45acp Target loads and O.A.L.

[mikejonestkd]

I just finished some testing of .45ACP target loads and had some questions and observations about my testing. I was attempting to determine if the OAL had any major effect on the accuracy of one of my colts. I have experience with many rifle rounds in which the seating depth/ OAL greatly affects the accuracy of the rifle, and I wanted to see if it would have a similar effect on a handgun.

Handgun- Colt Gold Cup Trophy, series 80, with a trigger job, and a 9 lb wolff spring. It is capable of consistently shooting 1.5" groups at 25 yards off the bench with my favorite handload. ( I know it can do better in the hands of a more talented shooter but that's another story )

Load - 3.4 grains bullseye under a 200 mastercast.net SWC. It functions 100% in the gun and is very consistently accurate, so I used it as a good test load with which to work.

Variable - Loaded up 25 each of the same load in 6 different lengths. 1.220", 1.230", 1.240", 1.250" and 1.260", and 1.270". In the past I had always just loaded them at 1.225" and didn't worry about it.

Results - 150 rounds down range today and I could not determine if the OAL had any impact of the accuracy of this particular colt. 5 shot groups averaged between 1.5" and 2" all morning long, with no clear trends to favor any of the above OAL of the handloads. I did notice that the longer rounds had a slight change in POI, which I expected due to the reduced pressure and associated velocity of the loads, but the change was very minor.

So, in conclusion, this colt seemed to like them all equally.

Questions: Is this atypical, or it is normal for a goldcup to shoot all loads so well? Does anyone have experience that is similar to this, or testing that showed a clear preference for a particular OAL in a handgun - especially a 1911? I'd love to hear anyone's experiences that either support my findings or contradict them.

Thanks in advance

 

[4runnerman]

Yes Mike I did same test in my 1911(not as big of a COL change,but it did not make the groups bigger just changed my POI. I stuck with the COL that kept me closet to where i was wanting bullet to go.

 

[mikejonestkd]

I found that the lack of change in group size to be interesting to say the least - mostly since I know how much a small OAL change can affect my centerfire rifle loads. I am guessing that peak accuracy in the 45ACP pushing cast lead bullets isn't too dependent on the OAL.
Anyone else have results to share about OAL and accuracy?

 

[spacecoast]

Thanks, interesting post. Since the .45 ACP headspaces on the forward edge of the case, it would seem like there is always going to be some kind of gap jump before the bullet contacts the barrel. What difference would (could?) it make if that gap is .002" or .05"?

Also, if it does make a difference, then it would seem that we would see more posts about .38 special ammo having lousy accuracy in a .357, but I don't see many comments about that at all.

 

[Casimer]

SWC loadings seem to be less sensitive to OAL - probably because of the headspacing. But for LRN and FMJ you can see a dramatic improvement by setting the OAL for the chamber, and headspacing on the bullet nose.

 

[Brian Pfleuger]

You should try loading them to touch the rifling if that load is low enough to be safe and the bullet long enough.

 

[zippy13]

I've found virtually no appreciable difference at 20 - 25 yards with my Gold Cup. My buddy's GI-style SA gets finicky about feeding when the SWC's shoulder is proud of the case mouth, but accuracy is consistent.

I suspect a lot of it has to do with the relative volumes of Bullseye and the sir space. In bottleneck high-powder cases, small changes in OAL make significant changes in the air space volume and the base pressures are much higher than the target pistol. With light loads of Bullseye in the .45 Automatic, OAL changes don't make major changes in the void volume, pressure nor consistency of velocity.

 

[buck460XVR]

Also, if it does make a difference, then it would seem that we would see more posts about .38 special ammo having lousy accuracy in a .357, but I don't see many comments about that at all.

Since in a revolver the bullet has to "jump" from the cylinder into the forcing cone and then into the rifling, distance from the lands is moot.

 

[Sarge]

I've loaded them to 1.250", over five grains of W231, for years and had them consistently shoot 3 to 3.5 inches for five shots at 50 yards, from mildly accurized 1911s. I'm sure they will beat that from a hard-fit match gun.

 

[mikejonestkd]

Thanks for the replies, it appears that my results ( or rather, lack of results ) seems to be consistent with other members findings. I called my local smith who is a lifelong bullseye competitor and his response pretty much mirrored my findings. Its nice to have a cartridge like the .45ACP that is so forgiving as far as OAL and accuracy.

 

[darkgael]

OAL

150 rounds down range today and I could not determine if the OAL had any impact of the accuracy of this particular colt. 5 shot groups averaged between 1.5" and 2" all morning long, with no clear trends to favor any of the above OAL of the handloads. I did notice that the longer rounds had a slight change in POI, which I expected due to the reduced pressure and associated velocity of the loads, but the change was very minor.

Yep. Same gun....4.0 grains and a heavier spring but the same result. Result of the result? I stopped worrying about OAL years ago. As long as they fit into the magazine, they are good to go.
Pete