7 mm barrel won't cycle

[diggerj 0]

Well, I will take my JSAR Out to a range soon (rare occasion for me) and will try to use my 7 mm barrel again. 

I stumbled on this in the archives and don't have enough savvy to know if this may be a cause -

 

Original JSAR 7mm bbl for some reason are not as desirable as 30/06 and as such, do not bring near as much. $350-650 seems to be the going rate. Chilean originals have a Navy Arms import stamp on the underside. Replacements are without the import stamp and may or may not have proof marks. One of the California parts dealers had a large stock of replacement 7mm bbls several years ago. Remember, these are all converted Mauser bbls and are "stepped" rather than belled over the chamber.

 

Anybody have input?

 

Diggerj

[clinocio 0]

In the US, the 30-06 is far more popular than the 7mm Mauser and the fact the few 1941 Johnsons that were actually used by US Marines were in 30-06, probably plays a big factor. I doubt the problem you are having with a 7mm that won't cycle has anything to do with the caliber because it that was the problem, there would probably be a lot of reports by the Chilean military.

Cycling requires the barrel to recoil until the cam within the receiver engages the bolt assembly as it moves back. This unlocks the lugs and allows the bolt assembly to complete the cycle. Anything that prevents or delays the barrel from recoiling can cause the gun not to cycle. Start with a good cleaning and a light lube and then push back on the barrel to see if it moves rearward easily. If it is too tight, either the front or rear bushing on the barrel may be a little oversize. One of my barrels is in 270 Win. with hard chrome plated bushings. It turns out Winfield added chrome plating if they had bushings that were undersize or perhaps if they had a rifle with a lot of wear in the inside of the receiver tube. However, the fit in my rifle is too tight. So it shoots, but won't eject the cartridge. I bought a shot-out 30-06 barrel for the hardware and haven't decided whether to use the bushings on the 270 or try to remove the plating.

[ArtR 0]

When you say the rifle will not cycle, do you mean, if fires, extracts, but will not strip and load another round, or it fires and will not extract? Or something else?

Are you using clean, factory ammo or inexpensive battlefield pickups?

Is the chamber clean and free of any burrs or other imperfections? (If it fires and extracts, check with a fresh, clean factory round...fire, and inspect the brass for any scratches, scrapes, etc after firing...may determine if chamber has a problem)

Have you pulled and checked recoil spring for length? (Search this site previous postsfor good vs bad length...if memory serves me right, a good spring measures about 12", but I may be wrong)

[diggerj 0]

sorry guys for poor input on posting.  I was in Art's country on our annual anniversary trip to Stowe and got lazy.

I use the same everything else when I change out the barrels, so the return spring, recoil spring, etc. are not a variable. Only the barrel is and I don't refer to caliber variance, but whole barrel variance.

I fired new Remington 140 gr 7x57 mm Mauser rounds. The very first attempt almost ejected but didn't have enough rearward force to fully eject and the spent shell got hung up. Subsequent rounds would not unlock the bolt lugs. I fired and manually ejected and reloaded without problem.

Putting a micrometer on both barrels shows virtually no variation to three decimal places on either bushing or followers.

I have a Joe Scott replacement 12" main spring, I know not NOS as it has an opposite twist to my original.

My closer look this morning back home at the 7 mm barrel looks like the thing could have had a little sloppy parkerizing or touch up park on the rear bushing. I just took my Dremel and jeweler' rouge and polished all the high points. It seems slightly harder in resistance to my 30-06 barrel in force needed to push back and start the rotating as it hits the cam. but then again, it may have been worse before. I may have made a poor trade, but the rifling is super and maybe just not used enough to break in the barrel.

The rifle is very clean always, and my 30-06 action is flawless.

I normally use a lube oil, do you think a silicone grease or other if I can't get her to eject and load a round from the mag or does this sound like a poor machining and a gunsmith? Since Joe Scott is retired, that means SOL!

Thanks for your responses.

Diggerj

aka John

[MGMike 0]

It's most likely an ammo problem; an insufficient recoil impulse.  See if you can find some 7mm with a heavier bullet that will stay in the bore longer.

M

[diggerj 0]

M... That was my first thought but couldn't find the ammo. Cabelas has a 173 gr round and I almost stopped yesterday going by Hartford from VT on 91. Too much traffic building, so I thought I'd inventory what I had first.  I plan to go tomorrow.

thanks and stay well.

Diggerj

[Joseph Scott 0]

Some years ago I had a 7mm with similar problem.  Turned out to be a ring in the chamber just at the end of the straight length before shoulder.  Hard to find but finally lapped it out and barrel cycled fine.  Polish some unfired brass with Skotch Brite  and inspect with magnifier after firing.  Seems like a classic chamber problem.

[diggerj 0]

Thanks Joe, glad to hear from you. I'll get the chance to try the brass exam next week and see what happens. Hard to find a high load round anywhere and I squirm at the prices online (shipping) for a single box. Guess I need that as a last measure.

John D.

[LoboMike 0]

In my experience using my own loads I found the 7mm very sensitive to light loads. With full factory loads or loaded to full factory specs it cycled fine. So my first thought is ammo.  Be sure to have it clean & lubricated. Otherwise I never had any 7mm issues, just my light load experience. It wouldn't take almost any reduction in the load.

 

HTH Lobo

[M48TANKER 0]

I feel sure that between following Joe's advice about checking the chamber and Lobo's input on the loading of the 7mm......you will find the problem. I was wondering if you might use a bathroom weight scale to push the muzzle end of the 30.06 barrel down onto, and then do the same with the 7mm barrel, just to check the force needed to push each barrel back? That would expose any binding issues with the barrel itself. I can't see that there would be any difference in force needed unless there was a problem with the 7mm barrel somehow. Maybe the chamber isn't cut just right...too tight or too shallow? You might consider the "timing" of the rear bushing in relation to the bolt lugs. You never know..... might be an issue with the bolt lugs binding, Try inserting the bolt into each barrel out of the gun and turning the bolt. The fit of the bolt lugs into the 7mm rear bushing might be too tight, or not aligning just right? Heck....I don't know...just grasping at straws. If you get really discouraged then you should give the old barrel to me.

