Plastigauge to check headspace

[autofix4u]

Had just another random thought this evening. Was at the autoparts store today picking up some parts for a hotrod Toyota engine I am building, and as usual I got some Plastigauge with the rod & main bearings. Then the lightbulb came on......could I use this to get a semiaccurate headspace reading. Has anyone tried it, and did it work? I will try it myself, after I get the engine built.

[ANeat]

What caliber? Many cartridges headspace in different spots. Some off the rim, the belt (belted magnums) some off the shoulder, some off the case mouth.

[MtGun44]

I presume you want to use a loaded factory round as a guage. Would be
reasonable, but not really precise. Are you setting up a new rifle, like putting a
bbl on a Savage or cutting a short chamber, or checking an existing gun just
for the heck of it?

Bill

[autofix4u]

I have more than one I would like to check, just for the reassurance of knowing. All are old rimed cals (30-30, 303, 7.62x54r ). don't really have issues, just like to know.

[ANeat]

It might be worth a try, on the bolt actions if you put it on the back of the case it may get smeared.

But then youre only gauging it off one piece of brass

[MtGun44]

I've said it before and I'll say it again. Tight headspace is overrated.

If you are reloading and trying for maximum possible number of load from your brass, then
tight headspace is very helpful.

If you are shooting factory ammo, you can have some pretty far out headspace and not
have any real issues except brass will not be reloadable more than once or twice at best.

If you have bad enough headspace to start to have ignition problems, well OK that is
a problem but this is extremely uncommon.

I don't mean to belittle your measurement of your headspace. I agree, it would be interesting
to know and I think for the leverguns plastigage should work well. The variability of the brass
rim thicknesses (which is what fits the available headspace in your rifles) would make the
measurement a bit inaccurate. Maybe using different brands of ammo would let you see
how much the rim thicknesses vary.

Have at it and let us know how it works. But, it isn't as big a deal as some folks seem to make
of it.

Bill

[3006guns]

I just checked the headspace on a Yugo M48 by simply placing one small piece of Scotch tape on the cartridge base. With the striker and spring removed, I can just feel resistance before the bolt closes. The Scotch tape measures .003" thick, so that's my headspace right?

No.....it's a cheap and cheesy way to avoid using expensive guages and depends on too many variables, i.e. Factory or military cartridge? Springy brass? Squooshy tape? Is the cartridge formed correctly in the first place? About all it does is give you a clue. One of my other rifles used THREE pieces of tape and STILL no resistance. It shoots just fine, no sign of case abnormalities.

I have to agree with MtGunn44, the headspace issue is pretty over-rated. It's important, but an unknown gun is not automatically a grenade. If you can get your hands on a copy of Hatcher's Note Book, there is an excellent chapter that will relieve your mind immensely.

[StarMetal]

I just checked the headspace on a Yugo M48 by simply placing one small piece of Scotch tape on the cartridge base. With the striker and spring removed, I can just feel resistance before the bolt closes. The Scotch tape measures .003" thick, so that's my headspace right?

No.....it's a cheap and cheesy way to avoid using expensive guages and depends on too many variables, i.e. Factory or military cartridge? Springy brass? Squooshy tape? Is the cartridge formed correctly in the first place? About all it does is give you a clue. One of my other rifles used THREE pieces of tape and STILL no resistance. It shoots just fine, no sign of case abnormalities.

I have to agree with MtGunn44, the headspace issue is pretty over-rated. It's important, but an unknown gun is not automatically a grenade. If you can get your hands on a copy of Hatcher's Note Book, there is an excellent chapter that will relieve your mind immensely.


Head space is the distance from the face of the bolt to the datum line in the shoulder (usually the center of the shoulder I believe). So what you have is clearance.

Joe

[Baron von Trollwhack]

You can check HS simply by using a decapper pin to push the fired primer in a case out half way. Then chamber gently and close the bolt. For rimmed, rim plus primer stickout is the HS measurement. For rimless, primer protrusion after bolt closing is the HS.

All is relative to your gun and your fully expanded fired cases. That's why there is a + ~ - tolerance on HS gauges.

To check your fired case /chamber relationship, for example in 35 Remington, slip a fired 40 cal pistol case with a smooth base over the Remington fired case. Measure OAL. Now if you F/L that case and the same measuremrnt is 2 thousandths less, you have just shortened dead nuts HS. Use a little longer case to accommodate a loaded round. Write the measurement in your die box for reference.

BvT

[405]

BvT is correct about the best of the "easy" ways. Just have to make sure the primer is a fairly easy slip fit into the pocket. In some very shallow-shouldered cases that are marginal on angle and amount of datum ring... the case could easily get forced forward if the "crush/slip gauge" resistance were too great at the bolt face. That would be the problem with something like plastiqauge. I think that stuff is designed to sqwash with quite a few ft lbs of bolt torgue for engine parts.... last time I used it was 1965 so CRS could've taken hold :)

[mike in co]

Head space is the distance from the face of the bolt to the datum line in the shoulder (usually the center of the shoulder I believe). So what you have is clearance.

Joe

thank you joe

if you use a brass case it will flex, so your measurement is fleible too.


ues a headspace solid steel gauge, and the plastigage will show you the CHAMBER CLEARANCE in your gun.
if you only have a go gauge, the plastigage may show excess clearance, indication the headspace may be out of spec.
all else is just nuttin honey.


mike

[stubshaft]

All cases that are measured on the shoulder datum line have a slight amount of clearance. Once they are fired they have zero headspace.

[405]

Yep I think the plastigauge method with a steel go gauge will work if enough force can be applied to the put bolt/breech block into full closed battery.

For headspace-on-shoulder cartridges/guns: It's only partly true that once fired, there will be zero case headspace. Above about 30,000 psi the case will go to near zero headspace fit with the chamber/gun. The problem is that the chamber/gun may still have too much headspace. If the gun has too much headspace then each case that has correct headspace when fired in that gun will stretch just forward of the head on the first firing and suffer a shorter life span. This situation, because the symptoms of excess headspace are hidden, leads many to believe all is well with a gun even with too much headspace.... out of sight - out of mind, I guess.

If, as with many cast bullet loads, the pressure is much under 20-30,000 psi then the case will not go to zero headspace with the chamber/gun. The tell-tale sign of excess headspace, in these lower pressure loads, is an obviously protruding primer after firing.

[oneokie]

As mentioned above, plastigage would smear in a bolt gun giving a false reading.

[John Taylor]

I have used masking tape many times to get an idea if there is a problem or not. Using a factory loaded round with layers of tape till you feel a drag closing the bolt. When I set up new barrels I don't leave enough room for one layer of tape. Most of the rimless calibers I do I use a head space gauge.

[Innovative]

This is what I use:


Digital headspace Gauge


http://www.larrywillis.com/headspaceSWEB.JPG

It works on ALL different calibers, and it doesn't require special bushings or attachments of any kind. This gauge displays the clearance (at the shoulder) that YOUR handloads have in YOUR particular chamber. Very simple, and it can also measure your bullet "jump" to the rifling.

- Innovative

[t4spine]

i''ve used plastigage before,cut a strip put some whitelube on the shoulder of a new unfired case w/the bullet pulled on rimless or bend it on an arc and place it on the rim or bothi also use a couple different brands of case .i double checked using gauges in my .308's and it's accurate and tells you exactly what things are