Caliper for Slugging a Barrel

[wacki]

I want to slug a barrel so I can make an educated mold purchase. For example my 9mm options are: .356 vs .357 vs .358

Anyone got a favorite caliper for that kind of work? I don't think the Harbor Freight calipers will cut it for that purpose.

[jmort]

Soft lead oversized Ball/slug and a micrometer.

http://www.beartoothbullets.com/tips/index.htm

Enco brand usually good deal. You can get really nice used ones on EBay like Sterrett or Mituyomo

[Bzcraig]

Soft lead oversized Ball/slug and a micrometer.

http://www.beartoothbullets.com/tips/index.htm

Enco brand usually good deal. You can get really nice used ones on EBay like Sterrett or Mituyomo

What he said

[bangerjim]

Starrett and Brown & Sharp are always nice brands!

You do not want to use a caliper. Use a micrometer.


bangerjim

[Ben]

Starrett and Brown & Sharp are always nice brands!

You do not want to use a caliper. Use a micrometer.


bangerjim

What bangerjim has said............

Many on this forum in the past few years " thought " that they had slugged their barrel and " thought " they knew the dia. of the slug only to find out that their caliper was off.

A good micrometer will give you a dependable reading.

Ben

[EDG]

>>>A good micrometer will give you a dependable reading.<<<

Not the cheapest old dogged out micrometer. Expect to pay $15 to $30 for a "GOOD" used one.

[bangerjim]

>>>A good micrometer will give you a dependable reading.<<<

Not the cheapest old dogged out micrometer. Expect to pay $15 to $30 for a "GOOD" used one.

"GOOD" means Starrett, Mit, B&S, and any other proven "lab quality instrument".

That does NOT include Enco, HF, Grizzley or any of that other garbage brands out there. If those are 2nd hand/used, they are probably wore out. Pass on those used brands!!!!!!

No one ever gets rid of the GOOD ones.......ever! I have the ones I bought new 35+ years ago. And they are still NIST quality. Unfortunately caskets do not have side pockets!

banger

[country gent]

Another thing to do before depending on a measuring tool for accurtate measurements is to measure things of known sizes (drill bits, pin gages) to be sure you are doing everything correctly. There is a feel to getting accurate measurements with these tools. Used michrometers can be a good but but if possible check them thru thier range 0, .250, .500, .750 to make sure they are accurate thru the range. Some tools see life in a very small range and all the wear is in that area. Keep in mind odd number or lands and grooves may not be as easy to measure.

[bangerjim]

So true.

I use sets of pins and gauge blocks (all NIST) to check all my measuring tools. Mics (GOOD ones!) are extremely accurate. Calipers (GOOD ONES!) can come VERY close. But grabbing a set of $10 cals off the HF shelf will not give you a KNOWN accurate result. You MUST check them against known standards. Granted, most reading this do not have access to lab standards as I use, but drill bit (again GOOD QUALITY!!!!) shanks are an excellent start. Avoid the stamped and galled areas! I have a set of fractional/letter/number AMERICAN MADE drills ($300+) I use for precision drilling only that are extremely close to standards.....so close most could not see the difference. No guarantee on cheep Chino drills!

But check you readings. And practice reading the mic spindle! Many do not have any exposure to them and can easily mis-interpret the readings. I spent some time in a manufacturing engineering college course (and tests!) practicing/learning how to read those "little scratches"` on the barrel of a mic!

Remember the rule for checking accuracy is: the thing your are using as the standard must be 10x more accurate than the device you are measuring/checking it with. To check 0.001" you need a standard that is known to be 0.0001" accurate.

bangerjim

[Dan Cash]

Starrett and Brown & Sharp are always nice brands!

You do not want to use a caliper. Use a micrometer.


bangerjim

Whether I use my Starrett micrometer or my Mituyomo (sp?) caliper, both of which are checked against a range of test blocks/pins, they both show the same measurement on the same test item. I don't buy the inaccurate caliper argument if you are using quality, calibrated instruments.

