.25 ACP rifle, what powder?

[Crank]

Yes you read that correctly. I just received my chambering reamer from PTG today and finally cut the chamber in my Lothar Walther barrel that now resides on a former Winchester 1903. All of the loading data out there is focused around pushing a pill out of a 2" barrel. I currently have 22.5" worth of barrel to work with until I decide if I want to shorten it and wondered if anyone has a suggestion for something other than Bullseye or Unique. I test fired 4 factory rounds (through a wadded up towel) without incident, but suspect the powder had lost all of its pressure by the time the bullet exited the muzzle due to the small amount of soot left in the towel. I do not profess to have a thorough knowledge of powder characteristics, so I am hoping that someone can suggest a powder that would better utilize the longer tube and still fit in the case. I don't know if this is the best section to post this since it is a handgun cartridge out of a rifle, but as you can see I am still the "New Guy" to the forum. Thanks in advance.

Mark

[MtGun44]

You will run out of pressure long before you run out of barrel. The expansion
ratio is hopeless. With a tiny, straight case, every roughly 1/4 to 3/8 of an inch
of bullet travel (bore length) will represent the case volume. If you look at a
.22 LR, they have a similar problem, and they slow down actually after something
in the neighborhood of 16 bbl length.

You will certainly fully expand your powder and it should be really quiet, but you
won't get just massively more velocity than from a 4 or 5 inch barrel, if any.

You have to balance the case volume ( which controls the quantity of powder) with
the barrel volume, measured in multiples. Some extreme varmint cartridges have
expansion ratios of maybe 3 or 4 where a .45-70 with a short barrel of 16 inches
has an expansion ratio of more like 10. A 16 inch .44 Mag should have an
expansion ratio of about 13-15 or so. Your rifle should have an expansion ratio
in the range of 60 or more, WAY outside of the normal range.

Have fun - it will sure be quiet!

Bill

[JHeath]

Others can provide guidance on the powder. But what bullet, how long a throat (seating depth) and what are you shooting at? Fast powders give low muzzle pressure, and little noise. You could probably shoot it in the garage. Crank up the pressure and you'll have to shoot outside. Pistol loads might be fun, unless you need flatter shooting or harder hitting.

[Catshooter]

What fun! I think, and this is just my opinion based on zero experience that I might try starting with Unique. 2400 might be worthwhile also.

I would think you'd get into compressed loads pretty easily.

Please keep us posted!


Cat

[Lonegun1894]

I can't say I would have thought to use a .25 ACP, but have considered a small cased medium caliber, say .30-.35 caliber pistol caliber rifle, just for quiet use like this. This seems like a great idea, somewhat special purpose, but still great for small game and such. Do you by any chance have any pictures? As to powder loads, I would actually prefer to stick with fairly fast pistol powders for the lower noise. If you were to insist on slower rifle-type powders, I would be concerned about not getting enough pressure built up due to the tiny case capacity to achieve the kinds of pressures some of the rifle powders need to actually get a good consistent burn, so you may not get satisfactory accuracy, but I wouldn't think you could stuff enough rifle powder in that case to reach dangerous levels.

[reed1911]

I would opt for 4756, it is likely the slowest powder you will be able to use to good effect. a 50g Cast RN and 1.6g works well for me in a 10" I suspect you will have the same good luck in your longer barrel. If you cannot get it where you need it, you may consider going to the 25NAA bit more capacity (.32ACP necked down to .25)

[texassako]

You will also need to consider the operation of the action since you put it in a semi auto that was designed around a certain bullet weight and velocity. You might need to duplicate a similar weight vs. speed to the original .22 Winchester Automatic. You say former 1903; so maybe you altered the action as well and I am wrong.

[Crank]

Wow! I didn't expect this much response. Thanks to all for the input. My thoughts are that using a slower burning powder that is dense/energetic enough, could optimize the longer tube. As MTGun44 put it so well with his input, the limiting factor will be case volume to bore. I am quickly leaning towards this becoming a 16.5" barrel.

texassako, I already did my homework on this one and matching bolt mass/spring rate is not an issue. When I discreetly tested it with some factory Winchester expanding points, the brass exited the gun without excessive speed and there was no sensation that the action was overworked. The original load was a 45gr. bullet @ 1200fps, so if I can get ahold of one of those GB 4 cavity molds, that will cast a 46gr boolit. I am hoping that there will be a ball powder that will flow and measure consistently. The other projo of choice will be the 35gr Speer GDHP.

I will take some photos and post them, bear in mind that I have not cut the barrel dovetail for the forearm hanger and still need to get sights/scope arrangements completed, so this is a work in progress. I am just happy that I finally got off my butt to get back on track with this project and that I have validated the proof of concept that it can work.
Thanks again.

Mark

[Outpost75]

In the tiny case you need a dense powder to keep the charge weight up.

In my converted Remington Model 580 .32 ACP rifle I use a "nominal case full" of H110 with an 82-grain cast lead hollowpoint and get about 1200 fps. I wouldn't want to shoot that in a blowback operated rifle, but in the bolt gun chamber pressure is not an issue and this rifle loves loads which would turn a pocket pistol into a grenade.

