Gas blowing back Remington 510

On a single shot, the only thing is the bolt sealing the rear of the chamber.
have you checked the headspace on the bolt, or the chamber can be severly worn if you are not puncturing the case.
I believe your bolt handle sets you headspace as far forward as the bolt will allow, and is the bolt stop

You can determine if the problem is excess headspace simply by holding the bolt handle forward while firing the gun. (Wear a glove if it stings a bit.) Wrap a clean sheet of paper around the action to see if that stops the gas escape.

I suspect, though, that thousands of rounds have eroded the chamber and the leade so that gas is coming back around the case. You can check the fired cases to see if they have carbon smudges on them. If so, you might be able to have the barrel set back and rechambered, but if the chamber area is bad, chances are the rest of the barrel is just plain worn out. For that, there is no real solution, other than a new barrel, which might be hard to come by.

Maybe it is time to retire that old timer and look for a better .22, new or used.

Jim

Actually the headspace is pretty easily adjusted on these rifles with shims in the bolt. Go to the Rimfire Central website and go to Remington. Do a search for headspace on 510 Remingtons. There may be a sticky at the top of the section covering it.

Yes, if that is all that is wrong. But in my experience by the time there is enough receiver wear to create excess headspace, the barrel will be about shot out.

Jim

@ Oklahoma Caveman
I too like the old single shot 22'S
I just picked up a Winchester 67A and fixed the extractor, and refinished the stock.
It is ready for me to do the bluing.
The Barrel was like new inside, but the outside was pretty rough.
It was probably some kids gun.

The Brownells 22 liners are a fairly economical way to repair these old rifles. Most smiths will install one for $150 or less.

Yes, a barrel liner is a good solution, though possibly at a cost greater than the gun is worth. My bad for not mentioning that option.

Jim

Something worthy of note for the future.
Most worn out .22 rimfire barrels / chambers are not worn out by firing, but rather by cleaning. The bullets are soft lead with lots of lubricant on them, the cleaning rods are usually aluminum with nice hard aluminum oxide on the outside of them. Cleaning without a bore guide will certainly wear the chamber mouth or the muzzle crown.
.22 rimfire rifle bores should be cleaned rarely and very carefully using a bore guide or a bore snake & never with a jointed aluminum cleaning rod.

Roger