The beat goes on…S&W 4” comparison

[38SPL HV]

Checking my records, I did test Federal’s 38G +P FBI load in my S&W HD 4 inch last month. This revolver has a barrel to cylinder gap of .004 is generally very generous in the velocity department even outpacing my 5 in version with same gap. Regardless, the Federal FBI load in my 4 inch is statistically similar to what I get in the .008 gap 4” S&W Model 10:

4 inch S&W HD - (10 shot string) 882 fps average
4 inch Model 10 - (10 shot string) 873 fps average

Yes, the Model 10 is slower but statistically in the same ball park. There is a bigger difference with the Remington +P version. Some things are not always explainable regarding ballistics…so many variables.

I’ve spent two months doing 2x to 3x per week chronograph test outings…I’m fortunate to be able to shoot whenever I want weather/winds permitting. I get a real kick out of it but I’m due to dabble with another hobby next month.

 

[71vette]

Your work is appreciated, HV. Unfortunately it’s getting cold, rainy, and dark here so my range trips are getting limited.

 

[Chuck Edwards]

About 15 years ago, when I was still an active IDPA competitor, I did a chrono comparison using my competition load and the nine 4" revolvers I had at the time. My K and L frames and Colt Official Police came in within ~20 fps of each other, while my 27-3 and 28-2 were about 80 fps slower. I never measured the b/c gaps, I probably need to.

 

[stansdds]

Barrel-cylinder gap has a negligible effect on velocity. Chamber and bore dimensions and bore smoothness have a far greater effect on velocity and accuracy.

 

[taz666]

Barrel-cylinder gap has a negligible effect on velocity. Chamber and bore dimensions and bore smoothness have a far greater effect on velocity and accuracy.

More specifically, would it come down to how the chamber lines up with the forcing cone? I'm curious why some (a) chamber in a revolvers' cylinder might produce a flyer, all things being equal as far as the reload is concerned.

 

[stansdds]

More specifically, would it come down to how the chamber lines up with the forcing cone? I'm curious why some (a) chamber in a revolvers' cylinder might produce a flyer, all things being equal as far as the reload is concerned.

It could be that one chamber has a throat diameter that is larger or smaller than the other chambers. Could also be an issue with alignment to the barrel.

 

[jem102]

Quote:
Originally Posted by stansdds
Barrel-cylinder gap has a negligible effect on velocity. Chamber and bore dimensions and bore smoothness have a far greater effect on velocity and accuracy.

More specifically, would it come down to how the chamber lines up with the forcing cone? I'm curious why some (a) chamber in a revolvers' cylinder might produce a flyer, all things being equal as far as the reload is concerned.

Good comments and question.


What makes a fast barrel? Is there a tipping point between smooth and rough interior finish where a slightly rough barrel builds more pressure and velocity than a dead smooth barrel? Or, does the super slick rifling with lower drag increase velocity?



If it's the last cylinder before a reamer change the charge holes would be smaller and shorter than when the reamer was fresh. This builds more pressure with the same loading density but a cylinder done with a fresh reamer may handle a few more tenths of powder creating greater energy and thus velocity.


If an individual charge hole is misaligned how well can the forcing cone correct the path of that bullet? If the bullet enters the bore misaligned it stays misaligned. Does it mean much at 50 yards or less? I recall reading some place along the way (might have been some of Lloyd Brownell's papers) that for every .001 the bullet is misaligned in the bore equates to .125 out at 100 yards. "If" we can extrapolate that working back it's .0625/.001 at 50 yards so .005 misaligned in the bore would be about 5/16" at 50 yards which is nothing to write home about. I don't know how far off axis that cylinder throat to forcing cone would be to allow .005 bullet misalignment after passing through the forcing cone but would imagine the gun to be "spitting" a lot at the cylinder gap at that juncture.


Does a bullet entering the forcing cone noticeably misaligned allow gas to blow by dropping velocity and cause a "flyer", most likely high in the group, when that charge hole comes up in the rotation? Or, does the "cocked" bullet reduce volume in the cone, thinking of it as reducing "free bore, raising pressure, increasing velocity and striking lower in the group?


None of this really means squat unless there is some gross mechanical issue with the gun but it's fun to think about how the various combinations might explain the 50 FPS difference between "identical" revolvers...well maybe and/or the flyer...well maybe.


As Richard Harris sang: "The Yard Went on Forever".

 

[Forrest r]

A mis-aligned chamber in the cylinder is going to spit lead along with splashing lead on the frame.

When a revolver is shot out/needs rebuilt, the timing need redone along with the bbl needs re-faced and set back.

Bought a 586 back in the early 90's. Shot the heck out of it & eventually it got sent back to s&w to be rebuilt. Shot it out a 2nd time and sent it back. The 3rd time was the charm. Accuracy wasn't affected that much @ 25yds or closer. Velocity on the other hand went downhill to the tune of +/- 50fps with the same 357mag load I've used for decades.

What the bbl looked like.

If you look closely, you can see a crisp side to the lands and a rounded side. That bbl has the typical flame cutting/forcing cone erosion at the 12 o-clock.

The real culprit of the loss in velocity in the cylinder of that revolver.

It has the "steps" burned/enlarged where the leade of the throats used to be. What a normal step/leade looks like in the chambers of the cylinders.

I had a 8" bbl for the dan wesson revolvers I owned. It was barely faster than the 2 6" bbl's I had. When you ran a tight patch down that 8" bbl you could feel several loose spots in it.

