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Colt Large to Small Pivot Pin hole Conversion Review
Over the years I have heard so many debates over who makes the best AR-15. Reasons range from the quality of finish to outward appearance, quality of internal parts to reliability and so on. One of the big arguments is over MIL-SPEC. While Colt was the first to successfully mass produce a commercial version of the M16 rifle they made a few changes to her. One of the big changes was the size of the pivot pin from the mil spec .250 to the Colt large pin .315. The provisions for the pin detent and spring were not included and the lower became known as a ‘slab side’ because the receiver of the Colt SP1 rifles was with out the pin and spring house for the pivot pin and was flat to include the fence around the magazine release. Many complain about the lack of a fence while others can’t get past the large pin and the Colt take down pin design. The ‘two screwdriver’ design is quite frustrating but it works. What is hard to overcome is the availability of upper options for your large pin Colt. Large pin A2 and flat top uppers demand a price for A2s starting at $150 stripped and flat tops in the $200 plus range. Few companies make large pin uppers and when they do it is limited production and they go fast. Again, they cost big bucks.
The photo above shows the large pin upper with DPMS replacement pin just above the modified SP1 lower.
What options do you have? Well, for less than the price of a stripped SP1 receiver (in most cases, I know you can find some deals so please don’t bust my balls because you could not get this done for $50 when I ‘said’ you could), you can get your trusty SP1 and other large pin Colts converted from large pin to small pin by American Manufacturing near St Louis, MO. How is this possible? Well, Mike at American is an expert at welding aluminum. Mike takes your lower, strips it down, welds it up, drills a new hole with his trusty old Craftsman hand drill (just kidding, he uses a no name brand hand drill) guided by his state of the art jig to ensure the holes are straight and true and refinishes the lower in your choice of finish (prices vary, please enquire). Your lower is sent back to you as good as new and ready for use with your MIL-SPEC top end. If you have the provision for the pivot pin spring and detent but no hole (newer pre ban, post ban and LEO Colts), Mike can drill that for you. If the large pin hammer and trigger is getting you down, Mike can fix that for you as well (I am currently having this done, update and pics to follow).
The photo above shows the modified lower with a small pin flat top upper installed with the replacement DPMS pin.
How do I know this and what makes me such an expert on this conversion? Well, I don’t claim to be an expert but I have had Mike do some work for me on a Colt SP1 and I have another post ban lower getting some trigger group holes converted right now. My receiver went to Mike a couple of months back via USPS. Since my family lives in nearby Columbia, MO I stopped in to visit Mike and check out his shop. He told me not to expect a state of the art manufacturing complex and warned me that I may be disappointed. While Mike does not have a huge shop he does have a well organized and well equipped work area and he turns out a wonderful product. Mike is quite the history buff when it comes to guns and we had a wonderful conversation about what he does, how he does it and so on. We also had a long talk about the F16 canopy that I had brought along with me that I brought back from Iraq to show off at my nieces high school while visiting home.
This is the DPMS replacement pin you will need to use with your converted SP1 lower. The ball detent keeps things in place. This pin runs about $6.
For you that own the dreaded slab side receivers, this conversion will not eliminate the need for the Colt style front pin. You will not have the ability to secure the pin without using the Colt designed pivot pin or a replacement pin (see my review of the DPMS replacement pin) in order to keep your top on. While we all like to see tops come off now and then most are better kept in place!
As you can see from the photos, my SP1 lower is a bit unusual. She now sports a small pivot pin. In addition, Mike repaired some marks that were on the receiver and he added SAFE-SEMI-AUTO on both sides of the selector. My lower is home to a DIAS so it was only appropriate for the upgrade. While Mike will change the name from AR15 to M16, he said the AR15 was too close to the Colt logo (horsy) and he did not feel comfortable welding that close to it. So, she still sports the name AR15 instead of M16. The top end is held in place by a DPMS replacement pin and it works great. Everything lines up just perfect and the molly coat finish looks great.
This is what the passenger side looks like. Since she is an old SP1 slab side, there are no raised areas for the spin and detent pin that hold a standard pivot pin in place. The small DPMS pin has one side flattened so it may be used with small pin Colts that have the raised areas but are not drilled for the spring and pin. Mike can drill these for you and install a USGI type pivot pin for you.
Once again, I have another lower at Mike’s getting a makeover. It is a post ban Colt that has the MIL SPEC front pin and detent system but sports the large hole fire control group. After some holes are tightened up and some other work, I will have this lower ready for a good work out and I will be posting the pics.
Mike’s website is located at www.american-manufacture.com. Mike also has a line of suppressors that are second to none as well as other services. Contact Mike for the latest pricing and turn around times as well as shipping instructions.
Bottom line, buy the Colt, get it converted and stop your complaining about her not being MIL-SPEC!
