Starting with the basic SP10 rifle as it came from the Factory with the standard rifle length gas system.



First with the bad.

Unfortunately the version I received had the Rifle Length Gas and no matter of fine tuning with the Gas or buffer weight could fix the abuse it played on the brass and crude cycling and bolt bounce that started premature wear on the rear of the bolt lugs.


The OEM Timney trigger had substantial and very noticeable creep when doing a slow controlled trigger pull so I replaced it with a TriggerTech AR10 Diamond. When I first received the rifle it had a bent gas tube that was binding inside the gas key of the BCG. I didn't care much for the barrel contour after the .750 gas block journal it would step down to .730 to the muzzle and seemed to suffer from poor Barrel harmonics and substantial barrel whip.

After encountering these issue one phone call to Seekins they completely revamped the rifle no questions asked with the exception of the barrel as it was thier current barrel offering and it was still shooting satisfactory, but bar none Seekins Customer Service is one of the best in the industry.

Now for the positives.

The Receiver Set and handguard have been phenomenal to date and after several thousand rounds the receivers still lock up tight with absolutely no slop. The 15" Handguard is perfect for shooting from barricades and fits a Arca rail perfectly.
The ATC Muzzle brake was surprisingly effective with maintaining sight recovery.

Out of the box as it originally came it maintained .75 MOA with all Harnady ammo but had unexplained flyers.

At this point I decided to pull the barrel and BCG and replace it with 22" Craddock Bartlein with the +2 gas system headspaced to a JP Bolt, APA Gen3 Little Bastard adjustable muzzle brake and a Lantac Carrier with the oversized rear boss and forward facing gas vents and a SA AGB. The end result is the softest shooting 6.5CM I've even owned.

The results were nothing short of spectacular.



But unfortunately the gas port in the the Craddock barrel took a catastrophic turn for the worst and developed a burr at the gas port that was unrepairable.



After contacting Craddock the current wait time for a barrel replacement would of put me 12 months out, but again with exceptional customer service Paul issued a full refund.

At this point instead of waiting 12 months I opted to go with a 24" Proof Research Carbon Fiber barrel that has shown to be a solid performer right out of the gate the PRCF barrel shot .5 MOA with Factory ammo.


After a healthy 200rd break-in the PRCF has become one of my top performers. I initially had some hesitation with how the barrel was performing with the groups opening up especially under high heat. It turns out is was just mirage causing sight disruption the illusion of the groups opening up.

First round of load development.


The below groups were shot today solidifying several load options that are all Sub .5 MOA




The Seekins SP10 has shown to be a true performer no matter what tube I install.

To date Seekins has rectified the earlier discrepancies with the addition of a + 1.5 Gas system and a updated bolt. I have absolutely no reservations recommending the SP10 to any shooter.

Thanks for reading.

Jake

I posted this in the 5.56 thread, but no one seemed interested in discussing it there. This is therefore a re-post.

Summary: bullets jump when slammed into battery in a semi-automatic action. I tried increasing "neck tension" and crimping. Increased neck tension did not stop the jump. Crimping did not stop the jump but seemed to limit how far it continued. We should expect some jump because a hard stop into battery works just like an inertial bullet puller. Is a crimp into a crimp groove necessary to limit this jump, or is neck tension on a bullet without a crimp groove sufficient? Crimp grooves can be detrimental to accuracy if they're formed by smashing the bullet (maybe not if cut on a Swiss lathe, but we like less costly bullets).

My die is setup with a bushing to size LC brass necks to .243" and then pull a carbide expander ball through them to leave an OD of .244". When I seat a bullet, the OD is .0246". This would be commonly referred to as two thou of "neck tension." The amount of tension also depends on how much of the deformation the brass undergoes when the bullet is inserted is plastic and how much is elastic. My brass was brand-new Winchester brand from Lake City, fired and resized only once by me. I haven't messed it up with improper annealing nor have I work-hardened the brass neck by resizing it many times. I'll refer to this two thou delta between sized and seated as two thou of neck tension with the understanding that there's a little more involved there.

Bullet Jump
With two thou of neck tension and no crimp holding the bullet, I measured the overall length and then let the action on the rifle strip it from the magazine and slam it into battery with the muzzle pointed down. I measured it again and saw the bullet had jumped 1 thou. The cartridges I'm using for these tests have no powder or primer. Because the rifle has a floating firing pin, I did not want to be trying to induce a slam fire. I'm not surprised the bullet jumped because when a semi-automatic action accelerates the cartridge toward the chamber and then abruptly stops when the breech closes, it works just like an inertial bullet pulling hammer hit against a hard surface. Newton's first law explains why the bullet, once accelerated, will continue in motion even if the brass is stopped. Friction in the brass case neck is the only thing stopping the bullet from continuing until it hits the lands, unless it is crimped. The friction was enough to allow the bullet to jump only one thou. However, I repeated chambering the same cartridge several times and the bullet continued to jump 1 or 1.5 thou each time.

