Headspace, 1911 Platforms..a Klue?

[saltydog452]

I've tried to read just about everything that I could find in this forum regarding headspace on the various 1911s and clones. Like most of us I suspect, I don't have a set pf GO/NO-GO gauges much less a set of incremental gauges for the two extremes.

My question(s)? have to do with indication that excessive headspace might be present. Assume that the extractor and firing pin have been removed from the slide. Also assume that as a control you are using a USGI hardball loaded round. WCC 72 Match to be exact.

The loaded round sits within +/- .002 of the end of the hood in a disassembled barrel. The pistol is then assembled (w/o firing pin and extractor), the loaded round is then chambered. The area from the back of the barrel hood and the breechface will accept an automotive feeler gauge.

At what approximate thickness of feeler gauge would you consider that to be an indication of possible/likely headspace concerns? .005, .010, .015...?

The gun is a Norinco, new to me, but used, does not appear to have been 'Bubba Smithed', and seems to function. Other than fired brass hitting me on my punkin head, all other indications seem to indicate that this is 'good un'.

Thanks,

salty.

 

[pcf]

Not quite following you.....I made a set a go/no-go gauges using a .270 and 30-06 case. The .270 is the GO gauge and was trimmed to .895". The 30-06 made the NO-GO and was trimmed to .910".

All you have to do is cut the cases off behind the shoulder, run it through an expander die, resize in the pistol die, and trim to length......

 

[1911Tuner]

Field Expedient Gauge

Salty...Good suggestion from pfc. A simpler way to determine headspace is with a fired, resized case and a set of small automotive feeler gauges.

Measure the length of the case and work it into the chamber. Find which feeler gauge will slip between the rear of the case and the breechface with a little drag. Add the two figures together. If the total is more than .920 inch, it's excessive.

There are two ways to have excessive headspace. One is potentially dangerous, and the other isn't.

If the chamber is simply cut too deep, it's not unsafe. It could lead to erratic ignition or even misfires...but not dangerous.

If the recoil faces of the barrel lugs are mislocated...or the faces of the slide lugs are mislocated, and allow the slide to move backward far enough on firing to allow the case to back out of the chamber far enough to lose support on the underside of the case very far forward of the web...it could bulge or even blow out a case.

Since your cases sit that close to the face of the hood, it's not likely that the chamber is over-cut, and I suspect that the latter is where your excessive headspace is coming from. A large gap between the hood and the slide is also an indication of that condition, but not absolute.

You can get a round in the chamber, insert a dowel rod or a pencil, push it rearward against the slide and look on the underside with a good light to see how much of the case is unsupported.

If this is on your Norinco, most of those did have fairly sloppy headspacing.
Average runs in the .914 to .918 range. Acceptable, but just on the edge.

 

[saltydog452]

Still looking for a klue..

Pcf and Tuner,

Thanks for your reply.

I'm not good at explanations, but will try again. If you buy a used 1911 platform pistol, and a loaded round will fit reasonably flush with the end of the barrel hood, the pistol when assembled (w/o firing pin & extractor) will accept a 'feeler gauge', at what dimensions would you consider the gap between the hood and breech face to be excessive?

The Norinco will close gently on a .022 gauge, but stops approx 1/10" from full battery on a .025 gauge.

Is .022 too much clearance?

Thanks,

salty.

 

[pcf]

Saltydog,
You have to know how long the case you are working with is before you can do anything. If your case is on the really short side (.865-.870") then you could be in dangerous terrority, not likely though. On the flip side if you're case is long (+.900") you're running outside of acceptable.

 

[1911Tuner]

re:

pfc done nailed it with:

>You have to know how long the case you are working with is before you can do anything. If your case is on the really short side (.865-.870") then you could be in dangerous terrority, not likely though.<

Except...

If the case is on the short side (.870) that measurement plus .022 inch (.899) isn't out of the acceptable range. A long case at .900 plus the .022...is...by .002 inch. A NO GO would let the slide go to battery on that.

Judgin' by the fact that pfc understands the headspace question, he musta got in a rush and turned it around...I do it all the time.

Salty, here's part of my original reply...Go back and re-read it from there down.

>>Measure the length of the case and work it into the chamber. Find which feeler gauge will slip between the rear of the case and the breechface with a little drag. Add the two figures together. If the total is more than .920 inch, it's excessive.<<

 

[saltydog452]

Fellows, I'm dumber than a stump. You two gents are talking from a different frame of reference. Although I'm trying to learn, my learning curve is kinda 'flat' at times. You, on the other hand, know what you are talking about. I've just gotta guess at it. Sometimes what I think, and what I think I said aren't exactly the same. So, please try to bear with me.

pcf says that you have to know what length case you are dealing with....I dunno, and neither would anyone else who bought a box of 45 ACP ammunition. Individual brass dimensions would kinda vary from mfgr to mfgr or lot to lot.

