Kimber GMII feed jams with Precision 200gr SWC

[Bob DuBois]

I've had pistols in the past that required throating, slight amount of material removed in the feed ramp area and the top of the hood to get 200gn cast bullets to feed. It can be done with a dremel and I'd try a fine stone then polish, remove as little as possible.

I'm heading out this afternoon to shoot mine using 200gn cast bullets.

[GregJ]

My OAL for Precison is 1.260, this leaves about a thumbnail thinkness of the full diameter above the rim. You might try this OAL. Based on my expierence the #38 mold bullets Precision SWC with the rounded edges feed best. Other SWC's with very sharp edges are much harder to get to feed in the gun.

CocoBolo: Thanks for the info. I loaded up three dummy rounds of Precision 200gr SWC at 1.260", and put them at the top of a Wilson ETM mag loaded with 5 rounds of the same load but at varying OALs. The 1.260 dummy rounds would hang up on the slide like the attached pic show. Even if very aggressively manally cycling them through, they would hang up almost every time in the Gold Match, and occassionally in the Kimber Target.

The OALs I tried manually cycling through were 1.250, 1.245, and .1240. The latter was the only one that I could get to reliably eject when manually cycling the GM. The Target seemed to be looser and could probably tolerate 1.245, but since this is my son's gun I'm not going to chance it.

I know this sounds like I'm going too far with this, but not only am I trying to get the best feeding (and performing) load for my GM and my 17yr old son's Target, but I also want us to be able to safely show clear at the end of a stage.

So it looks like 1.240 OAL is optimum for us using Precision 200gr SWC.

[Powder Finger]

My pictures ain't that great but...

On terminology I call the:

I call the extrctor hook the portion that goes in the groove of the case

I call the extractor groove the portion behind the hook that case rim hits

Now if you look at the extractor from the front end the bottom edge of the hook should be radiused close to the same as the radius of the groove of the case.

The bevel at the bottom of the extractor groove should be beveled (and corners rounded) close to the same radius as the rim of the case.

When done like this the case rim and groove have a little mechanical advantage on these angles to get under and move the extractor outward. Then the forward slide movement and chamber finish raising the round under the extractor and chambers the round.

The bevel in the Wilson link that is at the bottom of the extractor hook and goes forward accomidates rounds coming out of the mag at different angles and lets the round start under the extractor sooner that a square cut would.

As you can see the left extractor has a little less radius on the bottom of the hook which is what I would say is minimum.

When you compare to yours if you were to hold a case below the extractor you can see the fairly square hook has to push the extractor out all at once as opposed to wedging it out on the angles.

Hope that helps.

[GregJ]

Thanks so much for the info. I will have to digest it tonight. I'll be out of town next week, so I wont have the opportunity to do much until I get back.

However, I did make it to the range today, and I believe adjusting the extractor (loosening it up) did help quite a bit.

I ran about 20 mags (approx 150 rnds) of varying OALs and powder charges, and didnt have one feed jam.

1.245 @ 4.8gr W231

1.240 @ 5.7gr W231

1.245 @ 5.4gr W231 <<< Worked quite nicely, will be using this for future matches

1.250 @ 4.8gr W231

Then I started on the 1.240 again and had 3 feed jams, then ran about 2-3 mags with no problems. Had one jam with 1.245. The pistol may have been getting a little dry at this point. I put a couple of drps of oil on the feed ramp, then shot 4 more mags with no problems.

I'll take a closer look at your pics tonight. Thanks again for the assist!!

Edited July 9, 2011 by GregJ

[GregJ]

Powder Finger: Attached pic is of the little bit of cleaning up and polishing I did on my extractor. Not a great pic, but hopefully it will be clear enough. I had a two FTE and one FTF today. I'll continue to tweak the extractor until I find the sweet spot.

[reptoid]

Also if you don't do anything yet I will try to post a good extractor shape pic tomorrow.

That would be most benficial. Thanks

Also, the round I had in the pic was NOT an empty case, it was a 200gr SWC, that's probably the reason for the tilt. An empty case did NOT tilt like that.

Follow, I see the bullet now. that looks/sounds about right.

Take a close look at your magazines. An often overlooked factor in feeding/timing is the cartridge "release point". This is the point at which the mag lips release the cartridge rim alowing the round to rotate and align with the chamber. SWC's and/or Hollow points make this point more critical because of the blunt flat nose. Magazines with an earlier release point work much better with SWC's.

