Micrometer recommendation for barrel slugging?

[PNW_Steve]

Hey Everyone,

I am going to slug the barrels on some of my guns and think that I have a reasonable understanding of the process except one detail.

The micrometers that I have used back in the olden days would not work for measuring the grooves left by the rifling lands.

Can you all recommend an appropriate tool? Link?

This is a tool that will see very limited use in my shop so I don't want to spend a fortune.

Thanks.

[M-Tecs]

For even number lands and groove a standard mic works. For odd numbers you need a v-mic of a specific angle. S&W uses a 5 groove so I use a cheap 108 degree $94.00 SHARS 0.2-1" 108 Degree 5 Flutes V-Anvil Micrometer Graduation 0.001” Ebay sells them but can't do ebay links here.

Some wrap the bullet with shim stock and use a caliper or standard mic for odd grooves.

[PNW_Steve]

OK.... I am reading some conflicting info.

Somewhere I read that I needed to measure the bullet both where it contacts both lands and grooves. I can't see how you could do that with a standard micrometer. Measuring the grooves left by the lands would be impossible as far as I can see.

Then I saw something that led me to think that I only need one measurement and that is the portion of the bullet the expands into the grooves.

If the latter is correct then I see how to use a common micrometer.

[PNW_Steve]

Any thoughts on this one: https://www.amazon.com/Beslands-Electronic-Micrometer-Thickness-Protective/dp/B07KC7YNR8/ref=sr_1_20?dchild=1&keywords=Micrometer&qid=1586100662&refinements=p_72%3A2661618011&rnid=2661617011&sr=8-20

[M-Tecs]

The issue may be terminology. The measurement that is of most importance to bullet casters is the diameter of the grooves in the barrel. Then land diameter is the bore diameter.
http://mcgowenbarrel.com/bore-groove/

Example is a standard 30 cal. barrel. The standard groove diameter is .308" with a standard bore diameter of .300". When determining proper bullet size the .308" diameter is what you are verifying and trying to match. On the bullet that will be the mirror image of the actual barrel. On the bullet you are measuring the largest diameters.

On bullets that are boreriders the bore diameter is also of importance. Unless ordering a boreriding bullet mold most people never check this. For the average person pin gauges or small hole gauges can be used to measure the actual bore of the barrel.

Also the bullet is normally slightly larger than the groove diameter of the barrel. The bullet should NOT be expanding into the groves rather the lands are forcing an impression into the bullet. Commonly referred to as rifling grooves in the bullet.

[country gent]

One trick that works for measuring the bore dia ( small) is to use a small set of thread wires in the grooves from the measurement. and subtract the dia x 2.

[PNW_Steve]

Any thoughts on this one: https://www.amazon.com/Beslands-Electronic-Micrometer-Thickness-Protective/dp/B07KC7YNR8/ref=sr_1_20?dchild=1&keywords=Micrometer&qid=1586100662&refinements=p_72%3A2661618011&rnid=2661617011&sr=8-20

Would this be a good choice?

[mdi]

I wouldn't for a couple reasons. First it's digital. I started using micrometers as a machine operator a couple years after I got out of high school and used a plain Starrett 1" mic. I used it steadily for about 12 years (daily) until I bought a Mitutoyo, again a 1" "standard mic. I used these to measure machined parts down to .0005" (learning to use a mic with a vernier type scale is simple and the "feel" is soon established). In all the time I used precision measuring tools I haven't found any digital type to be as reliable as a plain "analog" mics., and I like to see the hash marks lining uo rather than some numbers that "randomly" show up on a readout. (life long machinist/mechanic). If I were to recommend mics I'd say the ones sold by Lyman are as good as needed for reloading and will last many, many years if cared for properly. (I got a "Lyman" 1" mic after my good tools were stolen and it is accurate and working quite well after about 15 years use for reloading).

There are lots of hints to measuring an odd groove slug, but I have used two. First is using a sheet of shim stock (.002" is about as thin as can be managed easily) and wrap the slug and measure. Subtract twice the thickness of the shim for the slug diameter (if using .002 shim stock, subtract .004" from the measurement). I've been using mics for quite a while and I developed a good feel so I am able to measure odd grooved slug directly with good accuracy; I can slowly close the spindle on the slug while I am turning it and I can get an accurate measurement by feeling the slug as it is being turned in the mic. I think if one learns to use a mic good enough to get no more than .001" variations in their measurements, that's good for all reloading measuring chores.