Tuner says that I need to measure stuff. Some stuff I can measure. But when buying a new (used) pistola, most of us don't have the expertise of you gents, much less the tools. What we MAY have is a set of feeler gauges. And the seller may let us stick a feeler gauge twixt the barrel hood and breech face.

If thats the case, at what point would you consider the possibility/probability of headspace problems and pass on the sale?


Side Note: I like my 'Rinco...Don't plan to sell it...May give it away though...Not gonna try to make a Kentucky Thoroughbreed out of a Arkansas Mule...Neither do I want one of my kids/grand-kids to lose an eye over excessive headspace if they put some +P+ through the dang thing...Just as a 'ball-park' figure, if the slide will close on a .022 feeler gauge, would you consider barrel replacement?

Thanks,

salty.

 

[1911Tuner]

Measurin' the Headspace

LOL Salty.

Take a fired, resized case and measure its length with a dial caliper. It will
likely be in the neighborhood of .888-.893 inch. Slide off, work it into the barrel and into battery. Push the barrel upward into the slide and watch it to see where the case rim is when in full battery. Push down on the barrel just a tiny bit, and insert a feeler gauge. Push it back into full battery position
and pull on the gauge. if it's easy to pull, repeat with the next thicker gauge
until you find one that's hard to pull out, but will still move. Add the two numbers together...Case length and feeler gauge thickness...to determine total, live headspace. If the gauge that will let it go to battery is really tight, subtract one thousandths of an inch to get closer to the truth.

This is to be taken between the case and the slide...NOT between the hood and slide. The face of the barrel hood doesn't mean a thing at this point,
and the fact that a cartridge or a gauge sits flush doesn't mean that headspace is good.

Example: Case=.895 inch long. Feeler gauge that fits with a light drag coming out=.022 inch. Total headspace is .917 and is ordnance acceptable.
If the gauge plus the above case dimension turns out to be .026 inch, the total headspace is .921 inch, and is .001 inch in excess of what is ordnance acceptable. GO and NO-GO gauges for the .45 ACP are .898 minimum and .920 maximum. All guns must go to battery on the GO in order to be within acceptable minimum limits. Any gun that goes to battery on the NO-GO
is outside of the ordnance acceptable limit and must be repaired before being okayed for service. These dimensions apply to the cartridge, regardless of
gun make or model.

NOTE: This has nothing WHATSOEVER to do with custom chambers and hand-built OR SPECIALTY guns, in which the builder may set his headspace to whatever dimensions and by whatever methods he chooses...including a peanut shell if he so desires. This is simply a means to determine whether the headspace on an existing gun is within ordnance acceptable limits, as set forth by the designers, engineers and the SAAMI.

 

[Canuck-IL]

I believe what they're suggesting is that you take an EMPTY case, measure it, take it with you to the store where you're shopping along with your feeler gauge. Slip in the empty case - now apply the feeler gauge - the sum of the case length plus the largest feeler you can get in there is the value you're looking for.

/Bryan

 

[saltydog452]

After being told the same thing by Tuner at least three times, it finally began to sink in what he was talking about. I told you that I was dumber than a stump and that may have been a generous description.

I fired three different types of ammunition to get some type of average. Old WW Match Target 185, WCC 72 Ball, & Cor-Bon 'Power Ball'. Case length varied from .888 to .892. I used the average of .890

A .022 feeler gauge placed behing a fired, re-sized case and in front of the breech face was loose. A .025 feeler gauge was tried and found to be tight. When the .025 gauge was withdrawn, I could feel the barrel move back toward the breech face a bit. I figure that about .023-.024 would be about right.

So, .890 added to .024 puts the sum of .914 within 1911Tuners recommendation of less than .920 and within spec.

When the oven, I mean garage, cools down a bit in the fall, I may call Kart and try to fit one of their 'E-Z Fit' barrels in the Norinco.

Thanks all,

salty.

 

[1911Tuner]

Measurement

Salty...Use one case of KNOWN length and go from there to get closer to the actual measurement between breechface and chamber shoulder.

