Home Forums Hunting & Shooting AR and Tactical Rifles 1st shot out of group with RR Predator Pursuit

too true, no vender really cares how the gun shoots as long as it goes bang.

The top line builders will. But typical vendors, unless its horrible, will tell you its within THEIR specs....

Maybe try loading 10 in a mag, drop bolt, shoot, lock back and eject next, drop bolt and shoot, repeat for 5 rd group and examine ones you ejected. Might just need to polish feed ramps.

Eagle; you, TC1 and jimmyp all have good simple easy to do diagnostics. I'll add them to my list of tricks to try next range session. I don't want to send the rifle to RR if a simple fix with no smithing will work.

How are you closing the bolt on the first round? Bolt release, Full pull on the CH, or slow release on the CH?

let us know if you get two groups from single loading and mag fed, I am very curious.

Grand, I have been using the bolt release with five rounds in the magazine. I plan to test all three methods on the next range trip, will post results.

jimmyp, also next range trip. I am curious myself.

Possibly going to the range Wed. 8/12, more likely next week. Our frequent high variable winds make careful testing difficult, but we do get some good shooting days and I will report as soon as possible.

THANKS FOR YOUR INTEREST AND HELP!

JIM

You have a sloppily chambered barrel.

Your bolt has too much over run. Basically, when it runs forward to chamber the round, it is sizing the case down, effectively increasing headspace for that round.

The only cure is a new, properly chambered barrel. There shouldn't be more than about 2 thou of clearance between the bolt and the barrel face when the bolt is firmly seated back against the barrel extension lugs.

Sorry about your luck.

So, how do the next rounds going into battery not be effected by same slop? I"d think, that would equate to just generally larger groups like you get out of rack hunting rifles and such.

I would think if he used the bolt release to slam the thing shut the results would be the same as a second shot?

After reading OP, does it do it only with handloads, or factory ammo too? Perhaps greater momentum of gas cycling is pulling bullets and seating them into lands, or contact with feed ramp is pushing them into case? How is your neck tension? I use Lee factory crimp on my cerchunkers, don't bother on the bolt gun.

I'm just curious to Barrys thoughts? I have no clue, he may be onto something and maybe not.

I"m certainly far from the best person to diagnose this, but I have theories that have proven themselves on other similar things.

Me, I think its the way the first round is loaded personally... though it never made a difference on my good guns, but I never knew what would happen the other way around.

It's a pretty well documented phenomena that any accuracy-minded auto rifle smith would know about. I guarantee Holliger & Frank White carefully control for this when they do a barrel. But when factories do them, all they do is screw on an extension and run a reamer in until a bolt closes on a Go.

Bigger rifles are more susceptible to it due to the increased mass of their bolts.

Pulling the bolt back and letting it fly (slingshotting) generates more energy than the automatic functioning of the rifle.

The OP can check this out with a Hornady Headspace gauge. http://www.hornady.com/store/Lock-N-Load-Headspace-Kit-With-Body-1-Each/

Use the gauge to measure the headspace length of a couple unfired cartridges. Next, slingshot them into the chamber and re-measure. Note the new numbers. Ideally, it shouldn't change or be more than a thou, maybe 2, different. You gotta have some clearance in the fit to allow for function and this is one reason why automatics will never equal bolt actions in accuracy.

Then do the same thing with a few more cartridges, only this time feed them out of a magazine by firing a round to chamber them. Don't shoot them, take them out and measure them, comparing the numbers to the new, unchambered and the slingshot fed.

It probably won't do a whole lot of good to single load every cartridge when shooting for groups. The loose headspace produced by single loading doesn't help accuracy.

To see if you are right, then we should load 6 rounds in a mag, load one by hand, fire it into the dirt, then group the next 5.

I hear you on good smiths being precise, but thats waht we pay them for.

I am not a smith by any means and was not aware that the slop in the chamber would make that much difference just on how a manually chambered and fired chambered round would group, to be so repeatable as to do it every last time.

Lets see how the 6 round test works and should answer your theory then.

jimone, one group was with factory ammo with the same results. However, it was American Eagle 50gr. tipped and may not have been crimped. In intend to try both crimped and uncrimped versions of the same load. I am thinking the bolt slam may be harder from the bolt release than during normal cycle. I will consider a lighter mainspring or heavier buffer.

I don't think I have a head space problem; the cases show no sign of insipient separation or other signs of problems. If I check the head space and it is excessive the upper goes back to Rock River.

You can have correct headspace and still have a bolt overrun problem.

is this one of the guns that RR guarantee's One MOA with 3 shots? If so send it back to them. If not buy a new barrel.

Seating the bullets out to near max and taper crimping seem to have fixed the first round problem.

I am with Jeff, cryo sure would not hurt. Cryo has the ability to relieve stress, and it sounds like the barrel is stressed and once it gets a little heat it settles down.

I thought the same thing until he confirmed that it did the same thing, hot or cold. Now that he says crimping has fixed the issue I doubt it was a stress related problem.