Help! Gun won't shoot accurately...well, SOMETIMES

D

dfaugh

New member
I'll try to keep this brief, yet get all the pertinant facts in:

As my first experiment in gunsmithing, I have sporterized a Turkish Mauser(known elswhere as "FrankenMauser"), as follows:

1) shortened military barrel (cleaning rod muzzle wear), recrowned with 11 degree target crown, still 27" in length. As I severely damaged my right shoulder a couple years ago, I also ported the barrel to help some with recoil and muzzle rise (very successful I might add, from bench I can pretty much stay "on target" w/ each shot) drilliling "starter" holes, finishing with end mill to minimize burrs.

2) Mounted 6x24 Tasco scope I'd bought L-O-N-G time ago, drilling and tapping for two piece mounts, etc. Bent/welded bolt to clear scope(barely, its a big scope)

Now the (possibly) important stuff:

3) found a nice old target stock at a barn sale ($5!)...I reinforced front and rear areas (recoil lug screw in front and action screw "sleeve" in back with epoxy. I then completely surrounded the rest of the action with fiberglass, and tightly bedded the barrel to just forward of the chamber. Initially rest of barrel was free floating.

On the initial trip to the range, sighted it in using commercial S&B ammo...When finished it shot a 10 round group a little over an inch, but the first 6 shots were one ragged hole(3/4")...didn't let barrel cool much between rounds, last 4 opened the group up. Happy-happy, joy-joy!

HOWEVER, subsequent trips to the range led to less stellar results(vertical stringing sometimes over 6" range), using up the rest of the S&B ammo, then some hand loads my buddy has made up. Found problems with scope mounts, and then set screws for vertical adjustment loosening up. So I rectified all of that and went back. same thing, vertical stringing over 4 or 5 inches- horizontally right on. Next trip, I had bedded the first inch of the forend to support the barrel and try varying the amount of pressure with card stock under this bedding...Now its shooting 6" groups, varying both vertically AND horizontally.

OK, so seems to like "free float" better, at least it holds shots horizontally, so Took it alll apart, checked bedding for any weakness/problems and removed forend bedding. checked and rechecked all the scope screws.

Went back to range this week, started out with a few rounds of Remington, hadda re-zero scope 'cause I'd moved things around...shot about 10 rounds, its shooting something resembling a group, now near POA. Let it cool a little, fired the last couple of Remingtons and 5 rounds of my buddies handloads, making minor sighting adjustments...Barrel is warm but not hot...Then fired 5 consecutive rounds into EXACT center of ten-ring, looked like raggedy 4-leaf clover--in short a 5 round half-inch group. VERY COOL! figure I got it figured out, and its great. Put the gun in the rack and we fired his .22 target rifle for a while.

Now, I take FrankenMauser up again, barrel is cooled completely. Started with the handloads again (which it seemed to like much better than the commercial stuff)...Went through 25 more rounds, and was back to vertical stringing again(though not as severe, 3")...even though barrel SHOULD have reached same temperature, at some point in series, where it had been when it fired the awesome group.

So..........any one got any ideas? Could I have bedded the action TOO tightly?
Should I try relieving the bedding just in front of the action, to allow for some expansion? Any suggestions a GREATLY appreciated! This is driving me nuts....
 
A couple of thoughts:

How much of the BBL is bedded? I don't do more than the re-enforce on a Mauser, usually.

Is the bore fouling? Some rare BBL's shoot at some strange point in "dirtyness".

If you are getting only vertical, check bolt lug contact. Had a Sako in my shop for bedding, shot 6 inch vertical, 1 inch horiz. Fixed bedding, same problem. Checked Bolt lug contact, Top Lug had NO contact. Customer lapped lugs to his satisfaction, shoots 1 1/2 inches now.
 
More detail

Currently barrel is only bedded about 2" in front of chamber (and around chamber)...The rest is free-floating, as mentioned above.

