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Posted: 6/29/2026 10:33:49 PM EDT
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So I bought a Ruger PC Carbine when they were first introduced. It's a great rifle for what it is - essentially a really heavy 10/22 chambered in 9mm. I've thought for years that I should get a PC Charger then SBR it and add a folding stock. It would make a decent (if still heavy) suppressed blowback package. And then I was developing some subsonic loads with some 147 HST bullets. For whatever reason, these seem to have a lot more drag than most other bullets. They do great in a pistol-length barrel, but really struggle in a 16" barrel. I should have taken note with some loads that produced 900+ fps. in a pistol were exiting the rifle at 750 fps. So then I switch to a different powder and come out another day to test them. The first shot doesn't register on the chronograph, and I figure it's a setup error. The next shot registers around 350 fps. I know that's not right. But the next shot is around the same velocity. Very strange. So I shoot a few rounds of some 124 gr. factory ammo and still get something under 400 fps. But then subsequent shots with the 124 gr. ammo are up over 1200 fps. It wasn't until later that I realized I had stuck that first bullet at around 15" down the 16" barrel. Each subsequent shot was compressing the air in the barrel between the bullets until it could just pop the plug out. What really gave it away was when ammo that used to shoot under 1" at 25 yards opened up to 3" or 4". It finally dawned on me what had happened. A tight patch and a cleaning rod confirmed it. There was a definite ring about an inch from the muzzle. It had swollen enough that I could not remove the thread protector, even using a pair of channel locks. The one thing I did right was to not test new loads with a silencer installed. The other good news was that the barrel appeared undamaged except for the very end. So I filed a Form 1 to SBR the gun. 81 days later I got the approval. I had subsequently sent the barrel out to be chopped & threaded. I decided to go with 10" so it would still work in the Backpacker stock with a silencer installed. And I confirmed today it shoots as well now as it did prior to my screw-up. So it's not as compact as a PC Carbine with a folder. But it's kind of growing on me.  |
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Originally Posted By chevrofreak: Man, what was your load data? I've loaded thousands of 147gr HST's and have never had them be slower out of a 16". That’s the interesting part. I was specifically looking for a hotter load for a rifle barrel. So the slower-burning pistol powders would be appropriate, being better suited to utilize that longer barrel for a more complete burn. I had initially used some WSF. Three different charge weights resulted in average velocities from a Glock 17 of 895, 929, and 929 fps. Those same loads in the 16” barrel produced 730, 809, and 870 fps. I then worked up a series of loads using Longshot, AA#7, and N350. I used Hodgdon’s online data for 9mm+P for the #7 & Longshot loads. The N350 was interesting. Viht has an online reference as well, but only for standard pressure loads. I also have a pamphlet published by Viht from the early 2000s. I see the starting load for a jacketed 147 gr. 9mm in that book is higher than the max load in their current online reference. I loaded using their max online charge of N350, and then a couple loads from the 2001 manual. My powder is of that vintage as well, so I’m not worried about any changes in formula causing the data change. I bulged the barrel in March, and am just now getting back to shooting the rest of the ammo, as I was waiting on the Form 1 and barrel chop. So I forget if it was the Longshot I fired first or the starting N350 load. I want to say it was the N350 that was the culprit. |
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Originally Posted By GarrettJ: That’s the interesting part. I was specifically looking for a hotter load for a rifle barrel. So the slower-burning pistol powders would be appropriate, being better suited to utilize that longer barrel for a more complete burn. I had initially used some WSF. Three different charge weights resulted in average velocities from a Glock 17 of 895, 929, and 929 fps. Those same loads in the 16” barrel produced 730, 809, and 870 fps. I then worked up a series of loads using Longshot, AA#7, and N350. I used Hodgdon’s online data for 9mm+P for the #7 & Longshot loads. The N350 was interesting. Viht has an online reference as well, but only for standard pressure loads. I also have a pamphlet published by Viht from the early 2000s. I see the starting load for a jacketed 147 gr. 9mm in that book is higher than the max load in their current online reference. I loaded using their max online charge of N350, and then a couple loads from the 2001 manual. My powder is of that vintage as well, so I’m not worried about any changes in formula causing the data change. I bulged the barrel in March, and am just now getting back to shooting the rest of the ammo, as I was waiting on the Form 1 and barrel chop. So I forget if it was the Longshot I fired first or the starting N350 load. I want to say it was the N350 that was the culprit. My go-to load for the 147gr HST is 5.1gr of N350 and I had issues with it going supersonic out of several of my PCC's  My velocity was 1057 FPS from a 5" barrel, and it is a slightly +P load according to the data I had at the time I was working the load up. The current data in their app seems to be far more conservative. 
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Originally Posted By USMC0352: Really like that and have thought about getting mine done just like that. Who did you use for the barrel work? I had sent the barrel to Chris Hipes in TX. He's done a number of barrels for me in the past. Message me and I'll send you his contact info. |
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