need some help with 77 gr SMK's
- Thread starter rebs
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Seating depth preference will be individual to the rifle. Sierra recommends 2.260" but their manual says they got best accuracy with 24.1 grains of Vihtavuori N140 in the AR, which that bullet was designed for. In your bolt gun, that load may not achieve sweet spot barrel time. You would need to shoot a load ladder to check for that.
What is your barrel length and rifling pitch?
What is your barrel length and rifling pitch?
That's more twist than the 77 requires. It's suitable for the 80-grain SMK's and some of the higher BC bullets from Hornady and Berger. If you are not loading your cartridges to minimize concentricity error in runout, the extra spin will open groups a bit, so you may need a concentricity testing tool if you don't have one already.
QuickLOAD suggests 23.3 grains is closer to one of Chris Long's sweet spot nodes. Give that a try and see what happens.
QuickLOAD suggests 23.3 grains is closer to one of Chris Long's sweet spot nodes. Give that a try and see what happens.
I run them with Varget at Sierra recommended length. What kind of groups do you get at 100? My mentor taught me to shoot at 100 to see what the load and rifle are capable of and at medium/long range to see how well I am shooting. If your load shoots half MOA at 100 then it is capable of half MOA at 300. Easier said than done of course
Well, not quite the same MOA at the longer range. There are some funny exceptional situations, but most group opening is due to drift away from the trajectory at a rate that stays constant during flight for all practical purposes. Because the bullet slows down as it flies, each successive 100 yards has a longer time of flight, giving the bullet more time to drift a larger number of MOA.
I have a radar drag function for the 77-grain SMK. It says a muzzle velocity of 2750 fps will give it times of flight that are:
0.1148 s first 100 yards
0.1271 s second 100 yards
0.1412 s third 100 yards
So, MOA at 100 is expected to be 11% bigger at 200 and 23% bigger at 300. Bryan Litz compared that expectation with real results in his first book, Applied Ballistics for Long Range Shooters, and found actual spread slightly bigger than it predicts, probably due to things like atmospheric irregularities over the greater distance randomly adding to the spread.
Rebs,
By changing assumptions, 22.9 grains is another number I came up with. If you can measure the actual velocities you are getting a better estimate can be made. Also, you can run a velocity ladder and look for flat spots, which helps find the nodes. Just load 25 rounds in 0.1-grain steps from 21.7 grains (10% below maximum; 24.1 grains, according to Alliant's site), and record the velocity of each on and graph them, looking for flat spots. I can help with the graphing if that isn't in your bailiwick.
For seating length, you need to know how far forward of the bullet your chamber throat is. You can buy a tool for doing this, the Hornady Lock N Load Overal Length Gauge being the most popular one, or you can take an old case, split the neck with a hack saw, debur the cut and squeeze the split neck down and set the bullet just barely into it. Then push the case and bullet all the way into the chamber with your little finger and use a cleaning rod from the muzzle to gently push it out. That case and bullet should come out with a COL that just touches the lands. You can take your load down to 21.7 grains and shoot some loaded that long and some that are shorter in steps of about 0.02" all the way to about 0.10 inch shorter or to 2.260", whichever is deeper. At some point along the way, you will find a depth that produces the smallest group. Use that depth and step it through different loads to find ones that group even smaller until you find the smallest one.
I have a radar drag function for the 77-grain SMK. It says a muzzle velocity of 2750 fps will give it times of flight that are:
0.1148 s first 100 yards
0.1271 s second 100 yards
0.1412 s third 100 yards
So, MOA at 100 is expected to be 11% bigger at 200 and 23% bigger at 300. Bryan Litz compared that expectation with real results in his first book, Applied Ballistics for Long Range Shooters, and found actual spread slightly bigger than it predicts, probably due to things like atmospheric irregularities over the greater distance randomly adding to the spread.
Rebs,
By changing assumptions, 22.9 grains is another number I came up with. If you can measure the actual velocities you are getting a better estimate can be made. Also, you can run a velocity ladder and look for flat spots, which helps find the nodes. Just load 25 rounds in 0.1-grain steps from 21.7 grains (10% below maximum; 24.1 grains, according to Alliant's site), and record the velocity of each on and graph them, looking for flat spots. I can help with the graphing if that isn't in your bailiwick.
For seating length, you need to know how far forward of the bullet your chamber throat is. You can buy a tool for doing this, the Hornady Lock N Load Overal Length Gauge being the most popular one, or you can take an old case, split the neck with a hack saw, debur the cut and squeeze the split neck down and set the bullet just barely into it. Then push the case and bullet all the way into the chamber with your little finger and use a cleaning rod from the muzzle to gently push it out. That case and bullet should come out with a COL that just touches the lands. You can take your load down to 21.7 grains and shoot some loaded that long and some that are shorter in steps of about 0.02" all the way to about 0.10 inch shorter or to 2.260", whichever is deeper. At some point along the way, you will find a depth that produces the smallest group. Use that depth and step it through different loads to find ones that group even smaller until you find the smallest one.
Id go to a different powder . Varget , IMR 4064 would be my suggestions in that order . Maybe even IMR-4895 . I’ll add the IMR powders are loooong extruded powders and with a 77gr smk in a 223 case . You will likely need to use at leats a 6” drop tube to get the powder to settle in the case leaving enough room for the bullet . Likely would need the same thing with Varget as well and expect all of them to still be compressed loads .
