Chamber throats in LCR cylinder?

[Super Sneaky Steve]

Ruger will not fix tight throats. I've tried. They will shoot it, even with poor accuracy and say it's good.

These guys will make what you need.
https://pacifictoolandgauge.com/512-chamber-reamers-gauges-cutters

Or Manson has a .32 in their product catalog.
https://mansonreamers.files.wordpress.com/2022/02/february-2022-catalog-1.pdf

My advise is to get the pilot pack and some Drill Do from Brownells. They don't say what the final diameter is so call them first.

 

[JohnKSa]

Without any accuracy results posted, he should spend money on tools and permanently alter his gun?

How does it make sense to do anything at all until he establishes that there's a problem by checking the accuracy?

 

[FrankenMauser]

Ruger will not fix tight throats. I've tried. They will shoot it, even with poor accuracy and say it's good.

They replaced an "old method" Super Blackhawk cylinder for me. There was nothing wrong with it, other than differing throat diameters. They fit it with a "new method" cylinder, and much more, for free. Okay, not totally free. I had to ask nicely and then pay $13 to send it to them.


Regardless....
I don't think the revolver needs attention unless proven to have issues.
And that requires testing, not tools.

 

[Super Sneaky Steve]

Without any accuracy results posted, he should spend money on tools and permanently alter his gun?

How does it make sense to do anything at all until he establishes that there's a problem by checking the accuracy?

The OP will have to make the decision. Personally I don't like sloppy work. These are mass produced guns made to a price point. I want mine to be the way it should be so if there's a missed shot I know it's my fault and not the gun.

There are other important dimensions when making an accurate revolver with throat size being just one.

The fact is he won't know how accurate it can be without anything to compare against. Getting the throats right may not make it more accurate, but I've never seen it hurt anything.

 

[jski]

I could simply request they make all the throats .314", according to the SAAMI spec.
What's wrong with that?

 

[JohnKSa]

What's wrong with that?

Unless the gun is actually not performing the way you want it to, it's a waste of your time and effort and their time and effort and money.

Ok, forget all that and let's just assume that you feel like you need to pursue this based purely on measurements--without verifying that the gun actually shoots accurately or not.

1. You need to do the measurements properly. For accurate inside diameter measurements you need a pin gauge set. Get that (or find a gunsmith/machinist that has a set) and verify the throat measurements. It would not be smart (or ethical) to send the gun off for work based on measurements that may not be accurate.

2. You need to slug the bore. If the throat measurements are about the same size or a bit larger than the groove diameter then there's no reason to expect accuracy issues.

3. Keep in mind that since you have no data to verify that the throat issues (if they really exist) are actually causing accuracy problems with the ammo you are using, nor have you verified that there is not some other issue that could cause accuracy problems, you could get the gun back after the work (assuming Ruger agrees to do it) and find that it's not accurate.

 

[jski]

I checked on the cost of a single “go” plug/pin gauge: $17.46 + shipping. Buying multiples of these would get quite expensive.

 

[JohnKSa]

Maybe, just maybe, (and I must admit that I'm surprised that no one has given you this advice so far) you want to shoot this gun to see if you're happy with its performance.

Because if you are happy with how it shoots, then the cost of pin gauges, the hassle of shipping, dealing with trying to get Ruger to modify the gun, all of it, is moot.

 

[jski]

I never said I hadn’t fired it. I did when I first got it. Took it to the range twice now. Put about 200 rounds thru it at 7 yards. My first snubby so it’s difficult to say if it’s me or the gun. The gun has a good feel in my hand but I’d like tighter groups. Just thought I’d consider all possibilities.

 

[jetinteriorguy]

Snubs are not easy to shoot, they definitely take practice. You could try slugging the chamber throats similar to the method used for bores. It would be a bit of a chore to remove the cylinder and properly support it in order to drive slugs through, but I think you’d get a more accurate measurement. If you have some round nose lead bullets that are bigger than the throats that would work good.

 

[JohnKSa]

I never said I hadn’t fired it. I did when I first got it.

Nice of you to avoid mentioning that for days even though the subject has come up repeatedly over the course of this thread, starting with the very first response.

Put about 200 rounds thru it at 7 yards.

