Slow powders in a CX4 Carbine.

[Mr_Rogers]

I am being careful guys so please have patience. I have plenty of experience loading bolt-gun rounds but I am new to reloading for blow-back actions so I would appreciate some help.

I am trying to work out a load for my Beretta CX4 40S&W carbine using Hornady 200grain XTP bullets. I cannot find any load data in the usual places. The best starting point I could find is in Handloads.com where a max. pistol load of 8.5 grains of 2400 is mentioned. This load is supposed to produce 925fps at 33,600psi in a pistol. I chronographed this load at an average of 850 fps out of the carbine.

Now, being used to using a combination of chronograph data, primer condition and extraction feel to judge pressure in a bolt-gun I am lost.

1. The chronograph data seems to be seriously off. Any comments please?
2. Is the primer condition of any value in a blow-back action, since there is not the solid surface of the bolt face found in a bolt-gun, for the primer to push against?
3. Extraction effort, short of tearing the cartridge rim off, seems to be of no help.
4. Can I do serious damage to the buffer mechanism or any other part of the carbine by experimenting with heavier loads?
5. Just how do you judge max. load on a blow-back action?

As you can see I am in new territory. I am sure you have worked out by now, I am trying to use the extra length of the carbine barrel to gain extra energy by using a larger charge of a slower burning powder.

Thanks for your advice.

[45ACPUSER]

First of all, a lot or reloading data comes from a universal receiver, vs and an actual firearm. Plus sometimes you really do not gain that much velocity with a carbine length bbl.

The best source of data is consulting the Hornady manual. Thier bullet so best source of data.

The online data does not list 200gr bullet in their data. Nor does it list the bbl length.

Me thinks you ought to consult a Hornady manual for the best source!

[Walkalong]

Speer also uses a lot of real firearms for testing in their manuals.

A pressure barrel gives no real test of velocities in real guns. Even two just alike guns can give different velocities.

[zxcvbob]

What's your overall cartridge length? You shouldn't be able to get that much powder in there unless you are going way over 1.135".

The long barrel (what is it, 16 inches?) is eating you up because of friction. You might want to try 180 grain cast bullets with it -- less friction, and more room for powder. HTH

[Mr_Rogers]

Thanks for the replies.

zxcvbob: The 1.134 OAL I get just puts slight compression on the powder - no more than results from tamping it down with a 9mm case to measure the available depth.

45ACPUSER:

The online data does not list 200gr bullet in their data. Nor does it list the bbl length.

That's just the problem. I did a pretty thorough internet search and I can't find data for the 200 grain 40 in a carbine barrel.

We know the 9mm only gains a little from the carbine barrel - my suspicion is that the 40 should do a bit better. Nobody seems to have published any test results. Now, since there is an entry for this bullet and powder on Handloader.com apparently somebody performed this test in a pistol. It would seem to make sense that there would be a slight performance gain in a carbine - I got a reduction in performance.

What about this theory - bearing in mind I am new to reloading for blow-back actions. What if 2400 burns so slowly that the blow-back starts while the powder is still burning and the combustion is not complete by the time the cartridge case starts to extract?

[45ACPUSER]

The source of the data on handloader.com com says ALLIANT! So, it was not an individual. There are a lot entries with data source that say Winchester and Alliant.

Again, you really are over estimating things. Till you chrono your loads you are pissing in the wind! Each bbl is a rule unto itself.

Short story. I have custom 308. It is has 22in bbl. The gun will shoot BHA match 308 at the same velocity as the factory bbl did with 26in. So, like I said each bbl is a rule unto it self. The 40SW operates at the same pressures as does the 9mm, so some things are sort of self limiting.

SAAMI Specs
HANDGUN PSI
17 Rem - 52,000 CUP
22 RF Short - 21,000
22 RF Long & LR - 24,000
22WRF - 19,000
22WRM - 24,000
25 Auto - 25,000
32 S&W Long - 15,000
380 Auto - 21,500
9mm Luger - 35,000
9mm Luger +P - 38,500
38 S&W - 14,500
38 Auto - 26,500
38 Special - 17,000
38 Special +P - 18,500
38 Super Auto +P - 36,500
357 Sig - 40,000
357 Magnum - 35,000
357 Remington Max- 40,000
40 S&W - 35,000
10mm Auto - 37,500
41 AE - 35,000
41 Remington Mag - 35,000
44 Special - 15,500
44 Remington Mag - 36,000
45 Auto - 21,000
45 Auto + P - 23,000
45 Long Colt - 14,000
45 Win Mag - 40,000
454 Casull - 65,000
480 Ruger - 48,000
50 AE - 36,000

[jibjab]

What if 2400 burns so slowly that the blow-back starts while the powder is still burning and the combustion is not complete by the time the cartridge case starts to extract?

That has been my experience in a Marlin Camp 45. any powder slower than Unique or AA#5 can be a challenge.

Can I do serious damage to the buffer mechanism or any other part of the carbine by experimenting with heavier loads?

I toasted a buffer in the camp 45, I replaced it and installed a stiffer recoil spring.

Just how do you judge max. load on a blow-back action?

Split cases and vanishing head stamps are a tell tail sign.
Sorry my situation is different from yours, but perhaps my experiences will be of some use.

[45ACPUSER]

Simply put use regular reloading data from reliable source. Trying to make a Corvette out of a Malibu is not going to happen! Why beat a gun up?

[fast_rope71]

200 grain bullets in .40 are for the 10MM auto. 180 is the usual maximum for the .40s&w.

I would recommend going to a much lighter bullet. using a 155 or 165 gr bullet will allow for a much bulkier powder charge which may give a longer burn time in the barrel.

Since the end results will be withing the specifications set out for the round, there should be no issues with the buffer being harmed or any other parts.

Most of our problems in reloading come from either lack of attention to detail, or exploring new territory.

[Mr_Rogers]

Thanks for the constructive comments Jibjab.

I appreciate your humorous comments about how to recognize overpressure but I would prefer to stop at more subtle indications.

Information from an informed source suggests that only little more than half of a charge of 2400 will burn in a carbine length barrel behind a 200 grain bullet under ideal circumstances. Take into account the loss of pressure in a blow-back action and I think I see why my chronograph readings did not match those of Alliant (ref 45ACPUSER). You are actually losing pressure at both ends of the barrel. At one end you have unburned powder, at the other end you have a pressure leak during case extraction. The Alliant figures appear to be very optimistic as regards both burning efficiency and case capacity. They were probably gained in a test barrel.

Considering new data that I have received it certainly seems that your guess that Unique may be the slowest powder to use effectively in blow-back actions with heavy bullets is correct. Other powders give slightly higher performance but with less efficiency.

Thanks B.

Thank you all for your advice. Between you my original question has been answered.

[zxcvbob]

You might also wanna try WSF powder. It's just a little slower than Unique (closer to Herco) but you can fit more in the case than Herco. I don't have data for it, but think Hodgdon's web site does.

[jibjab]

Unique may be the slowest powder to use effectively in blow-back actions with heavy bullets

I have used Blue Dot with 230gr in the Camp 45 with ok results, but heavy bullets don't shoot any faster from the 16" barrel than from my 5" 1911 however with the 185gr and Unique I can get around 1,250 fps from the Camp 45.

[Poppy Aston]

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