Rem 700 headspace issue

[WalterJones]

Shooting a Remington 700 in 30-06 I noticed the primers are pushing back out of the cases. About 5/1000 of an inch on average according to my calipers.

The left bolt lug shows significant wear in the bluing on the contact surface but the right side has very little.

Borrowed some gauges and the bolt closes on the no-go.

Nearest gunsmith that will work on it is 2 hours away.

Before I take it in, what am I looking at here? Trying to get an idea of cost, because if it takes a new barrel and bolt...well...ouch!

Thanks guys.

[MongooseV8]

What brand headspace gauges are you using?

[slamfire1]

Do they look something like this?



You do not have a problem. Everything is fine.

I am sad that the website, the Well Guided Bullet, is now longer around. Professor of Mechanical Engineering James Boatwright wrote a very technical series of paper, with numbers!

This is the relevant article:


Yielding of Brass Case Walls in the Chamber A Technical Note 30 June 2009 James A. Boatright

He used a 243 Winchester case as his starting point, and in this article he calculated the frictional forces between the case and chamber. Also, he calculated the pressures it took to stretch the case sidewalls.

When the firing pin hits the primer, the case is forced forward. The primer backs out of the pocket once it ignites, and stays backed out as the internal case pressures built. As case pressures build, the front of the case sticks to the front of the chamber. At some pressure point, the pressure in the case is sufficient to stretch the case sidewalls and shove the primer back in the case.

Varmit Al shows this in a finite element model, in the middle of the page.

Finite Element Analysis of Structures

https://www.varmintal.com/aengr.htm#ActionAnalysis

Now your pressures are low enough that the case sidewalls are not being stretched!.. That is not bad at all if you are getting the velocity you want, and the accuracy you want.Your cases will last a long time as the sidewalls are not being stretched, and you will have negligible primer pocket expansion.


If it bothers you, then lubricate the outside of the case. At the range in February a shooting bud was experiencing a similar issue in his 308 Win M700. It was an accurate load, the primer was backing out, holding the case forward of the extractor, and he was having extraction problems. The case rim was not sliding under the extractor hook, he was having to knock the case out of the rifle with a cleaning rod. What I did was find some oil. I would have to look in the truck, but I have bottle of motor oil, cans of spray oil, and a small bottle of Hoppes Gun Oil. I probably used the Hoppes Gun Oil and dribbled a drop on his loaded rounds and rubbed the oil all around. And then fired the case. The primer was backed flush into the case. That oil had broken the friction between case and chamber, the case slide back to the bolt face, and he was able to extract the case normally. Also, his cases were stress free and perfectly fireformed to the chamber.

I do this all the time with new cases. I will grease them up so I do not get any sidewall stretch on the first firing.

These are 300 H&H Magnum cases, were about $2.00 each, I have no idea how much gold it would take to buy one right now in the Biden panic.





The base to shoulder distance is not controlled in belted magnums, and I did not want my cases to develop sidewall stretch on the first firing. Which could have happened. So, I lubricated the cases, fired them, and upon ejection, I had a stress free, perfectly fireformed case. When I sized them, I made sure I did not bump the shoulder back more than 0.003". I want clearance between the case and chamber, enough clearance that I do not have to crunch fit the case to the chamber. And I do not want so much clearance, that my cases look like this in a couple of firings





A benchrest shooter would sneer at this group, but as long as they stay in the ten ring at distance, I am happy. Even if they are not to "Benchrest standards", ten shots within 5 3/4 inches at 300 yards will do most anything, expect win a benchrest match. As if that matters to anyone but Benchrest shooters.



Greased cases at 100 yards.



This will not cause your gun to blow up.

[pacrat]

[1]... Shooting a Remington 700 in 30-06 I noticed the primers are pushing back out of the cases. About 5/1000 of an inch on average according to my calipers.

[2]... The left bolt lug shows significant wear in the bluing on the contact surface but the right side has very little.

[3]... Borrowed some gauges and the bolt closes on the no-go.