Jes an old phart's opinion/experience...

[Green Frog]

mdi has answered this question about as well as anybody could. If you are serious enough to actually measure down to half a thousandth, ignore all of the digital stuff out there. Ignore the dial calipers... they are useful, but not for this purpose. Get a good old fashioned micrometer and learn how to use it... anything else is just an unacceptable short cut for those too lazy to use proper tools.

I have found that for most hobbyists, the inexpensive imported micrometers will measure as well as most casual users will be able to use them. Yes, I have Starrett and Mitutoyo mics, but I also keep a Chinese mic marked Lyman in my box for measuring bullets and other small parts at the range.

While we're on the subject of measuring tools, a dial micrometer has its place... measuring case length, etc comes to mind. I bought a couple by Mitutoyo that stay in my shop as well as a Lyman-marked Chinese one that goes out to the range in my box. Are you starting to see a pattern here?

Back to the OP's question, I also go with mdi's advice that for an odd number of grooves, a thin shim wrapped around, or two shims placed one on either side of the bullet provide the simplest technique. Just don't forget to subtract the two thicknesses of shim from your measurement. The number you get is the groove diameter and I generally like my bullet to be a thousandth or so larger than that number.

Regards,
Froggie

[PNW_Steve]

Thanks for the recommendations.

I don't know yet how many lands and grooves that I am dealing with. The only mention of odd numbers that I have been in Smith and Wesson guns.

Initially I am going to slug my new 9mm's. A Walther PPS M2 and a PSA 9mm AR (16").

Then my Colt 1911's and then my S&W 586 and my 5.56 AR.

The 5.56 is going to be the last one that I am considering casting for.

I will look around for a standard micrometer. I have a couple of digital calipers and have not had any issue.

I have not used a standard micrometer in 35-40 years but if I can see it, I can figure it out.

Thank you again.

S.

[M-Tecs]

Digital micrometers are widely used and they have there place. The issue with the one the OP asked about is it is digital only. Ones that have both digital and conventional readout campability would be the way I go if I wanted a digital. Here is and example. https://www.amazon.com/Holite-Micrometer-Electronic-Conversion-Resolution/dp/B07NYGYN1T/ref=sr_1_10?crid=27JJU1EB1O4GD&dchild=1&keywords=digital+micrometer&qid=1586209990&sprefix=digital+micr%2Caps%2C171&sr=8-10

I don't have clue as to quality. It appears to be metric on the conventional readout so I would not recommend this one. Just used it as an example.

Micrometers definitely are more accurate than dial calipers. For the average user with limited experience + or - .0005" is realistic accuracy with a mic. With a quality dial caliper it's more like + or - .001". After you develop a good technique and feel you can do better.

[ulav8r]

https://www.amazon.com/Mitutoyo-193-211CAL-Micrometer-Calibration-Graduations/dp/B00CHR9JWY/ref=sr_1_21?dchild=1&keywords=digital%2Bmicrometer&qid=1586213021&refinements=p_89%3AMitutoyo&rnid=2528832011&sr=8-21&th=1

This is a mechanical digital as opposed to an electronic digital. The digital part reads to the nearest thousandth, but the barrel graduations reads to the nearest ten-thousandth. This is the type I purchased in 1975, maybe the same model.

[Dinny]

I don't understand why anyone would measure the bore. I size cast bullets to fit my chamber throat. Even then I find which diameter slip fits into a fired case from that chamber and voila, I get good groups using published load data. Seems every diameter that fits the throat also magically fits the bore. Please explain how all the extra trouble pays any dividends.

Thanks, Dinny

[bmortell]

I don't understand why anyone would measure the bore. I size cast bullets to fit my chamber throat. Even then I find which diameter slip fits into a fired case from that chamber and voila, I get good groups using published load data. Seems every diameter that fits the throat also magically fits the bore. Please explain how all the extra trouble pays any dividends.

Thanks, Dinny

not every gun has a throat it sometimes tapers right from case to rifling. found that out when trying to slug and size to my throat lol

[country gent]

You will need the bore dia if your loading traditional Paper Patched bullets since they are bore riding. BPCR PP bullets are loaded only 1/7"-3/16" into case and set in the bore when chambered.

