Long Range Hunting Online Magazine

Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Gunsmithing


338 Seekins DM

LinkBack Thread Tools Display Modes
Unread 09-29-2010, 03:30 AM
Junior Member
Join Date: Jun 2009
Posts: 21
338 Seekins DM

Hi there, has anyone had any major issues with the 338 Lapua Detachable magazine system from Seekins precision for the 338 edge?

My gunsmith ( who is a very well known and trusted gunsmith in New Zealand) had a hell of a time and i was wondering if it was normal because it is not the case it was designed for.

From my gunsmith:

The main issues I had with the magazine system largely stem from the fact it is really set-up for the Lapua type cases which are shorter and fatter than the ultra-mag cases.

When I inserted some of the .338 EDGE dummy rounds into the mag the feed-lips barely held the rounds in the mag, and caused excessive scratching on the sides of the case body. Due to this it was necessary to bend the feed lips inwards slightly to better retain the smaller diameter cases, and to minimise the scratching/scraping of cases.

However, this then meant a fair bit of trial and error on the feed lips to get the feeding of the long cases to a reasonable and acceptable consistency. With what I have done you can now have one in the chamber and 3 in the mag, and they should all cycle and feed fine. Any more than 3 in the mag now and the rounds will sag down at the rear and not self-correct. I had to build up the top engaging surface of the retaining latch to get the mag to sit up hard to the underside of the receiver, so that the bolt nose would then reliable catch and push the case head, rather than riding over the top of it.

From what I can determine, the main problems in relation to using this mag with the .338 EDGE (or .300 Ultra Mag) cases are:

The cutout/recess on the follower is too short. This needs to be longer for the ultra-mag cases.
The feed lips were too far apart, and are way too short. They need to extend further forward towards the shoulder of the cartridge case to minimise or prevent the ‘rocking’ effect of the cases as they currently sit in the mag (with the feed-lips only supporting about 2/3rds of the way up the case body).
The follower spring may need to be altered to give more upward pressure to the rear of the follower if the above suggestions are not sufficient to correct the issues for reliable feeding.

Thanks for any insight
Reply With Quote

Unread 10-01-2010, 07:19 PM
Join Date: Aug 2009
Posts: 85
Re: 338 Seekins DM

I built a customer a 300 ultra on the seekins system. I had some minor issues to over come with his mag, but Glen told me that when I orderd it. I did have to modify the feed lips on the mag.( bent in a hair) I also used a flat follower instead of the cut out one for the lapua. I believe all new mags( as of 2 weeks ago) will come standard with the flat follower. So yes some customizing the feed lips and the flat follower glens mags will work great with 5 rounds.
Jason Rigby

Reply With Quote
Unread 10-02-2010, 11:38 AM
Bronze Member
Join Date: Mar 2005
Location: Lewiston ID
Posts: 99
Re: 338 Seekins DM

There are allot of guys modifing the mag to use the RUM cases. If you are having issues i would be happy to help. We have had great sucsess withe the lapua kit and rarely do we have any issue at all with a mag modified or not.
I just got some dummy rounds from a friend and if you like you can send me your mag and i can send one back tuned up for the RUM case. The main thing is the feed lips. We re designed the follower so everything fed smoother.

Also, make sure that whoever installed the system either used the supplied pilars OR cut some to the same length. If you pillars are too tall the mag will not go up high enough into the action and the bolt can miss the rim of the case. When we do have a issue 99% of the time this is the reason.
Glen Seekins,
Reply With Quote
Unread 10-02-2010, 02:44 PM
Junior Member
Join Date: Jun 2009
Posts: 21
Re: 338 Seekins DM

Hi Glen.

Thanks a lot for the offer. I might have to take you up on that.

As for the pillars, the supplied pillars were not used as the McMillian A5 stock came with pillars installed and action inlet for the mag system. Do you have a length for your supplied pillars so i could check mine?

Will PM you for you address to send mag box.

Sam Merrin
Reply With Quote
Unread 11-07-2010, 02:29 AM
Junior Member
Join Date: Jun 2009
Posts: 21
Re: 338 Seekins DM

Does anyone know how i can get hold of Glen Seekins? I have sent him a PM, an email and left a message on their answering machine but have still not managed to make contact.
Reply With Quote
Unread 11-07-2010, 08:08 AM
Official LRH Sponsor
Join Date: Jul 2006
Location: Harrisburg, PA
Posts: 2,764
Re: 338 Seekins DM

The length of the pillars that Glen supplies are as follows:

Front: .680"
Rear 1.650"
Reply With Quote


Thread Tools
Display Modes

Similar Threads for: 338 Seekins DM
Thread Thread Starter Forum Replies Last Post
seekins 20 moa - browning LA Petersen Optics For Sale 1 07-27-2011 10:15 AM
WTB seekins 338 dbm strictlyRUM Gun Parts - Stocks, Barrels, Actions, etc. 2 05-17-2010 05:56 AM
Seekins rocks!!! gahlizard Long Range Scopes and Other Optics 3 08-07-2008 02:24 AM
Seekins Detachable Box Mag For A 700 Shawn Carlock Equipment Discussions 17 03-30-2008 08:08 PM
Seekins Precision soren Equipment Discussions 1 03-24-2008 09:50 AM

All times are GMT -5. The time now is 11:27 AM.

All content ©2010-2015 Long Range Hunting, LLC