Felt Recoil as a function of bullet weight and speed

[Rule3]

The original GI hardball load for the 45 ACP was a 230 gr bullet and around 4.8gr of Bullseye. Been the standard load for a 100 years or whatever.

General "rule of thumb" you use more powder for a lighter bullets (I know it seems counter intuitive) but that's the way it is.

Faster powders are fine but be alert to double charging as those fast powders get "lost" in a 45 case.

 

[mikemyers]

.........General "rule of thumb" you use more powder for a lighter bullets (I know it seems counter intuitive) but that's the way it is.........

I know you're right, but I'm puzzled as to the "why".

If I'm shooting with the heavier 230 gr bullets, I use a certain amount of powder.

If I switch to a lighter bullet, the powder load (for the same powder) is greater (as you said).

But, the velocity of the bullet has also gone up.

So, what is the reason, if there is one, why you can't use the same amount of powder for the lighter bullet? The only negative I can see, is the bullet won't go as fast with the lighter load, but it should still be faster than when using the heavier bullet.​

The only reason I can think of, is that for most purposes in shooting a 1911 the objective is to have "enough" power, and the lighter bullet, without an increase in powder, will have less power. That makes sense for general purpose shooting, but (to me) not for target shooting. I must be missing something here.

 

[mikemyers]

..........Faster powders are fine but be alert to double charging as those fast powders get "lost" in a 45 case.

Back when I was still in Reloading 101, someone (I think it was you) suggested this as a reason not to use Bullseye powder, and that by using more of a slower burning powder, Unique, any mistake would be more obvious. Back then I think I was reloading for a 38 Special, but that concept is now burned into my brain.

 

[Rule3]

http://www.speer-bullets.com/getstarted/faq_reloading.aspx

From Speer.

Q. I have a light bullet (e.g. 125 grain) and the only load data I can locate is for a heavier bullet (e.g. 158 grain). I need a safe starting point to develop a load for this lighter bullet.

A. The physics of loading cartridges indicates that a heavier bullet will build pressures faster than a lighter bullet owing to its mass. The greater mass of the heavier bullet resists change (acceleration) more than a lighter mass so the powder charges for the heavier bullet will nearly always be lower than those for the lighter bullet of the same construction. This indicates that, without other data to follow, the heavier bullet data can be used as a starting point for the lighter bullet.

 

[mikemyers]

.......without other data to follow, the heavier bullet data can be used as a starting point for the lighter bullet.

If what I've learned so far is correct, if I use a 185 grain bullet instead of the 230 grain, the recoil should be reduced (mass of bullet is reduced), and because the bullet is lighter, the velocity of the bullet as it leaves the muzzle will be higher.

What you've posted verifies that this is safe to do. I wonder why the technician at Speer didn't say anything about this? He knew what I was trying to do, and when I got off the phone with him, I was about ready to drop the whole idea, and buy some more 230 grain bullets.


In your opinion, is any of this related to the amount of time it takes for the powder to burn? As in, if the bullet weighed 5 grains, it would probably accelerate out of the gun so fast that powder would still be burning long after the bullet had left the muzzle? The technician at Hornady said something about fast/slow burning powders, and that somehow relates to how long the bullet is in the barrel. I'm making such a small change that I doubt that this applies, but it's one more thing I guess I need to learn.

(I started reading the Hornady manual, reading it like a book, not looking up information. I'll do the same with the Speer manual. Maybe I'll find other nuggets of information as useful as what you just posted.)

 

[Rule3]

What that question was asking was if you do not have data for a certain weight bullet, you can use the data for the NEXT HIGHER weight bullet. What will happen is there will be more velocity. I only posted it as it also answered you question of why a lighter bullet needs more powder.

I will leave the faster powder compared to a slower powder question for others. The powder burn rate chart is only relative to all the other powders on the chart which include the fastest pistol powder to the slowest rifle, so to me the small difference between say Bullseye and HP 38 or Unique is not the big of a range,

Kinda like how many Angels can fit on the head of a pin

The fast powder burns very quick and raises pressure rapidly. Slower powders the opposite. Which is why most true magnums are the slowest powders,but with that you also get more blast and flash along with the recoil.

But even if it is a fast or slow powder this all happens in a millisecond.

Without re reading the whole thread did you mention what gun you where shooting these in? A 1911?