[silverado]

I havr been wondering the same and lgs has this for reasonable price.
https://m.hornady.com/store/Micrometer-1-Each/
I don't understand how the say .001 accuracy followed by needing 1/10th of that. Anyone use the hornady?

[bangerjim]

Whether I use my Starrett micrometer or my Mituyomo (sp?) caliper, both of which are checked against a range of test blocks/pins, they both show the same measurement on the same test item. I don't buy the inaccurate caliper argument if you are using quality, calibrated instruments.

No argument there!

That is because you ARE using QUALITY instruments! Not HF, Grizzley, Enco, etc. as many seem to migrate to due to costs.

The Mit cal will give very compatible readings to a mic......as long as someone has not abused the digital encoder. If fouled with dirt and grime....all bets are off. That is why a mic will ALWAYS read accurately and a cal can sometimes drift.

bangerjim

[bangerjim]

I havr been wondering the same and lgs has this for reasonable price.
https://m.hornady.com/store/Micrometer-1-Each/
I don't understand how the say .001 accuracy followed by needing 1/10th of that. Anyone use the hornady?

That unit will read in 0.001 graduated increments. You have to interpolate between the 0.001 marks to get into the 1/10th areas.......SWAG most times. That is more than likely a Chino cheap import with their name on it. No different than HF or Grizzly or Enco brands.

banger

[Wayne S]

I want to slug a barrel so I can make an educated mold purchase. For example my 9mm options are: .356 vs .357 vs .358

.
9 MM ? an auto loader ?? If so, then take it apart, then find an "egg" sinker just barely to big to fit in the muzzle, or a cast bullet. and a wooden dowl no bigger that a 9MM case and "slug" the chambers throat, not the bore from the muzzle but the chambers throat.
As to mold selection, IMHO, unless you are buying a used mold where you know first hand what OD the mold casts, I would not consider lee, Lyman, or RCBS molds, as I have experienced variations in the OD of bullets cast from two different molds. Ask for first hand experiences from casters that have bought the mold of your choice {shape & Wt.} from NOE or MeHic

[Dan Cash]

All my mikes and calipers are non digital, in fact I even have a vernier caliper but it is a chore to use.

[mdi]

Well, a lot of fellers have told you not to use a caliper when checking a barrel slug, but none said why!

Calipers have narrow jaws that are pretty long and can flex, especially when used by one without a lot of experience, also narrow jaws can slip into "low spots" and give bad readings. The amount of pressure exerted on the thin jaws is critical too. Some "spring" can/will affect the readings/measurements, and it takes some "feel" to get correct measurements. Getting good consistent readings with a caliper is a bit harder to learn (from experience and teaching new machine operators how to use them), anybody can use them, but many get erroneous readings, off by .001"-.002". Having been a lifelong machinist/mechanic/electrician, I prefer dial calipers over digital. I tried 2 digital calipers, not cheap ones either, and dealing with dead batteries, wandering between SAE and metric, and auto shut-off, I just don't trust some numbers appearing on a little screen as true measurements (I know, lots of fellers use them to measure into the millionths, but not me).

I started using micrometers in about '67 or '68 and while most of my tools were stolen I have a lot left, but none of my top of the line measuring tools (Brown&Sharpe, Starrettt, Mititoyo, etc.). I now have a "Lyman" micrometer with carbide anvil and tip, reads to .0005" and is pretty solid. I use a Craftsman 6" dial caliper and I get measurements about as close as humanly possible with these tools...

[CastingFool]

Well said, mdi. I have a 6" Mitutoyo dial caliper that is my go to measuring instrument when reloading. I worked a number of years as a machinist, so I have plenty of experience using it. I also have a set of 1"-5" mikes in my toolbox, but they hardly ever get used.

