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Light loads and oversize O rings

Moderators: ripjack13, John A., MikeD, DHonovich

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Posts: 36
Joined: Tue Apr 05, 2016 6:34 pm
PostPosted: Thu Jun 14, 2018 5:12 pm
Starting a new thread as my previous problems now seem to be sorted.
Following the excellent advice of The Virginian I purchased some oversized O rings (BS119) but found that the bolt would not fully go into battery, thus preventing the firing pin from striking the primer. I now realise that the O rings I bought were not quite the size declared, or that I had ordered. (due to metric sizing in the UK) I borrowed an accurate micrometer and measured the various O rings that I had and also those that I have subsequently purchased. (all are declared metric sizes)

All sizes nominal, all are inner diameter;

15/16" 945 thou 24 mm

Cross section measurements

My original Remington O rings are
1/16" 59 thou 1.5mm

recently purchased:
5/64" 79 thou 2 mm


3/32" 98 thou 2.5 mm

The BS119 (too big?)

7/64" 103 thou 2.62 mm

I have found that the 2mm (5/64") gas seal,(one size up from standard) allows full forward battery, the 2.5mm (3/32") seems intermittent so on my next trip to the range I shall start with the 2mm seal and 24g (7/8 oz UK no. 8 fibre wad) Bornaghi cartridges (a nice soft load that I use frequently in other guns) I shall take other size O rings and ammunition and will report back in due course
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Posts: 36
Joined: Tue Apr 05, 2016 6:34 pm
PostPosted: Tue Jun 26, 2018 10:25 am
OK so I have now finally got the 1187 running reliably on light loads (24g - 7/8ths ounce) Following advice from The Virginian on this forum I sought out a variety of O rings. I had some original Remington ones and these were unreliable on this load.
Unfortunately, here in the UK, we are standardised with metric measurement. I therefore produced a chart so as to compare and notate the performance. Hope it helps if you are looking in the same direction;
o ring paint.png
o ring paint.png (76.59 KiB) Viewed 128 times
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Posts: 174
Joined: Mon Apr 10, 2017 9:41 am
PostPosted: Wed Jun 27, 2018 10:00 am
Glad some effort and T&E has worked out to the good for you.

When I got my Charles Daly maximag, it didn't even have a oring in it. Someone had taken it long before I ever got it and had been running it that way.

I have replaced it but don't pretend to know the purpose of it, other than to reduce some of the battering when the pieces bang together.
When people ignorant of guns make gun laws, you end up with ignorant gun laws.

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