 

[mikemyers]

Sure, no problem. I think you gave me all the info I need here:
"the heavier bullet data can be used as a starting point for the lighter bullet".
I'm glad you posted that, as it resolved a LOT of questions buzzing around in my head.


I'd like to understand all of this, so I'm thankful for all the information so many people, you included, have posted. (I'm curious about the burn rate, only because the technician started to talk about it, but that's way off in the future.)

The gun is a 1911 Les Baer Premiere II 45 ACP. The 185 grain bullets with the 7.2 grain Unique seem to work very well for me. Thanks to this discussion, maybe I'll try to make them even more to my liking, but in the meantime, I'm happy with how it's shooting now.

 

[njl]

Get a different (fast) powder, and you should be able to run those 185gr bullets at closer to 800fps without having to change the recoil spring. Those will definitely be low recoil.

 

[Rule3]

Why not use lead bullets or coated lead with Bullseye or similar?

They require less powder to get them moving and you can load some real mouse fart loads. May have to put in a lighter recoil spring but that is no big deal.

 

[mikemyers]

'njl' -- I bought a bottle of 'Bullseye' powder, which means I load with 5.7 grains of powder. I haven't tried that yet, but once I've shot a couple of hundred rounds with Unique, I will give Bullseye a try. Regarding springs - the support lady at Les Baer sold me lighter springs. I called back with a question about them, and Les Baer got on the phone himself - he insisted that I leave the stock spring in place.

'Rule3' -- that's another option for the future, but I'm curious - why would it matter in terms of recoil if i used lead bullets, if they weighed the same as the ones I'm loading now? If the bullet weight and shape remained the same, why would it make any noticeable change?

 

[Rule3]

'njl' -- I bought a bottle of 'Bullseye' powder, which means I load with 5.7 grains of powder. I haven't tried that yet, but once I've shot a couple of hundred rounds with Unique, I will give Bullseye a try. Regarding springs - the support lady at Les Baer sold me lighter springs. I called back with a question about them, and Les Baer got on the phone himself - he insisted that I leave the stock spring in place.

'Rule3' -- that's another option for the future, but I'm curious - why would it matter in terms of recoil if i used lead bullets, if they weighed the same as the ones I'm loading now? If the bullet weight and shape remained the same, why would it make any noticeable change?

Second line of my post above. Less powder, less friction, less pressure,

 

[mikemyers]

Second line of my post above. Less powder, less friction, less pressure,

I just loaded 50 rounds with Unique. I'll load another 50 with Bullseye. I accept that the Bullseye should be better. The data in the reloading book confirms that it is better for my purposes. I'll find out for myself at the range. Thanks!!!

 

[RecoilRob]

Mike...a simple momentum calculation should get you close to answering which will 'feel' more recoil as I believe this is what more accurately determines whether a recoil operated gun will function with a particular load or not.

Bullet weight x velocity= momentum The units aren't important as you'll get a number at the end, and if it's higher you'll feel more 'shove' when you touch one off. In your original question of 185@900 vs [email protected] 185 will give you more shove. The 185@700 would be VERY soft shooting..but might not function in a stock gun set up for full power ammo. We used to have some 'Softball' Gold Cup target pistols that were just delightful to shoot with their specified ammo...but full power 230 ball was verboten!!

Once you've found the level of recoil you find acceptable, another thing to keep in mind is the time of travel down the barrel. When shooting really slow bullets, you must 'follow through' much more than with a really quick one. Airgun shooters know this very well as most of the target guns only shoot about 500fps as that has been found to be a consistently accurate velocity to drive diabolo pellets.

Assuming your chosen bullet will shoot accurately at the velocity you choose might be worth investigating too...sometimes you'll need to drive them fast enough to shoot tight groups. Then balance the barrel dwell time with recoil sensitivity and you'll end up with what works best for you. Of course, this all is assuming the loads will run the gun reliably, and if you get too light then some decisions will need to be made.

Do you modify the gun to run the light loads, or keep the gun shooting standard ammo and work with just the various bullet weights that can deliver that level of momentum? I find that a heavy bullet driven moderately is much more pleasant to shoot than an equal momentum lighter bullet driven much faster. Blast and flash will be less, and you're burning a lighter weight of powder (normally) so less is consumed which also reduces what goes down the barrel. The powder charge contributes to recoil...so less is better.

You are asking some very good questions Mike! Thought provoking and I'm sure everyone is learning something new as everyone offers their inputs. I know I have.

