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Heavy 9mm vs .40 for minor PF


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Right, so for context -- this is about loading for minor for practical shooting events.

I've read a couple of places about NOT going too heavy on 9mm (let's say 147 or higher) if you're trying to stay close to the power factor floor of 125 (let's say the goal is a 130pf) because, despite the fact that it will produce a softer shooting round than a lighter bullet at the same power factor, precision/consistency will suffer. The explanation was that the round needed to go "fast enough" for the barrel to stabilize it, and a 147 at about 885fps at the muzzle (130pf) wasn't moving fast enough to have adequately stabilized. Basically, the argument was you were better off going with a 124/135 moving around 1050/960 because you need 925+ feet per second to for the bullet to adequately stabilize.

SO my first question is: is the above in any way true? I can wrap my head around it just fine, but I don't know whether or not to believe it because I know that people light load 180 grain .40's for 130ish power factors so they can shoot .40 in Production and Limited, but I don't see anyone saying those bullets don't stabilize adequately enough to be consistently accurate, and those would be down around 725fps.

So what gives? When I was reading about the heavier 9mm, was I reading BS? It wouldn't be the first time. ;-) Basically, is what I read true? And if it is, why isn't that the case with .40's, or .45's for that matter? A 230 grain .45 at 170 power factor is doing about 740fps, and people use .45's for bullseye competition, so I'm not seeing how slow = inaccurate/imprecise/inconsistent.

TIA

--Matthew

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The answer to your question is yes, no, and maybe... and let me explain a bit :)

90% of it depends on your gun and the powder you are using. I use a load I found on this forum in my M&P Pro that is 3.6 gr of N320 with a 147 gr 9mm and it works great....in *MY* gun. I know other people that have used it in their 2011's and other guns, and it did not work as well. It still worked, but not as well as a different load did.

Too many people try to chase "minimum power factor" and load to the lowest load they can and still make it...my suggestion is ignore the lowest power factor you can load to and use a load that makes YOUR gun function properly and is accurate! In general I have found that if I load my Minor loads to around 135 to 145 in both 9mm and .40 that my gun functions well and I maintain accuracy at longer ranges with less drop. I even load my .38 special loads to around 130PF for that exact reason.

I had a .40 load that was great at short ranges, but the second I went to 15+ yards it fell apart and started tumbling/key-holing. I bumped the load up .2 grains and the problem went away.... but again, that was what worked in my gun. Yours may be different depending on the throat, chamber length, rifling twist, rifling type, timing of the slide...etc...

In short, there is no "magic answer" to this question. You need to experiment with different loads and power factors in your gun and shoot them at both short range and up to 25 or 35 yards and see which one maintains accuracy at ALL ranges the best in YOUR gun.

Edited by Classic_jon
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Classic_Jon hit a lot of the points. One very big factor in it is the barrel twist. Even the barrel makers will tell you when you buying a barrel to watch for the twist rate and the bullets you are using. For the S_I crowd, they usually come in 1/16, 1/24, and 1/32 twist rates and it should match up the twist with the loads you'll be using. Not everything but this has a lot to do with it...

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I've been toying with a steel load in a .38 super using 9mm cases with a 160gr lead bullet. So far I've used HS-6, WW231, AA5, and ww452AA (discontinued) and they all have been pretty accurate (2" or less at 20 yards) with velocities in the 800 FPS range. They also work great with .38 special at about 800fps out of a S&W686. Probably more accurate from the revolver.

Somehow I ended up with a bunch of these Competition Specialties 160grain round nose bullets and I figure they could be put to good use on steel and save the jacketed stuff for major.

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Thanks for the replies, gentlemen. I believe I get it:

A given bullet has to maintain a particular angular momentum to remain stable in flight (to not tumble). Higher spin rate on the bullet = higher angular momentum, so ALL of the factors that play into creating that spin rate are relevant. All else being equal, higher muzzle velocity = faster spin rate, so a particular bullet from a particular barrel has a particular muzzle velocity below which it will destabilize at particular ranges.

AND since relatively heavier bullets with a greater diameter would have greater angular momentum for a given spin rate, it stands to reason that larger, heavier, bullets would on average need progressively lower muzzle velocities to remain stable, thus on average a 9mm needs a higher muzzle velocity to remain stable and accurate than does a .40, which needs a higher muzzle velocity than does a .45. ON AVERAGE. :-)

Thanks. I feel like I learned something. :D

--Matthew

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Just read something interesting. I read about the Greenhill formula created in 1879 to determine the necessary rifling twist rate needed to impart gyroscopic stability to a projectile.

For bullets of lead, the necessary twist rate is ((bullet diameter squared) * 150 / bullet length). That means that given a particular diameter, the longer the bullet is, the higher the spin rate needs to be to maintain stability. Since most bullets of a given caliber get longer as they get heavier, that would mean that the lighter (and thus shorter) the bullet is in a given caliber, the lower the velocity is at which the bullet destabilizes and tumbles. ON AVERAGE. It doesn't make lighter bullets more accurate, obviously, but it does mean that for a given caliber lighter bullets will maintain their accuracy over longer ranges.

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Now this is just my opinion, but I think you're thinking about it too hard.

