Rifle cartridge adapter experience

[FSJeeper]

Finally got around to installing a 7.65 x 53 to 7.62 x 39 cartridge adapter in a 1981 Argentine Mauser.

This rifle is in excellent condition and shoots very well with handloads and a Lyman 48 peep sight.
Installed the adapter correctly, checked headspace which was spot on, and cycled the action with rounds to make sure everything functioning properly.

I went above and beyond the call of duty cleaning the chamber and used the lock tight which glues the adapter in correctly and in the right amount.

Rifle fired and functioned without any issue.

Accuracy went from 2.5" to over 8" at 100 yards. Totally unacceptable.

The insert came out on its own when extracting about the 20th round fired.

Bottom line, this method of changing to 7.62 x 39 is not viable.

I had bought a custom barrel to do this but wanted to see if the cartridge adapter would work. it did not. New 7.62 x 39 barrel will be going on soon.

I had had acceptable luck with 18" shotgun to rifle cartridge adapters with rifling. Also have a friend who had had decent experience with the pistol cartridge to rifle adapters.

Be wary of the glue in adapters.

 

[12Bravo20]

Even the red loctite will break loose after a while. Heat is how you remove something that has loctite on it.
I could be wrong, but the original 7.65x53 barrel twist rate of 1 in 11 being for heavier 170-180 gr bullets might not be fast enough for the lighter 7.62x39 bullets. If so, I can see where your accuracy went from 2.5 inches to 8 inches. Does the insert have any kind of rifling or is there a big jump/free bore before the bullet actually engages the barrel rifling?

 

[Varminterror]

The only conversion products I have used which seemed to work well have been full length sleeves. I have had 410 and .45-70 sleeves for SxS shotguns in the past, and for a reasonable expectation of moderate accuracy at best, they delivered.

The idea of a drop in chamber adapter is simply wrought with opportunity for disappointment. They've always been a niche product, and I have been saddened to see a lot of "preppers" recommending them around the Internet in recent years - folks who aren't marksmen and who don't understand basic marksmanship, but have a half million dollars in a bunker, ammo, and non-perishables and can sway blog reader opinions...

It's America, if someone will buy it, I won't knock a company for making money off of them.

 

[Art Eatman]

12Bravo20, generally, the lighter the bullet (shorter, actually) the slower the twist needed for stability.

Probably the most discussions for twist rate vs. stability involve the .223 in ARs. Note that as heavier bullets are considered, faster twist rates are called for.

 

[Varminterror]

I could be wrong, but the original 7.65x53 barrel twist rate of 1 in 11 being for heavier 170-180 gr bullets might not be fast enough for the lighter 7.62x39 bullets.

You do have this backwards. Lighter bullets don't need as much twist to stabilize, for a given velocity. Since the x39 runs about the same speed as the x53, maybe 100fps short, just with a lighter bullet. The x39 typically have a twist between 1:7.5" and 1:9.45", where the Argentine runs 1:11", but I wouldn't personally expect that much of a difference, having shot a 1:10" twist barrel ".308x39" in the past (used a US 30cal barrel in a single shot pistol, chambered for x39, so I used .308" bullets).

Guys use high temp epoxies for barrel and chamber sleeves & liners all of the time. It can be done. But it's probably a fools' errand to put a lot of effort into it.

 

[12Bravo20]

You do have this backwards.

I couldn't remember for sure if I had it correct or backwards (not enough coffee yet when I first replied)

 

[Scooter22]

I had a 7.62x39 from Ace Dube. I put it in a Spanish 1916 Short rifle in .308. Worked well for a 3-400 rounds. Accuracy was 2" at 50yds and 3-4 at 100yds. Cartridges actually fed ok from the mag is you worked the bolt on the slow side. Eventually it started getting hard to close the bolt on rounds. I'm thinking it started to back out. So I removed it with a broken shell extractor as instructed in the instructions. Unfortunately it got tore up in the throat area. I didn't buy another one. I would have left it if I didn't start having problems.