 

[Jim K]

Tuner has it right, but maybe I can try to explain it another way. Headspace is ALWAYS (yes, ALWAYS) the distance between the support point of the cartridge and the breech face. That applies to rimless cartridge rifles (e.g., .30-'06) where the support point is a point on the chamber shoulder, rimmed and semi-rimmed cartridges where the support point is the edge of the chamber, belted cartridges where the support point is the ledge at the front of the belt, and rimless pistol cartridges where the support point is the sharp shoulder for the case mouth (e.g., .45 ACP).

The end of the barrel is not really relevant in headspace measurement for rimless rounds, but the barrel has to support the cartridge case enough that it won't blow out under pressure. The barrel hood of a 1911 type pistol is not the place to measure headspace. In fact, it gets in the way of determining if the chamber is too deep (Tuner's first type of excess headspace). That is why the only valid headspace test is with headspace gauges, either commercial or improvised. Feeler gauges on the barrel hood do not give a valid headspace check. (Improvised gauges using cartridge cases are OK to a point, but brass is soft and won't last long, and also has too much elasticity (spring) to really work right.)

Jim

 

[1911Tuner]

Adding a Bit

Good post by Mr. Keenan, and spot on.

To sum it up...

The notion of dropping a round into a chamber and having it sit flush with the barrel hood as an indicator of good headspace is not only absurd, it's a potential trouble spot, and possibly dangerous. Don't trust it!

You can have that "ideal" and still have excessive headspace...in either direction.

File the hood .030 inch shorter than spec...sink the chamber deeper by the amount required to have a round or a GO gauge dead flush...and you've got excessive headspace, even though it "looks good".

Find a barrel with hood and chamber perfectly in-spec so that a round or gauge will sit dead flush...with good headspace (.905 from breechface to shoulder)...use a square pillar file to cut the recoil faces of the barrel lugs back by about .035 inch, and you've got guaranteed bulged cases forward of the web, and very likely a ka-boom in the not-too-distant future. It achieves the same thing as overcutting the barrel ramp...or throat...and destroying head support at the bottom of the chamber. Nasty surprises are just...nasty.

 

[saltydog452]

Gotcha..., Tuner and Mr. Keenan thank you for your replys.

The pistol is a used Norinco..There is a lot of space behind the hood, and in front of the breechface..The original question was, is so much room an indication of the possibility of excessive headspace?

Judging from the replys and other posts that I have read on this forum, I figured the answer was, yeah, maybe..

Tuner finally got it into my thick head that the barrel hood length wasn't relevant in any type of measurement of headspace and suggested a more appropriate way to measure. I know that it isn't exact, but it does suggest that, unless someone uses 45 GAP ammunition, the factory ammunition that I tried from Match 185 loads to GI Ball to Cor-Bon +P will not fall into the area of excessive headspace condition. So, it seems that the pistol is safe to shoot and the headspace, while far from ideal, is marginally acceptable.

I realise my tools and measuring ability aren't up to proper speed. But I think I'm gaining ground and the 'learning curve' isn't guite as flat as it was a few days ago.

Sometimes I can get fixed on a direction, tunnel vision gets involved and I don't seem to be able to 'see the forest for the trees'.

Thanks for your help, insight, and beating me on the head often enough, that I was able to open my eyes a bit.

salty.

 

[Old Fuff]

Also, once excessive headspace develops (or if it existed in the first place) it will allow the front face of the barrel's lugs to batter against the front of the grooves in the slide, and in doing so make the condition worse. This should be easy to see if one examines the barrel and slide, but some (many?) users don't notice. That's why I won't use an "almost, but not quite too much" headspace condition. Also, when checking a potential purchase for headspace, also take a good look at the barrel to be sure some ding-bat hasn't "throated" a barrel that came ramped in the first place.

 

[saltydog452]

Fuff,

Thanks to you also. I 'spect that I'll replace the Norinco barrel in the fall. As I tried to indicate in a previous post, I don't intend to try to make a racehorse out of a mule, and for this pistola, safety and reliability are most important.

The dang thing certainly wasn't new, but showed signs of limited use. Upper locking lugs on the barrel and slide were sharp and no apparent drag marks on the stock ChiCom barrel from the bushing. It really looked (looks) good, except for that really large space behind the hood and in front of the breech. That is what prompted my original question.

Thanks to pcf, Tuner, Mr. Keenan, and to Fuff. 'Appreciate your time and thoughts.

salty.

 

[brickeyee]

Has anyone noticed if Norinco is still using two piece barrels? The last one I saw about 2 years ago had a braze joint forward of the chamber.
After replacing the slide bushing it shot pretty well, and a friend used it in IDPA (casual competitor).