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Problems in accuracy of a Mauser

T

TQB

Member
Hello,

I've recently shot a 1937 Portuguee contract Mauser and it grouped terribly... At 50m there were shots 50cm apart, using benchrest equipment.......

The bore is not bright or shinny, but the riflings are clearely visible.

The crown of the muzzle seems to be in order (without kinks)...

Does anybody have an idea of what it might be?

Is lapping a solution? or should I think about re-barreling?

Thank You,
 
That is shotgun accuracy and even a rough bore should do better than that.

Make sure your bullets are the right size for the bore; undersized bullets, or the correct bullets in an oversized bore, could cause that. It could be the ammo, a bad crown, excessive throat erosion, excessive head space just to name a few. The action being loose in the stock could also be a problem. Without examining the rifle for each of those things, and more, it's impossible to render an opinion. It could be a combination of these things. The best thing you can do is get the rifle to a person who shoots bolt actions in competition or a good gunsmith who really knows bolt actions. There is really nothing exotic about K98k's, they're basic bolt guns.
 
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What jimdvan said...

I would start by putting a bullet in the muzzle end of the bore and see how much of it she swallows up....

Bad stock bedding can cause some pretty eratic results also.

Eliminate the possibilities one @ a time and proceed from there.
 
Before looking at the rifle, let's take a look at the shooter. The Mauser trigger is not exactly a smooth operating work of art, it is actually pretty hard to pull and in the process of doing so, you could have accidentally raised the barrel, causing it to shoot too high. It is also important to rest the buttstock FIRMLY against your shoulder, hold on tight to the foregrip, take a breath, hold it, aim and fire within 5 seconds. The longer you aim, the more your muscles get tired or start twitching, resulting in poor control of the rifle and shots going everywhere. Keep your eyes on the target while firing the shot (that's why you need to wear safety glasses), don't close your eyes. Make sure the rifle still points at the target after the shot. If in doubt, try another rifle. If that one performs better, than you need to take a look at your Mauser.

Check your rifle for loose front or rear sight parts. Everything should be tight and not wobble at all, up or down or sideways. Make sure the screws in the floorplate aren't loose. Hold on to the stock, grab the barrel and move it left/right, up/down. Does it feel loose, like it's not bolted to the stock? Insert one round into the muzzle, bullet first. How deep does the bullet go into the barrel? Can you still see part of the bullet sticking out or does it go in all the way to the neck of the cartridge?
 
Unless my metric mind is out to lunch, that is around 20 inch groups at 50 yards! I think we can forget the small stuff like throat erosion or action bedding. And Mauser sights don't usually flop around. So I would look at something more extreme, like the wrong ammunition, a barrel completely shot out, or a dinged up crown.

It could be the shooter, if he has never fired a high power rifle and is really flinching!

Jim
 
To give a bit more context.

The rifle was shot by me and a veteran competitor in bolt action weapons (smallbore and high power rifle) which used extensively the mauser 98k in the army and in 300m military rifle competitions.
A front and rear benchrest rests were used.

About 50 shots were fired at 50m (Russian 8x57 ammo from 1955; handloaded 8x57 with minimum loads (40,8grains of Vectan Tubal 3000 with 198 grains PRIVI bullets); INDEP match ammo).
The dispertion was considerable. Sometimes the shots were rather close but the next was off by 30 to 50cm. Some of the hole on the target were normal others were wider than normal (almost as if the bullet was sideways…).
The rifle was not properly cleaned before commencing shooting or between shots.

I hope that the following pictures can help.

http://cms.piso5.net/images/mauser2/01.JPG
http://cms.piso5.net/images/mauser2/02.JPG
http://cms.piso5.net/images/mauser2/03.JPG
http://cms.piso5.net/images/mauser2/04.JPG
http://cms.piso5.net/images/mauser2/05.JPG
http://cms.piso5.net/images/mauser2/06.JPG
http://cms.piso5.net/images/mauser2/07.JPG
http://cms.piso5.net/images/mauser2/08.JPG
http://cms.piso5.net/images/mauser2/09.JPG
http://cms.piso5.net/images/mauser2/10.JPG
http://cms.piso5.net/images/mauser2/11.JPG
http://cms.piso5.net/images/mauser2/12.JPG
http://cms.piso5.net/images/mauser2/13.JPG
http://cms.piso5.net/images/mauser2/14.JPG
http://cms.piso5.net/images/mauser2/15.JPG
http://cms.piso5.net/images/mauser2/16.JPG
http://cms.piso5.net/images/mauser2/17.JPG
http://cms.piso5.net/images/mauser2/18.JPG
http://cms.piso5.net/images/mauser2/19.JPG
http://cms.piso5.net/images/mauser2/20.JPG
http://cms.piso5.net/images/mauser2/21.JPG
http://cms.piso5.net/images/mauser2/22.JPG

The bullet that went further in was a factory INDEP 8x57 IS TARGET ammo. The one that went in the least, was a 198 grain PRIVI 8x57 bullet.
I will try to see if the bedding is correct, the stock lose or tightened, etc.
Both bullets had the diameter at the neck of 8,20mm.