Crimp Test
Next, I used a Redding micro-adjustable taper crimp die to crimp the case of a different cartridge in the bullet's crimp groove. I repeated the process of measuring the overall length, chambering the round with the full force of the action, and measuring how far the bullet jumped. With the crimp, the bullet still jumped a thou. However, when I repeatedly chambered the same cartridge, the bullet jumped a total of three thou and then stopped moving farther with subsequent chamberings. I suspect the edge of the crimp groove slid forward against the crimp, and that it would take more force to push the crimp open.

More Neck Tension
To get more neck tension, I first removed the carbide expander ball from the die. Now the brass would be .243" before seating the bullet and .246" after -- three thou of neck tension. I also selected a different brand brass, a Speer nickel-plated case, and after sizing it with the .243" bushing without expanding it and then seating a bullet, it measured .247". The Speer case's brass is thicker in the neck -- four thou of neck tension. I repeated the tests on uncrimped cartridges and found the bullets would still slide forward about a thou every time they were slammed into battery. The bullet in the Speer case continued to jump as far forward as eight thou with repeating chamberings.

Crimp + More Neck Tension
I resized cases and seated bullets with 3 and 4 thou neck tension, and this time I also crimped them. I repeated the tests. I found the bullets would jump a thou, and after repeated chamberings they had jumped about three thou. After that, they would not jump farther.

Conclusion
My results suggest to me that increased neck tension will not stop bullet jump. I don't have more bushings to test 5 or 6 thou or more of neck tension, but at some point seating the bullet is going to plastically deform the neck so that it is not actually holding the bullet under any additional spring tension than that which is achieved with a larger bushing.

My results suggest a crimp will not stop all bullet jump, but that a crimp into a crimp groove can limit bullet jump to some smaller distance within the groove provided the inertial force on the bullet does not overcome the crimp. Certainly, my hammer-style bullet puller will overcome the crimp.

Not all bullets have a crimp groove. Many more accurate bullets do not because pressed crimp grooves deform the bullet and result in poor mass concentricity and wobbly bullets. Perhaps crimp grooves cut into a solid bullet on a lathe do not create this problem. Certainly, bullets into which a crimp groove is smashed by a Factory Crimp Die do. For bullets without a crimp groove, it seems best practice not the crimp them and to be aware they can jump some when slammed into battery by a semi-automatic action. If they jump one thou, that doesn't seem to be a big problem to me.

If a bullet has a crimp groove, a taper crimp of the case mouth into the groove can help limit the distance of bullet jump from the cartridge being slammed into battery. However, unless the cartridge is expected to be repeatedly slammed into battery many times, it's not clear that any benefit is derived from the crimp since the crimp is not likely to prevent the 1 or 1.5 thou the bullet is likely to jump upon being chambered the first time, and any ability of the crimp to limit further jump upon additional chamberings won't matter after the cartridge is fired. It could matter more if the recoil spring rate was greater. The M249 uses a piston operated gas system with a greater reciprocating mass, fires from an open-bolt, and has a higher rate of fire that is expected to be sustained for longer. It is highly likely therefore that it has a higher recoil spring rate, and that the cartridge is accelerated to a higher velocity before it is stopped in battery.

Questions

• Do bullets in 5.56x45 cartridges jump when chambered in your semi-automatic rifle? If so, how much?
• How much delta is there between your sized and seated necks?
• Do you crimp your cases when the bullet has a crimp groove? If so, taper or roll?
• If you crimp your cases, why do you do so? Have you done any tests to verify that it is effective?

Vortex 30% cert. Expires soon. 4/16/25.

$75 to me and I’ll send a picture of the other side.

New never used only removed from the box for pictures $125 . Going to keep it.

Guys what would be the most accurate 7.62X39 piston upper with 10" 0r 12" barrel? Using Russian ammo such as Barnaul, Belom and Golden Tiger

Found a good load but brass shows pressure signs well below max charge: flat primers, faint extractor marks, and occasional heavy bolt lift.

43.8gr Varget
Berger 168 hybrid
Federal brass, twice fired. Same pressure signs with Lapua.
Federal 210 primers
Criterion 24” 1:10. 250 rounds thru.
2725 FPS

Max charge per Hodgdon is 46gr. Not sure why the high pressure. I’ll adjust the load. Just trying to understand what’s going on.

Fde sr15 16” upper

Low round count

Un-notched

Phosphate bolt/ bcg

Noveske super bad ass fde charging handle

1500

700 SA RH Fixed. ARCA. New in box.
$1300 $1200 $1150 $1100 shipped CONUS
PayPal, Venmo, Zelle FRIENDS AND FAMILY only unless you wish to cover the 3% fees.

Looks like Noveske just dropped their DDF barrel line:


These look pretty interesting. I'm curious to hear people's reports on them when they start to get in the hands of some SH'ers.

Maybe @padom or @Bigjake83 can test some for us...

In perfect as new condition, just a couple months old.

NF 4-20 ATACR comes with Hawkins ultra light rings 1” with offset bubble level plus all original packaging and accessories.

