Different powder: better accuracy?

[dyl]

Please explain how this could happen:

Today I tried 2 loads through a service size 9mm pistol. Same 125 grain LRN, same primer, same OAL, but different powder. (Bullseye vs AA#5). Yet that gun liked bullseye better.

At the same trip I tried the loads in a second service size handgun and that gun liked AA#5 better.

Any clue what's going on here? I understand a barrel working better with different bullet profiles and weights (surface area) but not so much powder except for extreme cases like snub noses.

[Sevens]

Most likely answer, in my opinion: the shooting and/or the shooter managed to shoot better here than there, or the opposite.

However, many other items could also have a hand in different outputs of "accuracy." First thing I'd want to look at was the lot of brass and consistency of that brass from piece to piece and the consistency of the bullet pull in each and every loaded round.

It may seem like the powder is the difference, but that may not necessarily be what is happening. Of course -- maybe it is indeed the powder. Being that it seemed that each gun preferred a different powder, perhaps it could have something to do with the unlocking cycle of the pistol seemed to be better matched to the complete combustion cycle of the round it preferred?

These things are typically chased down a little better in long range rifle shooting, where on-target accuracy can be nailed down a little more clearly. Even then, it remains a very mysterious and compelling subject. Or perhaps, more like a form of art.

It often seems to be a subject with a lot more questions than answers.

[Jimro]

Different throats have different profiles which cause different amounts of resistance which gives different powders different time to achieve optimal pressure for the barrel.

Try sealing the barrel in with some asphalt tree sealer and doing another workup with both powders. Years ago people found out that military 45 ACP ball ammo was more accurate because it allowed better ignition prior to the bullet entering the bore.

Jimro

[bfoosh006]

If only I could answer that question !!! You have just experienced the tried and true ... " Work up the load for your gun , and, Every gun shoots different.. "

There is a excellent article on "Why doesn't my gun shoot at the Reloading Manuals Velocity ? " ... while that seems to have no bearing on your question... it really does help show that in shooting ... not all is what it seems. Note the velocity difference between the same type and make of the guns....http://www.leverguns.com/articles/ballisticians.htm

[Mike / Tx]

Any clue what's going on here? I understand a barrel working better with different bullet profiles and weights (surface area) but not so much powder except for extreme cases like snub noses.

You somewhat answered your own question here.

The same is true with powders and burn rates as with bullets and profiles. In one load your using a pretty fast powder and the other somewhat a medium powder or slow depending on the case. In your case it would be slow as compared to say a .357 where you could use more of it, but you could also move to 296 which is very slow.

The burn rate will effect the function of your pistol as well as the pressure developed when the primer lights the charge. The load of #5 has deterrants in it to slow it down where the BE is more like flash powder by comparrison. It hits it's peak pressure almost instantly and while it might not seem like it is slower the #5 will hit it a little after resulting in a seemingly milder start and recoil. Even if your hand doesn't notice it it does happen.

If your shooting lead bullets the BE will usually expand the base of the bullet a bit quicker which allows it to seal off and fit the chamber as it enters. THe #5 will also but it might be after the bullet has started to jam into the lands before it happens. Depending on the lead in each barrel one might have a steeper cut in the rifling than the other which may explain why one shoots each powder differently. If they both were reamed wioth the same reamer to the same throat and leads then they would shoot a lot closer than what your seeing.

As mentioned, this is why what shoots great in my pistol or rifle, may or may not shoot worth a hoot in yours. I have a couple of rifle s that will not shoot the more reccomended powders for that caliber worth a darned, but with something close in burn rate ie, RL22 instead of H4831, they shoot 1" or less out past 200yds. You might also find that your crimp may or may not have something to do with this as well. If you have good case tension, all you should need is enough crimp to remove the bell on the mouth, if your going more then you may be effecting the initial pressure as well as possibly distorting the bullet if it is cast.

Just ideas.