Barrel was about 29", as mentioned above its now about 27". It was recrowned using the proper tools from Brownells(not some home-grown process)....Looking at pattern around muzzle, after a few shots, I get a nice even pattern all around bore, so it appears I did a good job with crowning.

Will check out lug contact at first opportunity, although just visually looked at it and it looks reasonable (remembering that this was used military, and has probably fired many rounds)...In other words no "high spots" getting worn. Certainly lapping the lugs won't hurt anything, worth a try.

As far as dirtiness, I did run a wet, then a dry, patch though it after first series of shots...But once again, would expect it to reach same level of "dirtiness" sometime during second series. Will pay closer attention that, though.
 
Opinion:
Changing bbl length may increase or decrease accuracy. It may come to a point of "Marrying" the ammo to the gun.

HJN
 
Turk Mauser

Dear Sir.
The only place to use glass bedding is in the recoil shoulder and the rear tang; DO NOT bed the entire action! DO NOT bed any portion of the bbl! Free float the bbl. relieve the action bedding and you will have no more trouble.
I did this years ago on my first military rifle and it did the very same thing.
I don't know about the barrel porting?
Make sure even the first dai. of the bbl. is not contacting the glass; only the action - your bbl. is expanding with heat and rising up as it elogates!
Good shooting - the Turk is as good as any 98.
 
one other thing to check

Turk mauser's are famous for having the threads of the receiver be out of allignment. When the barrel is tightened up, causes the barrel to off center with the receiver. The vertical stringing is due to the bedding. Like Mr. Bonar said, relieve it except the recoil shoulder and the rear tang. You may need to pull the barrel and run a tap into the reciever to true up the threads, and when you put the barrel back on, don't crush fit the barrel.
 
re-turk mauser

Dear Sirs:
Brownells article on Turkish Mausers is very innacurate. I've written them and told them that the supposed 11 1/2 tpi thread is a machining error. They differed until they took a cerosafe cast of the receiver threads and found out that they were indeed 12 TPI! They never changed their article.
You're totally correct about threads and the inner shoulder.
When I rebarrel a Turk I put a well fitting mandrel in the action, chuck it between centers and turn off the threadless flange Brownells calls a "recessed" barrel seat; it is no such thing all it does is hold the upper handguard on - when you turn it off the reciever ring is the same length as a vz24 or other 98 large ring. The threads however are .980x12!!. These are small ring threads. Barrels first were offered in low-pressure cartridges but now are in 308, 30-06, etc.
After turning off the threadless flange I just true up the FACE of the action. This gives a new accurate seat for the bbl.
Then if you measure down to the inner bbl. seat many times you will now find it is not "square" with the new front trued reciever! So I fit my bbl. to just barely contact the least variation and seat it on the front trued action. I feel this is no different than a Howa, Rem, or Win. fitting?? Use a 60 degree cutter and thread about 85% and you'll be AOK. :)
 
re-turk.

Dear Shooters:
I will add that some rather rare Turks will have a short reciever ring after the above work and have strange markings on the top reciever ring and have 1.100x12 thread!! Then you will find that AT THE FACTORY they only fit the bbl with about 4 threads. I called Douglas and asked their advice and they said they did it all the time! So I fit a 30-06 bbl, test fired and AOK.
Also on the "standard" (if there is such an animule) 38 turk, some of them, the bbls are in TIGHT and one, I honestly believe I could have unscrewed by hand!. So, it pays to check headspace/bbl/ etc, on any Mauser. I like vz24s' the best but have built 338-06, 7mm. mags on the Turk and they work out fine; -- they are soft on outside but HARD in the locking lug area - they may have been made in a vz24 plant?? :)
 
While I appreciate the advice....

Please read my 2 posts describing the problem..We're WAY off topic here!

Gun was NOT rebarrelled

Have checked scope and its OK. (rotated it 90 degrees, still vertical stringing, fast and dirty way to check, as originally horizontally shots were in perfect (1/2")alignment, so we know that axis is OK.

When first assembled gun shot decent groups...Now it doesn't....hence the dilemma...
 
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