$2,475 shipped
2,375 shipped no rings

Open to face time or texts or whatever makes serious buyer more comfortable with transaction.

PP F&F or GS (fee on buyer)
Zelle
NO TRADES

Sig Sauer Tango-MSR 1-8 LPVO with BDC8 reticle, SFP. Horseshoe is illuminated and bright AF, works really well as a QCB red dot with lots of magnification. Huge eyebox and little distortion, way better than the 1-6 Tango. Just went in a different direction with the project.

Scope was mounted and sat on a rifle for one range trip, maybe 20 rounds. Basically brand new. Comes with scope, mount, flip covers, paperwork, battery, cleaning cloth, operator-grade Sig Sauer sticker, and original box. Coyote brown makes it more accurate. Not really, but you'd think it would do something to justify the $100 higher MSRP, lol.

$380 $325 shipped, DM me if you are interested in buying, PayPal FF or Venmo preferred. I pack things well and ship them quickly. Thanks!

Fellas, I’m taking delivery of a second Gen 3 Razor 6-36 tomorrow. I want to send it in, along with my existing unit, for the locking feature delete on both windage and elevation. I have no use for locking turrets, I only shoot for fun.

When Vortex does this mod, what specifically happens to the turret? Can you no longer pull it up? Does it change how it feels? Is it like a vasectomy where it can be reversed in the future?

Couldn’t find any details in the search. Thanks.

Next thermal adventure question for the NV crowd. Looking for an external pack for my helmet. Does the mAh rating matter as far as frying a thermal? Looking at various Anker options so I know that voltage is good to go a 5 volts but will a "bigger" pack do anything bad to a unit. Seeing 10k to 20k options and want to experiment from a counter weight standpoint but don't want to kill a unit either. It's a MH25 if it matters. To my simple mind it seems like more mAh's just means more run time between charges but want to make sure I'm not missing something. Thank you for the advice in advance!

Got the new Trijicon VCOG that Eurooptics is offering. This is the SCO USMC version that comes with a scope molle pouch, scope cover, and flip caps. The mounting system is the Larue LT-799 QD. It has a tree reticle in mils. It even has the Bible verse that military issued Trijicon have on them.

“If we say we have fellowship with him while we walk in darkness, we lie and do not live out the truth.”
-1 John 1:6

First impressions:

Glass is extremely clear, provides sharp contrast and colors. The tree reticle is great and provides up to 20 mils in each direction at 8x. The reticle at 1x feels similar to a EOTech xps. Eye box at 1x is very forgiving and less so as you progress to 8x. The Larue mount is easy to use and can be adjusted by hand. No need for a wrench. This scope is THICCC. Not only is it heavy, it also takes up a lot of space. If your looking to minimize weight this is not the option. This optic reminds me of an Elcan because of how rugged it feels.

I plan to put this on my Scar 17S with a side/top mounted T2 or RMR.

looking for a chad muzzle brake

preferably a black dlc 3/4 thread 6mm

open to others....

225$ shipped Zelle/venmo

Includes the level and diving board

35mm, 1.25” 20moa

Sealed in the box.
No bolt release, top safety
$180 shipped conus

I am about to upgrade my Leica HDB's to a newer unit. The ranging on close targets less than 100 yards can be a bit off depending on how reflective the target it. I will get a few yard difference ranging a Morrell field target bale (big round flat target) or ranging the water-resistant target faces that are pretty shiny. They will be used mostly for ranging 3D targets, which all the Delta/Mckinsey 3D targets seem to have about the same sheen. My sons Sig Kilo 6k's do not do this, they are much more accurate at ranging, glass is just no where near the Leica glass. Having a RFB that is more accurate than the older HDB can mean the difference in catching a 12 or dropping into an 8 or a 10. So I am looking at the Sig Kilo 10k Gen2, Leica Pro 10x42, or the Vetronix 10x42. Does anyone have experience using them for archery ? Or even just playing with them at close range ?

THANKS!

I am selling a Thompson Center Pro Hunter in .280 Remington with Vortex 6-24 with a .243 barrel & 22-250 barrel.($1,600) I also have a Ruger Vaquero with a birds head grip stainless in .45 LC ($1000)

TriggerTech Field Trigger - Right Hand
New Takeoff from Horizon Vandal X
Rem 700 Clone - No Bolt Release
$85 Shipped OBO
Paypal F&F

Just introducing myself so I can use the buy/sell/trade forums! Just need to participate! Thanks!

new, never worn. Polarized Emerald Mirror lenses.
$125 shipped OBO

LMT MWS H Quad Upper - $800 Shipped
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I found this rummaging through my mom's stuff. Does anyone have an idea about what it is? Or where to start looking. Thanks!

A buddy was just telling me that LPM released their Muzzle Brake End Cap today... looks like they're offering them for their LPM cans, Dead Air & showing the OCL Infinity coming soon. Hadn't seen any mention of it here yet but might be of interest for the PRS/comp guys!