 

[mikemyers]

I'm learning that this is far more complicated than I would have thought a week ago. I accept all those calculations as being mathematically correct, but I'm pretty sure the reality is more complicated - which is why people talk about "felt recoil".

• If the gun is small and light, it will seem to have more recoil than if it is very heavy.
• If the rise in recoil is very high, presumably that will reduce how hard the gun seems to be pushing against the shooter.
• The louder the gun, the more recoil it will seem to have.

Please write more about "'Softball' Gold Cup target pistols". First I've hear of that.

To answer your question, my gun is 100% stock (except the grips, which the previous owner lost), and Les Baer himself told me not to change the recoil spring for shooting lightweight ammo. (I kiddingly told him that people in the forums would think that's wrong, and to use a lighter spring. He said something sarcastic about the nonsense in many forums, and told me if anyone ever questioned this, to tell them that Les Baer himself told me to do it.)

• I'm happy with the 230 grain bullets with 5.2 grains of Unique.
• The 185 grain bullets with 7.2 grains of Unique were fine.
• I think now I've got lots of good suggestions to try, the first of which will be 185 grain bullets with 5.7 grains of Bullseye powder (all of these right out of the Hornady or Speer reloading manuals).

I should add one more thing - it's enjoyable to be trying all these things, along with learning SO much more about them.

 

[RecoilRob]

You know...a fun project would be to find out just where that pistol will function reliably. I agree with Mr Baer (and many here) that the recoil spring is mostly there to reload after the shot, and the firing pin stop radius is what does most of the slide timing control...so if you'd load up a bunch of ammo with reducing charges until it won't reliably feed/eject...then at least you'd have a hard-deck of recoil impulse for that pistol.

Years ago I bought a Coonan .357 (still have it...nice gun!) and went to the range with a couple boxes of ammo loaded from +P 38 level to full house 357's with the intent of finding what the gun would run. When just poking holes in paper, doesn't seem to make that much sense to be making basketball sized fireballs when a light 'pop' would work just as well. In the case of the Coonan, it was about 1100fps w/158's where it started running reliably IIRC.

One guy came over after I put it away and politely asked about all the malfunctions it looked like I was having. I'd never even thought that someone would notice that the first 5-6 mags through it needed manual ejection for each round. Once I found where it ran good...the experiment was done for the day so I put it away. The fellow seemed relieved when I showed him what I'd been doing and told him that the gun was VERY reliable with proper ammo.

The 'softball' guns were at a range off base near Camp LeJeune and I visited them every weekend as I wasn't old enough to buy one. Walking in..they'd put one up on the counter for me...didn't even have to ask. The 185 FMJ target loads were just SO nice to shoot! Memory says they're like 730 fps? Your light 185 loads coming up should be very close to this. The range was happy that they'd be nice on the guns too...and I never even tried using anything heavier, so they might have worked OK with full power FMJ's.

If you're shooting something where a 'power factor' doesn't need to be met...the gun will determine how soft you can go with the ammo. If you do a 'minimum load' test on the LB it would be interesting to hear about the results. Good shooting Mike!

 

[mikemyers]

Around 30 years ago, a friend at work sold me his reloading gear, and taught me how to use it. This was for "44 Special" type loads in 44 Magnum shells, and 45 ACP for my Colt. For a lifetime after that, I never varied - I had it all written down, and using an old style beam scale, I replicated what he taught me, over and over. I never dreamed of changing anything (and didn't really understand much, just how to follow a recipe).

It wasn't until I got into this reloading THR forum that I began to question "why", and consider that there are/were options I never knew existed. In this forum, there are SO MANY helpful people. Out in the "real world" (at least my "real world) there wasn't even one.

That's a little better now - I joined a gun club not too far from me. The secretary of the club has been explaining how she reloads, and I learned from her, although I haven't yet tried to make the bullets that she shoots. I also met two people who made mistakes in reloading, that ruined their guns, and could have done worse damage. Both were supposedly "experienced", one much more so than the other. If nothing else, that taught me to be Extremely Cautious about things, double check, triple check, and follow every safety instruction I've read about.


Anyway, what this is leading up to, is for my whole life until now, I was just reloading because I enjoyed it, and because I enjoyed shooting my own loads more than what I could buy over the counter. Not until now though, did I get so interested in adjusting the load to make it more of what I want. .....and for that, I can thank all of you guys!