[4]... Nearest gunsmith that will work on it is 2 hours away.

[5]... Before I take it in, what am I looking at here? Trying to get an idea of cost, because if it takes a new barrel and bolt...well...ouch!

Thanks guys.

OK by the numbers

[1]... No biggy, and is not an excessive headspace indicator. More a low pressure indicator. See Slamfires post re "case stretch".

[2]... UNLESS the lugs/receiver were hand lapped. THEY ALL DO.

[3]... Bolt closing on No-Go is not an indication of excessive headspace. It's just NOT MINIMUM.

[4]... Good thing you don't need him.

[5]... SEE [#4] ABOVE.

You're Welcome.

[WalterJones]

What brand headspace gauges are you using?

I'm not sure, they belonged to one of our local range officials.

Do they look something like this?

Look just like these.




Thanks guys. First time I've come across this issue and glad it's not catastrophic. Learn something new every day.

Just a couple more easy questions.

1) Would you guys recommend having it checked out by a gunsmith just to see where the tolerances are?

2) how do you tell when a No Go gauge is really just a Maybe gauge? I'm not trying to be snarky but I just figured there was a reason it's called No Go.

[smoothy8500]

I'm not sure, they belonged to one of our local range officials.


2) how do you tell when a No Go gauge is really just a Maybe gauge? I'm not trying to be snarky but I just figured there was a reason it's called No Go.

To be honest, I never trust "borrowed" gauges. There is no way to know if the previous "borrower" was ham-fisted and pushed the bolt closed on the NO-GO, thus ruining it.

It only needs finger pressure on the stripped bolt to check headspace.

[MongooseV8]

The reason I asked the brand is they dont all measure the same. A Forester No Go is typically the mid range of saami spec. So unless you can figure out what gauge you used you havent really any useful info.

[WalterJones]

For kicks I checked the spent cases in my Dillon case gauge and they look like they just came out of the sizing die.

For reference, I'm using milsurp cases head stamped TW 54.

ETA: spent brass chambers fine in both of the Garands I lost in the house fire as well as my wife's Rem 710 we lost in a boating accident.

[ShaunBrady]

1) Would you guys recommend having it checked out by a gunsmith just to see where the tolerances are?

No.

People get excited about chambers being long, but it doesn't happen that often. They rarely measure ammo, and you'd be surprised about how much of that is below minimum.

The pressure is low with your ammo and that's not uncommon with factory ammo in factory chambers. It's not a bad thing. The case is held forward before firing by the ejector. On firing, the primer backs out to the bolt face. If there is enough pressure, the case follows. At pressure, the primer is stuck in the case at the backed out position. The primer face flattens if the case extends to the bolt. It stays proud of the case if it doesn't.

2) how do you tell when a No Go gauge is really just a Maybe gauge? I'm not trying to be snarky but I just figured there was a reason it's called No Go.

No Go gauges are always Maybe gauges. They're an aid used in chambering and deliberately short of maximum. Excessive headspace is determined with a Field gauge.

[WalterJones]

Thanks guys, I appreciate you helping me sort this out. I've shot guns for 40 years and reloaded for 20...and there's always more to learn.

[divingin]

My 308 700 was like yours: reasonable contact on one lug, very little on the other. When I rebarrelled it, spent a lot of time sitting in front of the TV with the action and some lapping compound. Eventually got it to nearly full contact on one lug, and about 75% on the other.

Long or short chamber doesn't matter that much depending on what you're doing. If you're reloading the same cases and not overly sizing (like by blindly following the die setup instructions), they're going to form to your chamber, so no harm no foul.

If you wanted to address that particular problem, you'd have the barrel shoulder shaved down the amount you want the chamber shortened. If you're careful about reloading, or only shooting factory ammo and tossing the brass, it's probably not worth either the hassle or the expense.

[LynnJr]

Which lug is making most of the contact the 9 O'clock lug or the 3 O'clock lug?