I hope you can help me.

Thank You,
 
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A sideways bullet impact is typically referred to as a keyhole, id definitely look at the bore and crown

Loose action in stock can cause bad accuracy, but shouldn't cause keyholes.
 
CanadianAR said:
A sideways bullet impact is typically referred to as a keyhole, id definitely look at the bore and crown

Loose action in stock can cause bad accuracy, but shouldn't cause keyholes.
Click to expand...

What can cause bullets to key hole is undersized bullets for the bore or the incorrect bullet weight/length for the rifling twist. If the bullet is not stabilized enough it can tumble. Sounds like your friend knows what he's doing so you have some detective work to do.
 
Ok...I looked @ your pics...crown doesnt look terrible,and she appears to have some rifling ,albeit rounded off lands,but that shot of the cartrige in the muzzel end of the bore screams stovepipe to me.

I have a gew 98 sniper with the original barrel that eats up about that much and it also leaves a shotgun pattern.

Dont waste your time looking any furthur ....you need a barrel my friend.
 
That muzzle swallows a lot of bullet. One thing you might try before rebarreling is to try and back-bore the muzzle down to good rifling. There are hand turned cutters you can get that will cut into the muzzle as far as you need to to pick up tighter rifling. I've done it with .30-06 and .308 barrels and the Russians did it with lots of Mosin-Nagants. That way you can keep your original barrel.
 
TQB said:
I was thinking about buying the Manson Military rifle crowning tool kit, to do the job.

http://www.youtube.com/watch?v=b23lfzpZrJ4

Has anyone tried this kit before?

Thank You.
Click to expand...

While a recrown certainly would not hurt ....I dont think it will help either.

As Jim said ,.you need to counter bore it @ least and see if that will help..plus you can square off the lands a little and it might possibly tighten up the groups some...how much..? Who knows ?

But..before I did that...I would determine what your ultimate goal is with the rifle..?

Plinking on occaision,and satisified with 3 or 4 " groups...then do the counterbore and see how it goes.

But....If you are wanting real accuracy in terms of target shooting.....1",2",or even sub moa,then dont waste your time or money on that...a new barrel,or a very,very, good used one is the only way to go....if the end of the barrel is shot out there is a possibility it has throat erosion also....so just bite the bullet(pun intended) and rebarrel.

BTW..stove pipe means you barrel is shot out,oversized....kaput..!

Also...dont waste your money on privi ammo...extermely underpowered....1900-2000 fps...m75 and other mil-surp is in the 2400+ fps range.
 
The idea was to enter 300m military rifle competitions (only Mausers 98k, Mauser Vergueiro and Lee Enfield) and 100m benchrest with open sights.

While re-barrelling seems to be the logical choice, I’m worried about the bureaucracy that it involves.
Living in Portugal has its perks, but there are little in shooting…
First, Lothar Walther tells me that I must contact the local dealer.
Second, local dealer told me “It’s an difficult process because of recent legal changes, we have done some in the past, but now…come to the shop and we will talk…”. This immediately says “it will cost a lot”…
Third, I’m not sure that the dealer can install the barrel, so… besides the actual cost of the barrel, some labour costs must be added…
Fourth, although I’m not certain, about this, I believe that the Portuguese Police will want to “proof” the barrel… at least 100€ more….

If everything goes well (and god knows that it will be difficult) the re-barrelling may cost up to 500€ or more…
The rifle was 308€….
Either I keep the rifle for parts, and buy a new one, or I’ll try to re-barrel it.

By the way the Mausers that I was able to find in local gun shops were all mixed numbers, incorrect stocks, incorrect bands, some lacking bayonet studs..... The price range was around above 850€ for one with a bright bore, but in the same condition as mentioned above...

I have to give a bit more thought to this.
 
