol.

I've never seen AA2 mentioned as a particularly good/accurate powder for .45ACP although it should be decent.

 

[alfack]

Between the 2, I think #2 burns cleaner and makes less smoke. I end up with a layer of soot on my slide (not that it hurts anything) that goes about 2" back, when I use #5 and have to wait for the air to clear so I can see my target again between mags.

 

[Unclenick]

That's the low pressure of burn issue I wrote about not bringing about a clean burn. Not much help, that. Note that he is not loading to similar pressures, but to similar velocities. The higher ballistic efficiency and lower smoke and soot levels will favor the faster powder where both achieve the same velocity within safe pressure limits.