45ACP straight blowback handloading considerations?

[alpining]

Hi all - I'm a new member here, though I've greatly appreciated gleaning information from this site over many years. Thank you all very much for that. I apologize if this is in the wrong section, please feel free to steer me straight.

I'm loading 45ACP for a straight blowback 18" barrel carbine (TNW ASR). There are three different types of loads I'm trying to work up, and I'm hoping you folks can offer some general (or specific!) advice about how things are different with the straight blowback action compared to the 1911 that I'm more familiar with loading for.

1. Typical modest 230gr plinking load, just trying to get a clean burn and minimize wear on the rifle and brass
2. Low noise load with 255gr SWC
3. High energy loads with 200gr and 255gr SWC

I am not satisfied with my understanding of how burn rate, bullet weight, crimp, dwell time and bolt mass are all working together (vs. early opening with the straight blowback action). I have TrailBoss, Universal, and Blue Dot powders to work with right now, and I'm open to other suggestions. (I also have LilGun, but probably not useful here)

Any advice is appreciated, thanks in advance.

[Char-Gar]

Keep your handloads to standard 230 grain milspec/factory specs and all will be good.

[reddog81]

I used Blue Dot in my Hi Point carbine with a 200 Grain SWC. 10.7 grains got 1233 FPS. The ejector was leaving a pretty good mark on the case at that point so I stopped there. Blue Dot seemed like a common powder used for hotter/faster loads in 45 ACP so that is what I tried...

Any number normal loads should be fine for items 1 & 2.

[barnetmill]

For what loads is your carbine rated for. HiPoints are usually rated for at least +P pressures. I have no idea what you gun is rated for. But as Char-Gar says load you ammo to .45 factory-gov specs and all should good. If necessary adjust the loads for function. In some cases this may mean less or more powder. Round nose bullets are most often best for feeding. Some times a very slight crimp may needed to facilitate feeding. Too much can cause other problems.

I looked your rifle and it appears to use AR15 buffer tubes that means you may be able to vary the spring and buffer wts. The CMMG rifles have a radial unlock delayed blow system and that is what i would buy if I wanted something better than a hipoint.
They have a version of it in 460 rowland

304682

[Gtek]

I have ran nothing but the cheap FMJ though mine at this point over the years. I purchased one when they first came out years ago and think it has ate 500 or so with zero issues. One thing I have done and would suggest you think about is a mod to receiver. I had purchased a couple more barrels since they are threaded now to make a long, medium, short. One to leave unaltered and two to cut. I screwed the can on the full length and that first round hurt, blasted in face from blow back from open left port. I mean sting of on fire over most of face and yes I had on glasses. So I found some 3/32" wall aluminum tubing and made a two screw cover for left port, right handed. First run triggers were horrible but they have improved those, it has went bang and run 100% with the ball. You go getting off the trail with boolits beyond a 185-230 designs I would suggest plunk testing and maybe even a good cast of throat to see whats out front. The supplied steel buffer I am sure is designed to run within an X parameter, once again, you get off the trail with heavies or hot rod that extension may remove itself after a while. Every time I have spoken to them back then they were very open and said what they thought, maybe a phone call to them? Or, you can be the experimental, order a new buffer and drill and use AR buffer weights/Tungsten to start heavy and lighten up till it runs. In a blow back system Mr. Newton's #3 is there for every squeeze! Have fun, be careful.

[405grain]

Since the 1911 pistol that the 45acp was invented for is a straight blow back action, any standard published 45acp loads should work well for your application. I have a 45acp bolt action carbine, and in my experience pushing to higher velocities also decreases accuracy. In my rifle 185 grain SWC feed well, but 255 grain SWC don't. Far and away the most reliable feeding and most accurate bullet that I've found for this application has been the cast 230 grain round nose using 6.5 grains of Unique.

[M-Tecs]

Since the 1911 pistol that the 45acp was invented for is a straight blow back action,

The 1911 is not a straight blow back action.

https://www.shootingtimes.com/editorial/how-the-1911-operates/100440

In simplest terms, the Government Model 1911 is a magazine-fed, recoil-operated, single-action autoloader with an exposed hammer. When the gun is fired, recoil energy from the discharging cartridge propellant powers the jointly locked slide and barrel a short distance to the rear while the bullet exits the muzzle and chamber pressure drops to a safe level. Then a toggle-link on the barrel pivots around the slide lock pin, stops the barrel from further movement backward, and pulls the barrel downward to unlock it from the slide, allowing the slide to continue its motion fully rearward, extracting and ejecting the fired cartridge case, compressing the recoil spring, and pushing the hammer into the cocked position.



https://www.youtube.com/watch?v=EjQrhDKDWFk&t=136s

[M-Tecs]

https://www.youtube.com/watch?v=jig-RvZr1OM

[M-Tecs]

You can find suitable loads 45 ACP loads for TrailBoss, Universal, and Blue Dot powders online or in manuals.