[diggerj 0]

Many thanks to all comments! I took tanker's suggestion and (with gross numbers output) pushed both barrels to the point of unlock against a bathroom scale. The no-problem 30-06 barrel took ~50 lbs and the problem 7 mm took 60 lbs.  Took the bolt and examined fit and resistance to rotation in each barrel chamber and found a "sticking point on the 7 mm not present in the 30-06 barrel. Chamber previously examined showed no pitting, although the ring Joe described really can't be easily seen with a bore light or flashlight, I don't think it is the cause. 

When I draw my finger backward from the shoulder of the chamber out the rear, I can feel a very sharp edge on the lug ridges - which is the face of contact - as if the barrel was milled and never deburred. From the land nearest the ramp up to the opposite ridge on the 7 mm barrel is ~ .010" shorter than the 30-06 barrel. Almost like the barrel was never "finished off", and possibly never fired to work the sharp edges off!

Does this seem like something a gunsmith with the proper equipment can fix by duplicating the 30-06 barrel dimensioning, or will a slow emery cloth rubbing by hand work? Ten thou is a lot of meat!

again many thanks. Look forward to comments (from Joe especially with all his knowledge). Good call Tanker!

diggerj

aka John

 

[LoboMike 0]

My first question is how similar/same are the .30-06 and 7mm chambers? Would finishing the 7mm barrel to like the .30-06 barrel do any harm? Questions because it's beyond my knowledge. The 50# - 60# does raise a real question!

 

HTH Lobo

Edited October 8, 2015 by LoboMike

[Joseph Scott 0]

If you are feeling sharp edges on the lugs or at the chamber entrance, try a jeweler's file to smooth them.  I have seen some rear collars that had  "hammered" lugs creating burrs. The chamber entrance should have a slight bevel.  It might require removing the rear collar to clean things up.  If so, soak the inside threads with penetrating oil for a couple of days first.

[diggerj 0]

Lobo - the chambers have to accommodate the same bolt, so similar dimensioning should be safe.

Joe - the sharp edges are at the interior surface of the chamber lug ridges and would most likely clean up easier by removing the  collar. That is a little above (a lot above) my pay grade. I don't even have a real good vise to hold the barrel, never mind returning the collar to the origin point to retain head space. I am encouraged to get this done, so I'll figure it out.

This board is super -- continued kudos to all. 

Jim, don't fail to underestimate the value of your effort.

I'll report in when it is figured out.

Many thanks and my best,

John

[diggerj 0]

Well, still investigating. I think the rough edges I detected on the 7 mm may not be all that different from my 30-06.

The rear collar on the 7mm is marked "6863K" with the letter larger font. It is 1.345" long overall length versus my 30-06 at 1.409 OL. From rear end of collar over the ramp to the chamber face on the 7mm seems to be 0.855" and for the 30-06 to be 0.865" - that ten thou extra room in the 30-06. I tried to measure seated rounds to the rear end of the collar but can't easily force a reproduce able seat... 

These dimensions above can't reflect the actual internal dimensions from inside edge of chamber lugs to chamber face accurately, but the 7 mm barrel locks down with correct headspace. Can't figure this out myself but something doesn't look right to me.

Any insights out there?

Maybe the heavier load round will work but I don't belong to a club, so I bring out the "closet queen" rarely and can't report that now. Maybe just have made a bad deal on this bbl.

John

 

[diggerj 0]

On October 9, 2015 at 9:35 PM, Joseph Scott said:

If you are feeling sharp edges on the lugs or at the chamber entrance, try a jeweler's file to smooth them.  I have seen some rear collars that had  "hammered" lugs creating burrs. The chamber entrance should have a slight bevel.  It might require removing the rear collar to clean things up.  If so, soak the inside threads with penetrating oil for a couple of days first.

Well, Joe Scott is the winner of the mystery round! I took down the high points on the entrance to give a better bevel and smoothed over with jeweler's rouge with my Dremel and it cycles like a new weapon.

I also cleaned up the follower (not really necessary), and took apart the buffer to clean. I had not done the latter previously, and it really needed it internally. Also put a replacement extractor in. Firing 140 gr 7x57 rounds was a real pleasure. The replacement mainspring measures 11-3/4" now FYI. 

Going back to 30-06 barrel using 165 gr Winchester rounds really banged up the brass. Only able to retain a single spent shell (threw the others too far into the range!). That's for another day or a lower load.

Once again, thank you Joe! Have you got a replacement spring for me?

Diggerj

 

[ryche_me 0]

Digger: you probably shouldn't run anything heavier than a 150 gr. bullet in the 30.06 barrel. Remember the gun was designed around a military load of the time and 150 was about max.

I made the mistake once and ran 170 gr. in mine. with the hit and dent the ejector left on the brass i was afraid i had broken the ejector.

I believe there have been a couple of discussions on this board about not going over 150.

Anyway glad to hear you got the 7mm running well, problems like you had can be really frustrating.

Ryche

[diggerj 0]

I'd like to express again the appreciation I have for the members of this forum who go the extra mile to help JSAR owners. Many of those are in the thread above and many more chime in when they think a contribution can be made or a situation clarified. We all want to build and keep a knowledge base beyond what is in print on these ever-so-quickly diminishing number of rifles.

BTW, when is the Joe Scott movie coming out? LOL

John D.