Headspace and the Gold Cup

[Don K.]

For those that know more than me (and that's not hard to do), how does headspace effect accuracy? The reason I ask is I was reading one of my old Handloader magazines and in a article written by Brian Pearce he talks about headspace on 1911's. The article was in May of 2003 Handloader #222 . I tried the same method of checking headspace on my GC and came up with a .017 feeler gauge being able to slip between the back of the cartridge and the slide with a case length of .892 (Mr Pearce took the barrel of a field stripped 1911 and put it back on the slide with a round in the chamber, made sure the barrel was seated and then measured the space between the back of the cartridge and the slide face while pushing the case forward to seat in the chamber, measured this and then measured the space between the extractor and the rim). In effect my GC is headspacing on the extractor and not the barrel with a case lenght of .892 when trying this method. So the way I measured it my chamber is approx .909 which is .011 more than minimum (presuming that min is .898 which I belive is correct). I realize that this isn't the ideal way to measure the headspace but was wondering if the chamber depth was closer to .898 would my accuracy be better than what it is now? And if it would theoretically be better, what could I do to get my barrel closer to the minimum chamber lenght?

Don K.

[RickB]

What you've discovered is pretty standard fare in a Colt .45. It sounds like your barrel is within spec. I have loaded sharp-shouldered bullets so that the bullet determines headspace; the bullet shoulder stops on the rifling, so all rounds chamber to the same depth, regardless of case length. I would set my seating depth by dropping test rounds in the chamber, and when the rim was "just" below flush with the barrel hood, that was my OAL. On another gun, I had the (short) chamber cut to ~.905, which means the rounds are not headspacing on the extractor, but it also means rounds chamber to various depths, due to differing case length. If you trim all of your cases, and cut the chamber to case length + .005", you'd probably get the most consistent accuracy, but don't know if it would be readily measurable at normal pistol range. If you want a shorter chamber, you need to get a match barrel with a short chamber, then ream it to depth.

[Don K.]

Thanks RickB

I have seen that the standard chamber depth for the .45acp is anywhere from .898 to .920 I have tried what you have suggested with the sharp shouldered bullet (H&G 68) and it didn't seem to make much difference in accuracy with my GC. I have replaced the collet bushing in my Series 80 GC and tightened the slide,while it did improve accuracy somewhat it wasn't all that spectacular of an improvement (from 4" at 50 feet from a Ransom Rest to around 2.5" at 50 feet). Am I just expecting a GC to do more that what it was designed to to accuracy wise?

[RickB]

Yeah, 2.5" at 50' is nothing to sing about, in a gun as expensive as the Gold Cup. Have you done much load development? I'm always amazed by different accuracy produced by changing ammo (basing this on reported accuracy in gunrag articles), where the best-performing round groups at half the worst. If you have a tight bushing, and good slide/frame fit, then there must be some problem with the rear lock-up, or . . . have you checked the muzzle crown?

[Don K.]

I have tried quite a few different loads. The 2.5" to 4" was the best of what I have tried, you don't want to hear the worst. I can shoot bullseye and score a 246 with a Kimber Custom Tactical and iron sights , the best I have done with my GC is a 116 with a 16 on the slow fire portion. the rest was just luck (timed/rapid). I'm not the best shooter but I think I'm better that what the GC is.

I'm just trying to figure out in my own mind if I should try to get this GC shooting and spend more money on it or is it just snake bit and I'm wasting my money.

don K.

[Joni Lynn]

My first Gold Cup was so inaccurate that the guys at the club would joke that it would be impossible to shoot myself with it, even on purpose. It wouldn't keep 5 rounds of match grade ammo on the target at 25 yards even when fired by a really good shooter from a rest.
If your's isn't performing for you I can sympathize and would suggest it's probably barrel fit at the rear. While it's a bandaid fix, you might try the Wilson guide rod with the Dwyer group gripper. Refitting the rear feet to the gun isn't a home remedy for most of us.
If you really like the GC, you might consider having a pistolsmith fit a new barrel/bushing for you. I have had two of my GC's (series 70 & 80) fixed up to shoot better and I'm quite happy with them now.