Work up some loads and test them! I personally prefer 124gr 9mm bullets. Also, what classic_Jon said I agree with about PF. I load mine to 135PF, IMHO, people who load 130 or less, are asking to fail a chrono test. It's not worth it to me, the difference isn't significant. My 124PF rounds felt the same as the 135's.

Edited by polizei1
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Oh, no no. I agree completely. I'm not trying to get loads down to the basement floor. I just read something in a thread started by someone who WAS looking for the basement floor with heavy 9mm bullets, read the responses, didn't quite get why the facts they were presenting would be what they were, so I came here searching for enlightenment on the subject. This was for my understanding, not application. :D

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Worked up some minor loads for my Trojan 9mm using Solo 1000 and 160 lead bullets. Pleased with results.

Shot 147 lead for a long time and had one box of 500 that gave me problems, tumbling. After reading in the forum,

others had the same type of problem so moved away from that bullet weight. The 160 is a bullet design that was

used back when we were shooting single stack 38 supers. Good bearing surface, accurate soft recoil in 9mm.

I also try for 130 PF as Solo tends to slow when temps rise. Keep it in the shade in the summer.

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I've found these forums are a great place to ride on the coat tails of greatness! When you see top shooters in the game shooting one particular bullet weight or another it may not be gospel, but it's certainly a good place to start. On the other hand, if you've got this wild idea no one has posted about to make the flattest shooting round in the world, it has most likely been tried and dismissed by hundreds of shooters on here.

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i run all my 9mm at 135 pf out of a 5" gun. will be about 130 out of a 4" gun. more than enough cushion for the gun games. I run my 40 minor at about 140 because that is what will reliably run in my gun.

!47's in my development and experience do not run well at lower velocities. Many time they will tumble.

A lot of people wish to skirt close the 125pf for whatever reason. If they use that ammo in a match that is chronoed, they might be going home or shooting for no score.

ladder your loads when developing them , figure out the most accurate load that give a good PF in your gun and stick to it is all i can suggest.

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FWIW, I've tried some 147's in my 3" EMP and I didn't like the feeling of it. These were Winchester PDX so I'm sure they were loaded pretty hot. When I shot my normal 124gr USPSA load through my EMP, I lost 11 PF, from 135 out of the 5" to 124 out of my 3". There may be some truth to it...though I didn't test for accuracy. I don't think 147's work well going too slow.

Some one should do some testing!

Edited by polizei1
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I run 160 Bayous over either 320 or Solo at 135ish in a Shadow. While I do get a kick out of how stupid soft the load is I shoot them because they are extremely accurate. Particularly so with the 320.

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I shoot 173gr SWC out of my 9mm all the time as it's my favorite load. I've been weighting them lately and there casting at 168/169 but I load 2.7gr of AA2 behind them and it pushes them to just over 800fps loaded with a OAL of 1.135 Power Factor comes in at 135. Accuracy is the best of any of the bullets I have tested so far so I don't plan on changing bullets but maybe tweaking the load.

Been thinking of getting some SOLO 1000 to put behind them but reloading supplies are hard to find around here.

Hows the recoil on this load? Makes you think you got a squib round if your shooting 115gr and switch to 173gr.

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Thomsoncustom,

Solo is a soft shooting powder and accurate in my Trojan. It's a light flake powder and it varies from lot to lot.

Chronograph work is needed and it will slow when summer arrives.. Polished the powder funnel to help bridging. I don't Think you can get enough Solo 1000 in the case to use a 115gn bullet at least with the lot I'm using now. works best with 147 and heavier bullets.

For all it's pains I like it.

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It's not about bullet weight, it's about bullet length. My Lyman 147gr mold will make a 147 gr bullet with really good lead (which I never do) or a 158gr bullet with Range Scrap (which I did all the time). Both accurate out of my KKM barrel with Solo at 132PF. 9 rds at 2.5 inch's at 25yds off hand. 10th rd opened it up to 4 inch's. Not bad if you ask me.

Solo is not as accurate at 125 PF in my experiance. Run it over 130.

Edited by 98sr20ve
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Solo is a soft shooting powder and accurate in my Trojan. It's a light flake powder and it varies from lot to lot.

Chronograph work is needed and it will slow when summer arrives.. Polished the powder funnel to help bridging. I don't Think you can get enough Solo 1000 in the case to use a 115gn bullet at least with the lot I'm using now. works best with 147 and heavier bullets.

Ya I going to have to wait for summer to build a load with a faster powder than AA#2 and I need to get a chrono. I assumed Solo was a ball powder I'm a bigger fan of ball powders seem to measure better for me. Tho running Solo through quickload instead of AA#2 I move from 98% powder burned to 100% powder burned which sounds great.

It's not about bullet weight, it's about bullet length. My Lyman 147gr mold will make a 147 gr bullet with really good lead (which I never do) or a 158gr bullet with Range Scrap (which I did all the time). Both accurate out of my KKM barrel with Solo at 132PF. 9 rds at 2.5 inch's at 25yds off hand. 10th rd opened it up to 4 inch's. Not bad if you ask me.

agreed, I once removed a crimp groove from a mold to gain more weight for the same length. A lot of work for 3grains tho.

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