In your '03 Winchester I think I'd start with standard charges of the fast burners and increase in careful increments.

[Crank]

I am very aware of the pressure concerns, but what I am saying is that I have a suspicion that the powder has spent itself long before the bullet exits the barrel. I wanted to do this conversion on a 1903 due to the extremely heavy bolt, which allows a long dwell time in battery before any rearward motion begins. I think it is safe to say that if I can match the ballistics of a factory round, with a significantly stronger case than a rimfire, I will have little concern. I am not trying to get 2000fps out of this gun, but I would like to scratch 1250fps with a 46gr and 1400fps with the 35gr pill.

Mark

[texassako]

I want a .25 ACP rifle as well, and am in the middle of deciding which project gun(bolt or single shot) it will go in. I think the 16.5" barrel is a good idea. You might try Red Dot or Clays with the 35gr bullets. I have had good luck with Clays under a 31gr cast and 35 gr Hornady XTP. They are all going to run out of steam before the bullet gets out of the rifle barrel; so I would look for which powder meters best in small charges. My pistol measure chokes on small charges of Unique and the Clays was more accurate than Bullseye, out of a 2" barrel though.

[Crank]

I also want to mention that your "hot" loads are in line with the original European loading of the 7.65mm Browning. I had some Geco years ago that was the only thing strong enough to cycle a Dreyse 1907 that I owned and it was barking like a 9mm. It worked in the other .32's I had at the time but they were zinging empties into the next county. I would love to know more about your rifle, if you would be kind enough to share. Since I have yet to catch a Dreyse Light Rifle, I may have to build an autoloader in that caliber. Thanks for the idea about H110, I will investigate that.

[bedbugbilly]

I may be talking through my hat here . . so if I am . . just consider it's because I'm an old fart.

First off . . . sounds like a really interesting project! I hope you'll post some photos of it.

I know very little about .25 ACP but is there any old loading data around in regards to what was used in the old .25 rimfire? The cartridge that was used in the old single shot Stevens and other like rifles? I didn't do a google of the .25 rimfire but were these BP or smokeless? Perhaps someone would have some information on that cartridge that could help . . . even if listed on an old cartridge box? Just a thought.

Good luck and let us know how it progresses please . . . it ought to be fun!

[Crank]

texassako,
The only tough pill to swallow is the barrel blank. The only manufacter of one with a .251 groove depth is from Lothar Walther and they are now over $200, the last time I looked. It seemed like too much work to weld a bunch of Raven barrel together to get one long enough The other option is using Clearwater reboring, but that will also set you back about $250, but his work is excellent and you keep the parent barrel on the gun.

Mark

[Crank]

bedbugbilly,
Excellent point about the .25-10 Stevens, but that is a much longer case and I don't know how much room was left after they transitioned to smokeless. In other words, you have pointed out something I overlooked and it makes a heck of a lot of sense.
Thanks

Mark

[Outpost75]

I also want to mention that your "hot" loads are in line with the original European loading of the 7.65mm Browning. I had some Geco years ago that was the only thing strong enough to cycle a Dreyse 1907 that I owned and it was barking like a 9mm. It worked in the other .32's I had at the time but they were zinging empties into the next county. I would love to know more about your rifle, if you would be kind enough to share......Thanks for the idea about H110, I will investigate that.

My rifle was converted by making a new bolt head, shortening an M16 firing pin and fitting an M16 extractor to the new bolt face. A Douglas 14" twist .30 caliber barrel was used, and chambered using the front half of a .30 M1 carbine chamber reamer, setting the gun to headspace on the case mouth, but also having the semi-rim fitted to minimum.

[Crank]

Here are pics as promised.





















I will get the dovetail cut for the forearm hanger and figure out a scope base this weekend hopefully.

Mark

[35remington]

No refinish on the receiver? I would think a nicely blued barrel on a patina'ed brown receiver would look kinda......odd.

As regards the powder thing, slow burning can be carried too far in a blowback action. 17 HMR blowback autoloaders were modified/discontinued for that reason. The pressure needs to be low when the breechface is some distance back from the fully closed position just before bullet exit, but I believe the 25 ACP case is thicker than the rimfire cases in that regard, so this might be somewhat self canceling given the very high expansion ratio of the little 25 case in a long barrel.

In any event, whatever you use for "slow" needs to be fine granuled so you can fit the required amount in the little case to obtain any hoped for velocity gain over something quicker.

[kootne]

Pure speculation on my part, but if .22 shorts work in rifles then so should .25 ACP as far as case/bore volume ratio goes. What powders are used in .22 short ammo? I'm also guessing a cast bullet would be better suited because normally less pressure is required to achieve a specific velocity. I"ll bet you are the first kid on your block to have that rifle/cartridge combo!
kootne

[Crank]

I have a habit of being "That Guy" when it comes to strange stuff.

Mark