[mvintx]

I bought one of these. $24 and it measures to .0001"

https://www.amazon.com/gp/product/B0045VKF5K/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

[John Boy]

Buy a set of pin gages .... https://www.amazon.com/HFS-Class-Steel-Gage-0-251-0-500/dp/B081TQ91KQ?ref_=s9_apbd_obs_hd_bw_bRB2gd&pf_rd_r=W0RR6NQH6HDTWWA05V6Q&pf_rd_p=f9279183-f122-5b66-bba1-0dce342e57f7&pf_rd_s=merchandised-search-10&pf_rd_t=BROWSE&pf_rd_i=401593011
For minus set tolerance: +0.0000" / -0.0002"
For plus set tolerance: +0.0002" / -0.0000"
Measures the bore ID, land to land

Then take a caliper and measure the ID in the bore, groove to groove

Fast and accurate

[GONRA]

GONRA sez - listen to everybody - slug the bore and use a really nice DIGITAL micrometer for Groove diameters.
Also, listen to John Boy and get a set of Pin Gages for Bore diameters.

[country gent]

Ive been looking at caliper style dros for on a lathe tail stock. 6" version of while they read ( resolution) to .0005 the acuracy over the range is +/- .0015. On the longer units it even more. My mitutoyo digital mikes are .00005.

[DougGuy]

I use and highly recommend a MITUTOYO 193-201 0-1" .001" DIGITAL OUTSIDE MICROMETER WITH CARBIDE TIPS. $48 on fleabay in the wooden case.

This is not the electronic digital, it is mechanical digital, you can see the numbers much like an odometer in a car speedometer, you can guess how many tenths between digits, and it has the .0001" scale around the thimble as well. It is a friction thimble which repeats the closing torque consistently. Been using an ebayed one of these for years and years, I mic my Zminus pin gages to check it's calibration and it's been rock solid.

Let me recommend a stand to clamp the mic in so you have both hands free, worth their weight in gold!!

[country gent]

I use Browne and Sharp slant lines for everyday use set of 1-6". Also have starrets a set of the "super mikes" . My best mikes are Mitytoyo digital used for gage work and fine measurements. these I have 1-3". At the bench a stand is handy at times. I normally wrap little finger in frame and use thumb and fore finger to close and tension. The big thing with Mikes is developing the "feel" of a measurement. Friction thimbles or ratchets can be a big plus for occasional users.

Several things that need to be done. Check zero when you pick it up. Only takes a min and assures they are right. clean anvils before use. Store partially open so the anvils arnt together. If you have gage blocks or pin gauges the mics can be checked at the measurement.

[samari46]

I'd have to echo the previous poster regarding mike's Starret,Brown and Sharp,and Mitutoyo. They aren't cheap and never were,but all are quality tools that will last longer than you. I have one old mike that is over 50 years old and still gages good with a 1" standard. And get a little mike stand while your at it. Flat base and the clamp that holds the mike is angled and sure makes it easier to hold a barrel slug and get accurate numbers. Frank

[country gent]

I also have used luffkin, Toledo, fowlers, and some other brands. The lufkins were my grandfathers and pushing on 100 years old as accurate today as when he bought them. A used well cared for mike with take up on threads will remain accurate for many many years. Back when he started out in the trade a lot of tools were made in house or locally.

[nuclearcricket]

I have kind of been following this thread and it has been interesting. Now let me back up a step. I have worked most of my adult life as a precision tool maker and have spent a lot of money on the best micrometers I can get, Swiss made and very good. For the average person, for checking diameters and such the low cost micrometers imported from (yuck) China are for the most part pretty good. I purchased a set before I retired to use at home and they are very accurate and have a nice feel to them. I would take a look at CDC Machinery and Shares to see what kind of prices they offer on mics. They also sell the V anvil mics to measure the odd groove diameters. As much as I do hate to recommend stuff from that country, in my experience it has been of good quality and a very good price.
Sam

[Green Frog]

Nuclearcricket, you have hit upon our national problem concerning commerce with C***a. Their business model seems to be to build to the market, with sufficient quality that the customer won’t walk away, but at a low enough price to beat the competition cost-wise. With a nearly unlimited supply of labor and a huge backlog of raw or recyclable material, they can do this.

