Accuracy issue with Israeli Mauser

BadAsMo

BadAsMo

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I have an Israeli Mauser chambered in 308 win that I shot for the first time last weekend. The accuracy was just awful, 10 inches at 100 yards. Then I spoke to a friend who once had one and he said that his shot really well with the old ammo that he got with the rifle but shot badly with any new ammo he bought.

So I go to thinking about bore size. I have a chambering reamer for a 308 which has a guide bushing to align it to the rifling. I actually have 2 bushings, a .300 and a .298.

The .300 bushing will slide right through the barrel of the Mauser but is too large to go into any of my other .308 barrels, but the .298 will. In fact the .298 fits tighter to my .308 barrels than the .300 bushing fits to the Mauser.

So I got to thinking…. The 303 enfield bullet is actually .310 not .308. Is it likely that the barrel on my Isreali Mauser is actually the size of a 303 bore and should therefore shoot .310 bullets?

It’s only .002 difference and I bet it will be just enough to settle the gun down.

Has anyone out there had experience with this?
 
"...have a chambering reamer..." Isn't what you need. You need to slug the barrel. Hammer a cast .30 cal bullet or suitably sizerdlead fishing sinker through the barrel, using a 1/4" brass rod and a plastic mallet, and measure it with a micrometer. Isn't likely the cause though.
"...303 enfield bullet is actually .310..." Nope. The barrels can measure from .311" to .315" and be ok. The bullets sold commercially measure .311" or .312".
I'd be looking at other causes before I mucked around with the barrel. Start with different ammo.
 
1 - Try to insert a .308 bullet into the muzzle, does it go in past the ogive?

2- Is the action loose in the stock? Take it apart, check for cracks, make sure action screws are tight.

3- Is the lower band tight? Can you easily move the barrel away from the bayo lug? Shimm the lower band to tighten it up.

I have had many Israelis, they all shot great with both Surplus and new .308 ammunition. Either the barrel is toast (unlikely) or something is loose. How does the bore look? If you find nothing loose or cracked I would try several rounds of Wipeout bore cleaner and see what comes out of the barrel.
 
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Commercial 308 and 7.62 are different animals though can both be fired from the same rifle. Your Mauser should be more accurate than that. My SVT 40 gets better accuracy with surplus. Try the above by J996. Also check your muzzle crown. It should be crisp and smooth without knicks or dents.
 
So slugging the barrel will tell me the outside diameter of the rifling. What is the point?
If the inside diameter of the rifling is about .301 then the depth of the rifling would need to be less than .005" per side to have at least 0.311 outside diameter.

How deep is rifling normally cut?

The rifling looks real clean and sharp.

The action is glass bedded and the barrel does not touch the barrel bands.
The crown is sharp.
Basically I have already ruled out all gun related causes and the only thing left is the barrel itself.

There are about 4 or 5 bullets on the Hornady web site that are 7.62ish.
I'm still thinking the barrel is more suited to one of the larger variants.
Hornady offers .308, .310, .3105, .312 and .321.
I figure .321 is too big so that is ruled out and that leaves somewhere between .310 and .312.

I assume nobody on CGN has ever tried this or considered testing these slightly larger bullets.
 
I might have found my answer on the castboolits web site. This is what those guys have to say. So maybe I should slug the bore to see if it is actually .311.

.312 projectiles in a .308 bore can and will cause excessive pressure problems.

.312 projectiles in a .311 bore is a safe combination.

I've recently conducted a pressure test of 123 gr AK/SKS bullets and Nosler 125 gr BT .308 bullets over the same load in a .308W rifle with .308 groove diameter. The load was 43 gr of 4895 in LC cases with a WLR primer. The 125 gr .308 Nosler BT ran 2836 fps at 45,300 psi(M43). The 123 gr Russian .311 FMJBT with a steel jacket ran 2798 fps at 46,100 psi(M43). Not a whole lot of difference and neither was any where near the SAAMI MAP for the .308W.

I also tested a Sierra 150 gr .308 SP, a Hornady .312 gr 150 gr SP and a .311 Albanian 7.62x54R 148 gr FMJBT with steel jacket and steel core. The load was the same 43 gr 4895 in LC cases with a WLR primer. The Sierra 150 SP ran 2717 fps at 50,600 psi(M43). The Hornady .312 SP ran 2805 fps at 62,100 psi(M43). The Albanian 148 gr ran 2872 fps at 73,000 psi.
 
