Follower / Spring / feed lip geometry just isn't favorable for the set up we are trying on the SP mags for the TCM short body the way we are trying it (using a stock body). Made a whole new set up tonight and total failure kicking the noses up. Going to go the opposite direction next week and throw more time and money away. Good news is, the TCM/Glock lower ran very well. I'm getting some carrier drag I need to solve, but for stock TCM rounds this is a no-brainer. We have the BCG glock cut figured out and can do it pretty quick. The mod on the PSA glock lower is very straight forward and you do have to cut a new mag slot in the TCM mag. But, its the best running TCM mag set up I've got and lord knows I've tried a lot.
Ran two tests today at local range: Test 1: modified glok lower to take TCM mags. Ran two full mags with zero issues. Man, you don't know how good that feels. Was starting to get some drag on the third mag and did not have my tool box with me to clean up the upper so I switched to test 2
Test 2: Old style Gen II TCM mag: first 5 rounds were 100%. Next 10 rounds were 50/50 run / nose high jam..... Was using factory bullets at 1.28"
The TCM mag set up is much closer to the chamber and the rounds are angled up, guiding them in. Our mags are more level and the short rounds "jump" out of the mag when they leave the feed lips. This distance is also where the round passes the neck of the next round. I think the only answer is to go back to the metal mags with longer feed lips..... but that presents another group if problems for the short round.
Frustrated with our TCM mag testing and reloading (have I mentioned its a PITA? I'll comment more in the reloading section....) I once again tried something new with our dedicated mag set up based on Tokarev testing last week. Have run 3 - 5 round tests out of two different mags and both have fed 100% out of our 16" carbine set up using 1.28 (or less) factory reloads. The first mags is a modified 1.38" mag set up and I ran 1.28 loads out of if dropping the bolt and firing all 5 rounds. I made 1/2 of the changes to our 1.28" mag (which was a total failure last test) and I had a snag on the neck during bullet drop and the remaining 4 rounds fed 100%. Both of these mags are the polymer body mags. I don't know if this is a breakthrough or fluke at this point, but going to load up more ammo and head to the range....
Tested 4 modified mag set ups this weekend with reloads from 1.28" to 1.54" using our dedicated mags. Operation was much better than our previous tests, but none ran as good as the factory mags.
The main difference is that factory mags are A: single feed so the rounds are centered towards the chamber; and B: The rounds are closer to and angled up towards the chamber.
With our mags we were feeding upwards of 80% with nose high jams the #1 jam. We are going to take one barrel and do some more lug grinding, but it looks like the rounds are being pushed nose up by the bolt action and not the barrel extension..... we'll see. The rims of the case are very sharp and grab everything. I'm tempted to take about 20 cases and "rebate" the rim and see if it helps feed....
The good news is that we spent more time shooting than clearing jams, so that's a good thing.
Also tested a Glock lower / TCM upper with 9R reloads and it fed 100%, so that's an easy build.
Reloaded some TCM with 36 gr HP and 40gr poly tip with OAL's of 1.52 - 1.54". These load would feed a stock TCM chamber with no throat. We used our new Gen3 M1 carbine mag set ups and loading 5 rounds we got 100% feed. Might take some more reloads and head to the range tomorrow to see if we can keep loading and firing these Gen3 mags.
Kinda…. we use AR mag bodies with the thickest side walls we could find. The metal mags all have clearance ribs and mess with the stacking. The poly mags are smooth, but the smaller dia of the 30 carbine almost requires that we shim the sides. PITA.... We are also working on two new mag adapters....
A while back, frustrated with lack of progress on dedicated TCM AR mags, I made up an adapter that allows stock TCM mags to (almost) fit into a standard AR magwell. Almost, because the TCM magazine is over .900" wide and has to be squeezed in to fit most AR magwells. Some fit, some, a little vise action and presto, the mag will slide into the standard AR lower. You just need to set depth and angle.
There are a number of Glock mag adapters for standard lowers, so its basically the same thing, but cut to fit a TCM mag.
I'm up at the main shop and getting some parts cut and we modified our Gen 1 TCM adapter and the Gen II adapters are ready for testing. Fit is much better and working on a mag release system. I'm going to try and cut a couple more before I have to head out.
Worked on geometry of the dedicated mags while we tested the new TCM-AR adapters at the range yesterday and going to make a couple more adjustments. Even the 1.28 mag ran better yesterday after some tweaking. Don't know how much time I'll have, wheels up in 3 hrs...