CDI DBM Kit
Posted: Sat May 21, 2011 10:57 am
People use DBM kits for a variety of reasons. Some are cosmetic, some are practical. On my SPS T I used a Badger one piece tapered base that is full width for the entire length. This made feeding rounds singly into the chamber and into the magazine difficult because there was not a lot of room for the rounds, the base, and my big Mick fingers. This was one reason I wanted to add a DBM. I also liked the idea of being able to quickly empty the rifle without having to deal with a hinged floorplate dumping rounds out, or removing the rounds through the chamber, which is less than ideal. The ability to quickly load five or ten rounds with minimal effort was beneficial too. In addition, when carrying extra rounds I could have them in a metal magazine for protection as opposed to a cardboard box. Finally, I could keep different loads ready for use in distinct and seperate magazines with the ability to rapidly change them as needed.
Once I decided on a DBM kit, the question became which one. HS magazines do not enjoy a good reputation. That pretty much left the AICS as the other option. The CDI kit was getting very good reviews, and Jeff had a very quick turnaround time and the price couldn't be beat. Using the AICS system meant that I could go to a match or class and either borrow or loan out magazines with the vast majority of users that would be there. The AICS is the standard as far as magazines for bolt guns go.
The basic kit comes with the bottom metal and two guard screws. Magazines are extra. However, the price for the kit and an optional mag is actually right at or under the price of just the DBM kit from other manufacturers. Jeff can inlet your stock for a fee, or will include a diagram so that you can do it yourself or have a local smith do it for you. At the time I had him do my stocks, they were $60 including shipping. His turnaround was less than a week.
The bottom metal is machined from billet 6061-T651 aluminum and is hardcoat anodized. It is ready to be installed, although your stock will need to be inlet for it. The system uses AICS mags, which come in 5 and 10 round versions.
Using the AICS mags, max OAL runs around 2.89" with the rib still inside the mag. If you remove the rib, OAL looks like it will go up to about 2.98" if you needed it. There are aftermarket mags that do not have the rib inside, so that may be an option if you really need long OAL rounds.
Once you have the kit, some minor fitting may be needed. The mag lever may need to be adjusted to fit, the action screws will need to be trimmed, and the feed ramp on your rifle may need to be relieved.
The mag lever that Jeff includes is left intentionally long. This allows for some variation in magazines, bottom metal, and action. The easiest way to deal with this is to simply leave the lever slightly over-length, and then fit it to your rifle by grinding down the top edge that engages the magazine latch. This is done with a Dremel or similar tool and grinding the lever down until the magazine will engage on a closed bolt. Then check to make sure the bolt will operate with the mag latched in. It may be necessary to take a little more off of the top of the lever after you've gotten the magazine to fit into the receiver to allow the bolt to operate. Check this with several magazines to make sure that you've gotten enough clearance for all of your magazines to operate.
Once your lever is properly adjusted check the feeding of rounds from the magazine to the chamber. This should be done with the safety on, and following safe gun handling rules. If you can load up some dummy rounds that are otherwise to the same dimensions as your actual rounds that would be the best way to go. That's what I used for this process.
When cycling the rounds, the bottom edge of the feed ramp on your rifle may tip the nose of the bullet on the rounds downwards, causing a misfeed. This was a very slight obstruction on my rifle, but enough to prevent the rounds from feeding into the chamber. I removed the action from the stock and used a grinding wheel to relieve the bottom edge of the feed ramp in a crescent cut to allow the rounds to pass freely from the magazine body to the chamber. The part of the feed ramp that needs to be removed is way below the actual surface that the rounds come into contact with as they are striped from the magazine into the chamber. Once the relief cut is made, the projos don't actually engage the feed ramp until they are above the area in question. The obstruction simply prevents the rounds from moving vertically and removing it does nothing to otherwise impact the transition of the rounds from the magazine to the chamber.
I made the relief cuts in several progressive passes until the rounds would feed reliably. I removed a very small amount of metal from the ramp with each pass, and test fit and fed the system several times. Once I had the cut right, I used a more fine wheel to smooth out the cut, and finished with a polishing wheel to smooth and blend the feed ramp alteration. The feedramp ended up with an almost mirror like finish. The rounds now feed without any interruption from all of my magazines. The total amount of metal removed is less than 1/16" from where the ramp originally was.
