All posts by westtexordnance

Alpha Munitions brass for the 7mm SAW

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  A couple of months ago, we built a 7mm SAW for one of our long time customers, and he sent us some Alpha Munitions .308 Winchester Small Rifle Primer brass to use for load development in his rifle. It was extremely consistent stuff and worked very well for his build, so I decided to run some in my personal 7mm SAW as well and let y’all know the test results.

If you’ve read other information we’ve put out about this cartridge, you know that we designed it around the Lapua .308 Palma Case. In comparing the Alpha .308 SR brass to the Lapua, the two lots we have tested are every bit as consistent on weight as the Lapua offering. The Alpha brass does have slightly less internal volume; my test lot averaged 53.4 grains of water versus 54.6 grains of water for the Lapua Palma. Also of note is the Alpha primer pockets. They are just slightly tighter than new Lapua pockets, which should help with even greater brass life. If you are using an adjustable jaw priming tool such as the Forster, you’ll want to ensure that the priming tool’s alignment to the pocket is perfect to avoid damaging a primer during seating. 

To form the cases to 7mm SAW dimensions, I used our custom Whidden Gunworks die set and a 2 step form process that has proven to work very well for me. First, I debur the inside and outside of all the necks, put a sparing amount of One Shot sizing lube on the cases, and then run all the cases through the Whidden sizing die, with a .325″ Neck bushing installed and the expander removed. For the second step, I install a .312″ neck bushing in the die and re-install the expander ball positioned as high in the die as it will go without interfering with the bushing. This keeps the case mostly supported by the die as the expander passes through the neck on the return stroke. I then run the cases through the .312″ bushing, which puts the neck to it’s final dimension. This method yields formed cases with very little runout, which are ready to load and as the test data below indicates are more than capable or producing match ready accuracy on the first firing. 

I’ve been building a load for my rifle to complete at the upcoming Precision Rifle Series match at Q Creek Ranch in Wyoming, and settled on the 180gr Sierra MatchKing bullet and Alliant’s new Reloder 16 powder. With my existing Lapua Brass, 44.5 grains of RL16 produced muzzle velocity of 2700 FPS and extremely consistent accuracy at all ranges. Here are the specs of my rifle:

  • Bighorn Arms TL3 LBRP short action
  • Bartlein 1-8.5″ #23 contour barrel, 26″ length
  • McMillan A5 stock
  • WTO Mk2 brake
  • WTO short action bottom metal with A/W mags
  • Huber Concepts 2 stage trigger
  • Kahles K624i with SKMR3 reticle
  • Hawkins Precision Heavy Tactical rings

This barrel currently has a little over 2000 rounds on it, and has shown no velocity change since initial break in. Based on the load already developed on Lapua Brass, I decided to run a test on the Alpha .308 SR brass to see if equivalent accuracy and velocities were achievable. Taking into consideration the reduced internal volume, I shot a modified ladder test with Reloder 16 to determine maximum pressure.

180 SMK, 2.950″ OAL, CCI #41 primer, Reloder 16

  • 43.0 grains: 2651FPS, no pressure
  • 43.5 grains: 2690FPS/15ES, no pressure. .7″ group at 200 yards
  • 43.8 grains: 2702FPS/5ES, slight ejector mark on case head, easy bolt lift. 1″ vertical group at 200. Established as max charge for this brass/bullet/barrel. 

  With a good load found at 43.5 grains of RL16, I loaded a few more and decided to do some longer distance testing. I had several customer’s rifles to collect field data on the following morning, so once done with them I pulled my rifle out and shot two 600 yard groups. Conditions were 75 degrees, with a 12-15MPH full value wind from left to right. The first is the group pictured at the top of this post. The highest shot was the cold bore, followed by the two stacked together slightly below. Total group size measured 3.2″ center. I followed this group with a second group at 600 yards using my established load on Lapua brass. The second group was shot on a warm barrel, and measured 3.4″ center to center. 

 Later that evening, I pushed both loads out to 1055 yards. With very similar conditions to the morning shoot, both produced 5 shot groups hovering right around 6 inches, which I was more than pleased with. Of note in the 1055 yard groups was that the Alpha brass load seemed to steer better in the wind. While both loads exhibited about the same vertical dispersion, the Alpha brass load all fell within about 2.5″ horizontal dispersion. This may simply have been caused by more consistent winds or better calls during that string of fire and have nothing to do with the brass itself, but I plan to continue side by side testing to see if this is an actual trend. 

  In summary, our testing showed the Alpha Munitions .308 Winchester SR brass to be a very high quality and useful alternative to Lapua brass for 7mm SAW shooters. This test also answered a relatively frequent question on this cartridge of “can you really get match grade accuracy on the first brass firing?” Unequivocally, yes you can!

 

SwitchLug Compatible Action List

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 SwitchLug Compatible Action List

      This list is broken into two categories; direct fit and retrofit capable actions. Direct fit actions have the correct index pin locations for the SwitchLug to be a drop in fit. You will still need to have a barrel properly machined and headspaced for the SwitchLug interface, i.e. an existing barrel cut for a standard .187” or .250” recoil lug will not work in its current state. Retrofit capable actions will not accept the SwitchLug without action medication, but are suitable for modification to function correctly with the system.

          We will continually update the Compatible Action List as information is received. If you have an action that is not listed and are wondering whether it can be fitted with the SwitchLug, please feel free to contact us. General requirements for compatibility are that the action must use a barrel thread tenon that is less than 1.0625” OD, and must have a flat action face i.e. the barrel does not fit into a recess with an integral scope rail or recoil lug that protrudes forward of the barrel mating surface.