[hermosabeach]

Randall who owns AR15 barrels has his websites in his signature line

He provides his costs for working on rifles... you asked what is a typical cost involved- your area and your smiths will charge different.

But this is what one excellent guy charges here.



--
different question- How accurate is the rifle? If it is safe to shoot and accurate enough- then my thoughts are enjoy the rifle.


No need to fix what is not an issue



If not safe or not accurate enough- is it time to sent to a smith for a rework?
Action truing, new bolt and new match barrel?

Or time to sell and replace with a 1K-2K Bergara?

https://www.bergara.online/en/rifles/b14/hmr-rifle/

[M1A Rifleman]

Make sure all oil/solvent is removed from the chamber and its dry before firing. This made a difference for me.

[slamfire1]

Just a couple more easy questions.

1) Would you guys recommend having it checked out by a gunsmith just to see where the tolerances are? .

Did you remove the firing pin and extractor before sticking a gage in the chamber? If you did not, than the resistance of the mainspring and the extractor snapping over the gage many have disguised you compressing the gage.

Headspace measurements are delicate things, powerful cocking cams will disguise resistance to bolt closure, and then a snap over extractor will do the same.

2) how do you tell when a No Go gauge is really just a Maybe gauge? I'm not trying to be snarky but I just figured there was a reason it's called No Go.

.

Go and No Go are important for function.

I forget what technical manual I stole this from



They are both based off the distance from base to shoulder of the cartridge.



If you push the shoulder too far back, the primer may be so far ahead of the firing pin, that it either won’t ignite, or won’t ignite fully. Either is bad. If the cartridge is too long, you may have bolt closure problems.

Neither one of these will cause a catastrophic failure of the mechanism. (hopefully)

The important measure, the one no one really (except for Randall) seems to understand, is cartridge case protrusion. That is, how much of the case sticks out of the chamber

Mauser Good




M1903 not as good. More case head is unsupported out of the chamber,
cone breech is not the problem. Its is how much of the case head is inside the chamber.



Everyone should read Chin Vol IV the Machine Gun, at hyperwar, and read the blowback section . Chin spends a lot of time explaining the criticality of case head support.

These are from Chin.





If too much case head sticks out of the chamber, the cartridge will rupture. And we ain’t talking much. That measurement is hard to make on an as built weapon, and the assumption is, that if the weapon was properly designed and built, than the cartridge head protrusion will be OK if the chamber headspace is between Go and Field. And if the chamber headspace is above No Go, and approaching Field, or is above Field, than the either the bolt lugs are recessing, or the receiver seats are deforming. Which will lead to a big bad kaboom

Ii is just amazing, that the "Gods" of the past, that is Hatcher, Whelen, Crossman, and even Narramore, don't understand cartridge case head protrusion. And because they don't understand this, every gunwriter since WW2, does not understand it either. They only understand headspace as it relates to reloading, because that is how Hatcher, Whelen, Crossman and Narramore discussed headspace.

A bud had a CMP M1903A3 drill rifle receiver. It looked perfect, could not see where the tack weld had been. When it was made into a drill rifle, a welder took an acetylene torch and tack welded the barrel to the receiver. The barrel had a plug driven up the chamber and down the muzzle. The welder got the receiver ring real hot, touched a welding rod to the junction of receiver and barrel, but in doing so, removed the heat treatment. Bud took off the ruined barrel and installed a new one, and used a chamber reamer to cut the chamber headspace. But, after shooting enough rounds, Bud found the headspace on his rebuild drill rifle increasing, so he put in a bigger bolt. And the headspace continued to climb. My Bud was smart enough to quit shooting the thing, and let me look at it. I could see the receiver seats were setting back.
I know very little other than the pictures, but since this was described as a drill rifle receiver with a new barrel. The most likely cause of the kaboom was a soft receiver due to annealing by an acetylene torch.





The shooter was not technical enough to have been checking headspace as he fired, Eventually, too much of the case head was out of the chamber, and kaboom!