Sub-Sonic Loads in Argentine Hi Power

[MoscowMike]

I have ordered a suppressor for my FM (Argentine) Hi Power. In prep I bought a threaded barrel from Brownells and have started working up 9mm sub sonic loads. The pistol is scarcely used, and has worked fine with various 115, 124 and 147 gr loads.

The Brownells barrel dropped right in and worked reasonably well with 115 gr factory loads. With heavier bullets I have had problems. 124 gr RMR TCFN and 4.4 gr HP-38 or 147 gr RMR TCFN 3.6 gr HP-38 seem to not move the slide back enough to reliably pick up the next round so I have stovepipes, FTE and FTF problems.

Brownells suggested the barrel needed breaking in, and it had a fairly rough finish. I polished the chamber, used a buffing wheel and Dremel rubber polishing tips to slick everything up as well as thoroughly oiled contact points.

Seems to feed the 115 gr a bit more smoothly, but has the same problems with 124 or 147 grain. The bullets feed fine, but don’t eject reliably. Those are close to maximum loads with HP-38 according to some sources.

I have a spare Hi Power spring. It seems to be a bit stiffer than the factory spring that came with the Hi Power. Seems to me my next step is to start trimming it down a bit at a time.

Any other ideas?

 

[Frankl03]

Try running just round nose bullets until the new barrel is broken in. That may help. I have had no experience with this firearm.

 

[MoscowMike]

I'm a bit low on primers to reload that much 9mm but it could be fun.

 

[Sgt. Stiglitz]

https://lonestarstatefirearms.com/surplus-fn-browning-hi-powers-mystery-box/

 

[JohnKSa]

If it won't work without the suppressor attached, I can't imagine that adding the suppressor will improve performance...

In your position, I would start looking for another suppressor host.

 

[BBBBill]

I have a spare Hi Power spring. It seems to be a bit stiffer than the factory spring that came with the Hi Power. Seems to me my next step is to start trimming it down a bit at a time.

Any other ideas?

Cutting springs is a crap shoot. Much better to purchace an assortment of lighter springs from Wolff. Does your suppressor have a Neilsen device (recoil booster)? Pretty much necessary with Browning pattern tilting barrel guns.

 

[MoscowMike]

In your position, I would start looking for another suppressor host.

Silencerco says the Hi Power can be suppressed. The Osprey does have a Nielson device. You just need to use the correct piston for that thin barrel. Ospreys are on backorder at this point and we can’t start the paperwork until it has been delivered and a serial number available, so I have time to figure out why this barrel behaves differently than the original one.

Cutting springs is a crap shoot. Much better to purchace an assortment of lighter springs from Wolff. Does your suppressor have a Neilsen device

An assortment of springs is not a bad idea. Hopefully I can find a solution so this works with both lighter and heavier projectiles.

 

[gwpercle]

It would be great if semi-auto's would function with all bullet weights and both sonic and subsonic velocities ... but truth is they don't . My advice , after polishing and breaking in is to select a load then keep swapping springs untill you get 100% functioning . Keep that spring in the gun and use that one load .
This is what I did with a 45 acp , target load was 200 gr. cast SWC and 4.2 grs. Bullseye and the lightest Wolff Spring that came in a 1911 spring kit ... it gave 100% functioning with the light load .
It was "The Load" for that 1911 with that spring installed .
Just pick one , load and spring , and stick to it .
Gary

 

[JohnKSa]

Silencerco says the Hi Power can be suppressed. The Osprey does have a Nielson device. You just need to use the correct piston for that thin barrel. Ospreys are on backorder at this point and we can’t start the paperwork until it has been delivered and a serial number available, so I have time to figure out why this barrel behaves differently than the original one.

I'm sure that there are reliable suppressed Hi Powers out there. I'm just saying that if you are having trouble getting standard loads to work in the threaded barrel, there's no way that function will improve when you add a suppressor--it's going to be worse when you hang that extra weight off the barrel, Nielsen device or not.