The question is, do we as Americans pay more to get the same stuff, or do we continue to let manufacturing of everything from toothpicks to jet planes move to where it is cheaper? I don’t have an answer, but I will say at this point, if I have a choice, what I buy isn’t coming from C***a. The stuff is so ubiquitous though, it’s hard to avoid! [smilie=b:

Froggie

PS As previously stated, I’ve had measuring tools from the US, Japan, and C***a, and all fulfill their duties nicely, but I don’t expect to buy any more from the latter.

[nuclearcricket]

Mr Frog, I do agree with you 100%. I much prefer to purchase American made if I can. Made in China is at the bottom of my preference list. When I got the imported micrometer sets, one english and one metric, cost was a factor. I am at the point now where I don't see me making any further purchases of precision measuring equipment. I was once told that when you need something, go and buy the best and it will only hurt a little while and you will not have to worry bout things. My Etalon mic's are that way. 2 I purchased new, 3 I got used and I will never wear them out. They were the best I could find for the work I was doing at the time. Now my machining projects are just a hobby as I am retired. If a person can find good used American made at a reasonable price that would be the best way to go the way things are these days. That being said, one still has to work within ones budget. If you shop around and are careful you can find good buys on quality used tools. Someone that uses precision tools for a living will take good care of them and when they are ready to pass those tools on to the next owner they will still be in good working condition, they may not be as pretty as new but they till still work.
I guess its almost down to the point where you need to let your conscious be your guide if you can.
Sam

[Green Frog]

Yeah, I bought a bunch of top shelf Starrett micrometers while taking machining classes, along with a couple of Mitutoyo dial calipers. I was given a 1” Mitutoyo mic that lives on a built in shelf on the side of my lathe.

BUUTTTT... I have a Chinese mic and dial caliper (marked Lyman) that get to travel around a lot in my range boxes and actually see the most use these days. They are counted expendable if lost, damaged, or stolen.

Froggie

[nun2kute]

I have two of the red Hornady digital calipers, @ 30$ each IIRC. And I think I've spent that much for batteries to keep them working. Got Fowler mic, the analog digital one. Better that way IMHO. For reloading purposes, I don't see the cost of the tool as an issue as long as you are not switching between say ... Lyman to Starrett ... tools while working on any particular project. But I am not a lifelong machinist, I could be wrong.

[Cosmic_Charlie]

It's interesting that dial calipers get a bad rap. I have measured quite a few objects with known diameter and they have always been spot on. Not saying a micrometer is a bad idea, only that I feel a good dial caliper can get you close enough. I have a micrometer too that I use for measuring valve shims on my motorcycles.

[country gent]

Several reasons for the calipers reputation Back in the day dial calipers were very suseptabled to chips dust dirt rough handling and coolant. Most didnt like the 1-100-0 dials 200 to revolution. A lot of them were also susceptible to imagination.
Newer dials and digital s are much better.A drop or bump on the older one would usually jump a tooth. The digital calipers are really pretty good nonmagnetic scale is encased and no rack pinion to be fouled, also a much "smoother" feel to them

[pcmacd]

I wouldn't for a couple reasons. First it's digital. I started using micrometers as a machine operator a couple years after I got out of high school and used a plain Starrett 1" mic. I used it steadily for about 12 years (daily) until I bought a Mitutoyo, again a 1" "standard mic. I used these to measure machined parts down to .0005" (learning to use a mic with a vernier type scale is simple and the "feel" is soon established). In all the time I used precision measuring tools I haven't found any digital type to be as reliable as a plain "analog" mics., and I like to see the hash marks lining uo rather than some numbers that "randomly" show up on a readout. (life long machinist/mechanic). If I were to recommend mics I'd say the ones sold by Lyman are as good as needed for reloading and will last many, many years if cared for properly. (I got a "Lyman" 1" mic after my good tools were stolen and it is accurate and working quite well after about 15 years use for reloading).

