Magazine trimming and fitting the gauge

[Skydiver]

For people pushing the 141.25mm and 171.25mm limits, my understanding is that it's normal to trim the magazine a little bit behind the feed lips and that this is accepted. I'm wondering why not just trim the rear of the base pad? Is trimming behind the feedlips perfectly legal, while trimming the base pads unsportsmanlike conduct? Or is just harder work to trim the basepad and keep the magazine looking good?

An an aside: I assume that it is unsportmanlike conduct to cut a notch into the base pad that is just wide and deep enough to fit the official EGW magazine gauge.

[BayouSlide]

There is not a lot of extra meat to play with on the Dawson extended pads...just ask a buddy of mine who tried to fit the gauge this way. The results were less than satisfactory. Just a light touch behind the feed lips will do it...it will take much more material removed from the basepad, due to the fact the gauge is already countoured for the shape of the feed lips.

Curtis

[al503]

Many of the basepads won't hold up well if you remove material/trim them. Some are very thin as it is to increase capacity.

I don't have a gauge and basepad in front of me but I would think that the notch would have to be almost or as wide as the pad itself.

[Skydiver]

For reference, here's what the gauge looks like:

http://egw-guns.com/...&products_id=39

I was thinking the notch would only have to be about as wide as the back of the feedlips based on the picture of the gauge above.

Edited August 13, 2010 by Skydiver

[Dan Sierpina]

The base of the magazine is not perpendicular with the back of the mag. You'll only be removing material on a small section of the base. Clamp the mag with the base installed in a milling vice and trim off what you need to. I've used the silver Dawson bases for this, the milled area doesn't match, but, doesn't stick out like a sore thumb.

[boz1911]

I remove material from both the feed lips and the basepad but my big stcks fit the gauge. You cannot remove more than a few thousandth's from the basepad. Ask me how I know??

[DrawandDuck]

I have "trimmed" the grams 7 mm basepads to fit and they have held up over 3 years....

Edited August 14, 2010 by DrawandDuck

[al503]

For reference, here's what the gauge looks like:

http://egw-guns.com/...&products_id=39

I was thinking the notch would only have to be about as wide as the back of the feedlips based on the picture of the gauge above.

The gauge is a lot thicker than you can tell from that picture. It's close to the width of most of the basepads out there.

[Skydiver]

The gauge is a lot thicker than you can tell from that picture. It's close to the width of most of the basepads out there.

Thanks for the info! DrawAndDuck's post with pictures of the gauge on a mag showed the thickness of the gauge well.

[davidwiz]

When the mag gauge was built, EGW tested a lot of different magazine/basepad configurations that were available at the time (mid-2000).

[wide45]

The mag with the stepped cut on the bottom of the base pad pictured above, is over length, and not legal.

The gauge makes checking most mags quick and easy. Mags that fit the gauge, but don't otherwise meet the length rule, are not automatically legal.

See http://www.uspsa.org/rules/nroi_rulings.php?action=edit&indx=33

...A magazine needs to conform to the length limit as well as the gauge to comply with our rules...

The rule for measuring mags, is shown in appendix E1

Edited August 14, 2010 by wide45

[DrawandDuck]

So is it only certain parts of the mag that must be within the 5.56"?? If you measure from the bottom of the basepad to the top of the feedlips it will be outside the 5.56 by a good 1/4" (this will vary...mine has been cut down and they are 1/4" higher......

Edited August 14, 2010 by DrawandDuck

[Skydiver]

From the ruling:

A magazine needs to conform to the length limit as well as the gauge to comply with our rules, also this means that the gauge extends to infinity, no curved magazines or other similarities.

Then in would follow that simply trimming the back of the feedlips to fit into the gauge will not be enough. If the mags feedlips did not intersect with the gauge initially and therefore need trimming, then the mag would have been legal, but if the feedlips did intersect and needed trimming then that would mean that as some point beyond the gauge the feedlips would intersect again.

Consider this profile sketch with angles exaggerated a little bit to show the problem where now the tip of the feedlips need to be trimmed as well:

(Of course the counter argument is that height measurement is from the tip of the feedlips at the rear of the magazine to the plane perpendicular to furthest extent of the base pad as shown in the diagram in appendex E1. If the counter argument holds water, then DrawAndDuck's magazines would be legal, but the ruling seems to be quite clear. )