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