There are lots of hints to measuring an odd groove slug, but I have used two. First is using a sheet of shim stock (.002" is about as thin as can be managed easily) and wrap the slug and measure. Subtract twice the thickness of the shim for the slug diameter (if using .002 shim stock, subtract .004" from the measurement). I've been using mics for quite a while and I developed a good feel so I am able to measure odd grooved slug directly with good accuracy; I can slowly close the spindle on the slug while I am turning it and I can get an accurate measurement by feeling the slug as it is being turned in the mic. I think if one learns to use a mic good enough to get no more than .001" variations in their measurements, that's good for all reloading measuring chores.

Jes an old phart's opinion/experience...

Those digital micrometers are fragile. I've bought a couple used and returned them as they were missing internal teeth here or there.

I've a boat load of micrometers; I bought them as an investment, used a few years ago.

Standard micrometers are pretty easy to read. 30 minutes fooling around and you will nearly be an ex spurt. The hardest part about using any micrometer is understanding how tight to turn the thumb wheel if it does not have a clutch, and how to position the tool against the part you are measuring.

For years I've been able to use a standard micrometer to measure to 0.0001" +/- 0.0001, but usually tighter.

0.0001" mics are great, and I would much rather have one than a typical 0.001" unit, but I never hesitate to read the less expensive mic down to gnat's eye. I'm usually right on, if not really close, over thousands of measurements.

(I always estimate the tenths on a 0.0001" micrometer before looking at the vernier..... and I am dead nuts on 9 of 10 times.)

[pcmacd]

I have two of the red Hornady digital calipers, @ 30$ each IIRC. And I think I've spent that much for batteries to keep them working. Got Fowler mic, the analog digital one. Better that way IMHO. For reloading purposes, I don't see the cost of the tool as an issue as long as you are not switching between say ... Lyman to Starrett ... tools while working on any particular project. But I am not a lifelong machinist, I could be wrong.

I've bought Harbor Fright stainless steel calipers in the past for perhaps $15. They were perfectly adequate for any reloading task.

[44magLeo]

I have a Harbor Freight mic. it has the mechanical digital readout. The readout gets very close then I use the markings on the tumbler to be exact.
The dial calipers I've had come from different places. Some are no name but have the seller's name on a sticker. I have both SAE and Metric dial calipers.
On a barrel slug using the thin blades of a dial caliper will fit in the grooves on the slug and can give you a measurement of the bore size. There are more accurate ways, a mic with knife edge anvils would be better but calipers get you close enough for loading.
On most fairly new weapons the bore sizes come close enough to not need slugging. Older black powder weapons and older weapons from foreign countries are more apt to not be at expected standards.
These I use a pound cast to get the throat a well as bore and groove sizes.
On any weapon I feel tight spots when running a tight patch through the bore I might slug to check.
Slugging is a good thing to understand how to do for when it needs to be done.
Even with slugging it still pays to experiment with different sizes to find what your rifle likes best.
Leo

[onelight]

It's interesting that dial calipers get a bad rap. I have measured quite a few objects with known diameter and they have always been spot on. Not saying a micrometer is a bad idea, only that I feel a good dial caliper can get you close enough. I have a micrometer too that I use for measuring valve shims on my motorcycles.
I agree a dial caliper was all I used for years on the loading bench and still what I use the most.
I would add I watched a video of the Barnes ammunition assembly line , and the quality control checks they showed in that video were with a dial caliper

[farmbif]

if you get a good starrett or mityoto veneer caliper it will work, but as others have said do yourself a favor and get a starrett or mityoto micrometer and the standard so you can calibrate it. if you can find a blade micrometer that's pretty darn good too. stay clear of the Chinese junk.

[Neverhome]

It's interesting that dial calipers get a bad rap. I have measured quite a few objects with known diameter and they have always been spot on. Not saying a micrometer is a bad idea, only that I feel a good dial caliper can get you close enough. I have a micrometer too that I use for measuring valve shims on my motorcycles.

I have to agree that a caliper is probably plenty as long as you trust it to about .001 resolution. The cheap FA branded one I have is dead on and has been for years now. I keep quality jacketed bullets of various sizes stored with it so I can check it periodically. You can get into the accurate vs precise argument blah blah blah but it’s shown itself to be repeatably precise by hitting the same numbers on these bullets for years and it has also shown itself to be accurate enough for what I do. My 6br regularly went under an inch at 300 yards in calm air. Never once measured anything to .0001.
I was a Master Chief Machinery Technician in the CG. I’ve used plenty of high dollar precision mics and dial indicators when overhauling engines. I really doubt the average shooter will ever benefit from measuring to .0001.
People like fancy toys though so if you have the cash why not go all out. Most people will convince themselves that the fancy toy helped. Me included! Human nature.

