C.O.L. Question


New member
I am loading 230gr XTPs in .45 ACP for my Glock 36.

I am using the Accurate Loading Data and setting the bullet to achieve the published C.O.L. of 1.230". Of the five clips I loaded with the rounds, three of them did not cycle (load) the first time. I had to pull the slide back, jiggle a bit, and then release to get the first round loaded. After that, the remaining rounds cycled correctly.

Would seating for a longer C.O.L. Remedy the problem, or should it be shorter? And, what effect will either have on the speeds and pressures?

Any help anyone could provide will be greatly appreciated.

Thank you.


PEW Professional
In my experience, stretching the .45 out a wee bit can help feeding if that is the issue. Load a few and test... you'll have your answer.


COL is determined by:
the ogive and meplat of the bullet.
the magazine lips and when they release the cartridge
the feed ramp geometry
the gun's chamber, particularly the throat length.
The manual only lists the COL they used for their gun, and this can only be considered the minimum COL that the data applies to.
The best way to determine the COL for your gun(s) is to load two inert dummy rounds, generally as part of die set-up.
You will load the bullet for the dummy rounds long and remove the barrel from your gun.
All you need to do is just seat the bullet in the case, usually at the SAAMI maximum COL or longer. For the .45 Auto, this is 1.275". You can also use the magazine to determine max COL, since you want your rounds to fit the magazine, seat the bullets deeper until they fit in the magazine (one reason to load two or three dummy rounds so you can verify magazine function).
Then, just remove enough case mouth flare so the inert rounds chamber freely. To do this, "paint" the bullet and case with black Magic Marker/Sharpee. Drop the rounds in the barrel and rotate back-and-forth once or twice. Remove the inert round and inspect it.
Scratches on the bullet means the COL is too long.
Scratches on the case mouth mean that the mouth is still has too much flare
Scratches on the case at the base of the bullet means the bullet seated crooked.
Scratches on the case above the extractor groove means the case has a bulge that was not removed during sizing.
Keep seating the bullet deeper until the round chambers without the bullet hitting the lede/lands/rifling.
Now re-assemble the gun. Load the dummy rounds in the magazine and hand cycle the gun. Do the rounds feed and chamber? If so, you have the max functional COL for that specific bullet. You may continue seating deeper in small increments until you find the COL that is too short to feed. You now know the functional range of COL for that bullet. In general, somewhere in the middle will be best for reliable functioning and somewhere near max functional COL will be best for accuracy.
I wish reloading manuals spent as much page length discussing the importance of case expansion and COL as they do their latest "toys."


Oh, for most handgun cartridges, a reduction in COL will raise the pressure and a longer COL will reduce the pressure.
However, it is not linear. A longer COL will give you a much smaller relative pressure loss than a shorter COL will give you pressure increase.
Thus, going longer has a much smaller effect that going shorter.
Finally, be sure to do a finger-pressure test on all your rounds (try to push the bullet into the case with finger or thumb pressure). There should be NO movement of the bullet. If there is, your set-up is wrong of the case has very thin case walls. If you can move the bullet by finger/thumb pressure, that bullet will almost certainly be shoved deep in the case during feeding and you will have problems when fired.
If the first round out of a MAGAZINE does not feed, that is often a magazine problem. How do factory rounds behave?


New member
Thank you so much for all of this great information.

I have not had a problem with any factory ammo. I have only used Winchester 230 gr FMJ that are 1.265" and Remington Sabre 230 gr HP that are 1.227.

I started reloading with the XTPs at 1.230 and am now up to 1.250.

Through trial and error I have found that if I load the last cartridge in the magazine with a little downward pressure on the base end, I have no problem, but if the tip is pushed down, I experience the FTL.

I am going to do your test for a definitive COL for my Glock 36 so I know what my maximum COL.

Thanks again.


New member
Just remember when you shorten the COL that you will need to reduce your starting load data to get the load that fits your gun. How dose your gun works now for what you have done on the COL.


New member
I have not had a chance to determine the max COL as I do not have any loose projectiles just yet. I have loaded all of the one box of 230 gr XTPs that I was able to find months ago. And I have not yet received my order of 185 gr XTPs. When I receive that shipment, I will be doing the max COL test.

As soon as I have done so, I will post the results here.

The load I am using (10 gr of Accurate #7 WL Primers and a 230 gr XTP) was done based on the shorter COL. All I have been doing so far is stretching the COL. As such, I am in no danger of spiking pressures.

As to my current load, at 45 feet, with the exception of a few 'stray' rounds (user error), I can put in a grouping with a radius of 3 inches. I expect to eliminate the 'strays' as I get more experience with the gun and the round. I am not financially able to go out and fire off 200 to 300 rounds in an afternoon, so ... I fire 25 rounds per month just to keep the feel of the gun and the view of the sight path current. I was never able to get a grouping of that size with any factory loads except the Remington Sabers which was in the 4 to 5 inch radius grouping.


New member
Got hold of some more 230 gr XTPs.

Did the test on max COL. For my Glock 36, it is somewhere in the vacinity of 1.274, so I am saying that my personal max COL is 1.270.

Thanks again for your help.


New member
I had a problem myself in the past on one round that the data I had and what the COL was not for the gun so,I did make up a dumb round to check to make sure the chamber .I do that always when I start a different bullet no matter if it is jacket or cast. and when I see it is not the same as what the data is when I do some test rounds I go below the starting load and test and then go from there.Do you use a dumb round to make sure it chamber? because of when it dose not chamber then you put the round deeper till the gun dose chamber the way it need to and then you will know what your COL is .Do not do this with a live round.Because of too many things will change if it dose not because you will need to change the powder amount .also when starting with new type of bullet you should do some test rounds and see how they work with your gun and go from there.


New member

Got hold of some more 230 gr XTPs.

Did the test on max COL. For my Glock 36, it is somewhere in the vacinity of 1.274, so I am saying that my personal max COL is 1.270.

Thanks again for your help.

I've been loading .45ACP for over 30 years and I prefer to make the COL as long as possible so that it barely fits in the mag. I started doing it this way for max power loads when I was loading a .451 Detonics Magnum which is basically a .45ACP brass lengthen .042". Longer brass, longer overall lenght, more powder = more power.

With my old Norinco 1911A1 I have fired over 10,000 rounds of my reloads using a 200gr LSWC with a COL of 1.275". This gives about .008-.009" of clearance in the magazine.



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