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Old 08-13-2012, 20:05   #21
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Originally Posted by pasky2112 View Post
I got to shoot my new G20 for the first time last weekend! Now I can see what everyone is talking about. I don't understand the "FBI...Heavy Recoil" thing.
Copo9560 covered the ammo angle. There is another aspect: The Glock polymer frame does make the recoil absorption easier to handle. The flexing of the frame DOES reduce PERCEIVED recoil. The original FBI experience was with all-metal guns.
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Last edited by samurairabbi; 08-13-2012 at 20:06..
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Old 08-13-2012, 23:30   #22
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Originally Posted by samurairabbi View Post
There are headspace tolerance considerations. There is far more play in the gap of the extractor holding the rim than there is in the chamber holding the cartridge MOUTH. That is equivalent to much greater headspace variation, even if the .40 round DOES fire consistently. Field strip a Glock, place a case in the extractor, and wiggle it fore and aft. THAT amount of wiggle is now the headspace variation. Would you tolerate that much headspace variation when shooting 10mm in a 10mm factory barrel?

"Getting along" with shooting .40 in a 10mm barrel is something I did (before scrounging conversion barrels), but I never contend it is an equivalent condition to shooting 10mm cartridges.
Of course, but the clearance is insignificant. The minimum/maximum case length tolerance is a LOT more than the mere couple thousandths of an inch behind the extractor (case rim engaged). Chamber depths can vary, between .992-.998" (SAAMI is .992"). Minimum case length is about .982" (most new brass is in the .985" neighborhood). The extractor will hold tension on the case, defaulting to breech contact in almost every case. In any case, it's a moot point, unless something is broken. So, yes, I do tolerate this head space variance. So do you, if you shoot this pistol. For the same reasons, it is recommended (by some) that the extractor be modified to accommodate this when using a G21 slide to fire 10mm or .40 rounds (in an appropriate barrel, of course). Unless something is broken, it will be well within the range of tolerance.

In my RBH revolver, the chamber depth is .992". After a few firings of the same brass (moderate to max-pressure loads), the brass will be stretched to .992, due to this condition. Light loads have no affect. It has no extractor to hold it back. When fired, the firing pin pushes the cartridge forward to case mouth engagement, then it slams back to the breech. This is normal for this gun, by design (or lack thereof). Firing 10mm or .40 in my 10mm G20 does not do this, at all. No stretch. Many other revolvers do not experience this, as they are head-spaced using moon clips, not relying on case mouth engagement (which is a better, but less convenient strategy).
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Old 08-14-2012, 20:18   #23
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After reading this thread and others I went to the range today and tried some range grade Federal 40 S&W in my 20SF. Functioned every time although the brass only ejected a few feet. Reminded me of shooting 38 wadcutters in a 357 Mag - very little recoil compared to a hot 10mm load. Only having a 50 yard target available today the accuracy was not as good as the 10 loads but I'll try again at shorter range next time out.

With Wal-Mart selling 40 S&W for around $27 per 100 my 20SF will be getting a lot more range time.
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Old 08-15-2012, 10:28   #24
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@copo9560: Oh definitely. I bought the PMC just to get the feel of the G20, overall and 'make some brass' until my back ordered brass comes in. Then handloads/reloads only for range time. The PMC brass has been good to me in .40 reloads. We'll see how they do in 10mm.

In fact I just got my 22# SS RSA today. Changed out my primer system to LP in the ol' Dillon...gonna crank 'em out then send 'em down! If the range isn't too busy, I'll throw up my chrono and see if there's a diff between the stock RSA and the 22# in ES, SD etc. Anyway, that's OT from the thread. But I want to see how my stk bbl (or should I say 'brass') holds up to 'real' 10mm loads with the new spring.

FWIW, Starline is shipping their new batches today 8/15.

Last edited by pasky2112; 08-15-2012 at 10:32.. Reason: directed reply
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