[smokeywolf]

I suggest acquiring a good micrometer. Mitutoyo, Starrett, Tesa, Brown & Sharpe are of known quality.

smokeywolf

[9w1911]

I had some soft lead boolits that I used a finish hammer to fatten and then i slugged with that , I have used sinkers too and they work great I also widen the sinker with the hammer

[cbrick]

I suggest acquiring a good micrometer. Mitutoyo, Starrett, Tesa, Brown & Sharpe are of known quality. smokeywolf

Absolutely. If you read the stat sheets on most calipers they are only guaranteed to .001" until you get into some really high dollar units. Doesn't matter how much experience you have or how careful you are using it if the tool is only good to .001" that's all you'll get. A good micrometer is a good investment.

Rick

[zuke]

I have a 0-1" ball nose Mitutoyo mike I like to use for slugging. Get's right into the groove's.

[ROGER4314]

I'm retired after a lifetime of working around machine shops and manufacturing plants. Granted, if I was running a machine and my job depended on producing good parts, Starrett, B&S and other classics would be my choice. Now, I use Harbor Freight measuring equipment, have also used Enco and a few others. They will all work well until you drop them or allow foreign materials to get into the works. You can kill a B&S caliper as easily as a HF tool by careless handling. That's what I do. Do as you wish.

I do NOT slug barrels! I won't sit and pound on my barrels......sorry. I use Cerrosafe chamber casting alloy. If you want to spend $20 on a 1/2 pound ingot, Midway has it. If you contact Rotometals, they have the same thing currently on sale for $12.99/pound!

Put a paper plug in the barrel and pour the melted Cerrosafe into it. The alloy melts at between 150-190 degrees Fahrenheit. For the first 30 minutes, the alloy shrinks, making it easy to remove. At the one hour mark, the alloy is true to size. Later, it continues to grow until it sets at .0025" oversize.

That's the way I do it. You may do as you wish.

Flash

[georgerkahn]

I agree with ROGER4314 100% -- I have two Cerrosafe ingots I've re-used many, many times -- so unless you lose or perhaps contaminate the stuff (???) -- it lasts! The only thing I wish to add to ROGER4314's post -- as hopefully a very friendly amendment -- is to CLEAN your barrel first, and then clean it again! I once slugged a S&W Victory .38 S&W, finding it to be surprisingly small -- this for a revolver which did in fact go through the (WWII) war! I then cleaned the barrel, jokingly thinking while enough lead and copper was removed to form a boolit for it, and then remeasured. Too many years back for me to recall how many thousandths larger the barrel diameter now was -- but I was impressed enough to never forget that "lesson".
BEST!
geo

[wacki]

For the micrometer folk, do you use the flat piston or pointed anvils?

[EDG]

No matter what quality of caliper you buy it will not have the capability of reading to the nearest .0001.
They simply cannot resolve parts of a thousandth. A vernier micrometer with read to .0001.
A fat thimble micrometer (some Swiss made mikes) will direct read on the thimble to .0005 and the verneir only needs to deal with the other 1/2 thousandth.
Any good micrometer, including those with no vernier, will allow you to estimate to the nearest .0002. You cannot do that with any caliper.


Whether I use my Starrett micrometer or my Mituyomo (sp?) caliper, both of which are checked against a range of test blocks/pins, they both show the same measurement on the same test item. I don't buy the inaccurate caliper argument if you are using quality, calibrated instruments.

[dromia]

I use Mitutoyo calipers and micrometers and am very happy with them. A friend whose business is in the measuring industry checks them no and again for me and they have been spot on from purchase.

[dikman]

I wanted to check the diameter of my revolver chamber, so I poured in some casting resin. Once it was set I knocked it out with a dowel via the nipple hole. I guess you could do a rifle barrel too, just put a piece of fine wire in, attached to a plug or something to seal the barrel and pour in the resin. Once it's set pull the wire to get the plug out - at least, that's the theory.....