If you slowly cycle a dummy round with your SWC loaded to your preferred length you will see what I'm talking about. CMC and std Colt 1911 mags with parallel lips have the earliest release points although I haven't run the new "Tripp reasearch" mags. I do use use Tripp's hybrid followers and springs in all my mags (simply the best there is)

Hope that helps.

Don

[GregJ]

I was perusing through some posts and came across one of mine, and thought I should close it out with what I had done to make my Kimber GM II run like it should. So far <knocking on wood> I have not had any ammo related issues since August, approx 6 matches.

1. Brass: Sounds simple, but I think one of the biggest improvements was sorting out brass headstamps. I sort out all the PMC, Winchester, Blazer, Starline (and a couple others that dont come to mind right now) brass for reloading match ammo. All others get loaded for the practice range only. I now believe a lot of my earlier problems very likely could have been due to crappy brass, not having enough neck tension.

2. Throating: There was a sharp corner midway up the left side of the throat that would occassionally catch on the shoulder of the case. I cleaned this up, as well as a little polishing on the top of the chamber, just behind the barrel hood.

3. Extractor tuning: With a lot of help from PowderFinger ( ) I beveled, polished and tuned my extractor. I used the Weigand tuning tool from midway, along with the guage set. Using a digital trigger pull gauge, I now know what tension works best in my Kimber.

4. General reloading tuning/adjusting: Though a lot of trial and error, I found the right crimp that feeds reliably (.469 - .470"), as well as the best COAL for the bullets used (1.254 for 200gr SWC, 1.200 for 200gr RNF). Also, I added to the process, running every round through a Wilson cartridge gauge. This is another item that I think made a big difference in creating consistent rounds.

Thanks again to all those that offered assistance, and I hope this helps others.

Edited November 29, 2011 by GregJ

[soe400club]

I thought I had a good load for my Kimber Gold Match II; Precision moly 200gr SWC, 5.4gr W231, OAL 1.245, crimp .4690 with mixed headstamp brass (except no R-P brass). This load worked great at the range with static targets, but under the stresses of a match, my Kimber became a jam-o-matic today at a match. Attached pic shows the type of jam. The round seems to get jammed going into the chamber at an angle. I absolutely know it's the ammo, because the last two stages today I used my son's ammo, which is basically the same load but with Precision's 200gr FPRN (OAL of 1.235 IIR). My GMII worked flawlessly. I'm using new Wilson ETM mags and my son was using new Wilson 47D mags.

My search turned up this post.

Interestingly, a post from superdude included the following:

1. try slightly beveling the underside edge of the hood.

2. polish the upper inside of your chamber.

3. try adjusting overall length.

4. stop using those bullets. not trying to be a smartass - i had feeding problems with the same design, tried everything, finally gave up.

AriM had some great pics showing the areas mentioned above.

My son shoots a Kimber Custom Classic Target, and his seems to run through the SWC just fine, so I pull the two appart and started comparing things. The throat of the two is pretty much the same - same angle and well polished, but I did notice the hood on his is beveled but is not on my GM.

How important is this bevel to the feed problem?

I may also polish the upper inside of the chamber as recommended.

If the OAL is much longer than 1.25 it seems the SWC hang up on the barrel hood when manually ejected (as in when showing clear), but I may try changing OAL a little.

I have a case of the SWC sitting under my loading bench, so I would like to get these to work. But in case I cant, I did order a case of the FPRN - because they do seem to work very well in my GMII, and I'll relegate the SWC to static target practice.

Any additional suggestions would be appreciated.

I had the same problem with my Kimber custom TLE. I got different mags and it fixed the problem and I made the OAL at 1.255.

[soe400club]

I had the same problem with my Kimber custom TLE. I got different mags and it fixed the problem and I made the OAL at 1.255.

[kalaur]

Often times with LSWC depending on the type of jam its not the OAL, its the amount of the shoulder of the bullet that is above the mouth of the case. Generally you want at least 15-20 thousandths or more of the bullet shoulder above the mouth of the case, or about the thickness of your thumbnail.

OP - a clear close up pic of your 'jam' ammo compared to your new stuff might help others who search for this issue in the future.