In order to participate in the GunBroker Member forums, you must be logged in with your GunBroker.com account. Click the sign-in button at the top right of the forums page to get connected.
3 shot groups
rong
Member Posts: 8,459
I see quite a lot now
that shooters are using
3 shot groups instead of 5
shot groups to determine
if they have a "tack driver".
A three shot group assessment
is great for deer hunting,hey
a 2 shot group is fine for deer
but for punching holes one can't
IMHO find the issues in their
rifle without a 5 shot group.
that shooters are using
3 shot groups instead of 5
shot groups to determine
if they have a "tack driver".
A three shot group assessment
is great for deer hunting,hey
a 2 shot group is fine for deer
but for punching holes one can't
IMHO find the issues in their
rifle without a 5 shot group.
Comments
Than run the "best" loads from the 3 shot tests as 5 (or preferably 10) shot groups.
3 shot groups are great for eliminating loads that don't group
Than run the "best" loads from the 3 shot tests as 5 (or preferably 10) shot groups.
I agree; with one side note: I would not recommend shooting more than 3 shot groups with any of the larger belted magnums or you will compromise the results with human error. Also, you will almost certainly find that your barrel is getting way to hot.
Some observations about some of the currently-available surplus guns. This applies to guns that have decent crowns and good bores:
Mosins frequently indicate a 2 MOA potential. Out of a group of 20 (all arsenal rebuilds), five of them would do less than 2 MOA
repeatedly, and one was an M38 carbine which did it in consecutive strings with two different bullet weights, 150-gr Igman softnose and 203-gr Barnaul softnose. The first four 203-grainers actually went into 1/4 MOA, and I may or may not have pulled the wild fifth shot out. But Jeez. Another was a still-new ex-sniper that somehow slipped through on the importers, which kept putting five shots into three holes, 1.6 MOA being the largest group, with 185-gr Silver Bear. But it could be expected that this gun would shoot well. I can only wonder what could be done with a scope, on some of these. Three run-of-the-mill 91/30's also held inside 2 MOA. The shooting was done at 55 yards, so note that the first four shots from the M38/203-gr actually made one 40-something caliber hole.
Yugo Mausers that I've shot all seem to be consistent at about 3 MOA, and Chinese SKS's (I've regulated 8) at about 4 MOA.
Each number of shot groups has a purpose.
As to MGM's report I will say it has amazed me how many "old military" rifles can shoot just awesome. I have a Yugo M48-BO that will shoot sub-.5 MOA with scope, and a K-31 that will shoot sub MOA with open sights (yes, there is a trick to it.) Both with standard issue rounds! The Yugo sure won't do it with Turk ammo. And the K-31 can do sub .5 MOA with handloads. My Turk M-38 is the only rifle that can put decent groups out with the super-hot Turk ammo. My 1910 built 1909 Argentino will do better than 2 MOA @ 300 yds. But those are all handloads. I also have a friend with an original (so is the barrel, a two groove wonder) P-1917 that shoots right @ 2 MOA. Amazing how some of those older rifles still get it done
"Rifle accuracy" is measured in groups on paper targets at known ranges, using steady rests. fired in as much time as you require.
"Shooter accuracy" is measured by hunters on game - one shot, at something that won't hold still and blends into the background. The range is almost always uncertain, the rest are unsteady or non-existent, and the time for a shot can be as little as a couple of seconds.
IMHO, rifle accuracy + shooter accuracy = success.
Thank you for that. I always wondered what possessed the decision makers to come up with 2 grooves? They shoot accurately enough though. Also, along that line, my Enfield No. 4 Mk. 1* has a two groove barrel. It has the big S inside a circle stamped on the LH side. If I remember right those were produced by Savage. With the right load it will do 3-4 MOA consistently.
Ambrose,
Thank you for that. I always wondered what possessed the decision makers to come up with 2 grooves?
Answer = Time.
It takes twice as long to cut a 4 groove as it does a 2 groove.
Remember, this was before the advent of button and hammer rifling, so all barrels were cut using sine bar cutter machines (cut rifled)
quote:Originally posted by sandwarrior
Ambrose,
Thank you for that. I always wondered what possessed the decision makers to come up with 2 grooves?
Answer = Time.
It takes twice as long to cut a 4 groove as it does a 2 groove.
Remember, this was before the advent of button and hammer rifling, so all barrels were cut using sine bar cutter machines (cut rifled)
Interesting, I just always thought they did it with a 4 bladed cutter head instead of a 2 bladed cutter head. Unless that is true and they need to make shallower cuts per pass?
Multiple passes per groove than index the barrel for the next groove. Change the sinebar angle for different twist rates, change the cutter blade for different groove widths, change the index angle to change the number of grooves (60^ for a 6 groove, 90^ for a 4 groove, 120^ for a 3 groove, 180^ for a 2 groove)
One of my local gunsmiths (Al Siegrest) has one of the origional Pratt & Whitney Sinebar Rifleing machines in his shop (he's one of the few smiths that does reboring/re-rifling). It's quite fasinating to watch in operation.