The max. time to leave Hoppe's #9 in the bore.


Ignition Override
October 30, 2013, 12:34 AM
A buddy who appears to always do everything exactly by the book (he was a pilot evaluator {Stan. Eval.} in the C-141) told me that 30 seconds is the max. time to leave it in the bore. He hunts, but my objective is basic plinking with the guns and to preserve Enfields or very nice Garands etc.

If only twenty rds. have been used since such a chemical was used, one could probably wait until dozens have gone through before using more Hoppes?

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October 30, 2013, 12:49 AM
Per the instructions, I have left the benchrest formula in the bore overnight....With ammonia in it, it has to be harsher than the regular stuff.

There is no need to clean after 20 rounds.

October 30, 2013, 02:25 AM
I've left the barrel of my XDm soaking in it for 24 hours in my SA XDm with no problem. My barrel was sparkling clean. It got the crud in the grooves out, too, which all my other cleaning doesn't get out. I've used it in a small bottle in my ultrasonic cleaner, but that didn't seem to improve the cleaning.

Willie Sutton
October 30, 2013, 06:07 AM
(he was a pilot evaluator {Stan. Eval.} in the C-141)

That says more to anyone in aviation than could be said using a full paragraph anywhere else... :barf:

USAF pilots "in general" don't tie their shoes without following the written procedures. Transport pilots don't put on shoes in the morning without being specifically ordered to do so (they were picked to fly transports out of UPT because they were the slow learners in the class, sorry to say...). Within that community the Staneval pilots are about the least likely people to think out of the box in any way, at any time, of any community of people I have ever met in my life. They do well right up until they meet something for which there is no published procedure, and then... all bets are off (this is based on being a pilot trainer and examiner in jets big and small myself). So if he finds a "rule" someplace, he's culturally inclined to follow it without thinking about it. Rules are rules, you know... :rolleyes:

With that said:

There's no magic 30 second rule, no matter what he says. It's...just...a...solvent.


(currently instructing in pointy-nose jets someplace out in the desert)

October 30, 2013, 07:20 AM
30 seconds or 30 minutes? It's impossible to clean a barrel in 30 seconds. 30 minutes is doable. IMHO, don't leave a solvent containing ammonia in the bore more than about an hour or even better, use a solvent that doesn't contain ammonia.

October 30, 2013, 12:36 PM
Which Hoppes 9 are you talking about?
If you performing normal cleaning on a well maintained bore there is no need to soak. If you are removing copper fouling you may have to soak the bore for extended periods multiple times to get it out.

October 30, 2013, 07:17 PM
If you mean standard Hoppe's #9, it can be left in a bore indefinitely.
Standard Hoppe's #9 has been around since 1903 and has a long reputation as being perfectly safe to leave in a bore for as long as you want.

A number of shooters I know left it in the bore during long term storage.
I knew several who'd clean their hunting gun bores and just leave a coat of Hoppe's in it until the season next year.
It protected the bore about as well as a thin layer of oil.

I've plugged really badly fouled rifle bores and filled the barrel with Hoppe's #9 and let them soak for as much as 2 days.

Use caution...READ THE BOTTLE LABEL of whatever bore solvent you have. Some more aggressive solvents warn not to leave it in barrels longer then 30 minutes.
Bore solvents work by a chemical reaction to remove copper and carbon fouling.
That takes time and you have to give the solvent as much time as the product will allow to do it's work.

You don't remove bore fouling by mechanical means. Brushing can be used to help the process along, but what gets the fouling out is soak time.

October 30, 2013, 10:16 PM
What dfariswheel said. I see there is a new No. 9 Synthetic Blend, Biodegradable / Non-flammable.

October 30, 2013, 10:50 PM
The max. time to leave Hoppe's #9 in the bore.Shirley, you jest!

See dfariswheel's post #7 for the correct answer!

Hoppe's #9 is a very very mild copper solvent, and it can be left in a gun forever if you want too without harm.