If you decide to back bore first slug the barrel. Drive a soft lead slug from the chamber to the muzzle. Oil the bore 1st. You can't really tell if the bore is as oversized as the muzzle unless you slug it. Measure the slug from high point to high point and low point to low point, which is actually measuring the lands and grooves but from a negative photo standpoint. In the process of slugging you'll also be able to feel variations inside the bore. If the bore is tighter than the muzzle then back boring might work well. If they're the same size then the only thing you could do is cast your own bullets .001" over bore size and use gas checks. There's lots of info on how to slug a bore on the Internet.

Using the Manson muzzle tool won't work like back boring. The muzzle tool will square the muzzle and cut the crown evenly but if what you have is essentially cleaning rod wear then the muzzle is shaped like a funnel and you'd have to cut the barrel way back to pick up good rifling. That's where back boring is a better option, the exterior profile stays the same.

You may be Euros ahead to buy one of the mismatched guns with a good bore to take to the competitions and keep your current one all matching.
 
some very good suggestions from knowledgeable folk - all I would add is find a used replacement 8x57 barrel in good condition and get a competent gunsmith to simply screw the old off and the new on - don't be put off by all the wrong and exaggerated claims you might see on the net about headspacing

if the current barrel is kaput, another option is get a machinist to use a 9mm drill bit to counter-bore , go in no more than 2- 2 1/2 " distance or to goood rifling if it is closer- at the end point run the drill briefly without pressure to get as much of a internal 90 deg cut as possible \\

a sharp bit will drill in easier than most people would ever imagine - barrel metal is not super hardened, its actually relatively 'soft'

then use 200 gr speer soft points as these have a longer bearing area than the mil spitzer projectile and will stabilize better in what left of your worn ‘oversize’ rifling

bring to range an try out -you should get a big improvement, if not nothing lost anyway and you suffered no cost or hassle
 
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The crown itself looks OK, but it looks like the end of the rifling behind the crown is pretty bad, with a land broken as if something were driven into the barrel.

What causes inaccuracy is any uneven rifling at the bullet exit that can cause gas to escape around the base of the bullet on one side but not the other. That causes the bullet to tip as it exits the barrel, sending it off in an unpredictable direction, and causing it to keyhole (go sideways).

You might be able to correct the problem by counterboring the muzzle. That involves putting the barrel in a lathe and using a drill of perhaps 10 mm to drill about 12 mm into the muzzle. That will even up the rifling at the point it ends, and improve accuracy. It will still not produce accuracy as good as the original barrel, but the only other alternative may be replacing the barrel.

Jim
 
James K said:
The crown itself looks OK, but it looks like the end of the rifling behind the crown is pretty bad, with a land broken as if something were driven into the barrel.

What causes inaccuracy is any uneven rifling at the bullet exit that can cause gas to escape around the base of the bullet on one side but not the other. That causes the bullet to tip as it exits the barrel, sending it off in an unpredictable direction, and causing it to keyhole (go sideways).

You might be able to correct the problem by counterboring the muzzle. That involves putting the barrel in a lathe and using a drill of perhaps 10 mm to drill about 12 mm into the muzzle. That will even up the rifling at the point it ends, and improve accuracy. It will still not produce accuracy as good as the original barrel, but the only other alternative may be replacing the barrel.

Jim
Click to expand...

If a barrel is badly pitted, I don't think counterboring or a recrown will help since the new crown will most likely have pits in it. A good gunsmith might be able to smooth out the crown to make it consistant. Of course, I had a very bad gunsmith that actually made the rifle shoot worse.

A "rebarrel job" will run $500-600 (quality barrel, remove and replace sights, headspace, reblue).
 
If your desire is to shoot competition then your choices are limited and your expenses are going to be equal to the results you want to achieve.

What is the point in entering competition if your gun will only give mediocre results.?

You will either need to spend the cash to rebarrel, or buy the best gun with the best barrel you can afford.

To do less will simply give you repeated dissapointment.

You are going to be spending money to compete in the matches with the purchase of ammo,reloading equipment,and accessories so why invest in that if you have a sub -performing weapon..?

Best to sit down and think long and hard about how much you want to spend,how much you can afford to spend,and how much do you want to pursue this.

In the end, money,and the lack thereof , is most likely going to be the determining factor in your final decision.

Good luck.
 
As usual, I'll be the odd man out here.

That's a ruined bore in a worn out gun. Why shoot it? Why own it? Why expect other than poor accuracy from it?

Not meaning to be critical in a personal way. It's just that the gun runs counter to a philosophy that's worked well for a long time, which is acquire the best that you can afford. It'll perform as intended, be a joy to own, and will bring a top price when it's sold.
 
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