| Marrakai |
| (.416 member) |
| 05/09/17 07:57 AM |
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Commercial Mauser Bore Codes
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Hoping for some early clarification regarding codes on the underside of a commercial Mauser barrel.
The rifle is an Oberndorf Type B currently heading to my location but not yet in my possession. Enjoying a bit of pre-ownership research and quickly discovering the limits of my knowledge on European sporters!
From the pics sent to me, it appears to be an 'I' bore, ie .318 rather than .323 (7.85 bore, 8.07 groove diameter?) but has a clearly visible 'S' stamp as well. The serial number dates it from the early 1920s, retailed in India by Walter Locke.
So, gentlemen, will my current stock of 8x57 reloading components feed this rifle?
I have owned an 88 Commission rifle converted from 'I' to 'S' bore by simply deepening the rifling grooves, but assume if this was done on a sporter the old codes would be struck out. Further, I would have thought 1922 is a bit late for this procedure.
Apologies for my ignorance, on the learning curve, any and all info gratefully received.
Cheers
| Vladymere |
| (.300 member) |
| 05/09/17 09:29 AM |
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Re: Commercial Mauser Bore Codes
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Slug the bore. That is the only way to know for sure. I have Gew.88 based actions (that are factory built sporting rifles not converted military rifles) that claim to be 8MM but are far under .320 grooves. One I have has .312" lands and .314" grooves yet is gauge marked as 8MM.
I look forward to photos when you get it.
Vlad
| kuduae |
| (.400 member) |
| 06/09/17 04:07 AM |
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Re: Commercial Mauser Bore Codes
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That "S" stamp means nothing here. It is a factory internal control stamp. The gauge number 156.14 is for a land diameter of .310". The actual barrel dimensions as marked by the factory, land 7.85 mm = .309", groove diameter 8.07 mm = .318", twist rate 1 in 12.2" are consistent with the 1926 Mauser factory dimensions for 8x57, table shown by Jon Speed in "Mauser Original Oberndorf Sporting Rifles" page 275. In this table both the 8x57 and 8x60 are marked with an*. There is a footnote below. Translated it reads: "*The hunting rifles for the cartridges 8x57 and 8x60 are chambered with the throat for S-type cartridges, so these may be used too." Strict 8mm I (.318) and S (.322) dimensions were prescribed by the 1940 proof law only. Even minimum 8mm I dimensions were set up as an industry standard in 1926, same year the American SAAMI was founded. So "undersize" barrels were quite common before WW1. The 1934 DWM and 1940 RWS handbooks told: "No accidents ever happened when 8x57S loads were used in modern 98 Mauser rifles in 8x57I. If you want to use S loads in other rifles, have the neck and throat area of your barrel checked and enlarged, if necessary,by your gunsmith." To check chamber and throat there is a simple trick: Fire an 8x57I or an emasculated American 8mm Mauser load in your rifle. If a S = .322" bullet slips easily in and out of the case'a neck and does not touch the lands on loading, you may use 8x57IS factory level loads.
| Marrakai |
| (.416 member) |
| 09/09/17 10:20 PM |
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Re: Commercial Mauser Bore Codes
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Thanks for your responses Vlad and kuduae, appreciated.
(late reply, been away from computer for a few days)
I regret not buying Speed's "...Sporting Rifles" book when it was readily available, both times! Might have to bite the bullet and grab one anyway.
When the rifle arrives in my hands I will try your recommended method kuduae, but will probably slug the bore as well for interest.
Sounds like I am worrying too much, though!
Will keep you all updated with results from the firing line when it gets here.
Cheers
| Marrakai |
| (.416 member) |
| 15/10/17 09:33 PM |
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Re: Commercial Mauser Bore Codes
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A quick update:
started with conservative loads under the 165gr .321 projectile (for the .32 WCF or .32-40), just to be on the safe side.
Grouping with that bullet was a bit discouraging but pressure seemed low enough, so today I tried a series loaded with 150gr .323 Sierras.
Using 40 to 45gr AR2208 (Varget) all loads managed 2-inch groups or slightly better at 50 metres.
That's good enough with the original iron sights to pursue the matter further.
More to follow....
| Vladymere |
| (.300 member) |
| 17/10/17 05:37 AM |
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Re: Commercial Mauser Bore Codes
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Well done Marrakai. I look forward to photos of the rifle and more info on your load development progress.
Vlad
| Marrakai |
| (.416 member) |
| 27/08/18 01:12 AM |
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Re: Commercial Mauser Bore Codes
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Apologies for my tardiness in getting the Type B shooting, but at long last I have progress to report!
First, a photo or two:
Here is the rifle, unaltered by human hand but unfortunately very much an "India" gun, considerably altered by the ravages of the tropics, monsoons, beetles, and excess gun-oil coupled with general neglect. There are no close-ups lest you be horrified!
Except one: here's the good bit!
Initial range tests were carried out with 150-grainers as reported above, however it shot rather high on the target. Thinking a heavier bullet might bring down the POI, I found a box of Norma 196gr Vulkans and bombed them up with AR2209 (H4350) starting low! ...and headed to the range.
48gr = 2340 fps
49gr = 2395 fps
50gr = 2410 fps
51gr = 2475 fps
52gr = 2505 fps
I was struggling to get the 52-grain load into the case without compression, had to use a drop-tube, but accuracy is just ridiculous for such a worn bore. So I'll just have to be happy with 2500fps and minute of angle accuracy from the open sights!
Here's the last two pairs of shots, at 50 metres from the bench, original open sights:
Pressure is still very mild: these are Federal 210 primers, not even flat.
The only down-side is that the POI is still about 10 inches high at 50 metres. Nothing for it but to make a taller front sight. Although I may just do a lower single-leaf rear sight as that would lower my cheek on the comb a little for a better stock fit.
If I can get that done in the next week or so I'll take it hunting.
Stay tuned...