[Scrounge]

Hey Everyone,

I am going to slug the barrels on some of my guns and think that I have a reasonable understanding of the process except one detail.

The micrometers that I have used back in the olden days would not work for measuring the grooves left by the rifling lands.

Can you all recommend an appropriate tool? Link?

This is a tool that will see very limited use in my shop so I don't want to spend a fortune.

Thanks.

Best tool for barrels with an even number of grooves is probably a Blade Micrometer like this: https://www.amazon.com/Anytime-Tools-Micrometer-Outside-0-0001/dp/B01FPTM5OY/ref=sr_1_5?dchild=1&keywords=blade+micrometer&qid=1594251689&sr=8-5

Not saying that's the best one, picked it because it has the best photo of why it works. I picked up one from Fowler in a pawn shop some years ago when I was gathering stuff for my machining class.

Bill

[country gent]

The big plus to calipers is 1 tool measures from 0-6" with reasonable accuracy. With mikes you normally need a set for each 1" of size ( 0-1" 1"-2" 2"-3" ) there are some larger mandrel mikes out there with different anvils for each step but they get awkward and clumsy to use. A comparator stand and indicator with gauge blocks to set can be very accurate but more work to set up and use

[Little Oak]

Here's my two penneth worth - what quality of instrument you get depends on what you can afford and how old you are.
What's age got to do with it I hear you ask. Well if you're young and want something to last a lifetime get some good quality stuff right off, regardless of price. If, like me, you're getting on a bit, more financially advantageous units will do, they only have to last maybe a quarter of a lifetime.
I purchased a Moore and Wright 0-1" mic and a standard 6" Mitotoyo caliper nearly 50 years ago and they're still perfect, even though I use them almost daily (I do look after my kit). I also have a Starrett and a spare M&W mic I picked up along the way.
I won't use anything that needs a battery, it's sure to go dead when you really need it and the only things I have with dials are my DTI's. Plain scales are, in my opinion, just as fast with practice.
I did once buy some cheap mic's just out of curiosity. They work fine but I could tell straight off they weren't built to last.

[Green Frog]

Well said, Little Oak. The only thing is, by the time we think we can afford the good stuff we’re too old to get full benefit from it. Better to buy better than you think you can afford while you’re young and benefit longer!

Regards,
Froggie

[Hossfly]

Amen to that. I don’t buy anything that has a life time warranty. Cause I wonder who’s life time is covered by it.

[cuzinbruce]

If you shop around a bit, you may be able to find good B&S, Starrett, Mitutoyo mikes used for not outrageous prices. I don't have one that I bought new. Just have to look at them, turn them, etc, to see which ones haven't been abused.

[EDG]

The ridges of the bullet are all that you really need to measure with a micrometer.
The hole in the barrel can easily be gauged with a set of .001" increment pin gauges.

Or You can mike the grooves of a bullet with a blade mike if they are even numbered.
Odd numbered grooves require a different measuring process beyond the knowledge of most home hobbyists.

[John Boy]

264719

43 posts about micrometers measuring to 0.0001" +/- 0.0001 for land/grooves...
When only standard measurements are x.xxx

264720

[EDG]

Please define what you think are standard measurements.
When possible gauging limits are supposed to be 1/10 the precision that is required.
If your precision required is plus or minus .001 you micrometer should be capable of plus of minus .00010.
This is standard practice for calibrating gauging equipment that will be used to accept product that will be sold through commercial channels in the US. When 10 to 1 is not really possible due to extreme tolerance requirements a 4 to 1 ratio is deemed acceptable.


264719

43 posts about micrometers measuring to 0.0001" +/- 0.0001 for land/grooves...
When only standard measurements are x.xxx

264720

[tankgunner59]

I too use a vernier mic and I believe they are much more reliable than digital. If you don't know how to read it you can check here and you can find youtube vids that explain it. Once you learn how to read it it's pretty easy to remember.

The only digital measuring device I have is a caliper, but it's for non-critical measurement, I also have a dial caliper that is my go to.