So what started this was accuracy issues at 7 yards? Again, that would have been nice to know. Whatever is causing your accuracy issues at 7 yards, it's almost certainly not undersize throats.

https://www.singleactions.com/files/RugerCylinderThroats.pdf

This guy did an extensive test before and after reaming undersize throats in a Ruger revolver. They did see an improvement in group size after reaming. Accuracy was tested by firing four five shot groups from the bench with each of several loadings at 25 yards and then taking the average size of those 4 groups for each loading.

After reaming, the average groups shrank by 0.6". That would be equivalent to shrinking 7 yard groups by about 0.17".

You could see improvements greater than that, but the people who ream throats for accuracy improvements are typically trying to shrink groups to under 2" at 25 yards or are concerned with 50 yard accuracy. You might see a 1" or 2" reduction in group size at 25 yards if your revolver has tight throats. That would be expected to reduce group sizes at 7 yards by 0.3" to 0.6"

 

[Carmady]

Maybe, just maybe, (and I must admit that I'm surprised that no one has given you this advice so far) you want to shoot this gun to see if you're happy with its performance.

See post #5.

 

[JohnKSa]

Yup. And post #2. I was being sarcastic.

 

[Carmady]

I missed that. Thanks.

 

[Double Naught Spy]

I could simply request they make all the throats .314", according to the SAAMI spec.
What's wrong with that?

Because you didn't use the correct calipers for the job, you don't really know if the throats are off or not.

 

[jski]

Well, there’s another variable involved here too. These 200 rounds were my own brew, so to speak:

32 H&R Starline brass ,
85 gr XTP bullets , and
either 11 gr of H110 or 7 gr of True Blue.

The True Blue load is hot but still comfortable. The H110 loads are relatively mild in comparison.

 

[Aguila Blanca]

Because you didn't use the correct calipers for the job, you don't really know if the throats are off or not.

Yes, he does. That was stated in the opening post.

I just purchased a new .327 LCR and was measuring the chamber throats. I first noticed that with all but one chamber I could drop my XTP bullets straight thru.

That's a qualitative assessment rather than a quantitative measurement, but it's certainly a "clue." Whether or not it makes a difference worth fretting over is a separate question.

Shooting some additional groups -- from a rest, at a distance longer than 7 yards -- might be useful if done in a scientific way. It would need a spotting scope. Mark the chamber with the tight throat, and always make that the last shot. Fire groups, using the spotting scope to look at the group after each shot. If the first shots make a good group and the tight chamber always produces the flyer that ruins the group, then you have substantiation for thinking that reaming that throat might make a difference.

As has been commented, though, any improvement is likely to be minimal.

 

[jski]

This whole journey into 32s began with:
Why the Best Snub Nose Caliber is .32

 

[JohnKSa]

That's a qualitative assessment rather than a quantitative measurement, but it's certainly a "clue." Whether or not it makes a difference worth fretting over is a separate question.

It's a clue that there's likely no problem. If the bullets were NOT fitting through then that could indicate a problem based on the rationale that they might be getting swaged down to smaller than groove diameter which might cause some issues.

But if he's going send the gun to Ruger to have them spec the chamber throats, he needs something more than "bullets pass through" or some inside diameter measurements made with calipers.

He could slug each throat and the bore and measure the slugs with calipers, or he could slug the bore and measure the throats with pin gauges. Sending it off based on inside diameter measurements made with calipers doesn't make sense--there's a reason they make pin gauges instead of just doing inside diameter measurements with calipers.

 

[Aguila Blanca]

John -- I think you are overlooking a potentially important point from the opening post, which I quoted in post #37:

I first noticed that with all but one chamber I could drop my XTP bullets straight thru.

If the bullets WON'T drop through one chamber, that chamber is different from the others. More important (perhaps), if a bullet won't drop through it, then a bullet when fired through that chamber throat will be squeezed down to the diameter of that throat. If that's smaller than the groove diameter of the barrel, then bullets fired from that chamber will be sort of rattling their way down the barrel.

According to SAAMI specs, the nominal bullet diameter for .327 Federal magnum is .313 inches. The nominal groove diameter of the barrel is .312 inches, which is smaller than the bullet, but the nominal diameter for chamber throats is .314 inches -- which is larger than the bullet.

The chamber throat isn't supposed to squeeze the bullets to smaller than the barrel grove diameter.