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Topic: Have a new Seekins SP10 coming. Which bullets to shoot? (Read 218 times) previous topic - next topic

Have a new Seekins SP10 coming. Which bullets to shoot?

I sold my 6.5 creedmoor bolt gun and now have a Seekins sp10 coming.  I had too many bolt guns so I went to a semi auto.  I've got a bunch of h4350 I'm going to use with hornady brass, all left over from the bolt gun.  With the bolt gun I was using the Berger 140 grain VLD.  I ended up selling all the bullets I had with the gun so I need to start load development with a new bullet.  I thought I read that the VLD bullets weren't good for the semi auto variants.  I do like the load development procedure from berger and have used it several times with different rifles.  What bullets you guys suggest I use?  I want a bullet that's good for hunting also as it'll double as a pig gun.  I'm also going to need a new set of dies for it as the guy wanted them with the rifle.  My last setup was the Hornady dies with the neck sizing bushing.  Think I may want to go with a small base die with this gun.  I also starting taking out the expanders out of my sizing dies and using a mandrel in a separate step after full length sizing.

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #1
The hybrid and vld 140gr bullets are difficult to load due to mag length restrictions.  The ar10 pmag allows for a max COAL of 2.83-2.85.  The VLD has a secant ogive which means the start of the ogive (where the bullet profile starts to curve to the tip) is closer to the base of the bullet relative to a tangent ogive bullet like the Eldm/scenar/nosler/etc.  You want the neck of the case to be situated on the "flat" bearing surface of the bullet, not on the ogive.  The length and shape of the 140gr VLD require the bullet to be loaded at the 2.87"+ length (which is somewhat dependent on what length you trim your cases to).  The hybrid although somewhat more forgiving, also has similar requirements.

So a properly loaded vld or hybrid probably won't fit or fit well in a pmag.  To get around this restriction some, like myself, use LaRue Tactical magazines (2.88" internal).  It buys me a little extra length.  BUT, long cartridges don't like to feed well in the ar10/large frame ar.  The cartridge has to "porpoise" or jump up the steep feed ramps and into the chamber.  With so little clearance between the end of the bullet and start of the feed ramp, more often than not the 2.87" cartridge simply jams into the start of the feed ramp or jams into the barrel area in front of the chamber.  The end result is a very damaged cartridge, with dents in the body as the bolt rides over the top of the case and pinches it OR the cartridge is bent at ~30° due the force the bolt ramming the bullet tip into the barrel.

In the end, the 140gr VLD and hybrid just don't work well in the ar10 unless you single feed them.

I would recommend the 140gr Eldm, 143gr Winchester, or even the 142 Sierra match king (which is great by the way).  If you're looking for velocity and flat shooting, I think the 130gr Berger ar hybrid is tough to beat...loaded to 2.79-2.80" you've got plenty of case capacity to add powder and hit the 2950-3k fps mark without running into pressure signs.

With a semi-auto, you want to full-length resize.  You'll need to bump your shoulders back .003".  The semi-auto starts to unlock with residual chamber pressure.  This allows growth in the rear of the case body and in the shoulder.  You might get away with neck sizing once maybe twice, but eventually that case isn't going to feed as well or not at all.

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #2
Thanks for the reply.  I just ordered the ELD-x by hornady and the 142 SMK.  I'd really like to use a dedicated hunting bullet so that's why I figured I'd try the ELD-x instead of the eldm.  I know the Sierra match king technically aren't bullets, many do use them to hunt.

So essentially any bullet I use with this semi auto ar should be loaded to magazine length?  Doesn't even sound likeI should try shorter Coal's in a semi?

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #3
Thanks for the reply.  I just ordered the ELD-x by hornady and the 142 SMK.  I'd really like to use a dedicated hunting bullet so that's why I figured I'd try the ELD-x instead of the eldm.  I know the Sierra match king technically aren't bullets, many do use them to hunt.

So essentially any bullet I use with this semi auto ar should be loaded to magazine length?  Doesn't even sound likeI should try shorter Coal's in a semi?

Shorter lengths work fine.  Obviously at the expense of reduced case capacity and higher (potentially) pressures.

For mag fed rounds, I used lengths from 2.79 to 2.85 with good results.  The issues come into play when you try load longer. 

You can load the 140eldm to SAAMI length and get factory velocities.  The issues only crop up when using long ogive bullets with short case neck bearing surfaces.  If you want to use a secant or hybrid ogive bullet (and utilize their attributes), you'll want to look at the lighter, shorter variations in the 129-130 grain range.

In a nutshell, you'll be fine.  The 140 VLD and Hybrid will be problematic. 

Edited to add: I don't think small base dies are necessary and they'll only overwork the brass.  A properly set up full length sizing die will be fine.  I use cheap hornady brass, with warm handloads, and still get 7-8 firings before the primer pockets get loose.

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #4
The Berger Hybrid can be loaded to 2.80 COAL and I've found my best accuracy with it at 2.80 to 2.82 in my Seekins SP 10 and LMT MWS.  Same with the ELD M - and 100% functioning.  JMO...

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #5
The Berger Hybrid can be loaded to 2.80 COAL and I've found my best accuracy with it at 2.80 to 2.82 in my Seekins SP 10 and LMT MWS.  Same with the ELD M - and 100% functioning.  JMO...

Bman, You using the Berger 130 grain AR OTM hybrids or just the regular 140 grain hybrids?

 

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #6
I am very happy with my "home built" AR10 built on a Matrix Aerospace billet upper and lower with a 22" BA heavy barrel.  I have had my best success using Hornady 140 BTHP (cheap bullets) sitting on a charge of 41.8 RL16.  Velocity av. 2780 fps with great accuracy.  It is my "fun gun" for 1K targets.  I use Hornady brass because the AR10 beat up brass so bad, I will sacrifice getting 2 or 3 loadings before the case head and primer pocket are trash. I have the JP hp bolt and adj. GB along with a 5.3 oz. buffer.  Still get ejector swipes. Just a note:  I get the same with factory ammo and similar problems with AR10 in 308 and 243.  The above load shoots great and keeps the damage to a minimum on this 6.5 CM.  I am just offering this info, so that you will find it a fact of nature with AR10's.

Like the others, I agree keeping OAL to mag. length max of 2.800" for reliable feeding.  Good luck with your new gas gun.
mike

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #7
130 grain AR OTM hybrids and 43 grns of H4350 work great in my gas gun

Re: Have a new Seekins SP10 coming. Which bullets to shoot?

Reply #8
Bman, You using the Berger 130 grain AR OTM hybrids or just the regular 140 grain hybrids?

Sorry, I've been quite busy.  Yes, the 140 hybrid - sub moa and some .4's pretty regularly.  Lately, I've been playing with the ELD 147's and am getting some .27" groups with those.  The ELD M is not a hunting round but the 143 X should give you good results with a little experimenting.