.458 frustrations

[Dean2]

Most of the subsonic loads I've seen for the 458 are with 500gr to 600 gr bullets. I suspect those heavy bullet loads would have enough pressure to cycle the action and still be be subsonic before your modifications. I think trailboss would be a better powder, unique is a pretty quick burner.

Trail Boss on the Burn rate chart is actually a significantly faster burning powder than Unique, 23 vs 41. I don't think the burn rate is the actual issue, it is the amount of gas produced/volume of powder and there TB produces significantly more gas volume because it was designed as basically a Black Powder substitute for heavier weight bullets. Ten grains of Unique occupies about 20% of the volume 10 grains of TB will use. Also, TB throws great and accurate from powder throwers so makes high volume loading very easy.

 

[John Klingenberg]

You can't put enough trail boss in the case to make it cycle. H110 or 4227 is a good powder for the 300, 450 and 458 subs. As others stated a gas block may fix the issue but you'll likely have to drill the port anyway as youre already using a full open port with a standard gas block. Also with a carbine length gas you'll have to be in a precise niche to get subs and supers to work and itll never be totally reliable because as it gets dirty the parameters change. Also consider that you're getting back pressure from your can which is never the same every time. If it's not working or barely working then it'll never work with the can off. Asking for everything is tough. Cutting springs wont do it. Changing your buffer weights is a better less permanent option.

 

[mtwarych]

This loading data does nothing for the OP. I'm sorry to mess up the thread but I can't figure out how to delete my post.

After looking around the web for a while, IMR4227 and H4895 appear in a lot of sub-sonic loads for the 458 Socom.

https://load-data.nosler.com/load-data/458-SOCOM/

 

[mtwarych]

Yup, it's me again.

https://forum.snipershide.com/threads/458-socom-sub-sonic.95110/

Take a look and maybe the OP can contact the guy and hash some stuff out.

Good luck OP.

 

[nbowlin]

I pulled the o'ring on the ejector and left the duties to the spring alone along with running an empty buffer and 8 loops trimmed out of the spring. Started cycling. I had a spare buffer spring so I wasn't sad sacrificing it. Only to learn that the stupid Docter red dot won't hold a zero on the rifle. Trying to run that so I can run a pvs14 in front of it with out the effect of looking down a culvert pipe for a field of view. It's pretty slick if it would have worked.
So obviously once one annoyance is conquered another must appear.

 

[mdvctry]

I have a .458 SOCOM 1-14 twist Assembled from Wilson Combat parts with a Carbine gas system. It has an adjustable gas block and I shoot supersonic and subsonic with a suppressor without any problems. I use starline brass and H110, Lil Gun, HS-6 and IMR 4198 powders using load data from several sources. As others have mentioned, I would get an adjustable gas block, make sure you have a spring and buffer designed for the .458 SOCOM.

Make sure you use the proper Extra Power Action spring, some manufacturers send a regular AR-15 with your kit. Make sure you use the proper Extra Power Action spring shipped with your kit. When adjusting your gas block ensure that you have enough gas for proper function. Test your gas block by adjusting your flow to allow lock back on an empty magazine. If your gun locks back on an empty magazine after 3 single-loaded shots it is reliably locking back. When adjusting your gas block ensure that you have enough gas for proper function. Test your gas block by adjusting your flow to allow lock back on an empty magazine. If your gun locks back on an empty magazine after 3 single-loaded shots it is reliably locking back.

 

[Dirtrax]

An adjustable gas block will only limit gas. That isn't you problem. Heavy bullets "may" help. What buffer are you using? Sometimes removing the weight can help, but you're gonna need a new spring regardless. Maybe a low mass bcg?

 

[ntsqd]

With his combo as mixed up as it is there's no telling what is and isn't the problem.

From a qwik read of the Spinco site I'd start with their Red buffer spring and an AGB. Run the AGB closed off and slowly open it until you get reliable function with either commercial ammo or ammo loaded to a book recipe. Get it running reliably before messing around with different powders etc.

 

[freddiej]

I have a 16" .458 socom. I have a thing on the end to help with noise. I ordered some 400gr sbr subsonic and it's supersonic. I ordered some black butterfly 500gr subsonic and it's supersonic. I ordered dies and bought some cheap Speer 400gr spfl stuff for the sake of science. Started at 11.5gr of unique and large pistol primers. Went backwards to 10.7 and got that air compressor nozzle being depressed noise I was looking for. Loaded some more to work on getting the thing to cycle. Well the first 3 were air compressor sounding. I am cutting down the buffer spring between firings. Then there for after back to super sonic. I went all the way down to 9.5 from 10.7 and never got back to sub sonic.
Nor does it cycle but that's another aggravation.
How can this be a thing?

OMG! okay. here is the first suggestion from a gunsmith that builds the 458 SOCOM on a semi-regular basis. Use Accurate Arms 1860. AA-1680 is the only powder I use in my own 458 SOCOM. The gas volume and pressures will make everything function very well. Second use a standard carbine buffer and spring (best I have ever found are Brownell's carbine buffer springs and Spikes Tactical TR-2 buffers). I have bought the JP Enterprises silent tune-able buffer and spring kits and had wonderful results with Sub Sonic along with super sonic ammo. Third suggestion; never cut springs, never take weights out of the buffer. this messes up dwell timing of the whole gun's gas system. Last, Suppression devices slow your pressure bleed off to your gas system. This means the pressure at your gas tap stays high longer so it should add reliability to your gun. the very minimum pressure you need at the gas tap is 16,800 PSI. the best is to have 17,400 PSI at your gas tap. now you need a decent amount of volume as well. Opening your gas tap will help if you are not cycling well. If that does not take care of the problem then putting 0.4-0.6 grains more powder in is the solution.

 

[nbowlin]

So
Back to factory spring, buffer weights etc... checked gas block to port alignment, blockage and such. Also swapped my attachment to a Bauer's 458 can. Loaded up at 1/2 gr increments to the point it went super sonic with both bullseye and unique. Going to have to find other powders I guess. Rifle would fire but would not consistently eject with out stove piping at 1/2 grain under super sonic.
Doesn't cycle proper and the first supersonic load either.

The gas tube is 8" up the barrel as well.

Called the Tromix place To see if they have a spring and buffer or something of a fix I can get from them but they must be busy as no answer.

 

[jfloyd]

You have to change powders for sure. Who's parts are you using for the upper, barrel and bolt? I suspect you went cheap and are paying the price now. I don't see where you have given any manufacturer information up to this point so I am only assuming. A 16" barrel should run a carbine length tube. It will run with a mid length but will severely limit you powder choices. If the bolt has an o-ring under the extractor REMOVE IT. If you do not have a Tromix extractor and you are using someone else's parts like Radical. GET ONE FROM TROMIX! Once again, there were a bunch of people jumping on the big bore bandwagon that did not know what they were doing. Even Wilson Combat screwed up their first barrel extensions. Between the powder choice and unknown expertise from the manufacturer side, you are in a money and time wasting battle you will not likely win. PM me if would like to chat or if you can't get Tony. I would truly like to help you get it running properly.