Pressure and velocity in the same gun?

[berettaprofessor]

I'm still trying to work up a 32ACP load with CFE Pistol. I know that projectile velocity is not directly related to published cartridge pressures because gun chambers are different volumes and barrels are different length, and powders burn at different rates, etc.

But, if I know that a commercial load with a 71 grain FMJ bullet averages 922fps, and a handload with 2.3 grain CFE Pistol behind a 71 grain FMJ bullet averages 716 fps IN THE SAME GUN, is it pretty safe to assume that the pressure is substantially less in the handload? Or is burn rate still a big unknown factor in pressure?

My 2.3 grain CFE Pistol loads are fairly soft in recoil, consistent, have no excess pressure signs and all make it out of a Beretta 70 barrel. I tried a 2.6 grain load yesterday. It's stiffer, but still no excess pressure signs, but the velocity is now jumping all over the place (range from 562.1 to 801.2), which, since I individually weighed each charge exactly to 2.6 grains, I take as an indication that the powder burn is not consistent. The charge is not compressed by any means, so I don't know how else I'd get that much variation (unless CFE Pistol is really sensitive to case volume, and it is not supposed to be according to Hodgdon).

Any thoughts THR'ers?

 

[Wreck-n-Crew]

But, if I know that a commercial load with a 71 grain FMJ bullet averages 922fps, and a handload with 2.3 grain CFE Pistol behind a 71 grain FMJ bullet averages 716 fps IN THE SAME GUN, is it pretty safe to assume that the pressure is substantially less in the handload?

No!

Or is burn rate still a big unknown factor in pressure?

Yes until tested (hopefully by professionals). That and case size as well as Powder traits other than burn rate affect the final results.

More velocity can be produced at lower pressures usually with slower powders and faster powders can produce higher pressure with lower velocity, much of the time this is true. However not all powders follow rules. For example one of the faster powders, Red Dot, Produces higher velocities in 9mm than many fast powders. Clays on the other hand produces some of the slowest velocities. Both powders are typically shotgun powders.

Shotgun powders usually are fast burners and rifle powders usually slow. However even Unique ( not a real fast powder) has loads for shotgun as well.

Many shapes, sizes, processes of manufacturing, as well as composition give the powder it's individual traits. Fast, slow, Consistency, stability, etc.

Get you a good manual like the Lyman 49th or Speer reloading manual. You can learn alot like the differences in ball powder, extruded, Single base ball or (SBB) or double base (DBB). Also they have reliable (published) reloading data not found as easily on line. The more data you have the more you can do.

My 2.3 grain CFE Pistol loads are fairly soft in recoil, consistent, have no excess pressure signs and all make it out of a Beretta 70 barrel. I tried a 2.6 grain load yesterday. It's stiffer, but still no excess pressure signs, but the velocity is now jumping all over the place (range from 562.1 to 801.2), which, since I individually weighed each charge exactly to 2.6 grains, I take as an indication that the powder burn is not consistent. The charge is not compressed by any means, so I don't know how else I'd get that much variation (unless CFE Pistol is really sensitive to case volume, and it is not supposed to be according to Hodgdon).

If the charge is on the threshold of fully expanding the case and causing a seal to not expanding and causing a little blowby you can get those kinds of big changes. Anyhow according to Hodgdon your Charcge is between 2.9gr and 3.7gr for a heavier 80gr Bar Tac XP. USually a lighter bullet requires more charge as well. Yet without real data I can not say what your start and max charge are.(another reason for more sources) If your cases have black streaks down them it is likely you have too low of a charge. If you decide to work up, go slow and keep checking for signs of pressure.

 

[gamestalker]

No, not necessarily. There is more to it than just raw peak pressure, which is where burn rates as they apply to a given cartridge and projectile come into play.

Have you checked for bullet set back? Set back can easily cause major inconsistencies with velocity, and pressures.

Is your brass different head stamps? Internal case volumes can also create inconsistencies.

Is there a major variation in neck tension? Neck tension is also another consideration.

But yes, there certainly are other variables that can also effect velocity and pressures, such as seating depth, case volume, projectile profile, chamber and barrel characteristics, and temperature.