 

DIRECT FIT ACTIONS

·       WTO Claymore, all lengths and calibers(does not fit XL action)

·       WTO Claymore HD, all lengths and calibers

·       Stiller Predator, short, medium or long

·       Stiller TAC 30

·       Stiller TAC 300

·       Stiller Spectre, short or long

 

 

RETROFIT CAPABLE ACTIONS

·       Remington 700, short or long

·       Surgeon 591

·       Surgeon 1086

·       Bighorn Arms TL and SR series

·       Lone Peak Razor

·       Lone Peak Fusion

·       Defiance Rebel Old style(pinned recoil lug)

·       Defiance Deviant

·       Defiance Rebel New style(integral lug)

·       Badger M2013

·       Borden Alpine

·       Borden Timberline

·       Kelbly Atlas

7mm SAW barrel length and power tests

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As part of the development of the 7mm SAW cartridge, we tested several different powders for suitability. We also started the test barrel at a length of 31 inches, and performed a cut-down test to determine the amount of velocity loss that could be expected with various barrel lengths. The test barrel is a Krieger 5R stainless 1-8.5″ twist, .277″bore/.284″ groove.  All loads shown were tested using formed Lapua .308 Palma brass. Hopefully you find this information helpful as you gather data for your next rifle!

Maximum overall lengths for various bullets

Short throat, .045″ Freebore. This chamber would be necessary for shooters using standard AICS .308 magazines,  Magpul AICS pattern PMAGS, the HS Precision DBM system, or standard length internal magazine boxes). These overall lengths were measured after barrel break in as well. In an unfired chamber, the lengths would be approximately .005″-.010″ shorter than listed.

162 Hornady ELD-M: 2.850”
180 Berger Hybrid: 2.915”
168 Berger Hunting VLD: 2.840”/1.414” measured bullet length
183 Sierra Match King: 2.988”/1.603  measured bullet length
171 Barnes Match Burner: 2.835”/1.410 measured bullet length

Long throat, .150″ freebore. This chamber is recommended for running the 162 ELD or 168 Berger VLD in the AI A/W magazine, Alpha Mags, Accurate Mags without binder plate, and 3.000″ internal magazine boxes.

183 SMK: 3.090”
180 Hybrid:  3.020”
162 ELD: 2.955”
168 Berger VLD: 2.945”

All four listed bullets would seat with bearing surface above the neck/shoulder junction in this throat length.

Powder Test, Hodgdon Varget

Break in Load
162 ELD-M, 2.830”OAL
39.0grs Varget
Fed 205M
2733FPS/11.5SD
.5” at 100 yards, all sub MOA during break in

162 ELD-M, 2.840 OAL, Federal 205M Primer

40.0: 2806FPS
40.5: 2832FPS
41.0: 2852FPS
41.5: 2886FPS
42.0: 2879fps
42.5: 2889FPS
43.0: 2913FPS
43.5: 2937fps
44.0: 2989FPS, MAX PRESSURE. Bolt lift still easy, but substantial primer flow back and small eject swipe.

 

Powder Test, IMR 4451

162ELD-M, 2.840”OAL, Fed 205M primer

45.5:  2865FPS
46.0:  2859FPS
46.5:  2908FPS easy extraction, but max case fill at this throat length

IMR 4955 powder
162 ELD-M, 2.850”
Fed 205M Primer

46.0: 2827/27ES, 2.5” vertical at 200

IMR7828SSC powder
162 ELD-M, 2.850”
Fed 205M Primer

46.0: 2725/26ES, 3” vertical at 200

H4350 powder
162 ELD-M 2.850”OAL
Fed 205 M primer
45.5: 2878/20ES, 1.5” vertical at 200
46.0: 2901FPS
46.5: 2924FPS
47.0: 2951FPS
47.4: 2948FPS
All shots from 46.0 to 47.4 were within .5MOA vertical at 200
Re-shot 47.0 at 100 yards, sub .5 MOA accuracy, 2933FPS/38ES

 
183gr Sierra MatchKing/H4350 powder, 2.978” OAL

44.5: 2670FPS
45.0: 2694FPS, primer looks great
46.0: 2751FPS, primer looks the same at 45.0
46.7: 2782FPS, max load, compression causes issues seating to 2.180”

 

All loads after this point were tested on chamber with .150” Freebore.

183gr Sierra Match King, 3.090”
46.0grs H4350, Fed 205M
2773/8.1SD
.5MOA 4 shot group, 3 rounds in bug hole and one slightly right

 
BARREL LENGTH CUTDOWN TEST

Test Load:
162 ELD-M, 2.945”OAL
43.3grs Hodgdon Varget
Fed 205M
Lapua 2x fired brass

Barrel length

31”: 2941FPS/6.8SD
30”: 2916FPS/3.3SD
28”: 2915FPS/7.7SD
26”: 2911FPS/11.6SD

Test notes

a.      Even with rough crown, all barrel lengths shot sub MOA at 100 yards. 26” and 28” were the most accurate, both producing almost bughole groups.

b.    The 26” barrel test was done again using brand new brass, to find the amount of velocity drop off, if any, between brand new and fired brass. The new brass loads produced a velocity of 2874FPS/8.4SD, with accuracy almost equal to the 2x fired cases. After final load development for this barrel was completed, the new vs. fired brass test was conducted again, with both new and fired brass producing groups in the sub .2″ range(.150″ for fired brass, .197″ for new).

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