doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com M Ugarteburu

The term �price point� is just the price at which a seller/buyer hopes his counter party buyer/seller will agree to a commercial exchange. All shotguns, Spanish or otherwise, are made to some price point.

French Double,

Artisanal Spanish shotguns, such as your Martin Ugarteburu (maker�s mark MU), are purpose made shotguns intended for some fairly narrow kind of use. This �kind of use� is generally described as falling somewhere on a continuum that runs from light game gun (carried much, shot little), through medium game gun (carried little, shot much), to heavy completion gun (not carried, shot continually).

Your MU, judging from your description, is most likely (but not certainly) built as a medium game gun. If you are running shells through it fast enough to get it really hot, you are using it as if it were a heavy completion gun. That�s going to cause problems, and wear the gun out pretty quickly. Think of it as using your putter at the driving range; that�s a fair analogy.

Hope this helps get a handle on what is happening, and likely why.

Kyrie

You are firing the wrong length case (long) in a short chamber gun. Successful firing and extraction is not the issue, the higher pressure, and resulting heat developed in the short chamber is. The pressure marked on the flats was the PROOF pressure the gun saw at the proof house, NOT the pressure the gun is supposed to be exposed to on a regular basis. The ammunition you run should ideally develop perhaps no more than 75% of that level. An occasional blast near proof won�t be an issue, most of us won�t live long enough to do any damage, but, sustained use will. Pressure developed is not only a factor of the weight of the charge, and velocity, but, the quality and type of components used, in particular, powder. Powders that consistently develop lower pressure at the same velocity cost more money. Bargain promotional loads are often some of the worst offenders.
I�d be willing to bet the payload in European 2 1/2� ammunition of the same era of this gun was smaller, and the load pressure was more conservative than what you can get here, now, in the US.
Again, firing and extraction, is neither here nor there. Have you inspected your spent case, keeping an eye open for pierced primers, flattened primers, ripped case mouths, or, perhaps, extractor marks in the base?

Best,
Ted

I collect Spanish shotguns, and have a few that were made by Martin Ugarteburu. Let's see if I can do some photos. If this works it should provide a link to some photos of three MU shotguns; a model 114, a model 115, and a model 125:

https://www.dropbox.com/sh/ruljz8k0z1bfmwk/AABJE1y_GakASElMLKs5ezbga?dl=0

The Commission Internationale Permanente pour l'Epreuve des Armes � Feu Portatives standards were adopted in 1969, but I don't know when Spain became a signatory.
The CIP transducer �Maximal Statistical Individual Pressure� is 850 BAR = 12,328 PSI for a �Maximal Average (Service) Pressure� of 740 BAR = 10,733 PSI, and �Mean Proof Pressure� of 930 BAR = 13,924 PSI.

In Bell's study, the pressure increase of one 2 3/4" 12g load in a 2 1/2" short cone chamber was 1200 psi - it would likely be higher in a 28g

My plan is to order appropriate ammo from RST, assuming no serious complications from the storm that is in the process of knocking at my door.
My MU is a significantly lower grade than the ones that Kyrie showed us the but engraving and checkering all seem to be hand done. Some minor overruns, etc.
Once again, I'm learning more and more from you Folks.

Will you be reloading for the 2 1/2 inch ammo??
Mike

I had no issues with primers or cases. In fact I collected them for an acquaintance who reloaded them several times over. My using the wrong size shells was due to lack of knowledge and not paying enough attention, not a deliberate choice. One could say ignorance and/or stupidity. I'm oh so glad I started this thread!!

Ignorance is actually correctable. Stupidity is a whole different thing.

Welcome.

Best,
Ted

Good point, I'll plead ignorance then. Which by the way, you folks have corrected on this matter.