The action screws that Jeff includes are overlength for the same reason as the mag lever: to allow for individual fitting of the action. I removed the bolt from the action, seated it in the stock and screwed the actions screws into the stock. Once they were completely screwed in and torqued I marked where they extended past the tang and bolt lug recess. I then removed the screws and trimmed them to the proper length. I then test fit the screws again and made sure that they were flush or below the tang and recess and made sure the bolt would operate freely. I then removed them again and finished the cut ends.
http://www.cdiprecisiongunworks.com/
Once I decided on a DBM kit, the question became which one. HS magazines do not enjoy a good reputation. That pretty much left the AICS as the other option. The CDI kit was getting very good reviews, and Jeff had a very quick turnaround time and the price couldn't be beat. Using the AICS system meant that I could go to a match or class and either borrow or loan out magazines with the vast majority of users that would be there. The AICS is the standard as far as magazines for bolt guns go.
The basic kit comes with the bottom metal and two guard screws. Magazines are extra. However, the price for the kit and an optional mag is actually right at or under the price of just the DBM kit from other manufacturers. Jeff can inlet your stock for a fee, or will include a diagram so that you can do it yourself or have a local smith do it for you. At the time I had him do my stocks, they were $60 including shipping. His turnaround was less than a week.
The bottom metal is machined from billet 6061-T651 aluminum and is hardcoat anodized. It is ready to be installed, although your stock will need to be inlet for it. The system uses AICS mags, which come in 5 and 10 round versions.
Using the AICS mags, max OAL runs around 2.89" with the rib still inside the mag. If you remove the rib, OAL looks like it will go up to about 2.98" if you needed it. There are aftermarket mags that do not have the rib inside, so that may be an option if you really need long OAL rounds.
Once you have the kit, some minor fitting may be needed. The mag lever may need to be adjusted to fit, the action screws will need to be trimmed, and the feed ramp on your rifle may need to be relieved.
The mag lever that Jeff includes is left intentionally long. This allows for some variation in magazines, bottom metal, and action. The easiest way to deal with this is to simply leave the lever slightly over-length, and then fit it to your rifle by grinding down the top edge that engages the magazine latch. This is done with a Dremel or similar tool and grinding the lever down until the magazine will engage on a closed bolt. Then check to make sure the bolt will operate with the mag latched in. It may be necessary to take a little more off of the top of the lever after you've gotten the magazine to fit into the receiver to allow the bolt to operate. Check this with several magazines to make sure that you've gotten enough clearance for all of your magazines to operate.
Once your lever is properly adjusted check the feeding of rounds from the magazine to the chamber. This should be done with the safety on, and following safe gun handling rules. If you can load up some dummy rounds that are otherwise to the same dimensions as your actual rounds that would be the best way to go. That's what I used for this process.
When cycling the rounds, the bottom edge of the feed ramp on your rifle may tip the nose of the bullet on the rounds downwards, causing a misfeed. This was a very slight obstruction on my rifle, but enough to prevent the rounds from feeding into the chamber. I removed the action from the stock and used a grinding wheel to relieve the bottom edge of the feed ramp in a crescent cut to allow the rounds to pass freely from the magazine body to the chamber. The part of the feed ramp that needs to be removed is way below the actual surface that the rounds come into contact with as they are striped from the magazine into the chamber. Once the relief cut is made, the projos don't actually engage the feed ramp until they are above the area in question. The obstruction simply prevents the rounds from moving vertically and removing it does nothing to otherwise impact the transition of the rounds from the magazine to the chamber.
I made the relief cuts in several progressive passes until the rounds would feed reliably. I removed a very small amount of metal from the ramp with each pass, and test fit and fed the system several times. Once I had the cut right, I used a more fine wheel to smooth out the cut, and finished with a polishing wheel to smooth and blend the feed ramp alteration. The feedramp ended up with an almost mirror like finish. The rounds now feed without any interruption from all of my magazines. The total amount of metal removed is less than 1/16" from where the ramp originally was.
The action screws that Jeff includes are overlength for the same reason as the mag lever: to allow for individual fitting of the action. I removed the bolt from the action, seated it in the stock and screwed the actions screws into the stock. Once they were completely screwed in and torqued I marked where they extended past the tang and bolt lug recess. I then removed the screws and trimmed them to the proper length. I then test fit the screws again and made sure that they were flush or below the tang and recess and made sure the bolt would operate freely. I then removed them again and finished the cut ends.
http://www.cdiprecisiongunworks.com/