BadAsMo said:
So slugging the barrel will tell me the outside diameter of the rifling. What is the point?
If the inside diameter of the rifling is about .301 then the depth of the rifling would need to be less than .005" per side to have at least 0.311 outside diameter.

How deep is rifling normally cut?

The rifling looks real clean and sharp.

The action is glass bedded and the barrel does not touch the barrel bands.
The crown is sharp.
Basically I have already ruled out all gun related causes and the only thing left is the barrel itself.

There are about 4 or 5 bullets on the Hornady web site that are 7.62ish.
I'm still thinking the barrel is more suited to one of the larger variants.
Hornady offers .308, .310, .3105, .312 and .321.
I figure .321 is too big so that is ruled out and that leaves somewhere between .310 and .312.

I assume nobody on CGN has ever tried this or considered testing these slightly larger bullets.
Click to expand...

Slugging the barrel will give you inside and outside dimesions. It will be an impression of your bore. Then just measure across the lands and across the grooves. Then you will have your answer.
 
#1 SLUG YOUR BARREL
#2 using a MICROMETER measure the slug
#3 get back to us with your accurate findings and then and only then look for alternate bullet sizes.

Just out of curiosity; how is it that you come to posess a 308 chamber reamer but lack the knowledge of how to slug a barrel?
 
BadAsMo said:
OK I slugged the bore and it measures .3103" OD.
Click to expand...

Ok that's a bit sloppy for 308. Your surplus ammo probably has open based FMJ bullets that are allowing them to "slug up" in the bore a bit. But your standard 308 solid bases are just rattling down the pipe.
That being said I know of a few BLR's in 308 with bores measuring .3095" that shoot like the wind... There may be more than one culprit at work in your rifle. But one problem at a time.

A .3105" bullets should do the trick for you.
Do you know the twist rate of the barrel?

You did slug the bore right? As simply measuring the muzzle with a set of calipers is not accurate.
 
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BadAsMo said:
.

The action is glass bedded and the barrel does not touch the barrel bands.
.
Click to expand...

How is the barrel not resting in the channel of the bayo lug and getting pressure from the handguard? If it is standard military configuration that front end needs to be held solid by the bands/lug. Is this a front end chopped off sporter?
 
I slugged the bore with cerosafe and measured the slug with a micrometer.

I didn't measure the twist rate but it's pretty quick. It's at least a 1 in 12 probably even faster. I don't want to shoot heavy bullets though since I just want to use the rifle for deer.

I noticed Sierra offers a 125 and 150 grain bullet in .311, maybe I should try those. The 125s would be perfect if they're reasonably accurate.
 
Tinman204 said:
I would try .311 bullets for a 7.62x54r if the bore slugs .3105.
Click to expand...

That's exactly what nobody should EVER do.

.311 bullets loaded in the 308 Win. cartridge will create excessive chamber pressure and can lead to a disastrous failure, damage to your health, life and property.

Don't do it!!!!
 
BadAsMo said:
I slugged the bore with cerosafe and measured the slug with a micrometer.

I didn't measure the twist rate but it's pretty quick. It's at least a 1 in 12 probably even faster. I don't want to shoot heavy bullets though since I just want to use the rifle for deer.

I noticed Sierra offers a 125 and 150 grain bullet in .311, maybe I should try those. The 125s would be perfect if they're reasonably accurate.
Click to expand...

Hornady makes a .3105 150gr SST. I would try that.
 
Well thank you all for your feedback so far.

Well today I tested out my 7.62 Israeli Mauser using Winchester 123 grain SP bullets that were .310 in diameter. I just cant believe what an improvement it made from .308 bullets. I'm convinced the thing has 303 rifling.

The gun could hardly hit a 2 foot circle at 300 meters using the 308 bullets, but using these .310 bullets, the gun shot fairly well. Since I was shooting on a military base we had paid target markers so I could not go measure my actual group. But to summarize, I was easily holding the 2 MOA (6 Inches) 5 ring at 300 meters and shot the odd (1 MOA) V-Bull, sometimes 2 in a row. That's no F Class gun but hey this is an old milsurp rifle and I am quite pleased with that.

There were no signs of high pressure. No flattened primers or stiff bolt lift.

I will try some Sierra .311 Match King bullets next time. Ya never know it might shoot just a bit better yet.

I wonder how many guys out there have milsurp rifles that don't shoot well for the same reason, and nobody thought to check the bore size.
 
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