I found developing a load for the 77 non tipped to be a easy bullet to develop for. They seem to be pretty tolerant of powder charge and seating depth. The only powder I have tried is Varget. I hear good things about RL15 on the forums though, just never used it
these were loaded dead on the lands
https://thefiringline.com/forums/showthread.php?t=600647&highlight=77
the three in the 9 ring would be me not the load
At 100 and 200 they sing at magazine length and as you can see are pretty charge tolerant with Varget
these were loaded dead on the lands
https://thefiringline.com/forums/showthread.php?t=600647&highlight=77
the three in the 9 ring would be me not the load
At 100 and 200 they sing at magazine length and as you can see are pretty charge tolerant with Varget
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Uncle Nick and others appreciate all your help.
My chamber measured with a Hornady gauge is 1.923 for the 80 grain SMK and 1.905 for the 77 smk. Also 1.914 for the 69 smk's. I will try to access a chronograph to get the velocities.
Also my groups are approximately I/2 inch at 100 yds if I do my part. Could it be that the amount of powder is light and needs to be increased to carry the bullet to 300 yds ?
My chamber measured with a Hornady gauge is 1.923 for the 80 grain SMK and 1.905 for the 77 smk. Also 1.914 for the 69 smk's. I will try to access a chronograph to get the velocities.
Also my groups are approximately I/2 inch at 100 yds if I do my part. Could it be that the amount of powder is light and needs to be increased to carry the bullet to 300 yds ?
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you never did answer as to what size groups you are getting at 100. As you can see from my targets above for me to get a .3 group at 300 is about a thousand times harder than getting a .3 group at 100, In F class shooting a 1.0 MOA group at 300 will still net you a perfect 200 score if it is centered on the X. Three shots out of 20 can land in in the 9 ring and it would still be a High Master score ( 98.5%)
Do not take this as a slam on your Tikka because I think they are excellent and very accurate rifles right off the shelf but if you want consistent .5 MOA or below groups at 300 and beyond you will need to get a custom BR rifle and spend a ton of time and ammo practicing and learning wind calls and mirage. As much as I like my home grown Savage's I do recognize their limitations as well as my own. If I were to get 300 groups the size (in MOA) of my 100 yard groups I would consider it to be be nothing short of a miracle
Like Clint Eastwood said in Magnum Force" A man's got to know his limitations."
Do not take this as a slam on your Tikka because I think they are excellent and very accurate rifles right off the shelf but if you want consistent .5 MOA or below groups at 300 and beyond you will need to get a custom BR rifle and spend a ton of time and ammo practicing and learning wind calls and mirage. As much as I like my home grown Savage's I do recognize their limitations as well as my own. If I were to get 300 groups the size (in MOA) of my 100 yard groups I would consider it to be be nothing short of a miracle
Like Clint Eastwood said in Magnum Force" A man's got to know his limitations."
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DukeConnor
New member
if i could shoot a 2 1/2 inch group at 300 i would be dancing in the street.
accckkk apologies Rebs, somehow I missed that. If you are getting .5 MOA at 100 then theoretically you can get .5 at 300. Just like I can theoretically get .3's or .4's however in practice my wind reading/mirage/shooting technique gets in the way. If it were as simple as getting the load right we could all shoot 5 inch groups or less at 1000 and all be F class High Masters
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reynolds357
New member
Back off to about mid level listed charge. Long seat 5 rounds. Let the bolt of the rifle seat them when you close it. If it won't group that, your rifle won't shoot that bullet powder combination. Of course you can't keep that as your load, but it can save you a pile of time on a bullet or powder that just will not shoot.
For a stock off the shelf rifle I think .5's with an occasional .4 or so at 100 yards is about the norm for a good factory rifle these days with good handloads in the hands of someone who can shoot halfway decent. I know there are some that claim they can get consistent .2's and .3's with their hunting rifle but I take those posts with a grain (box) of salt. I know I don't have that skill level even with trigger/stock/barrel upgrades. Of course maybe I am just a crappy shot, or maybe there is a reason that people who are serious competitors buy Panda actions and Bartlein barrels. Like I posted earlier I don't expect my garage built Savages to shoot as well as a Kelby or Stolle Panda put together by a professional gunsmith that specializes in benchrest rifles and costs $4K to $5K.
As far as velocities go a 200FPS ES at 300 (2800 FPS - 2600 FPS) would make a .9 inch difference (. 3 MOA) a 100 fps difference about half that
As far as velocities go a 200FPS ES at 300 (2800 FPS - 2600 FPS) would make a .9 inch difference (. 3 MOA) a 100 fps difference about half that
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3 inch groups at 300 yards is 1 MOA. 2.5" is under 1 MOA. What are you expecting out of a commercial hunting rifle? Assuming it's consistent, I'd leave it alone.
"...seating depth..." That'd be fiddling with the OAL for the off-the-lands distance. There is no formula to determine that. It's a 100% trial and error thing with your rifle's chamber. And there's no guarantee fiddling with the off-the-lands stuff will make any difference.
"...seating depth..." That'd be fiddling with the OAL for the off-the-lands distance. There is no formula to determine that. It's a 100% trial and error thing with your rifle's chamber. And there's no guarantee fiddling with the off-the-lands stuff will make any difference.
Well, as I described in post 8, the expectation is for about 23% moa increase at 300 yards. If he is getting about half an inch at 100, he has 0.48 moa at that distance and we expect it to grow to 0.59 moa at 300, or 1.85 inches in perfectly still air. Litz found actual group growth at distance is a bit more than that expectation (just over 10% more in one example he gave and about 24% more in another¹) so 2.05" to 2.3" at 300 would match Litz's examples scaled for a gun shooting 0.50" groups at 100 yards. Rebs, you are already pretty close with your 2½" groups, so I don't think you are as far off as you think. In your shoes, I would look at concentricity and check case head squareness and if the group error tends to be vertical, I would look at reducing velocity standard deviation.