How blowback guns work:

https://www.luckygunner.com/lounge/blowback-versus-recoil/

https://www.classicfirearms.com/news/general/blowback-operation-explained/

https://www.housemorningwood.com/delayed-blowback-straight-blowback-pcc/#:~:text=Straight%20blowback%20systems%20work%20si mply.%20The%20bolt%20rests,force%20that%20propels% 20the%20bolt%20to%20the%20rear.

https://www.shootingillustrated.com/content/review-cmmg-mkg-guard-45-acp-pistol-caliber-carbine/

[barnetmill]

https://www.youtube.com/watch?v=jig-RvZr1OM

M-Tecs is correct on it being a short recoil system and I watched about to where Vickers shows the slide and the barrel locked together as is typical in a short recoil system a la Browning. The only factory blowback pistol that I am aware of in .45 and also .40 cal are the HiPoints where it is only the wt of the slide and pressure of the spring that keeps the slide close long enough for pressure to go down and allows the action to recoil, eject and feed another cartridge.

304693

[405grain]

I stand corrected. Anyway, loads that work best in the pistol are usually also good in the carbine.

[barnetmill]

I stand corrected. Anyway, loads that work best in the pistol are usually also good in the carbine.
There were people some years ago in gun magazines that were referring to recoil operated pistols as blow back and I think not everyone has since got that straight in the gun world.
A successful .45 ACP carbine must be able to function properly with standard fmj loads for sure.

[Moleman-]

Reloaded 45acp for 1911's for many years before getting a semi Thompson 1927 15-20 years ago. Didn't change anything since the 1911's are the primary use for the ammo. The Thompson mainly gets shot with ammo that is fmj loaded to standard velocity.

[alpining]

Wow, thanks for all the replies, folks! Great info here, it will take me some time to digest.

The TNW ASR in 45ACP has exactly the same parts as the version they make for 460 Rowland (well, everything except for the barrel). It can handle hot stuff. And, it's been surprisingly happy with light TrailBoss loads.

Can anyone comment on early opening issues with straight blowback actions? Do I figure correctly that a heavy bullet combined with a slower powder is going to have the worst potential for causing it? Or are load specifics insignificant compared to having the "correct" bolt (and buffer) mass?

[Baltimoreed]

Have a couple .45 Olympic pccs that are of course blowback and 2 cmmg rotary bolts. I’ve used the same reloads in both but with different shaped bullets. The Olympic will eat anything but not the cmmg. Plus I had to get Midway Stoner uppers with bigger ejection ports for the rotary bolts. My first 45 pcc build was damaged because of not having a heavy enough buffer. I’ve played with the buffer springs and extra springs trying to mitigate the forward buffer motion, tinkered with them a bunch years ago. Good luck on your build.

[Cast10]

I shoot a 10mm 16” carbine that’s a blowback action. Blowbacks usually have a massive bolt/spring combo, thus requiring a pretty good load to ‘blow it back fully without malfunction.’ Mine is a MechTech and the bolt is very heavy. It handles the 10mm fine, as well I’m sure, all the calibers supported, included 45ACP on a 1911. Pertaining to plinking rounds, I’m not so sure a light load in a 1911 would fully function in a carbine, unless the bolt is similar in size/weight as the 1911 slide/barrel, etc. Just my .02.

[bimus]

I found out that a 45 ACP in a UZI needs a +P load to push the heavy bolt Alliant has information on line using BE-86 powder . I started with a low charge of powder and worked up to 7.5 grains with a LEE 200 grain cast bullet .

[barnetmill]

Wow, thanks for all the replies, folks! Great info here, it will take me some time to digest.

The TNW ASR in 45ACP has exactly the same parts as the version they make for 460 Rowland (well, everything except for the barrel). It can handle hot stuff. And, it's been surprisingly happy with light TrailBoss loads.

Can anyone comment on early opening issues with straight blowback actions? Do I figure correctly that a heavy bullet combined with a slower powder is going to have the worst potential for causing it? Or are load specifics insignificant compared to having the "correct" bolt (and buffer) mass?
That is a most complicated question and I know I can not answer it and probably most of the forum members can not. The degree to which the shell casing gripes the chamber wall upon expansion will impact rate of bolt opening in a blow back and also most other semi-autos. I have no idea about how a slow power, say a slow rifle powder will behave in the scenario that you suggest relative to a pressure curve in the chamber.

