POI Shifts/Mostly Rambling

Psywar1-0 · 05-15-2008, 06:24

I just got my 700 PSS back from Gemtech where they installed overbarrel Bi-lock. I had planned on going to Quantico and re-zeroing at 100yds with 118LR and then shooting groups with M852, 118SB and M80 Ball to capture POI Shift.

Due to bad weather Quantico was shut down on Sat so I had to use a 25 yard range. Knowing that I probably would not get any good dope at only 25 I went ahead and shot just to get out of the house.

I zeroed at 25 using a conventional crosshair zero target then went on to shoot the different ammo types on Shoot NC targets that I can stick in my data book. The groups were as follows:

118LR- .9in group, horizontal string
118SB- .8in group
M852- .5in group
M80- .6iin group

The results were not what I expected, with the "Lesser" types of ammo shooting better groups than the high end ammo.

All ammo was real milspec ammo, not any of that XMPD seconds that is on the streets.

The long and the short of all this is

a. Do I need to research the lot numbers of the 118LR and see if there are issues with it

b. Was I over compensating for the lesser ammo and just shooting better due to applying the principles of marksmanship, or was the gun just warmed up and happy?

Im hopefully going to Quantico again this Sat to get a good 100yd zero, and shooting in a F Class match there on Sunday.

**Peregrino** · 05-15-2008, 12:23

Quote:

Originally Posted by Psywar1-0

I just got my 700 PSS back from Gemtech where they installed overbarrel Bi-lock. I had planned on going to Quantico and re-zeroing at 100yds with 118LR and then shooting groups with M852, 118SB and M80 Ball to capture POI Shift.

Due to bad weather Quantico was shut down on Sat so I had to use a 25 yard range. Knowing that I probably would not get any good dope at only 25 I went ahead and shot just to get out of the house.

I zeroed at 25 using a conventional crosshair zero target then went on to shoot the different ammo types on Shoot NC targets that I can stick in my data book. The groups were as follows:

118LR- .9in group, horizontal string
118SB- .8in group
M852- .5in group
M80- .6iin group

The results were not what I expected, with the "Lesser" types of ammo shooting better groups than the high end ammo.

All ammo was real milspec ammo, not any of that XMPD seconds that is on the streets.

The long and the short of all this is

a. Do I need to research the lot numbers of the 118LR and see if there are issues with it

b. Was I over compensating for the lesser ammo and just shooting better due to applying the principles of marksmanship, or was the gun just warmed up and happy?

Im hopefully going to Quantico again this Sat to get a good 100yd zero, and shooting in a F Class match there on Sunday.

Doesn't sound good, especially for 25m. Sounds like you need more rounds at longer range to confirm. Couple of questions: Was this with or without the suppressor? What was it shooting BEFORE you sent it to Gemtech? Did they have to thread the barrel? Have you checked to see if they damaged the crown? Depending on the answers, you might want to seek the services of a competent gunsmith. Good Luck.

jbour13 · 05-15-2008, 14:07

If you don't get the performance you want let me know, I know of a man in NOVA that is a brilliant man when it comes to accurizing and addressing problems.

He has built a few rifles for the MC Scout Sniper sections/ SS course for Quantico.

If you get the data that PG was speaking of and give an established baseline vs. current issues, he may be able to help.

I will warn you that his turnaround time is long, and prices are pretty high.

PM me if you'd like more info

Psywar1-0 · 05-15-2008, 16:50

Thanks for the info folks. I was not shooting with the suppressor as it has not been made yet, I just had the down time to get the bilock put on now vice later in the summer when there are lots of matches that I dont want to miss.

Im not going to get concerned till after I get to shoot at some distance. I think its safe to say that its not an issue with the threading/recrowning as its a better(Cleaner) crown now than when it left the factory.

kgoerz · 05-15-2008, 18:13

Something is definitely wrong with that Gun. Those groups are way off the mark at 25 Meters. I would say way off the mark at 600+ Meters. This is a Remington 700 Bolt Gun right?

Psywar1-0 · 05-15-2008, 20:04

KG, Yes its a Rem700 PSS, 24 in barrel.

