doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com help with AYA barrel questions

Hi I am a new member and have been studying all the information on this site about evaluating used guns for safety. I have just acquired a 20ga AYA #3 manufactured in 1983. The gun is proof marked at 1000 Kp/cm2. The bores measure exactly as marked at 15.9mm and the chambers measure a normal size per CIP tables, the chokes seem original. The barrel wall thickness of the thinnest barrel measures 0.065” at the end of the chamber, 0.065” at the end of the forcing cone and 0.043” at 9” from the breech. The original barrel weight was marked at 1080 grams. I’ve weighed the barrels and they are currently 1067 grams. I’m baffled were the 13 grams of material went.

I’m wondering if I should be concerned at all or just use the gun and enjoy it. Thanks for any advice.

Welcome on your first posting

Initial weight, some work need to install and contour
Should stay within 98% of the stamped weight

Use it and enjoy it

https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=363428

Thank you for the welcome. Are you saying that the stamped weight isn't necessarily the weight as final assembled? I had assumed the proof was done with the barrels fitted to the action. I guess if I were in the manufacturing business I would want the proof done before I invested production time in the final finishing?

Two possibilities. First the barrels have been refinished at some point and your metal loss occurred then. Second possibility is they were struck lighter after the proof and then finished. I vote for the second. Either way it sounds to be in great shape for shooting.

What KY Jon said... ^^^^^^^

Did you really mean .065" at the forward end of the chamber?!?
The CIP "standard steel" 20g minimum would be > .075", and most smiths recommend > .090"
Are the chambers marked 70mm and now measure 2 3/4"? If someone lengthened the forcing cones, and the chambers slightly in the process, that might explain the barrel weight discrepancy.
You are correct that the weight is stamped at the time of proof. Belgian proof was after final fit and finish. I couldn't find what the Spanish proof house process was.

BTW: Spanish 1000 kg/cm2 proof = 14,223 psi + 10-14%, for a service load of about 10,500 psi

Any chance the chamber was altered?

I took some more measurements and made a mould of the chamber to better understand the shape of the forcing cone. A plug gauge of 0.685” diameter inserts 71mm into the chamber. This is the middle of the CIP length range using the minimum diameter gauge from what I see on their tables. The forcing cone length is 0.42”. Bore diameter at the end of the forcing cone is 0.632” which is less than the CIP max of 0.637 and only slightly more than the main bore diameter. I remeasured the wall thickness and the thinnest spot is on the top of the right barrel closer to the rib. Left and right barrel wall thickness are as follows:

End of chamber left=0.070”, right=0.065”
End of forcing cone left=0.85”, right=0.78”
Another 0.625” down the barrel left=0.070”, right=0.065”

It would seem to me the chambers are original, the right chamber is closer to the top of the barrel, eccentric by about 5-10 thou.

If the outside of the barrels were refinished it was well done, the barrels profile is very nice and smooth.

Does anyone have any hints on how to tell if the barrels might have been re-profiled? This gun came from Europe through an importer of surplus guns. From what I understand I can’t imagine this gun would have been worth the expense to do that kind of thing to restore. The stock looks like it was refinished and I think someone cold blued the barrels to cover some bluing wear on top of the barrels.

Thanks everyone for taking an interest.

My compliments on your careful evaluation obuerkle, which should serve as both an example and warning to everyone
There is a good collection of end-of-chamber wall thickness measurements here, and none measured < .084"
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=615227