Caliber verification...

[thereisnospoon]

O.k. so I bought this old Mauser at the last gun show and was told by the previous owner that it was a Spanish 7.62X51. I am sporterizing it (because it was in such bad shape...keep your rocks in your purse ) and I ordered a crowning tool to recrown the barrel, after cutting it back to 18".

So the .308 guide for the crowning tool won't fit in the barrel? I get out my handy-dandy micrometer measuring thingy and it says the barrel is .285-290. So I start thinking, maybe it is really a 7mm Mauser and the guy didn't know what he was talking about (and I'm wondering how I fired 10 rounds of .308 thru it at the range before I started the project). So I get a 7mm bullet and it drops all the way though without touching the lands/grooves. So I get a .308 bullet and it will only go in to the barrel about half the length of the bullet.

Now, I could just order a .280 guide for my crowning tool, but I am wondering if any of the "Spanish" Mausers were made in odd calibers?

Any ideas...please help.


Thanks for your time.

 

[timuchin]

Well, Absolutely first thing...

Slug the bore, and measure that. Then, measure your fired cases. Write down the measurments, get out your handy dandy reloading manual, and start looking. See what matches your measurements.

 

[yesterdaysyouth]

So I get a .308 bullet and it will only go in to the barrel about half the length of the bullet.

that's normal, you should have to use a hammer to get the bullet any further than that...if you've already shot 10 rnds of 762 through it then i would say you're safe...

spanish 1891 7.65x53
spanish 1892 7x57
spanish 1893 7x57
spanish 1895 7x57
spanish 1916 7x57
spanish 1933 7x57
spanish 1943 7.92x57

the fr7 and fr8 are the rifles converted from older models, that were chambered in 762... these models have 18.5" barrels to start with...

then there's the chance that the rifle was converted in south america, most of which were chambered in 762..

if it was rechambered by a military aresenal, or imported, there should be a caliber marking on the rifle somewhere...

 

[thereisnospoon]

Thanks guys, I just wanted to verify that I wasn't crazy, but .285-.290 seems awful tight for a .308...

Thanks again.

 

[BluesBear]

but .285-.290 seems awful tight for a .308

Which diameter are you measuring? Lands or grooves?

Here's a helpful hint.

Make sure your bore is freshly oiled.
Take a cleaning rod and put a tight patch over the tip.
Insert it from the breech until it's about one inch away from the muzzle.
Take a Crayola™ crayon, hold it over a flame.
Let the melted crayon drip into the muzzle.
Use a crayon, paraffin or a candle just won't hold the shape well enough.
When it hardens use the cleaning rod to push the plug out of the bore.
Then you'll have a proper slug that you can more accurately measure.

 

[thereisnospoon]

BluesBEar

Thank you very much for that excellent suggestion, I will do so and report back.

 

[Chawbaccer]

How did yo cut the barrel back? Is there a possibility that you have a burr on it that prevents the pilot from fitting?

 

[Jim K]

If that rifle is an FR-7 or was converted from a 7mm Model 1893, I don't recommend shooting it with 7.62x51 and especially don't recommend shooting it with commercial .308 Winchester. The gun won't "blow up", but those guns are soft and eventually will develop dangerous headspace if fired with .308 Winchester ammo, which develops higher pressure than the NATO standard 7.62x51mm.

An easy way to tell the older rifle is if it is cock-on-closing and has no safety lug. The newer Model 1936 is pretty much a standard Model 98, and is OK for rebarrelling to .308, even though all Spanish rifles are a bit soft compared to German, Belgian, or Czech rifles.

Jim

 

[armoredman]

The 1916 Spanish short Mauser in 7.62x51 was extensively tested to destruction by HP White Labs several years ago,(1987), and was found to be as strong if not stronger than several other 308 caliber rifles. Samco has the Guns and Ammo atricle featuring the 1916 and the test data.

 

[BluesBear]

The FR-7 has a downturned bolt handle. While the FR-8 has the straight version.

 

[Jim K]

Hi, Armoredman,

I have seen that report before but I have also seen a couple of FR-7 rifles that were "tested to destruction" with .308 Winchester ammo and "destruction" (severely battered bolt seats and excess headspace) took less than 400 rounds. Those rifles were designed for a 40k pressure level, not the 52-55k of the commercial .308.

The FR-7 conversion was made as a trainer for the CETME rifle and was intended for use with the same low power 7.62 CETME ammo, not the full power NATO spec ammo or the higher pressure commercial .308 ammo. As I said, I have never heard of one flat blowing up, but they will go bad pretty quickly. If one is going to use the gun as a "deer rifle" and fire a box of ammo every 5 or 6 years, they might be OK, but I can't recommend them.

Jim

 

[thereisnospoon]

Pics and Range Report

Range Report:

After cutting the barrell back [I used what every good garage smiff would use...skilsaw... ] I proceeded to use the crowning tool I purchased from a fellow on gunboards. As you know, I had some trouble with the pilot (which prompted this whole thread), so I made one...just happened to have a brass candle stick that was about .290-instant pilot {the wife never liked those candle sticks anyway}.

I form/force fitted a scount mount into the rear sight leaf.

I did not have a I.E.R. scout scope, so I mounted an old (read ancient) Tasco red dot scope, just to shoot a few groups and see what I was dealing with.

From a bench a 50 yards, using a non magnifying red dot I shot two gruops, using 7.62X51 ball ammo (Hirtenburger). Cases extacted well, but I had some feeding problems. I think the mag spring is weak, b/c the round wouldn't click all the way under the extractor and were therefor off center.

Anyway, the groups surprised me...they were off Point of Aim, but I didn;t really care about that at this point. Grouping was the question and as you can see from the pics below, it was not bad. (both groups ~ 2 inches)

I think an actual 4X I.E.R. scope, a trigger replacement and some handloads will decrease groups even further.

NEXT: DuraCoat the action/berral/mount.

 

[thereisnospoon]

I think the gun is safe...if you use appropriately loaded ammo.

 

[entropy]

I'd keep the .308 Win. and hotter 7.62x51 NATO round count down, but these look like excellent candidates for light cast handloads.

 

[thereisnospoon]

Exactly, as I said I only intend to shoot handloads through this baby anyway. I have ordered a scout scope and can't wait to see how that, coupled with some tasty handloads print.

Anyone out there got a pet load for a 168 gr BTHP that would keep pressures down? I like Varget and thought about starting at 40.0 gr and working around it.

 

[entropy]

That's a good starting point. I have had good luck with 40-42 gr. of IMR 3031 and 165 Ballistic tips or Hornady 168 JHPBT. 4064 is an excellent powder for light to medium .30 cal. loads also.

 

[thereisnospoon]

Thanks Entropy...

The gun is in painting, so it will be 3 weeks before I can put it back together and test the loads. I'll try to update as I can.