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8 round magazine for auto mag

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Gerry View Drop Down
Callahan's Auto Mag
Callahan's Auto Mag


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerry Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 2018 at 2:24am



What I found with Triple K is the channel is not high for the pin to trip the bolt hold open mechanism.
Gerry
MI







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Bellarmament View Drop Down
180 Auto Mag
180 Auto Mag


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bellarmament Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 2018 at 4:29am
I have been very busy and have not posted in a while and since it is cold as heck in the shop figured I would try and answer the question about the magazines on the Auto Mag website and a little more.

The magazines that are selling for 135.00 are the original Stainless Steel Auto Mag magazines. They have the stainless steel skeletonized follower with the pressed in knurled follower pin that engages the hold open after the last round is fired to hold the bolt back. Once you press the knurled follower pin in and out several times to disassemble the magazine the follower pin will no longer grip due to the erosion caused by removing the knurled pin from follower pin hole.  They are all original vintage Auto Mag magazines and a great deal at the 135.00 as they are collectable and will only get more scarce as time goes by.

The magazine that sells for 145.00 is the improved current production made by Excel. It is a take down magazine with a removable floor plate and the follower pin can be removed easily without damaging the follower to remove the follower. Definite advantage over the old magazine as there is no knurled pin to press out and the floor plate is removable. You can now clean your magazines quickly and easily and make adjustments to your magazine spring to suit your pistol.

 I am not sure whether they are using a polymer follower or if they decided to stay with the stainless steel follower. I questioned whether a polymer follower would hold up indefinitely as when there is a empty magazine inserted into the pistol there is constant pressure on the follower pin applied to the follower as it tries to lift the hold open but cannot since the bolt is closed. I imagine if the polymer is of an adequate shore hardness it may not be an issue. With a stainless steel follower there is no issue.

I found when testing that much of the problems with the Auto Mag loading all seven rounds were contingent on several factors.  There is a stacking tolerance issue of the .44amp due to the tapered cartridge case that increases as you load more cartridges into the magazine. Off the top of my head it seems it was .011 per casing. When two casings are in the magazine you have a frontal cartridge case stacked tolerance of 22 thousandths. Naturally the more rounds that are in the magazine the more stacked tolerance builds and the front of the cartridge has a propensity  to nose dive when pushed by the bolt. This is accentuated by what I call bolt tipping. If you put a empty magazine in your pistol and retract the bolt fully so the hold open engages push downward and lift upward on the cocking piece and look through the ejection port at the front of the bolt and watch how much your bolt is able to tip up and down. What determines the severity of the bolt tipping is directly related to how loose your bolt fits in the bolt ring on the frame. Careful while doing this! If you have a marginally functioning hold open you could cause the bolt to be released by the hold open and bite your hand or fingers so be careful. The tipping bolt was determined to be a factual issue with high speed photography as the bolt was not able to level out before contacting the case head of the next round to be loaded. The tipping of the bolt is also enhanced by the design of the low slung recoil rods which accentuates the bolt tip upon reversal of motion ( rearward motion to forward motion ).  If your upper is loosely fitted you can actually watch the bolt lift the barrel extension vertically as the bolt moves downward at the cessation of it's rearward movement. The casing was pushed very high on the case head by the bolt and this compounded the propensity of the nose diving low into the feed ramp and increased resistance to traversing the feed ramp into the chamber.  Another friction braking issue was the constant rotational pressure applied by the rotation spring on the bolt causing friction against the rotation pin and inside the bolt ring. A well lubed bolt, bolt slot and rotation pin are a must and negates most of the rotation spring applied braking. Another friction braking issue that can only be addressed with a good lubricant is the twisting of the recoil rods by the rotational forces of the cocking piece due to the rotational torque from the bolt rotation spring. Put a empty magazine in your unloaded pistol and pull retract the bolt fully so that the bolt hold open engages. Now look at the cant of the cocking piece and look where the recoil rods enter the spring tubes. You will notice the recoil rods are touching the spring tubes low on the left and high on the right. I have seen frames where a lack of lubricant has wallowed a groove in the spring tube entry holes low on the left and high on the right. The canting is more noticeable on the .182 recoil rods than the .200 recoil rods but both have torque bind that is lessened with a good lubricant. Friction issues do stack. We all know I am sure that limp or weak wristing or gripping a recoil operated pistol can cause cyclic problems as with the Auto Mag pistol. A good strong two hand grip is advisable. All of the talk about bouncing followers under recoil and the next round in succession not being presented to the front of the bolt for pick up in a timely manner were disproved with a bump gauge inserted into a magazine and with high speed photography. On the test pistols when testing magazine followers and other loading issues I always bead blasted the feed ramp. This was so I could see where the individual rounds were connecting with the feed ramp as the jacketed bullet would leave a copper smear on the rough feed ramp. I could take a long wooden stemmed q-tip with some ammonia, go in and remove the copper smear and check the connection of bullet against initial contact with the feed ramp of the subsequent round and get an idea of how much nose dive was occurring.