It will eventually turn brass case ammo green, but it positively will not harm the gun it is in if left forever.

Unless it is an air-rifle with a brass barrel liner.

I wouldn't do that!!


November 2, 2013, 10:29 PM
Depends on which Hoppes #9 your using. The original formula you can leave in forever. I didn't see the Hoppes #9 Bench rest formula mentioned. This has ammonia and shouldn't be left in for more than 30 minutes or so IIRC. Anything with ammonia shouldn't be left in the bore for long periods. It will attack the metal and cause "crazing"(microscopic cracks in the metal). Now if you have a sewer pipe or dark bore on a old milsurp a longer soak with a ammonia based cleaner probably won't hurt much compared to all the old jacket fouling it will remove on a initial cleaning. But you don't need it after shooting 20 rnds or so. Old saying: More guns have been ruined from over/improper cleaning than from shooting.

November 2, 2013, 11:54 PM
Depends on which Hoppes #9 your using. The original formula you can leave in forever. I didn't see the Hoppes #9 Bench rest formula mentioned. This has ammonia and shouldn't be left in for more than 30 minutes or so IIRC. .
I mentioned it earlier...It says right on the bottle you can leave it in overnight.

November 5, 2013, 02:18 PM
A couple of very wise people above are certainly correct on leaving Hoppe's #9 no prefix no suffix in the bore indefinitely.

I'm not so sure the implication that standard Hoppe's #9 no prefix no suffix as sold today is quite the same formula it once was is equally precisely correct. Just possibly past experience is no guarantee of future performance here too.

Seems to me that when I was young Hoppes #9 had a little benzene in it. The benzene was said to help in effect cracking - crazing as mentioned - copper deposits and made the original - and as described in Hatcher's Notebook including a perhaps guessed at perhaps known process for making larger quantities at home - more effective as a sole cleaner and preservative product than -IMHO current production is.

Though to repeat I do believe the current formula is as safe or safer than ever though also IMHO less effective - despite claims to be unchanged in a century. Current production is rumored to be more effective after multiple reformulations than the product immediately after the benzene was dropped with maybe no other changes.

Then too Hoppe's #9 once cautioned against corking the bore. There are some issues with mixed gun cleaners and whatever might be in the bore including combining say ammoniated cleaners with chlorinated solvents like the old spray brake cleaners/gun scrubber solvents.

November 5, 2013, 09:09 PM
Douglas makes some very good air guaged barrels and if you read their website the instructions say to leave solvent in the barrel after cleaning to soak the copper fouling between shooting sessions. I have been doing this with the original Hoppies #9 and the result is a cleaner barrel. I wouldn't do it with a solvent that I didn't trust.

November 6, 2013, 09:30 AM
I used to leave Hoppes in the barrel of my .264 overnight.


November 6, 2013, 01:17 PM
The only ingredient that is listed on my newest bottle of Hoppies #9 is kerosene. I think kerosene would cause light rust to form in a rifle bore over a long period of time but the copper removal would be more benificial than the possible damage from rust.

Willie Sutton
November 6, 2013, 06:20 PM

Why in the world would you think that Kerosine would cause rust?




November 6, 2013, 06:24 PM
15 years ago i got 1,000 rounds of Bulgarian steel case 308 ammo, advertised in ShotgunNews as corrosive, delivered for $100.

A few cases had corrosion on the outside.
I pulled down some cases and went through the corrosive primer test process.
The products of combustion from the primer actually PREVENTED corrosion compared to the control samples of steel.

What does it all mean?
I have seen Sweet's 7.62 etch steel, but I have never seen Hoppess #9 etch steel.

November 6, 2013, 08:02 PM
Willie, if you look at the characteristics of kerosene as listed in the Wikipedia website it says that kerosene is used as a rusting agent when testing metal. I also share your opinion and I think it would take a long time for light rust to occur on the type of steel used in a high quality rifle barrel.

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