GS

 

[berettaprofessor]

Yet without real data I can not say what your start and max charge are.(another reason for more sources)

Yeah, Wreck-N-Crew that's exactly the problem, lack of data. Not even Hodgdon's website has data yet for CFE Pistol and 32 ACP of any flavor. And I sent them a query via their customer support email and got no reply. I have Lyman's 49th, and Lee, and Hodgdon's 2014 and 2015. That's a good thought about being near the threshold of sealing. I don't think the cartridges I've found show soot, though.

Gamestalker, there shouldn't be a change in neck tension as they were all crimped at the same time and die. I didn't check for setback, but I will now. There was likely some variation in the head stamp. I haven't been able to purchase any commercial 32ACP so it was whatever little brass I had saved and I don't have a lot because this gun tosses it to the moon. I shot a full magazine of commercial yesterday, for instance, and couldn't find a single case despite shooting in an area where the grass is cut very close for 20 feet away in every direction.

 

[rcmodel]

Not even Hodgdon's website has data yet for CFE Pistol and 32 ACP

That is what I like to call A Clue you are using an unsuitable powder for the application!!

If the powder manufacture doesn't have published data for it, it is not suitable for the caliber.

rc

 

[berettaprofessor]

RCModel, I agree with that in theory, except that CFE Pistol is new enough I just figured they didn't have any data yet.....but maybe I'd better just go back to something else. They've had a year to run the tests.

 

[berettaprofessor]

I'd add that neither Lyman's nor hodgdon had much data at all on 32ACP. Since I started loading a year ago and have never seen a bottle of HP38/Win231 nor Clays (I consider them mythical entities known only to the ancients), I've had to make do with what I can find. I could work up a load with Lyman data and 7625, but that would be a waste since its been discontinued.

 

[gamestalker]

You might want to construct some type of brass catcher, no way I would put up with 100% brass losses.

As far as powder is concerned, you'ed probably best wait until you can get a suitable published powder for it. So I'm with RC on this, when there's no published data, it's usually a good indication that, that particular powder isn't suitable.

GS

 

[TimSr]

I used to load a lot of 32 acp, and loaded with Red Dot, which has been around forever, with data easy to find.

I shot a full magazine of commercial yesterday, for instance, and couldn't find a single case despite shooting in an area where the grass is cut very close for 20 feet away in every direction.

A 10'x10', $7.00 Walmart tarp solves that problem. Hold the gun straight out and fire once, while waching to see where brass lands. Adjust your position, or the trap position accordingly. .25 acp is even harder to find than .32.

 

[cfullgraf]

I shot a full magazine of commercial yesterday, for instance, and couldn't find a single case despite shooting in an area where the grass is cut very close for 20 feet away in every direction.

I took an inexpensive folding canopy (aka Sleezy-up), made two side curtains from drop cloths for the side and back and use it to corral scarce cases like 32 ACP and 25 ACP. Works well and provides some shade in the hot summer months.

Down side is not all ranges may allow this to be set up. Fortunately for me, I shoot at home.

It seems that my 25 ACP, 32 ACP and to some extent 380 ACP pistols scatter cases to the four winds.

 

[berettaprofessor]

Yeah, I'm working on a brass catcher; just taking some time to make sure its constructed so it's easily carried and I can break it down and put it up quickly.

loaded with Red Dot, which has been around forever

Another mythical beast in my area. In 13 months, the ONLY pistol powders I've seen for sale in the 6 gun or 2 Big Box stores (Cabelas in K.C. and Academy in Topeka) I routinely frequent were IMR7625 (1 lb a year ago), 700X (1 lb a year ago), Trail Boss, and CFE Pistol. My supply of 7625 is dwindling and I don't want to work up a 32ACP load for it since it is no longer available. I can't use Trail Boss in 32ACP for obvious reasons, and, although I've got a decent 700X load for 32ACP, I'd like to save my one pound of 700X for 38 Special and 9 mm. That leaves me trying CFE Pistol or waiting for the backlog to break. I've been hesitant to order powder online and most of it is/was backlogged anyway.

 

[mstreddy]

OP, Cabela's online had HP38 and Win231 recently. Yes, you have shipping charges, but they only charge $20 for hazmat.
I've been loading 32 using Promo (Red Dot data). One of the online places had Promo last week as well.