 

[BBBBill]

The Osprey does have a Nielson device. You just need to use the correct piston for that thin barrel.

Neilsen device = piston/spring/bushing assembly installed on rear of suppressor.

 

[MoscowMike]

My advice , after polishing and breaking in is to select a load then keep swapping springs untill you get 100% functioning . Keep that spring in the gun and use that one load .

That makes a fair bit of sense. It still intrigues me that the new threaded barrel has problems with loads that work in the factory barrel, but sometimes machinery is perverse. So far nobody has suggested that the loads I am using are on the weak side.

Assuming I find a combination that works, I may have to tweak it when the suppressor finally shows up, but I'll deal with that in (hopefully) a few months.

 

[MachIVshooter]

I'm sure that there are reliable suppressed Hi Powers out there. I'm just saying that if you are having trouble getting standard loads to work in the threaded barrel, there's no way that function will improve when you add a suppressor--it's going to be worse when you hang that extra weight off the barrel, Nielsen device or not.

John is correct. A recoil operated handgun that is unreliable without a can is only going to be worse with it. Booster assemblies (Nielsen devices, LIDs) momentarily decouple most of the weight on one axis, but the can will still be pulling down on the barrel causing it to drag the underside of the slide, and the extra mass is 100% there during return to battery.

That said, there's no reason a Hi Power can't be a good host. You just might have a bad barrel.

Try Fiocchi 158 gr subsonic. I've never found a 9mm host that wouldn't run that ammo.

 

[MoscowMike]

A recoil operated handgun that is unreliable without a can is only going to be worse with it.

I’m sure you are right, that’s one reason I am trying to get started on this rather than waiting until sometime next year when the paperwork has (hopefully) processed. The Brownell’s threaded barrel is accurate, and seems to work fine with lighter bullets, so I would be surprised if it was a ‘bad barrel’. Perhaps it’s a matter of finding where it’s rubbing or what’s the correct weight spring for that combination. I'll see if I can find some Fiocchi 158 subsonics, but the slide is off to Novaks now.

 

[MoscowMike]

Try Fiocchi 158 gr subsonic. I've never found a 9mm host that wouldn't run that ammo.

Got the slide back from Novaks, and really like the new sights. Also found some Fiocchi 158 subsonics, so I slogged my way out to the range today.
Strangely enough, I was the only one there, but I was too lazy to hack through the snow to set up targets and just plinked at snowballs.
The Fiocchi worked fine, fed and extracted well, locked the slide back on the empty magazine. Thanks for the suggestion. Like before, my 124 grain reloads also worked, but did not lock the slide back. Federal 115 grain worked fine.
Interestingly, the Fiocchi subsonics had significantly more recoil and sent the cases about 8’ where the others dropped them much closer.
I’m happy to have found a subsonic round that works, now we’ll have to see if I can find a successful load for the 147 grain. Perhaps a slower powder than HP-38 or a lighter spring.
Anyhow, I’m happy. The next thing is to check with Silencer Shop for updates on when the suppressor is available.

 

[MoscowMike]

Update on loads. Thinking a slower powder might work better than the HP-38 with 147 gr bullets, I loaded some with 5.6, 5.7 and 5.8 grains of Blue Dot. 5.6 had one stovepipe, 5.7 and 5.8 ran fine. Felt a bit more recoil than 3.6 gr of HP-38. In the Speer book 5.8 is a maximum load, but the primers aren’t flattened. Unfortunately Blue Dot doesn’t seem to meter well in my Ohaus Duo Measure, but it’s nice to have found a load that works with the threaded barrel as well as the Fiocchi 158s.
Might have to look into other options now that powder is becoming more available.

 

[wolf695]

Mike, had one of those once! I wish I still did, they were made to get beat. Most subsonic rounds were made for wheel guns, but hand loaded ones by a good smith will help solve your cycling problem.