.45 Colt Hornady bullets with 2 crimp grooves?

[hc18flyer]

At a recent gun show I bought a box of Hornady 300 HP/HTP bullets for my large frame Ruger Blackhawk. The Hornady Manual says to use the forward crimp groove? My Blackhawk cylinder has plenty of length for the longer oal? Should I use the shorter oal? Why?

[Pipefitter]

I could be wrong on this but, if I remember correctly the second crimp grove was for the 454 Cascull and the 460 S&W, to allow seating the bullet out further for a larger charge of the slow burning powders these cartridges usually require.

[hc18flyer]

Will the extra case capacity raise pressures? They chamber just fine.

[ReloaderFred]

More case volume, using the same powder charge, reduces pressure. It's reduced case volume that increases pressure with the same powder charge.

Hope this helps.

Fred

[lar45]

If it was me, I would use the longer oal.

[nawagner]

What is the difference in COL between the two crimp grooves? As Fred indicated longer COL than published loads will yield less pressure. Good reason to head to the range. Load a few and go test them.

[44MAG#1]

I will put this out there in testing the 44 Magnum. In testing the 44 Magnum Hornady 300 grain XTP with the 2 crimp grooves i chronoed these results.
Seated to the top crimp groove (short length) gave XXXX FPS velocity with XX.X grains of H110.
With the bullet seated to the bottom crimp groove (long length) I had go 3 grains heavier on the powder charge just to equal the same XXXX velocity of the short length load. All other components were the same shot on the same morning back to back in the same gun with the same lots of components.
Please excuse the X's as I am cautious of the load data police. I dont give out data now
I know I related the 44 Magnum example but it will give you an idea on the 45 Colt albeit with different charges.

[Tackleberry41]

The book data is based on the front crimp groove. Move it out to the rear one, the velocity will drop.

[hc18flyer]

Thanks for the info. Looks like I will do a little testing of my own. Longer OAL May have an edge on accuracy, shorter OAL more efficient? Pistol ranges, any improved accuracy May be negligible? I need a nice day to play hooky from work for a couple of hours! hc18flyer

[hc18flyer]

Dang auto correct- That's oal!

[str8wal]

If you are using a powder that like a full case, eg H110 or 296 et al, you might be undercharged if seating longer than recommended in the manual.

[hc18flyer]

I have 6 each loaded up with Alliant 2400 and Accurate #9 powders. Neither are max or full case loads. Neither load would be a full case with the shorter oal. hc18flyer

[bisleyfan41]

There was an article in American Handgunner by Randy Garrett some time back addressing this very topic with the 44 mag. The 2 grooves on the bullet allowed him to load long for improved performance. Seating out to the second groove will dropped pressures. So this allowed him to use more powder for more velocity, but still stay below max pressure. So he could get more velocity than normal while staying within acceptable pressure limits.

Here's the article:
https://americanhandgunner.com/getti...gnum-revolver/

[44MAG#1]

I read the included article. Saw no legitimate pressure data on the seating depths when reaching the same velocity. Not saying seating long is good or bad. Dont know. I do know this through actual chroning that in the 44 Mag with the 300 gr XTP seated short with XX.X gr H110 I got XXXX velocity and when seated out (long) it took 3 gr more H110 to just reach the same velocity. All components were of the same lot and the loads were chroned back to back the same morn.
Lets see actual pressure data on these faster loads with the bullet seated out. Using the same lot of components. From a legitimate source.

[lar45]

What are the two loaded lengths? I don't have any 45-300XTPs on hand to measure.
What is your barrel length?
Do you have a chronograph?
I can run the two loaded lengths through Quickload to get an idea of pressure and velocity.
If you have access to a chronograph, then you can see if the Quickload predictions are close or not. Velocity isn't free, it either comes from burning more powder, or operating at a higher pressure. So if the chronograph says you are getting more velocity than predicted, then you can assume that the pressures are higher also.

When you seat them to the longer length it effectivly gives you more case capacity. So with the same powder charge it will give less velocity and less pressure. This has already been stated, just saying I agree...
With the longer length and more useable case capacity, you can load more powder and get a little more velocity while staying at the same pressure.

[hc18flyer]

Yes I have a chronograph, hope to shoot Sunday? I have both 1.660 and 1.580 oals loaded with 17 grains of Alliant 2400. I have a 7.5" barrel. Thank, Tom

[lar45]

Okay, here's the Quickload guestimate. Remember this is not load data, just a simulated guesstimate.

45 Colt 7.5" barrel 2400 300gn XTP
1.580" 17gn 2400 should give 1248fps @ 27.7kpsi 85% load density

1.660" 17gn 2400 should give 1192fps @ 22.6kpsi 75% load density

1.660" 17.8gn 2400 should give 1245fps @ 25.3kpsi 78% load density
If everything else before this is about the same over the chronograph, then you can start working up and watching for pressure signs...

1.660" 18.5gn 2400 should give 1291fps @ 27.8kpsi 81% load density

Remember, just a computer guess

Let us know how things go on Sunday and we'll see how close it was.
Glenn.

[hc18flyer]

Thanks for the info! I have several loads I want to test tomorrow. I will report back, Tom

[hc18flyer]

My velocities were a bit lower than Quickload predicted. The 1.580 oal averaged 1088 fps, with 79 fps variance. The longer 1.660 oal averaged 1040 fps and 67 fps variance. hc18flyer

[hc18flyer]

Sorry, that was with 17 grains of Alliant 2400. hc18flyer