[Don K.]

Hi Joni

This is the same Bright SS Gold Cup that you responded to last week. Well I got my parts new bushing, plunger lever, and a Wilson guide rod w/ group gripper. I'm loosing faith in this particular gun and think I may return it to it's original state and keep it as a safe queen. Maybe someone in the future will want an almost new (less that 500 rounds) Bright SS Series 80 GC. I could send it to someone like Clark but I really don't feel like spending another $800 + on this pistol. I checked my receipt that I have from the distributor and the original price I paid was $732. from Zanders + $20 for shipping, a 1911 A1 at the time cost only $366. I still feel that this GC should be shooting better for what is considered a "target gun" without having to correct what the factory didn't do properly. If the gun shot anywhere as good as it looked I would be happy but that's not the case. I'm sorry I sold my old GC that I got back in the 60's, now that one was a shooter!

Don K.

[pa_guns]

Hi

Gold Cups are not good Ransom Rest pistols. They don't fit the slides to the frames tight enough to get good performance in one. That can make it *very* hard to tell what's going on with one. That in no way means that you are wrong about your pistol.

My *guess* is you are about right on the cost of a good accuracy job with barrel ....

The only other option would be to put it back to original and send it in to Colt under warranty. If it's going to be a safe queen anyway, it can't hurt.

Bob

[Hill]

Don,
Do you have any "Dykem" or other steel layout fluid?

I'm in the process of trying to look closely at how the barrel feet, frame notch, and slidestop interact and have found some interesting and possibly inaccuracy causing contacts between the lug feet of the barrel and both the bottom and sides of the frame notch as supplied in my new SS Gold Cup with only 30 firings.

It'd be easier to see what's going on if the parts were blued, I think, so my Dykem is drying at this moment.

I'll presume that you've seen my thread about barrel fit in my pistol. What I didn't say outright is that I'm at the point of realizing that this dog don't hunt. My out of the box Springfield XD shot much better as in 3-4" two handed groups compared to 8" with this Colt. My pistol shooting is cold as in out of practice but still I'm sure I can do better than 8" at 25 yds using both hands. I was a fair bullseye shooter too many years ago.

[1911Tuner]

Don...With the dimensions that you provided, your static headspace dimension is .909 inch...or just about mid-spec...which is no more than a figure. Working headspace will vary with the length of the cartridge case. A shorter case will show more headspace, and a longer one will show less.

Less headspace generally results in more consistent primer ignition, but I've never really been able to tell a difference in accuracy in any of my pistols. In a gun built for, and chasing one-inch groups at 50 yards...it might make enough difference to be a concern. Otherwise...Shoot it.

[Don K.]

1911Tuner.

Good answer about the 1" @ 50 yards, i should have been thinking along the same lines.I realize that .909 is just a number and my chamber is "average" I was just wondering because I don't know if being closer to exact (if that's the right word) would yield me better accuracy. Seems from the responses I have gotten like yours that the difference at 50 feet wouldn't be all that great.

Hill

I do have dye marker but I didn't read your thread as of yet but you can bet that I'm going to. Good way to put it "this dog don't hunt" because that's the way I'm feeling about my GC too. I'll read your thread and see if I can pick anything up from those that know more than me.

Don K.

[Joni Lynn]

You're correct that the older pre 70 series GCNM was a good shooter, I have some of them and they all do quite well. If it was mine I'd send it to someone like Bob Rodgers for a barrel. It would cost a lot less than $800 and when he was finished with it accuracy and reliability would be there. There's several good 'smiths that could do the work, I wouldn't send it to Clark since all it probably needs to make you a happy shooter is barrel/bushing installation.
I have a few safe queens, but they are that for other reasons.