 

[Forrest r]

I have a beater 629 that's one of my favorite plinkers with blammo ammo.

Was testing loads one day (pc bullets vs traditionally sized lubed). Put a scope on it and setup @ the 25yd line. This is the 1st target I shot. Shot 3 shots and saw they were hitting left. So I adjusted the scope a couple clicks to hit the bullseye. OK, went the wrong way!!!! Saw the 2 3-shot went further left. Gave the scope Sevel clicks back to the right. Thought about it and decided I actually didn't to hit the target because I was shooting groups. If I hit the center of the target, I'd loose my aiming point. Anyway I started shooting groups/testing bullets with this 1st target. 5-shot touching 1 out.

And this target 5-shots touching and 1 out.

Interesting, starting to see a pattern here. Another 6-shot group @ 25yds with 5 touching and 1 out.

All the targets above had a flier to the right. So, when I shot this target, I assumed the far-right hole is actually the flier.

When I shot this 50yd 6-shot group I believe I pulled the high left shot. And the low right shot was the revolver/flier.

That revolver consistently throw 1 shot. It depends on the bullets shape/design as to how far out it throws the shot. The other thing that affects that flier is the loads pressure. Higher pressure ='s less deflection.

I've measured the chambers in that cylinder with minus .0002" pin gages. One of them is definitely different.

There's no lead spitting, no detectable difference in velocity. Just a flier compared to the other 5 chambers in that cylinder.

 

[Forrest r]

Myself, I'm not all that hung up on velocity. But when it comes down to getting the biggest bang for the buck while maintaining accuracy. I'm all in.

I reload my own sd ammo. Ya I know, fire and brimstone time so don't turn this into a you should or shouldn't do that show.

When using shooting snubnosed revolvers, everything is important and affects velocities.

Anyway, I made sure the cylinders were even in this revolver (38spl/2" bbl) along with setting the gap to 3/1000's.

Then I tested 10 different bullets using 5 different powders. These 8 bullets and 2 not shown. All the bullets tested were hp's

At the end of the day 4 bullets always had the highest velocities and 1 bullet always had the lowest. The difference between the fastest and slowest was +/- 70fps. That huge!!!!

You can get 70fps difference by simply switching bullets.

Did testing for a 2 1/2" bbl'd 357mag that I winter carry.

I decided to use a 170gr rnfp bullet that I cast. The mold casts a 170gr rnfp or 158gr hp's.

Used 3 different powder for the testing and that 170gr rnfp bullet. Loaded up a couple hundred loads with each powder and tested then in that 2 1/2" bbl'd revolver long with 4", 6", 8" and a 10" contender bbl.

Ended up with a +/- 1200fps load with that 170gr bullet in that short bbl'd revolver.

Did a lot of testing another ccw, with this 2 1/2" bbl'd 44spl. After testing a bunch of different bullets I found that bullets in the 180gr to 220gr weight range performed the best velocity wise along with having the same poa/poi @ 25ft.

Any one of these loads will do. I typically use/carry the bullets/loads on the upper and lower left.

 

[Forrest r]

IMHO:
Most shooter/reloaders overlook the basics of firearms. They start playing with triggers, lighter spring, etc. The end result is inconsistent ignition. Inconsistent ignition will show up on paper along with a chronograph.

Inconsistent will affect accuracy, 1 fp hit is normal, the next lite & it shows up on paper.

Spending a relaxing day testing loads in a snubnosed 44spl and a couple 22lr pistols. I bought a ruger MK IV and had ignition issues (lite fp hits) so I sent it back and they supposedly fixed it.

1 of the targets shot that day.

Interesting that the 2 loads with the 44spl had extremely close velocities. Both loads had 8.0gr of power pistol. The left target was shot with a 245gr swc hp. (red) The right was a 200gr wc (green). The wc was 45gr lighter but was faster. The 245gr swc hp seat deeper in the case.

That ruger still had fliers!!!! Ended up putting an aftermarket spring in it and they went away.

Crimp and neck tension play huge roles when it comes to accuracy also. Bought a 686 and was testing loads in it. Was getting 6-shot groups @ 50ft like these with reloads it liked in 38spl cases.

Switched over to 357mag cases and was getting this @ 50ft with the same 686.

Took a hard look at the cases I was using. Looked like the puppy played with them. Ended up culling most of what I had and bought 2000 new cases from starline. The fliers went away.

At the end of the day there's a lot of things that can and will affect velocities and accuracy. Sorting thru and eliminating the variables makes it easier to identify issues with other reloads or firearms or bullet selections.

 

[taz666]

Great stuff guys.

 

[38SPL HV]

Great responses…now I’m more confused than ever lol, only kidding…best to you all!

 

[jem102]

Forrest r

"At the end of the day there's a lot of things that can and will affect velocities and accuracy. Sorting thru and eliminating the variables makes it easier to identify issues with other reloads or firearms or bullet selections."



Agreed. There is another thread running about cleaning primer pockets and a lot of folks say not necessary. This, in and of itself, is true and depending on the gun and the shooter decent results may well be achieved. But "decent" does not mean you have gotten all there is to get from a particular firearm or load recipe. To each his own but I have always enjoyed the chase and believe I have benefited with a greater utility of the individual firearm. Consistency and reduction of tolerance "stacking" brings rewards "if", you want them. But it must be something you enjoy doing and recording the results. If the shoe fits wear it but it depends on your goals and needs.