This is the M852 group, 5 shots at 25 yards

http://i21.photobucket.com/albums/b2...k/100_0247.jpg

I know I can get the group smaller.......

kgoerz · 05-16-2008, 04:27

OOOOHHHH, .5" not 5". Your good to go

Psywar1-0 · 05-16-2008, 06:01

Quote:

Originally Posted by kgoerz

OOOOHHHH, .5" not 5". Your good to go

LOL, yes half inch aka .5 If it was a 5 inch group I for sure would write it off to the nut behind the gun

longrange1947 · 05-16-2008, 10:31

.5 inches is still 2 moa. Not good, LR is pushing 4 moa. Something is wrong. What is the twist rate on the barrel. the rounds may be "sleeping", where the round not only spins around the axis but loops around the axis of flight. Usually occurs when the round is under stabilized. That would explain why the lighter bullets shoot better. They are more stabilized.

If this is the case then you should find a markedly better performance by the heavier rounds at longer ranges.

Psywar1-0 · 05-16-2008, 12:21

LR1947,

Thanks for weighing in here.

Its a stock Rem 700 PSS in 308 with 1/12 twist

Ive done nothing to it, other than put a steel plate over top the bipod/swivel studs and marine tex that in. A folded 3X5 card slides between stock and barrel with no issues, so its not a free float problem.

kgoerz · 05-16-2008, 18:23

Quote:

Originally Posted by longrange1947

.5 inches is still 2 moa. Not good, LR is pushing 4 moa. Something is wrong. What is the twist rate on the barrel. the rounds may be "sleeping", where the round not only spins around the axis but loops around the axis of flight. Usually occurs when the round is under stabilized. That would explain why the lighter bullets shoot better. They are more stabilized.

If this is the case then you should find a markedly better performance by the heavier rounds at longer ranges.

Dammmm.....I knew you were going to see this

Rick. We are buying Sniper Rifles for the Team. Ill need some recommendations. Ill send you the particulars in a couple of weeks. Only thing I know so far is Money is not an option and it has to be A Semi.

**Peregrino** · 05-16-2008, 20:55

Quote:

Originally Posted by kgoerz

Dammmm.....I knew you were going to see this

Rick. We are buying Sniper Rifles for the Team. Ill need some recommendations. Ill send you the particulars in a couple of weeks. Only thing I know so far is Money is not an option and it has to be A Semi.

K - Not Rick but I will offer a recommendation. If it has to be a semi and money is no object get Mark H. to build you some AR-10s. My .02 (cause I've seen the results). Rick and or Ed H. can chime in.

jbour13 · 05-16-2008, 23:52

I wish our's was out by now, you'd appreciate it I'm sure.

If you've got at timeline and would like to take a look, I may be able to arrange a demo for you, and other interested parties.

PM me

I still have a few to get to LR1947 I believe.

Sinister · 05-17-2008, 04:32

Stock factory 700 barrels are OK but have an extremely long throat. You'd probably have been better off having them cut off about a quarter inch off the ass end and rechambering to give you less free-bore.

The factory 700s usually shoot the lighter (and flat base) bullets straighter at close range (which is why benchresters use flat-base bullets to 200 and long-rangers shoot boat-tails).

I have no idea how tightly GemTech torques the bi-locks on to the muzzle, or whether they are hand-timed and Red or Black (Rocksett) Lok-Tited.

George Gardner at GA Precision does awesome AR-10s but uses the gay Badger free-float tube (more a square profile than round like a Superior Weapons Systems, Daniel Defense, or LaRue). If I had to go straight commercial that's where I'd send my money.

Kit, since you're federal you can also contract the AMU Custom Shop down at Benning to build your AR-10s as well. You'll get top shelf without having to pay for gunsmith hours and shop labor.

kgoerz · 05-17-2008, 06:37

Quote:

Originally Posted by jbour13

I wish our's was out by now, you'd appreciate it I'm sure.

If you've got at timeline and would like to take a look, I may be able to arrange a demo for you, and other interested parties.

PM me

I still have a few to get to LR1947 I believe.

I am off for two weeks. Ill know more when I get back to work. I would definitely be interested though. But like Peregrino said, we might go with something already proven reliable but custom built.