DTA marking brass

[Treedave]

One for DTA users / ex-users or generally knowledgeable folk.

 

I bought the DTA in the knowledge that the mags where far from popular, so no surprise when it came to filling them and the slightly sloppy fit to a beautifully engineered rifle. The issue is the damage that is being done to my brass.

 

After examining the brass and firing a few without them going in to the mag I can narrow it down to the top lips on the mag. It gouges two short lines, just below the shoulder as the round is pushed into the chamber. Its doing bad enough for me to find the resulting brass waste in the breech.

 

Anyone any experience / advice on DIY alterations to the mags before I get my hammer and chisel out!

 

FYI - I've already a taken some 420 grit 3M to the top edges of the mag to take the edge off and needed to squeeze the mag sides back in to get it to feed again. They're the mags for the 308 family.

 

Cheers

[Ronin]

Other than doing what you've already tried Dave, i don't have a fix.

 

Polish or chamfer the lips so they are not gouging the brass.

 

Use pliers to re set the feed lips unless you have a slotted tool to bend them in one go..

 

A very well thought out system spoiled by poor magazine design (as I've said time after time - if only they'd used AW mags……)

[dannywayoflife]

I've just polished the feed lips using emery paper and then wire wool. I'm currently having my mags altered to take mid length cals that's my main gripe really with the mags is that they aren't that long. I think the mags are the only week link in the system.

[Treedave]

Well, I love it when I get it wrong! Just in case it happens to someone else, here's what I've found.

 

Polished and adjusted the feed ramps/lips to no avail. After going back to the brass and taking the barrel out I noticed that on some brass there was a little burr of brass at the shoulder end of the gouges (2 parallel gouges about 5 mm long). Having found the burrs I went back to the barrel extension, and after a massively technical feel around with my finger, I found no sharp edges but some brass remains.

 

In the process I noticed just how strong the ejector spring is, it hurts to push it back with a finger end.I also found the bolt face end of the bolt assembly has play, both lateral and rotational.

 

Sherlock says that the gouges are made by the case being forced against the locking lugs in the barrel extension. This is probably made worse by the play in the bolt end and super strong ejector spring.

[Ronin]

You could polish the feed ramp or take a coil out of the ejector plunger spring,,though id just live with it after polishing the feed ramp rather than mess with cutting spring coils.

 

 

Yes I know its 3am,,,,long shift

[Treedave]

Not sure what gain I'll get from a polished feed ramp, as they go in fine, the damage is done on the way out. Might try reducing spring pressure, as the cases go a couple of feet on ejection.

 

3am is late mate, started at 6am today, still got 4 roe to deal with after the last firewood delivery of the day, one of those days that make you wonder what's gonna give - my patience or my back

[Ronin]

If you polish the ramp which is scoring - remove any burrs and round off (very lightly) it should reduce witness marks.

 

Reds for me in the morning