[ June 05, 2004, 18:02: Message edited by: Vulcan ]
Over the years I have heard so many debates over who makes the best AR-15. Reasons range from the quality of finish to outward appearance, quality of internal parts to reliability and so on. One of the big arguments is over MIL-SPEC. While Colt was the first to successfully mass produce a commercial version of the M16 rifle they made a few changes to her. One of the big changes was the size of the pivot pin from the mil spec .250 to the Colt large pin .315. The provisions for the pin detent and spring were not included and the lower became known as a ‘slab side’ because the receiver of the Colt SP1 rifles was with out the pin and spring house for the pivot pin and was flat to include the fence around the magazine release. Many complain about the lack of a fence while others can’t get past the large pin and the Colt take down pin design. The ‘two screwdriver’ design is quite frustrating but it works. What is hard to overcome is the availability of upper options for your large pin Colt. Large pin A2 and flat top uppers demand a price for A2s starting at $150 stripped and flat tops in the $200 plus range. Few companies make large pin uppers and when they do it is limited production and they go fast. Again, they cost big bucks.
The photo above shows the large pin upper with DPMS replacement pin just above the modified SP1 lower.
What options do you have? Well, for less than the price of a stripped SP1 receiver (in most cases, I know you can find some deals so please don’t bust my balls because you could not get this done for $50 when I ‘said’ you could), you can get your trusty SP1 and other large pin Colts converted from large pin to small pin by American Manufacturing near St Louis, MO. How is this possible? Well, Mike at American is an expert at welding aluminum. Mike takes your lower, strips it down, welds it up, drills a new hole with his trusty old Craftsman hand drill (just kidding, he uses a no name brand hand drill) guided by his state of the art jig to ensure the holes are straight and true and refinishes the lower in your choice of finish (prices vary, please enquire). Your lower is sent back to you as good as new and ready for use with your MIL-SPEC top end. If you have the provision for the pivot pin spring and detent but no hole (newer pre ban, post ban and LEO Colts), Mike can drill that for you. If the large pin hammer and trigger is getting you down, Mike can fix that for you as well (I am currently having this done, update and pics to follow).
The photo above shows the modified lower with a small pin flat top upper installed with the replacement DPMS pin.
How do I know this and what makes me such an expert on this conversion? Well, I don’t claim to be an expert but I have had Mike do some work for me on a Colt SP1 and I have another post ban lower getting some trigger group holes converted right now. My receiver went to Mike a couple of months back via USPS. Since my family lives in nearby Columbia, MO I stopped in to visit Mike and check out his shop. He told me not to expect a state of the art manufacturing complex and warned me that I may be disappointed. While Mike does not have a huge shop he does have a well organized and well equipped work area and he turns out a wonderful product. Mike is quite the history buff when it comes to guns and we had a wonderful conversation about what he does, how he does it and so on. We also had a long talk about the F16 canopy that I had brought along with me that I brought back from Iraq to show off at my nieces high school while visiting home.
This is the DPMS replacement pin you will need to use with your converted SP1 lower. The ball detent keeps things in place. This pin runs about $6.
For you that own the dreaded slab side receivers, this conversion will not eliminate the need for the Colt style front pin. You will not have the ability to secure the pin without using the Colt designed pivot pin or a replacement pin (see my review of the DPMS replacement pin) in order to keep your top on. While we all like to see tops come off now and then most are better kept in place!
As you can see from the photos, my SP1 lower is a bit unusual. She now sports a small pivot pin. In addition, Mike repaired some marks that were on the receiver and he added SAFE-SEMI-AUTO on both sides of the selector. My lower is home to a DIAS so it was only appropriate for the upgrade. While Mike will change the name from AR15 to M16, he said the AR15 was too close to the Colt logo (horsy) and he did not feel comfortable welding that close to it. So, she still sports the name AR15 instead of M16. The top end is held in place by a DPMS replacement pin and it works great. Everything lines up just perfect and the molly coat finish looks great.
This is what the passenger side looks like. Since she is an old SP1 slab side, there are no raised areas for the spin and detent pin that hold a standard pivot pin in place. The small DPMS pin has one side flattened so it may be used with small pin Colts that have the raised areas but are not drilled for the spring and pin. Mike can drill these for you and install a USGI type pivot pin for you.
Once again, I have another lower at Mike’s getting a makeover. It is a post ban Colt that has the MIL SPEC front pin and detent system but sports the large hole fire control group. After some holes are tightened up and some other work, I will have this lower ready for a good work out and I will be posting the pics.
Mike’s website is located at www.american-manufacture.com. Mike also has a line of suppressors that are second to none as well as other services. Contact Mike for the latest pricing and turn around times as well as shipping instructions.
Bottom line, buy the Colt, get it converted and stop your complaining about her not being MIL-SPEC!
[ June 05, 2004, 18:02: Message edited by: Vulcan ]
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