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Do you think perhaps a 1-9 twist would be more than adequite for the 75-80 grain bullets. I understand A-Max bullets don't take velocity well, so maybe I would be better off at 3300 and under in velocity.
I have seen heavy bullets blow up in fast twist 22 hotrods. The guy said his throat area started to look like a "dry lake bed" , firecracking had set in causing his thin jacketed match bullets to go "poof".
The 9 twist will work with the 75's. Gets iffy with the 80's - might work, might not, lots of variables, not the least of which is altitude. Closer to sea level, less likely the 9 will work with 80's (but it still might...).
The heavy bullets starting to go poof in the large capacity fast twist .22 calibers is just part and parcel of that kind of a rig. How soon it starts to happen depends on many things. With my 8 twist .22-250AI, the particular barrel I had (3 groove Lilja - there is some indication that a regular 6 groove might be a better choice for this application), and the way I used it, the barrel was history after 700 rounds. By then I was shooting 80 gr. SMK's at a reduced velocity (3150 fps), but could not get off a 10 shot string without the SMK's starting to go poof. At that point I just unscrewed the barrel and tossed it in the corner with the rest of the toasted barrels.
The guys who shoot a lot of these .224 VLD's tell me that they work best at around 3100 - 3200 fps anyway, so the extra velocity available from the large capacity case (and especially with a longer barrel) may or may not be a good thing. Depends on exactly what you want to do with it. I do know that you have to be careful about trying to run too much pressure with the VLD's. Those long BT's have a tendency to "slump" when kicked in the rear too hard, and then accuracy suffers signficantly.
Lots and lots of variables though. Not to mention the various applications and what an individual shooter wants to accomplish, and/or is willing to put up with. I think my 8 twist .22-250AI was pretty typical, for the way I used it. Most guys I've talked to who use them in similar fashion don't get a thousand rounds out of theirs before they become tomato stakes either. But then there are drastically different applications where the same barrel might be made to last much longer. Going with a slower twist, 9 vs. 8, if you can, will only help. But, at the end of the day, YMMV!
- DAA