9mm Carbine Loads

[Lee Q. Loader]

I took a trip out to the desert today and I really got my new Ruger PCC 9mm dialed in.
I was consistently hitting soda cans at about 65 yards with the stock sights. On the target I shot about a 4 inch group at the same distance. I'm sure I could tighten that up with an optic of some sort. I was very pleased with my load: 5.7 grains of BE-86 with a RMR 124 JHP MPR seated to 1.08". I love those bullets and I just received 2000 more last week.

After shooting one magazine of 17 rds, I went to find the brass. It was scattered about 12feet away between 2 and 3 o'clock. The primers all looked good but the brass was filthy! One side of every case was almost black with soot and the other side was dirty but not as bad.

Previous trips to the range with 5.5 and 5.6 grains of BE-86 I noticed the brass was a bit dirty but I really didn't pay that much attention to it. Maybe I noticed it more today because I was outside in full sunlight instead of indoor range.

I've seen cases come out like this before but only on very mild loads. My load is near max and should seal the chamber. Is it because of the blowback design of the carbine?
As I said I really like the accuracy of the load.
Sorry for the long story, I would appreciate any comments or thoughts about any of the above.
Thanks,
David

 

[egd]

I have a Colt 6951 and mine does the same thing. I use WSF powder though. I think it is mostly the result of the blowback design, but I'd also like to hear what others say.

 

[LiveLife]

One side of every case was almost black with soot and the other side was dirty but not as bad.

I've seen cases come out like this before but only on very mild loads. My load is near max and should seal the chamber. Is it because of the blowback design of the carbine?

Yes.

In locked breech barrel design (most semi-auto pistols like 1911, Glocks, etc.), barrel is locked to breech wall/slide with barrel lug(s) and when primer ignites the powder charge, case base pushes against the breech wall while case mouth/neck expands to seal with the chamber wall.

In blowback fixed barrel design (many 380 and smaller caliber pistols like Walther, Makarov, etc. and blowback carbines), breech wall is held to barrel with force from recoil spring. When primer ignites the powder charge, case base will immediately push back on the breech wall and how long case mouth/neck stay in contact with chamber wall before moving away (and leaking gas/soot around case) depends on the weight/mass of slide/bolt/buffer and recoil spring tension (Reason why Hi-Point pistols have hefty slide).

To reduce soot on case, try using longest working OAL/COL that brings bearing surface of bullet (part that rides the rifling) closer to start of rifling, sufficient neck tension that resists bullet setback during feeding from magazine, least amount of taper crimp that does not reduce the bullet diameter and brings case mouth closer to chamber wall (I usually add .022" to bullet diameter for taper crimp), longer resized case length that brings case mouth closer to smaller taper of chamber, faster burning and high enough powder charge, etc. that all contribute to case mouth/neck sealing faster with chamber wall to reduce gas leakage which reduces soot on outside of case.

My load is near max and should seal the chamber

If trying my suggestions above to modify your rounds does not reduce soot on case, you could try higher powder charge towards published max charge (unless you are using shorter than published OAL).

With blowback carbines, even with optimized bullet diameter to barrel groove diameter, faster powder and sufficient powder charge, you are still going to get some soot on case. With faster burning W231/HP-38/Sport Pistol and Promo (Red Dot burn rate) pushed to near max , I get cleaner cases but they still have some soot on them.

at about 65 yards with the stock sights ... I shot about a 4 inch group

I got these groups at 50/100 yards using W231/HP-38 and Promo with 100 gr plated bullets. Since lighter faster bullets drop less vertically, if you are shooting longer distances, consider trying lighter bullets like RMR 95 gr FMJ - https://www.rmrbullets.com/shop/rmr-in-house/380-95-gr-rmr-fmj-round-nose-bullets-new/

 

[Walkalong]

I have a Colt 6951 and mine does the same thing. I use WSF powder though. I think it is mostly the result of the blowback design, but I'd also like to hear what others say.

It is definitely from the blowback action. A fast powder loaded to max pressure will leave cases the cleanest, not that it is important. Every 9MM load I have leaves the brass dirtier in my 9MM AR than it does in locked breech pistols.

 

[Ironicaintit]

I have a 9mm Unique load that runs clean in the BHP and other locked breeches, but the same load in the Sterling carbine will have soot on the cases.
its just the nature of the beast, and I don't worry about it.

 

[Lee Q. Loader]

I'm grateful for the responses. I personally don't know anyone who is a reloader so finding this site has been great.
I'm happy to know that there isn't a problem with my load. On top of how well I shot it, it just felt right in the carbine. Not sure how to explain that.

BDS, I'm already at max OAL for my carbine. The chamber seems very short as I've mentioned before, but I'll try your other suggestions.

Thanks again! Now I can continue to shoot this load with confidence.

 

[Dudedog]

I never worry about soot on the cases if the load shoots well.
Cases get cleaned before they are reloaded so no big dea.

Glad you are liking your new Ruger.
I may pick one up in in a couple months. (Christmas present to myself) at least for now they are not on CAs list of evil guns.

 

[kidneyboy]

Thanks bds for that explanation.

My PC9 does the same, filthy brass thrown off to the 2 or 3 o'clock area. Same bullet, same powder - RMR 124 JHP MPR/BE86. However I run mine at 1.120 OAL with 5.0gr of BE86. The first ladder I tried with this combo was 4.8 to 5.7gr at 1.120 and the 5.0 was far and away the most accurate. It wasn't till I ran a batch of the 5.0 that I noticed how dirty the cases were so I went back and redid the ladder from 5.0 to 5.6 with a slightly tighter crimp with the same results - the 5.0 was the most accurate and all the cases, regardless of charge, were dirty.
My brother also has a PC9 and we ran all these loads through his rifle as well as mine with the same results.
FWIW mine is at the gunsmith having some trigger work done. My only complaint about this rifle is the trigger which wasn't bad to start with.