I had designed several followers to address the stacked tolerance issue. Some worked better that others with one really showing great promise. If you angle the follower enough to remove all of the stacked tolerance on a fully loaded magazine the front of the follower would try and catch behind the bottom lugs of the bolt after the last round was fired. Also if only two or three rounds were loaded the case head would sit at too low an attitude to be picked up by the bolt to load.  The other issue was keeping all of the follower movement in check within the limits of the slot channel in the side of the magazine that the follower pin rides in with no binding. The last follower I designed that showed promise was able to remove stacked tolerance and was able to adjust proper attitude as the round count in the magazine lessened.

The other issue is the magazine spring. The pressure of the top round of a fully loaded magazine with a strong spring acts as a friction brake on the bottom of the bolt. The fewer rounds in the magazine the less friction braking you have and the more forward bolt speed / thrust pressure you have to push the cartridge out of the magazine lips and up the feed ramp into the chamber. By being able to clip coils on strong magazine springs you can adjust the follower pressure to your individual pistol. Remember your recoil springs are the only forward pressure basically pulling your bolt toward battery while pushing a round out of the magazine and pushing it into the chamber, overcoming extractor momentary resistance and ejector resistance and finally closing and locking into battery. My advise is to make sure you have good recoil springs before making magazine adjustments.

One last note is the problem with magazine fit into the magazine well. Many of you have problems finding original magazines that fit nicely. There is a wide variance in the dimensions of the magazine well from pistol to pistol and from the variances of the external dimensions of each individual magazine but what I found most disturbing was squirreled frames. Take the right grip off your pistol and look at the bottom of the butt of the pistol. Lay a straight section of cleaning rod or a straight edge on the side of the grip frame between the bottom grip screw boss and butt of the pistol running from front to rear of the pistol. Some of you will find that the frame is squirreled badly and I found these were the hardest to find magazines that would fit nicely and drop free.

In closing I am quite sure that you guys will soon receive your founders edition Auto Mag and you will be very pleased. The guys doing the machining of the uppers in Ohio are in my opinion unparalleled in ability and craftsmanship. Larry Grossman is a great guy and has more experience than anyone with the Auto Mag and probably is the only "guru" in the bunch. I look forward to hearing the reviews of the new pistols. I have the pleasure of owning and shooting the new improved design much like the ones you will be receiving with the rotation spring and a new design that no longer uses an accelerator or rotation spring with great results. 

I apologize for such a long winded post.
Happy New Year!
Tim


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jw4570 View Drop Down
Callahan's Auto Mag
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jw4570 Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 2018 at 10:18pm
Triple K did a run of Stainless a few years ago, different than the hard chrome or the blue.

That looks like a Stainless Triple K.  And yes you have to modify the follower pin on them (replace with a different diameter head) to get it to lock the bolt holdopen sometimes.


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desertmoon View Drop Down
International Auto Mag
International Auto Mag
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Post Options Post Options   Thanks (0) Thanks(0)   Quote desertmoon Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jan 2018 at 1:04am
Thank you for the AWESOME tech write up, Tim!!!

Stay warm over there!  I hear it's pretty bitter right now!!!!
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Bellarmament View Drop Down
180 Auto Mag
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bellarmament Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jan 2018 at 2:36am
Thanks Tony!


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desertmoon View Drop Down
International Auto Mag
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Post Options Post Options   Thanks (0) Thanks(0)   Quote desertmoon Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jan 2018 at 2:04am
Originally posted by Bellarmament Bellarmament wrote:

Thanks Tony!




My pleasure, Sir!!!!  THAT is one gorgeous gun, right there!!!!!
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Mark F View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark F Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jan 2018 at 6:55pm
Thanks for all the great info. What a beauty! 
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