[Kosh75287]

I agree with recommending against "hot-rodding" the .45 ACP in a straight blow-back action. If you have a locking system of some sort (more than a roller delayed blowback), then you have the potential to "up the performance" A LITTLE.
The loading data below are out of Hodgdon's online site, or Modern Reloading 2nd edition by Richard Lee, which is nothing more than a compilation of load data from other manuals. I recognize the data as being from one of Speer's loading manuals when they listed loads for their 260 gr. JHP in .45 ACP. Of course, use this or any other data at your own risk, and with your best judgement.
1.) TYPICAL .45 ACP: If memory serves, the original load for .45 ACP was 5.0/Bullseye/230 gr. FMJRN. I'd THINK that it'd be safe to use in your carbine. Given its rapid burn rate, it MAY give you lower velocities in a longer barrel (friction) than from a pistol barrel.
Slower-burning propellants (Unique, Herco) might give you greater velocity, but I've never chronographed .45 ACP reloads from a carbine. Anything's possible.
5.1-5.6/Universal/230 FMJFP is what Hodgdon lists. There's a load for TB, but it's pretty anemic. Hodgdon lists NO data for Universal nor TB using 250(ish) grain bullets.

For 255(ish) grain bullets, the following data is available:
4.3-4.5/Bullseye/260 gr. JHP ~725 f/s
5.1-5.6/Unique/260 gr. JHP ~760 f/s
5.6-5.9/Herco/260 gr. JHP ~740 f/s
8.1-8.3/Blue Dot/260 gr. JHP ~790 f/s

PERSONALLY, I'D start at 10% under maximum and stop when you get reliable feeding and ejection, or perhaps increase by 0.1 gr. over that, for when actions get gritted up and dirty. I would also use the 250 gr RNFP by Lee, as the heavy projectile. Feeds better than LSWCs, etc.
A .45 ACP case loaded with a near-max charge of Blue Dot and a 250 gr. HiTek coated RNFP MIGHT get you into the 900 f/s range with your carbine. I don't know what it will do in terms of premature bolt travel, nor what kind of noise it might produce, but I'll bet it'd drop small deer out to 50 yards.

Okay, end of dissertation...

[M-Tecs]

The TNW ASR is chambered in the 460 Rowland and the 357 Sig. Both of those are 40,000 PSI. The 10mm that it is chambered in is a 37,000 PSI. Standard 45 ACP is 21,000 PSI and +P is 23,000 PSI.

On my Mech Tec carbine I ordered the 45 Super version so I am good to 28,000K.

[Bmi48219]

…Can anyone comment on early opening issues with straight blowback actions? Do I figure correctly that a heavy bullet combined with a slower powder is going to have the worst potential for causing it? Or are load specifics insignificant compared to having the "correct" bolt (and buffer) mass?

A blowback action relies on the inertia of a bolt’s (or slide’s) mass to delay opening until propellant gas has exited the barrel. Chamber grip of the shell case helps a little but even a ring grooved chamber (look up the Kimball 30) is insufficient for higher power cartridges. Chamber pressure of 45 acp ball ammo is around 20,000 psi. Muzzle energy is 350 ft lbs.
‘For every action there is an equal and opposite reaction’. If a recoil spring were to help delay the bolt’s first 1/16 inch of rearward movement it would have to be one heck of a strong spring. Since you can compress most recoil springs a half inch with your little finger they aren’t doing much to delay early opening. It will slow the bolt more as it compresses but not at first.
In my opinion a fast burning powder & heavy bullet will produce high chamber pressure faster and would be more likely to overcome the bolt’s inertia faster, all other conditions being equal.

[alpining]

Sorry for the delay folks, I haven't had much time to look into this lately.

Thanks very much for all the helpful info. This mostly confirms my poorly educated understanding about what's going on with straight blowback actions. There's really no effect that the action spring has on opening, it's all about the reciprocating mass. Since this ASR carbine is the same as the 460 Rowland version (just a different barrel), it's capable of handling some stout loads. I don't need to get every last bit of energy out of it, I'm happy with "soft" 45 Super performance at the high end.

The surprising thing to me is that my unmodified carbine also cycles softball TrailBoss loads so well (255gr LSWC with 3.6gr TrailBoss at about 730fps). These are nice and quiet, though I'm sure it helps that I have an 18.75" barrel on mine (standard length for us here in Canada).

[alpining]

...In my opinion a fast burning powder & heavy bullet will produce high chamber pressure faster and would be more likely to overcome the bolt’s inertia faster, all other conditions being equal.

I see your point. Do you think the bullet's dwell time in the barrel is a factor?

[Cast10]

It was already stated and should be well heeded; Carbine barrel may/will be a tighter chamber than that of a pistol. Adjust accordingly.

[sse]

I have not tried to hot rod my AR-45, but I did have to do a lot of work to find what shot most accurately.
What my ar liked was a Lee 200 gr loaded out just a tad longer than what will work in a 1911. Group size at 50 yds dropped by 30-50%

[243winxb]

Worry more about, if the action is fully closed, before pulling the trigger.

The 10 + grs Blue Dot load with 200 gr lswc is a hot one, for any 45acp.