Recommended ammunition for my '74 MKIV series 70 GCNM

[Lazlo]

After a very long search, I finally have my Colt 1911. I ask this ammunition question, as I have read conflicting accounts given the types of modifications the pistol has. The slide is skelletonized as the extractor lug is visable due to cutouts on the slide when viewed from underneath. Some suggest that full power loads would not be a good idea, but rather lighter target loads. Other mods include a spring guide bushing, deactivated grip safety, and a squared trigger guard with serations. So the question is, given the modifications, what can, or should be shot out of this firearm? Seems to me that it is set up for competition, so getting the correct ammunition is critical.
Thanks all, for your help.
Laz

[WoodSmith]

I'm new to 1911's, but what I've read is that the Colt GCNM is designed to shoot target loads (i.e. 185 gr.) and come equipped from the factory with a 14-lb. recoil spring. It would seem that this combo would be appropriate and safe. Others here can correct me if I'm off base.

[skipsan]

The concensus seems to be for lucky owners of GCNMs (pre-70 Series) with factory lightened slides, that factory ammo is OK provided that the proper--16#--recoil spring is used. How that would apply to a field-modified 70 Series where the extent of the slide lightening couldn't be determined, I don't know, but others much more knowledgeable will probably opine oj the subject.

[gmiller0737]

I have a Pre 70 Series Gold Cup & I have always used Remington's 185gr "Targetmaster" or most often a Handload with the same Remington Targetmaster 185gr bullet Midway Sells the bullets as well as some other places.

[Lazlo]

The concensus seems to be for lucky owners of GCNMs (pre-70 Series) with factory lightened slides, that factory ammo is OK provided that the proper--16#--recoil spring is used. How that would apply to a field-modified 70 Series where the extent of the slide lightening couldn't be determined, I don't know, but others much more knowledgeable will probably opine oj the subject.

skipsan,
I believe this is a factory lightened slide as the blueing is consistent throughout the slide. It is a '74 vintage MK IV GCNM 70 series. I have no idea of the # of the recoil spring.
Thanks all for the quick replies.
Laz

[skipsan]

The experts say there was some "spill-over" of the slide lightening from the '60's era GCNMs to the early Series 70 GCNMs. How deep that spill-over went, I haven't a clue. If you search some of the Colt Forums with key words " slide cracking", you can probably turn up some photos for comparison with your pistol.As for the spring in your pistol--change it to a 16 pounder, which will probably function just fine even with modest reloads (mine do), as well as factory loads. You might even consider a dreaded "shock buffer" for a little added protection.

[Lazlo]

Very good, skipsan. It has a "buffer" on the base of the spring guide rod. A 16 pounder spring change, thanks.

[OIF2]

Here's my input, for what it's worth. The NM Gold Cup was originally designed to compete, out of the box, in the centerfire and .45 phase of the National Match Couse. It wasn't designed to be used in the Service Pistol phase, which uses 230 gr hardball. Even if you use a later 70-series gun without the lightening cuts, the gun will have problems with ball. The Elliason sight roll pin will break; if you use ball, cut a drill-rod bit to size and fit it. The trigger stop will work loose, using ball, so you need to add loc-tite to that. The best course of action is to use lighter loads (doesn't take much to kill a paper target), put in a 16 lb GI spring (should be fine, as mentioned, with light loads) and bang away. Enjoy it for what it is, a superb target pistol that will be a pleasure to shoot.
Bob

[Lazlo]

Bob,
You know, I have been reading "cracked slide" threads all day today, and given the firearm I have, in it's current configuration and modifications, I've reached the same conclusion: lighter target loads with the 16 lb spring. A superb target pistol it is.
Laz